Studies on Transmission of Schistosoma Mansoni in New Halfa Scheme, Kassala State, Sudan

Studies on Transmission of Schistosoma mansoni in New Halfa Scheme, Kassala State, Sudan

Moddathir Abd el Rahman Kheir Alla Gabir

M.Sc.(University of Khartoum)

A THESIS SUBMITTED FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY IN ZOOLOGY

FACULTY OF SCIENCE

UNVERSITY OF KHARTOUM

July,2006

DEDICATION

To the Soul of my Mother whom I miss

To my Beloved Father

To my Wife , Children , Brothers, and Friends

With Love and Respect

Moddathir

ABSTRACT

The overall objective of this study is to provide the basic microepidemiological and microecoological information of Bilharzia from New Halfa Scheme that might enable a real and meaningful intervention. Concerning the microepidemiological part of the study, the achievement of the objective was attained through two parasitological surveys, one year spaced, for four selected residential sites in the scheme. In these two villages and two camps, 25% of the inhabitants were randomly selected and all school children of the four residential sites were included in the study. A pre-tested questionnaire was conducted for collection of the basic family information and the base line data of the socioeconomics and practices related to perpetuation of the diseases. Some accessible interventional techniques were conducted and their efficacy was assessed, reflected in knocking down the infection parameters. Regarding the microecoological part of the investigation, field observation were conducted on monthly basis, for a year, to assess the snails’ population dynamics as fluctuation was related to the observed aquatic ecological variables e.g. water temperature speed, turbidity and depth, vegetation cover, as well as the abundant natural enemies and competitors. From the other side, an array of laboratory experiments were designed and conducted to determine the most risk time for Man to acquire infection, considering both naturally and laboratory infected snails. All obtained data were coded,

III entered and analysed utilizing a microcomputer and the relevant technique of the statistix statistical packages. The overall prevalence of the intestinal schistosomiasis among the school children in the study area was 54.6% while the intensity was 80.6 eggs per gram. On the other side, the overall infection parameters of the villagers were 41.8% and 79.4 eggs per gram, respectively. Most of the infected candidates had light or moderate infection, while a very small proportion of the villagers and schoolchildren had heavy infection. The overall infection parameters varied with gender and age- classes, where the males significantly outnumbered the females and the infection peaked at the age- group (15-19) years. On the other side, the two infection parameters among the schoolchildren overrode those of the villagers, where the farmers and the agricultural labourers scored the highest prevalence rates. These finding were expounded on the basis of the socioeconomic status and water- contact activities, which were systematically observed during the study. The adopted interventional approaches were chemotherapy and health educational programmes that concentrated on acquiring better habitats utilizing the religious message as an entry- point. The overall reduction among the villagers was 62.2%, where the reduction among the males and the females were almost equi- distributed, 65.4% and 60.2% respectively. From the other side, the overall knocked down of the infection among the children was 76.3%. Considering the gender reduction among the schoolchildren, the infection rate of the males declined by 78.1% while those of the females reduced by 65.6% respectively. The systematic observation of the water- contacts in two minor canals suggested a concomitant peak with the infection parameters among age- group of (15-19) years of both males and females. Swimming represented

IV 50% of the important water- contact and no females were observed to practice any important water- contact in the two minor canals. The monthly malacological surveys ensured that Biomphalaria pfeifferi snails were abundant in the observed water bodies during the hot season (March- June) with a peak in May. The relative abundance of macroaquatic forms was significantly dominated by Biomphalaria pfeifferi snails followed by the shrimps, cyprinus fish, dragonfly nymphs (Crocothemis erythrea), and water Bug (Shaerodema nepoides). The local strain of Biom. Pfeifferi was proved in the laboratory to be highly susceptible to the local of S. mansoni strain. In all natural and laboratory infected snails, the cercariae emergence began around 7:00 AM and peaked at 01- 03 PM, then sharply declined at 7: 00 PM. Finally- based on the findings of the investigation, some effective measure for combating the disease were highly recommended.

CONTENT DEDICATION……………….……………………………………I ABSTRACT IN ENGLISH….……………………………………II ACKNOWLEDGEMENTS……………………………………...IV CONTENTS………………………………………………...... V LIST OF TABLES…………………………………..……………X LIST OF FIGURES……………………………………………XIII LIST OF PLATES……………………………………... ……..XVI CHAPTER ONE: GENARAL INTRODUCTION………………1 1.1 INTRODUCTION:…………………………………………..1 1.2 Importance of the study:……………………………………...2 1.3 Overall Objective:……………………………………………3 1.4 Specific Objectives:…………………………………………..3 CHAPTER TWO: LITERATURE REVIEW…… ……………...4 2.1 Biology of Schistosomiasis: ………………………………….4 2.2 Morphology and Life Cycle: ……………………...... 4 2.3 Intermediate-hosts of schistosomiasis:………………………7 2.3.1Biology of Freshwater Pulmonate:…………………………7 2.3.2 Ecology of Pulmonate Snails: …………………………….8 2.3.3 Factors Affecting Schistosomes’ Snails: ………………….8 2.3.3.1 Physical and chemical factors…………………………...9 2.3.3.1.1 Temperature:……………………………………………9 2.3.3.1.2 Rain fall:………………………………………………..10 2.3.3.1.3 Light:…………………………………………………...11 2.3.3.1.4 Turbidity:………………………………………………11

VI 2.3.3.1.5 Oxygen Tension:……………………………………….12 2.3.3.1.6 Aestivation:……………………………………………12 2.3.4 Snail-parasite Relationship: ………………………………..13 2.4 Bilharzia Diagnosis:……………………………………….. ..13 2.4.1 Diagnostic techniques of intestinal schistosomiasis:……. ..13 2.4.1.1 Parasitological Techniques ...... 14 2.4.1.2 Immunological Technique:…………………………...... 15 2.4.1.1.1Qualitative and Quantitative Parasitological Techniques16 2.5 Pathogenesis of Bilharzia:……………………………………17 2.6 Bilharzia Epidemiology:…………………………………...... 17 2.6.1 Incidence of Infection:……………………………………..18 2.6.2 Prevalence of Infection:……………………………………18 2.6.3 Intensity of Infection:………………………………………20 2.6.3.1 Arithmetic Means:……………………………………… 20 2.6.3.2 Geometric Means:……………………………………….20 2.6.3.3 Distribution of Eggs Output:…………………………….21 2.6.4 Incidence of Infection:…………………………………….22 2.6.5 Variation in prevalence and intensity of Infection:……….23 2.6.6 Stability of egg output:……………………………………24 2.6.7 Distribution of infected snails in the field:………………..24 2.6.8 Cercarial productivity:…………………………………….25 2.6.8.1 Cercarial dynamics:……………………………………..26 2.6.8.2 Daily rhythmicity of schistosome cercariae:…………... 27 2.6.8.3 Effects of infection upon snail:…………………………27 2.6.8.4 Factors influencing shedding patterns:……………… 28 2.6.8.5 Ecological and Genetic aspects of cercarial rhythm:… 29 2.6.9 Human water contact pattern:………………………… 30

VII 2.6.10.1 Planning control programmes:…………………… 34

2.6.10 Schistosomiasis Biological control………………… 35 2.6.11 Schistosomiasis in Sudan:…………………………… 36 2.6.12 Intermediate host in Sudan:………………………… 39 CHAPTER THREE MATERIALS AND METHOD……… 42 3.1 STUDY AREA:………………………………………… 42 3.1.1 Ownership of the Agricultural Land:………………… 42 3.1.2 Climate:……………………………………………… 42 3.1.3 New Halfa Agricultural Scheme (NHAS):…………… 43 3.2 METHDOLOGY AND ORGANIZATION OF THESTUDY44 3.2.1 Preparatory Phase:………………………………………44 3.2.1.1 Ethical Considerations:…………………………… 44 3.2.1.2 Villages Selection and Geographical Recognition:… 45 3.2.1.3 Sample Size Determination and Randomization:…… 45 3.2.2 Intervention Phase…………………………………… 48 3.2.2.1 Parasitological Surveys:…………………………… 48 3.2.2.1.1 Collection of Urine and Stool Samples:………… 48 3.2.2.1.2 Utilized Diagnostic Techniques:………………… 48 3.2.2.1.2.1 Urine Samples Examination:………………… 48 3.2.2.1.2.2 Faecal Samples Examination:………………… 49 3.2.2.2 Adopted tools for reduction of Schistosomiasis:……. 50 3.2.2.2.1 Chemotherapy Approach:………………………...... 50 3.2.2.2.2 Health Education and Community ParticipationApproach.50 3.2.2.2.3 Latrines for Excreta Disposal:…………………………… 50 3.2.3 Second Survey:………………………………………….. 51 3.2.4 Water-contacts Observations:………………………………... 51 3.2.5CERCARIAL RHYTHMICITY AND PRODUCTION……... 52

VIII 3.2.5.1 Snails Collection:…………………………………………... 52 3.2.5.2 Breeding and Screening of Snails:…………………………. 52 3.2.5.3 Miracidial Harvest and Snails Infection:…………………... 54 3.2.5.4 Cercariae Preparation and Enumeration:…………………... 54 3.2.5.6 Data Handling and Statistical Analysis:…………………... 55 CHAPTER FOUR: EPIDEMIOLOGICAL PARAMETERS OF SCHISTOSOMIAS………………………………………………..56 4.1 Villagers Epidemiological Surveys:……………………... 59 4.1.1 Infection Parameter by Residential Sites:……………………. 56 4.1.2 Infection Parameter by Gender:……………………………... 59 4.1.3 Infection Parameter by Age-groups:……………………. 61 4.1.4 Infection Parameter by Ethnicity:………………….………… 63 4.1.5 Infection Parameter by Occupation:…………………………..65 4.1.6 Infection Parameter by Socioeconomic Status:.…...... 67 4.1.6.1 Water-supply Accessibility:………………………………... 67 4.1.6.2 Infection Parameter by Excreta Disposal System………… 69 4.1.6.3 Infection Parameter by Number of Rooms………………. 70 4.1.6.4 Infection Parameter Quality of Building………...... 71 4.1.6.5 Infection Parameter History of infection: ……………….... 73 4.1.6.6 Infection Parameter by Awareness of Bilharzia and snails 74 4.1.6.7 Infection Parameter by Water-contact Activities………….76 4.1.6.8 Infection Parameter by Water-contact Categories………...77 4.1.6.9 Infection Parameter by Educational level…………………79 4.1.6.10 Infection Parameter by level of infection………………80 4.1.7 Reduction in infection Parameters:…………….……………..81 4.1.7.1Overall Reduction in Prevalence:………...... 81 4.1.7.2 Residential reduction in Prevalence Rates………………… 83

IX 4.2 Epidemiological Surveys-School Children…………………… 84 4.2.1 Infection Parameter by Residential Sites:…………………… 84 4.2.2 Infection Parameters by Gender:………………...... 84 4.2.3 Infection Parameter by age-groups:…………………………. 88 4.2.4 Infection Parameter by level of infection …………………….89 4.2.5 Reduction in Prevalence Rates among school children……… 90 4.2.6 Eggs-output Reduction………...... 91 4.3DISCUSSION:………………………………………………. 94 CHAPTER FIVE: MICROECOLOGY OF SCHISTOSOMIASIS...101 5.1 Seasonal dynamics of macrofaunal form in two canals:………101 5.1.1 Seasonal dynamics of Biomphlaria pfeifferi:……………….101 5.1.2 Seasonal dynamics of Cyprinus species fish………………..103

5.1.3 Seasonal dynamics of Waterbug: (Shaerodema nepoides)………….104 5.1.4 Seasonal dynamics of Dragonfly Nymphs(Crocothemis erythrea…106 5.1.5 Seasonal dynamics of Freshwater Shrimps:………… ……...108 5.2 Seasonal fluctuations of some microecological factors:………110 5.3 Water-contact observations:…………………………………...113 5.3.1. Prevalence of infection related to water-contact activities….113 5.3.1.1Prevalence Related to Categories of water-contact activities.115 5.3.1.2 Interval and duration of water contacts:……………… 118 5.4 Discussion: …………………………………………………... 122 5. CHAPTER FIVE: GENERAL DICUSSION AND RECOMMENDATION……………………………………………128 5.1 Discussion:…………………………………………………… 128 5.2 Conclusion: ……………………………………………………132

X 5.3 Recommendations:…………………………………………….132

REFERENCES…………………………………………………….134

ARABIC ABSTRACT…………………………………………….181

LIST OF TABLE

Table(1):Recent situation of schistosomiasis in the Sudan (2000- 2005)…………………………………………………... 43 Table (2): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2002-2004)…. 61 Table (3): Overall Prevalence and intensity of S. mansoni Infection among the surveyed samples from New Half Scheme, by Gender (2001- 2003)…………………………… 63 Table (4): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by age- groups……………………………………... 66 Table (5): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Ethnicity……………………………………….. 68 Table (6): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Occupation…………………………………….. 70 Table (7): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Water Supply………………………………….. 72 Table (8): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by latrine accessibility……………………………. 73 Table (9): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Number of Rooms……………………………... 75

XII Table (10): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by quality of building……………………………... 77 Table (11) Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by history of infection…………………………….. 78 Table (12): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Bilharzia and snails………………………..... 80 Table (13): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by water contacts……………………………………………………... 83 Table (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by categories of water contacts……………………………….. 85 Table (15): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by educational level……………………………………………. 87 Table (16): Distribution of S. mansoni egg-outputs among villagers in New Half Scheme, by level of infection (Based on WHO, 2005)………………………………………………… 89 Table (17): Overall reduction rate in prevalence of S. mansoni among the villagers in New Halfa Scheme (2002 - 2004 )………………………………………………………… 91 Table (18): Overall reduction rate in prevalence of S. mansoni among the male villagers in New Halfa Scheme… 91

XIII Table (19): Overall reduction rate in prevalence of S. mansoni among the female villagers in New Halfa Scheme………………………………………………………. 92 Table (20): Residential reduction of S. mansoni infection among the surveyed villages and camps of New Halfa scheme (2002 – 2004)………………………………………. 93 Table (21): Overall infection parameters of S. mansoni infection among school children in some selected residential sites in New Half Scheme………………………………….. 95 Table (22): Overall Prevalence and intensity of S. mansoni in four residential settlements in New Half Scheme, by children gender ……………………………………………... 97 Table (23): Overall Prevalence and intensity of S. mansoni infection in four residential settlements in New Half Scheme, by children age- groups……………………………….. 99 Table (24): Distribution of S. mansoni egg-outputs among school children in New Half Scheme, by level of infection (Based on WHO, 2005)……………………………… 100 Table (25): Overall reduction rate in prevalence of S. mansoni among the villagers in New Halfa Scheme (2002 - 2004 )………………………………………………… 102 Table (26): Overall reduction rate in prevalence of S. mansoni among the male villagers in New Halfa Scheme………………………………………………… 102 Table (27): Overall reduction rate in prevalence of S. mansoni among the female villagers in New Halfa Scheme………………………………………………… 103 Table

XIV (28): Eggs-output reduction of S. mansoni infection among the surveyed villages and the school children by the level of infection in New Halfa scheme (2002 – 2004)…… 104 Table (29):The relative abundance of the macro-aquatic forms collected from canals (16 & 12) in New Halfa scheme…………………………………………………. 114 Table (30): Monthly fluctuation of Biomphlaria pfeifferi snail collected from canals (16) and (12), New Halfa Scheme…115 Table (31): Monthly fluctuation of Cyprinus species collected from canals (16) and (12), New Halfa Scheme…117 Table (32): Monthly fluctuation of waterbug collected from canals (16) and (12), New Halfa Scheme…………… 119 Table (33): Monthly fluctuation of dragonfly nymph collected from canals (16) and (12), New Halfa Scheme…121 Table (34): Monthly fluctuation of freshwater shrimps collected from canals (16) and (12), New Halfa Scheme…123 Table (35): Seasonal fluctuations of some microecological factors monitored in longitudinal surveys of canal (16), New Halfa Scheme………………………………………….. 126 Table (36): Seasonal fluctuations of some microecological factors monitored in longitudinal surveys of canal (12), New Halfa Scheme………………………………………… 127 Table (37): Genderized frequencies and types of water-contact activates in relation to the proportion of intestinal Bilharzia by age-classes (Village (16) minor canal)…….. 129 Table (38): Proportions of important and relatively unimportant water-contacts among villagers in waterbodies around Village (16), New Halfa Scheme…………….. 132 Table (39): Frequencies of water contacts of the villagers in

XV waterbodies around Village (16), by interval and duration of exposure ……………………………………………… 137

XVI

LIST OF FIGURE

Figure (1): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2002)...... 62 Figure (2): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2004)...... 62 Figure (3): Overall Prevalence and intensity of S. mansoni Infection among the surveyed samples from New Half Scheme, by Gender (2001- 2003)...... 64 Figure (4): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by age- groups...... 67 Figure (5): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Ethnicity...... 68 Figure (6): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Occupation...... 71 Figure (7): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Water Supply...... 72 Figure (8): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by latrine accessibility...... 74

XVII Figure (9): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Number of Rooms...... 76 Figure (10): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by quality of building...... 77 Figure (11): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by history of infection...... 79 Figure (12): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Bilharzia...... 81 Figure (13): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Snails...... 82 Figure (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by water contacts...... 84 Figure (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by categories of water contacts...... 86 Figure (15): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by educational leve...... l88 Figure (16): Distribution of S. mansoni egg-outputs among villagers in New Half Scheme, by level of infection (Based onWHO, 2005)...... 90

XVIII Figure (17): Residential reduction of S. mansoni infection among the surveyed villages and camps of New Halfa scheme (2002 – 2004)...... 94 Figure (18)(19): Overall infection parameters of S. mansoni infectionamong school children in some selected residential sites in New Half Scheme...... 97 Figure (20): Overall Prevalence and intensity of S. mansoni in four residential settlements in New Half Scheme, by children gender...... 99 Figure (21): Overall Prevalence and intensity of S. mansoni infectionin four residential settlements in New Half Scheme, by children age- groups...... 100 Figure (22): Distribution of S. mansoni egg-outputs among school children in New Half Scheme, by level of infection (BasedonWHO,2005)...... 102 Figure (23): Eggs-output reduction of S. mansoni infection among the surveyed school children by the level of infection in New Halfa scheme...... 106 Figure (24): Monthly fluctuation of Biomphlaria pfeifferi snail collected from canals (16) and (12), New Halfa Scheme...... 116

Figure (25): Monthly fluctuation of Cyprinus species collected from canals (16) and (12), New Halfa Sche...... 118 Figure (26): Monthly fluctuation of waterbug collected from canals (16) and (12), New Halfa Scheme...... 120 Figure (27): Monthly fluctuation of dragonfly nymph

XIX collected from canals (16) and (12), New Halfa Scheme....122 Figure (28): Monthly fluctuation of freshwater shrimps collected from canals (16) and (12), New Halfa Scheme....124 Figure (29): Genderized frequencies and types of water-contact activities in relation to the proportion of intestinal Bilharzia by age- classes (Village (16) minor canal)...... 131 Figure (30): Proportions of important and relatively unimportant water- contacts among villagers in waterbodies around Village (16), New Halfa Scheme...... 135 Figure (31):Frequencies of water contacts of the villagers in waterbodies around Village (16), by interval of water contact...... 138 Figure (32): Frequencies of water contacts of the villagers in waterbodies around Village (16), by duration of exposure...... 138

LIST OF PLATE

Plate (1): Human schistosomiasis Life Cycle (Ross et al., 2002)...... 7 Plate (2): Laboratory Examination of Faecal samples...... 52 Plate (3): Health Education Lecture in a Basic- school in New Halfa...... 53 Plate (4): Snail scooping from the canalization system.... 56 Plate (5): Laboratory Infection of bred snails...... 58 Plate (6): Collecting Water from the canals ...... 134 Plate (8): important water- contact activity, Washing animals at mid- noon...... 136 Plate (9): Contamination of water-bodies by urination.....136

XXI

CHAPTER ONE

GENARAL INTRODUCTION

1.1 INTRODUCTION: Schistosomiasis is a waterborne parasitic disease of man and other vertebrates in tropical and subtropical regions. The disease recognized as one of 10 tropical diseases of most concern to the world Health Organization. Schistosomiasis is one of the most wide spread and is second only to malaria in term of socioeconomic and public health importance (WHO, 2003). The causative agents are small bisexual blood fluke of the family schistosomatidae. It was estimated that about 300 million people in more than 76 countries are infected with schistosomiasis and other 600 million people are at risk of infection (Ahmed et al., 2002).

In Sudan, construction of irrigation schemes and agricultural development projects had been properly designed for maximum production without consideration to the side effect on the environmental changes. Thus, the price had been paid for agricultural and economic development, a dramatic increase in both prevalence and intensity of schistosomiasis in these schemes (Omer et al., 1976, Kardaman et al., 1982, Hilali 1992 Babiker et al., 1996, Ahmed, 1998, 2003, 2004 & 2005).

Data obtained from famous endemic countries has clearly indicated that an increase in the prevalence of schistosomiasis is closely related to water resources development (Nadamba et al., 1991 & El Tash, 2000 & 2005). Poverty and inadequate sanitation and water-supply are also conditions associated with the disease infection parameters (WHO 1998). The transmission of human schistosome is a complex process consisting of a vicious cycle events involving

1 man as a definitive host and reservouir of the adult schistosomes. Transmission of schistosomiasis may occur in many different types of waterbodies with especial emphasis on man- made habitats. The risk of becoming infected from an infested waterbodies depends on duration of contracts, degree of body exposure and the time of day (El Tash, 2000).

Data on intensity of infection among the population represent a valuable epidemiological indicator of the morbidity level and intensity of transmission. Variation in transmission patterns in different endemic areas makes it almost impossible to set up a “standard” disease control strategy, Ahmed (1998).

Schistosomiasis is a socioeconomical problem, its meaningful and real control posses a major social challenge. Furthermore, many extensive previous reports stressed that no single control method is enough to control schistosomiasis effectively (Ahmned, 2005). Ideally, effective control should involve the combined application of different measure i.e. adoption of integrated control as recommended by the World Health Organization (2003).

In this document, they have suggested two approaches for schistosomiasis control, morbidity control and transmission control. Activities like mass chemotherapy of all human cases reduces the release of eggs (morbidity), whereas snail-host control reduces transmission of the disease to man, health education and provision of adequate safe-water supply and sanitation decrease both morbidity and transmission (WHO, 2003).

1.2 Importance of the study: Basic information concerning the epidemiology of schistosomiasis provides an essential background for planning and implementation of the control strategies and tactics. Variation in transmission patterns in different endemic areas makes it

2 almost impossible to set-up a standard control strategy. In fact, real and meaningful control requires recognition of the importance of this disease, commitment at the Federal, State and Local Authorities to the control programmes, adequate organizational structure and sufficient manpower and financial resources. The present investigation was the first deep trial for highlighting the transmission pressure of Bilharzia in New Halfa scheme.

The sugar cane as a plant needs substantial amount of water flowing for 16 consecutive months, which provides a favourable environment for the sustainability for the intermediate hosts. Furthermore, some sort of intensive population movements were observed from other agricultural schemes, where Bilharzia is a real health problem. In addition, the situation was further aggravated by the miserable heath situation of the inhabitants in the agricultural camps in the scheme. Thus, a serious intensive longitudinal epidemiological investigation was pivotally needed to throw some light on the factors behind the transmission pressure of the disease in the scheme.

1.3 Overall Objective: The main objective of the study is to investigate the epidemiological factors influencing schistosomiasis transmission in four residential settlements at New Halfa irrigation scheme.

1.4 Specific Objectives: 1. To determine the infection rates and the worm burden of schistosomes infection in two villages and two camps of the scheme, per- and post- intervention. 2. To monitor the two infection parameters of the disease among the children in six schools of the scheme, per- and post-intervention.

3. To assess the villagers' KAP (Knowledge, Attitude and Practice) as well as the socioeconomics that correlate to the infection parameters of the disease. 4. To evaluate the efficiency of some interventional tools for knocking-down the infection parameters among the villagers and the school children. 5. Elucidation of the innate diurnal rhythmicity of schistosome cercariae, from naturally and laboratory infection, and to determine the most risky time for man to acquire infection. 6. To highlight the influential role of the recreational and occupational water- contact activities in Bilharzia transmission among the inhabitants of the scheme. 7. To provide the seasonal fluctuations of the intermediate-host snails and their monthly infection rates in two waterbodies of the scheme.

CHAPTER TWO

LITERATURE REVIEW

2.1 Biology of Schistosomiasis: The epidemiology of human schistosomiasis involves three major components, the schistosome parasite, the intermediate-host snails, and the definitive human host. Therefore exhibits great variability and complexity governed by local geological, geographical and climatic condition (Jordan &Webbe, 1982). Schistosomiasis was reported in ancient Egyptian medical papyri, and the first evidence was the finding of calcified egg in Nakht, by Sir Armand Ruffer (Ruffer, 1910). Theodore Bilharz was the first who realized these wonderful worms which has a divided sex (cited by Rollinson & Johnston, 1996).

Rollinson and Southgate (1987) reported that there were six species of schistosome to infect man, these are S. haematobium (Bilharz, 1852) S. mansoni (Sambon, 1907) and S. intercalatum (Fisher, 1934) which are transmitted in Africa, S. haematobium and S. mansoni are transmitted in Indian Ocean Island and Western Asia. While S. Japonicum (Katsurada, 1904), S. mekongi (Bruckner, Bruce 1978) and the new Malaysian (Green et al., 1980 & 1989).

2.2 Morphology and Life Cycle: The complex process of the life cycle of schistosomiasis needs three important ingredients, people, freshwater and snails. The human water-contact behaviour plays an important role in the distribution of schistosomiasis, Rollinson and Johnston (1996). The basic life cycle of schistosomes involves as intermediate host (snails) and a definitive host (man). Adult schistosomes live in pairs within

5 their human host for several years, during such time they steadily produce eggs between (200 - 2000 eggs) a day as an average for about five years according to the species (WHO, 1998). However, many of the eggs, about 50% or more, fail to complete their intend migration to the bladder or bowel and become lodged in tissues else where in the body, including more or less serious damage (WHO, 1998). The proportion of the eggs that reach the freshwater, after excretion, hatch into microscopic free-swimming miracidia, and each miracidium has a life-span up to 24 hours, which it spends searching for a snail of specific variety. Inside the snail, the miracidium becomes a mother sporocyst; this gives rise to daughter sporocysts which produce free-swimming cercariae that penetrate directly the skin of the final host. After penetration they enter the blood circulation and pass via the lungs to the liver, where they develop into adult schistosomes, and depart to their normal location in the mesenteric veins or the terminal venules of vesicle plexus to lay their eggs. The whole phase of development from skin penetration to adult schistosomes' formation takes about 8 or more weeks (Jordan & Webbe, 1982).

In any community, the way in which schistosomiasis is contracted and transmitted depends on the contact between man and the infected snail in waterbodies. Man comes in contact with infested waterbodies, practicing different water-contact activities, some are domestic like water collection, and others are recreational such as swimming, while others are of occupational nature like fishing or irrigation (Christensen et al., 1987 and El Tash, 2000). Transmission may occur in many different types of waterbodies with especial emphasis on man-made habitats. The risk of becoming infected from an infested waterbody depends on the duration of contacts, degree of body exposure and the time of day (El Tash, 2000).

Plate (1): Human schistosomiasis Life Cycle (Ross et al., 2002)

2.3 Intermediate-hosts of schistosomiasis: Various species of snails act as intermediate-hosts of the notorious parasite. The snails belong to the class Gastropoda, Family Pomaiopside. Different subspecies of the amphibious snail Oncomelania hupensis, transmitting S. japonicum, and two species of truly aquatic, basommatophoran genera Biomphalaria and Bulinus which transmit S. mansoni and S. haematobium, respectively. The S. intercalatum transmitted by Bulinus forskalii and S. mekongi by Bobertsiella kaporensis (WHO, 1993). Some human parasite species have no reservoir host at all, like S. haematobium, while others have small variety of mammalian acting as reservoirs like S. mansoni and S. mekongi (WHO, 1993).

2.3.1Biology of Freshwater Pulmonate: Intermediate hosts of schistosomiasis are hermaphroditic; some species reproduce through self-fertilization, while other requires cross-fertilization. Eggs are deposited in-group, egg-masses, which are flat and the terminal edge of the mass is attached to the first part giving them a round or oval outline. Egg-masses are fixed, after deposition, to the available substratum e.g. plants, stones, sticks, plastic or shell of other snail (Madsen, 1985).

The hatching period of Biomphalaria and Bulinus species is around 6-8 days at 25˚C. The newly hatching size is 0.6 mm (shell diameter for Biomphalaria) and 1.7 mm (height for Bulinus). In favourable condition, snail reaches the maturity after 4-5 weeks from hatching. The shell size at maturity is about 5-mm diameter in Biomphalaria and 5-7 mm height for Bulinus species. The average egg production during the first 6-7 weeks of egg laying 300-1000 eggs under optimal condition. These parameters differ between field and laboratory condition, in field maturation period is longer, growth is slower and the egg laying is lower (Madsen, 1985). Fresh water snails feed on periphytic growth, fungi, bacteria, decaying parts of aquatic plants, fresh plant leaves, etc., (Madsen, 1995).

During the desiccation period, both species Bulinus and Biomphalaria can practice aestivation for 10-12 months; either bury themselves into the mud or plug shell opening to the mud. Snail survival depends on the relative humidity in mud, and the surviving snails have higher egg laying capacity after aestivation and the egg-masses can not tolerate desiccation (Madsen, 1985).

2.3.2 Ecology of Pulmonate Snails: The understanding of snail ecology was improved just over the past years (WHO, 1999). Schistosomiasis intermediate-hosts are surface dwellers of different type of water bodies (Slootweg et. al., 1993). Their habitats include natural or man- made water bodies, small and temporary or large, permanent and small ponds or streams or large lake or rivers. Man-made waterbodies, irrigation canals and dams, are excellent snail habitats. In these waterbodies, contact sites used intensively by human, these have influential role in the transmission of Bilharzia. Aquatic vegetation (floating, emerged or submerged) represents a substrate for snails feeding and site for laying egg-masses. In addition, they provide the suitable protection for snails against their natural enemy (Madsen, 1985).

The intermediate hosts can tolerate a wide temperature range, (0º-40º) C, where their optimum temperature range is (20º-28º) C. The snails usually found when the water current is less than 0.3 m/sec. Geographical distribution and density of Pulmonate snails concerned to some factors e.g. temperature, oxygen dissolved in water, flooding, desiccation, predators, and the main factor is food resources (Madsen, 1985).

2.3.3 Factors Affecting Schistosomes’ Snails: The intermediate host is a crucial link in the parasite life cycle, thus precise information about its crucial microecological aspects. These include the snails’

9 bionomics and the population dynamics, which are highly determinant factors in the understanding the transmission pressure of Bilharzia, and its subsequently control activities, planning, intervention and evaluation. It is very conspicuous that some sort of complex interaction of microecological factors, representing key factors in the focal distribution of the intermediate hosts (Shiff, Personal Communication). 2.3.3.1 Physical and chemical factors: 2.3.3.1.1 Temperature: Temperature has a direct influential role in metabolic activity of the snail, and indirectly by affecting the distribution and growth. Furthermore, it affects the photosynthetic pathways and bacterial decomposition rates, thus, influence oxygen availability in aquatic environment. The intermediate hosts can tolerate a wide temperature range, (0º-40º) C, where their optimum temperature range is (20º-28º) C. Malek (1962) expounded the low reproduction of both Biomphalaria and Bulinus snails on the basis of the summer high temperature. Later on, Hilali (1992) stressed that the seasonal variation in the population density of Biom. pfeifferi and Bul. truncatus seems to be related mainly to temperature. He also suggested that the other factors like the irrigation cycle, water level, current speed, turbidity and composition and density of aquatic vegetation might play a limited role.

Earlier Dazo et al., (1966) reported that the seasonal fluctuation in temperature, tops in summers and downs in winter, reduced the number of Biom. alexandrina and Bul. truncatus or stopped the breeding of the snails. Latter, Demian and Kamil (1972) observed that the breeding of Bul. truncatus under semi-field conditions was through most of the year except in late summer, where egg production was significantly reduced due to high temperature.

They reassured that Biomphalaria snails have two conspicuous peaks of growth, autumn and spring. First, they have observed that the daily mortality rate of snails was highest in the interval (June – September) and lowest in the cold months (December – April). The second observation, breeding of Biomphalaria snails occurs throughout the year with the apex of reproduction between November and March. They have expounded these observations on the basis of the variation in temperature between season. In Tanzania, Sturrock (1966) concluded that temperature as high as 32º C stopped colonization of the coast via Biom. pfeifferi. Later on, in Ghana, Klumpp et al., (1985) observed Bul. truncatus rohlifsi were burrowing in mud, when the water temperature exceeded 38º C. The outstanding experimental laboratory- designs were conducted to illustrate the reproduction of Biom. glabrata. They have measured the egg production, number of eggs oviposited, and hatching rate at five different temptresses. They concluded that the egg production and spawning rates were peaked at temperatures between 27.5º C than at 17.5º C. But the number of eggs per spawning as well as the hatchability did not varied with temperature.

2.3.3.1.2 Rain fall: Rain cycles are probably the most important factor affecting snail life cycles and population densities in the tropics. Seasonal variations in snail populations have been reported from a wide range of natural and man-made tropical habitats in Brazil, East and Central Africa and the Caribbean (Shiff, 1964). The effect is more pronounced in the semi-permanent or temporary habitats of the intermediate hosts of S. mansoni and S. haematobium and where the hosts of S. japonicum extend into subtropical areas in Japan and China, in periods of heavy rainfall, scouring floods dislodge snail populations from flowing habitats (Sturrock, 1973 a & b), but rainfall fills standing water habitats, sometimes transforming non-productive and often polluted sites into ideal snail habitats

(O’Keefe, 1985 b), in such habitats, the main populations growth may be delayed until after peak rainfall (Webbe, 1964). The delayed hatching of N. aperta eggs in the Mekong River appears to be an adaptation to protect the hatching snails from the high flows during the rainy season (Upatham et al., 1981).

Prolonged dry intervals between periods of rainfall have opposite effects on flowing and standing habitats, smaller standing pools dry out, causing high mortalities unless the snails are adapted to evade the effect of desiccation, however, diminished water flows can change unfavourable flowing habitats into ideal snail sites, although these too may eventually pool out into standing sites and ultimately dry-up in prolonged droughts. Normally, rainfall acts locally where it falls, but there are examples in very large river basins where rainfall produces delayed seasonal effects many hundreds of kilometers downstream as, for example, in Lake Volta, Ghana (Klumpp & Chu, 1977), seasonal effects in such areas may be modified by man-made interventions for the provision of perennial irrigation water to improve agriculture (Diaw et al., 1991).

2.3.3.1.3 Light: Day light is essential for snails' growth, this was observed among snails population in Sudan where turbidity levels were dropped seasonally, so the dramatic of the snails population increasing (Babiker et al., 1985) but Watson (1958) reported that Bulinid snails can be reared successfully for several generation in total darkness suggesting that day light is not essential. Snails avoiding either light or high surface temperatures might conceivably reach depth where hydrostatic pressures could affect their buoyancy but with the possible exception of the central African lakes (inhabited by specially adapted species such as B. choanomphala) and man-made reservouirs, snails' habitats are rarely more than 1 or 2 meters deep. The pressures created at this depth do not appear to affect adversely either snails (Jobin & Michelson, 1969) or their eggs (Nojima &

Sato, 1982). In addition, as observed day light is essential for sexual activity and development of embryos and young forms.

2.3.3.1.4 Turbidity: Snails are found in extremely turbid water, but the population growth not proper; depending on the turbidity levels. Adult and juvenile snails appear not come to harm due to turbidity, but the slit deposition harm the egg-masses. The slit deposition also limits the growth of aquatic plants, such surges of flood water along major rivers serving irrigation scheme as in the Sudan (Babiker et al., 1985b). Both Biom. pfeifferi and Bul. truncatus occur at high densities with great abundance of young snails in marginal grasses along major canals indicating that the turbid water in itself is not determinant to the snails’ population (Madsen, 1990).

2.3.3.1.5 Oxygen Tension: Oxygen tension is the chief limiting factor in the snails' ecology that the snails showed distress when the oxygen tension falls below 75 per cent of saturation and suffocate when it falls bellow 10 percent.

2.3.3.1.6 Aestivation: Aquatic intermediate-host snails have the capacity to survive out of water for some weeks or even months, aestivation. This has influential impact on the epidemiology of schistosomiasis and ultimately its control measures. Infections with schistosomes, however, appear to render snails less tolerant to desiccation, where Babosa and Coelho (1954) reported that sporocysts and cercariae of S. mansoni degenerate on the 20th day in B. glabrata subjected to desiccation. They also found that mature S. mansoni infections in B. glabrata die during aestivation, but the snails exposed to miracidia within 25 days of aestivation retain the infection. Later on, Webbe (1962 a) reported that S. haematobium

13 infection in B.(P.) nastus productus survived drying for 98 days. It is apparent, therefore, that immature infections of both S. mansoni and S. haematobium may be carried in aestivating snails from one wet season to the next, which is of considerable epidemiological significance.

In the aestivation process, the aquatic snail retracts into its shell and closes the aperture with a layer of mucous. In populations frequently exposed to drying, snails often develop apertural lamellae to strengthen the shell. Snails survive rapid drying less well than slow drying over several days. Sometimes they disappear before the habitat dry out, presumably burying themselves in muddy substrates as conditions become unfavourable, they may also seek refuge under vegetation, especially in shaded places where lower temperatures and saturation vapour deficits minimize the severity of the desiccation. Mortalities tend to be least in young, sexually mature adults and snail eggs have little resistance to drying Greany (1952) reporting on snail intermediate hosts in the Gezira irrigation scheme, stated that a proportion of both Bulinus and Biomphalaria snails can survive desiccation for up to 3.5 months. He found that after 3.5 months 10% of the Bulinus and 7% of the Biomphalaria revived in different canals. Otherwise mortality as effect of infection is generally higher among infected snails than that of uninfected both in the laboratory and the field (Sturrock, 1970). Also mortality is normally least in young adult snails and relatively higher among females than males. Infection frequently alters snail growth rates although the effect may depend on the age when the snails were infected (Sturrock, 1966).

2.3.4 Snail-parasite Relationship: Susceptibility of the snail to the parasitic infection varies between geographical areas, populations in the same area and among individuals in the same population. Susceptibility is also affected by biological factors of which are snail size, number of subjected miracidia, water illumination and darkness (Shoukry et al., 1997). The

14 trematode that have certain deleterious effect on the snail mainly due to mechanical damage of snail tissues caused by the migrating larval stages, consumption of digested food materials and excretions from the parasite. Furthermore, schistosomes direct their host metabolites to their own uses by stimulating the production of a neuro-peptide in the central nervous system of the snail which inhibits snail oviposition (WHO, 1993). Madsen (1985) concluded that trematodes infection may be important factor causing fluctuation in density of natural snail population.

2.4 Bilharzia Diagnosis: 2.4.1 Diagnostic techniques of intestinal schistosomiasis: There are three main methods for diagnosing the parasitic infections: First, the clinical diagnosis (based on examining the clinical manifestation caused by the parasites. Second, parasitological diagnosis (based on finding stages of the parasites microscopically. Third, immunological diagnosis (based on measuring the specific host reactions against the parasitic antigen. Parasitological diagnostic techniques are either: 1. Qualitative (gives information about the species of the parasite(s) present. This is useful for clinical practice. 2. Quantitative (indicates the number of eggs excreted by the patient and expression of the load of infection. This method used in epidemiology, control and drug trails (Simonsen et a l., 1986).

2.4.1.1 Parasitological Techniques : (a) Direct Smear Technique: The method recommended for diagnosis of intestinal schistosomiasis if no other techniques available (Simonsen et al., 1986). It based on examining a small portion of faeces directly under a microscope. This method used for detection of moderate and heavy infections, but not for light infections (Salih, 1989).It is a

15 fast qualitative method and needs only simple equipment.

(b) Sedimentation/Concentration Methods: The sedimentation method was first described by Hoffman et al., (1934). This method based on sedimentation or centrifugation and has been developed for detection of light infection. The method requires minimum equipment and reagents and is suitable for field studies. It involves removal of faecal debris and then the concentration of the eggs in a container. Other concentration methods such as formal either (Ritchie 1948) and acid either (Hunter et al., 1948) techniques involve removal of fat. These techniques have been modified to improve sensitivity but they are in generally not used in the health units since they are time consuming (Simonsen et al., 1986).

(c) Bell’s Techniques: This method based on sedimentation (Bell, 1963). It involves removal of faecal debris and staining of Schistosoma eggs. The method is highly sensitive in detecting light infection.

(d) Kato Method: A cellophane-thick smear technique for stool examination in Japan was described by Kato and Miura (1954). This technique was tested, used and modified by many workers (Martin & Beaver 1969; layrisse et al., 1969, Katz et al., 1972). Higher ova count per gram of faeces was obtained in several studies by the Kato technique than that obtained by other techniques (Dantas & Ferreira, 1973; Coura & Conceicao, 1974; Teesdale & Amin, 1976). The technique is less useful in lightly infected population except where the objective in only to detect individuals with relatively high ova output (Kinght, 1976; Barreto, 1978). During an epidemiological study in the Sudan, a temporary difficulty in obtaining cellophane led to its substitution by thick glass cover-slips (Teesdale & Amin,

1976). A disadvantage of the locally modified technique is that the slides can not be stored, hence examined later. The subsequent evaluation of this modification by comparison with the Bell’s technique (1963) indicated that the locally modified method was sensitive and most suitable for field conditions (Salih, 1989). Other parasitological techniques reveal higher prevalence rate and are valuable for confirming diagnosis in individual cases e.g. rectal or hepatic biopsy (Garcia, 1976). Diagnosis of schistosomiasis can readily be made by finding eggs in stool, while in chronic stage of infection recovery of eggs is much more difficult. 2.4.1.2 Immunological Technique: Immunological technique is based on the assumption of the presence of antibodies formed against schistosomiasis. These serological tests of vary complexity used to confine the clinical findings. The most important immunological tests include: 1. Cercarian Mullen Reaction (CHR), Jordan and Goatley (1963). 2. Circumoval Perception Reaction (CPR), Hillyer et al., (1979) and Salih (1989). 3. Compliment fixation Technique (CFT), Jordan and Webbe (1982). 4. Enzyme linked immuno-sorbent Assay (ELISA), Polderman and Deelder (1977) and Hillyer et al., 1979).

2.4.1.1.1 Qualitative and Quantitative Parasitological Techniques: The world Health organization (1976 & 1980) has repeatedly advocated the use of quantitative methods in all aspects of epidemiological studies on schistosomiasis. Quantitative technique replaced qualitative one because of the useful addition information provided by qualification of ova output (Ahmed, 1998) the advantages of quantitative technique are: (a) Rabid and low cost.

(b) Provide an estimate of intensity of infection. (c) Give quantitative results, which can be submitted to statistical analysis. (d) Provide results, which can be compared between different endemic areas and different observers. (e) Sample obtained and prepared in the field may be examined microscopically later. (f) Important in evaluation of schistosomiasis control activities devoted to reduction of morbidity. (g) Promote further understanding of relationship between intensity of infection and morbidity (Kloetzel, 1971 a & b). (h) Provide reliable baseline data for intervention studies in the areas of chemotherapy (Dalton, 1976; Dalton & Pole 1978), malacology (Jordan 1978). Klummp and Chu, 1977) and sociology (Dalton 1976, Dalton & Pale 1978). (i)Provide precise information on which to base control strategies (Jordan, 1977). The small samples used in quantitative techniques limit the sensitivity of ova count. The recommended volume of urine to be examined is 10 milliliters. The actual volume of faces examined in cellophane fecal thick-smear range from 10 to 125 milligram. Sensitivity may be increased in hospitals or public laboratories by examining several thick smears slide prepared from the same specimen or by examining large volume of urine or stool.

2.5 Pathogenesis of Bilharzia: Five species of schistosomes infect man with a schistosomiasis disease, three of them are most important (S. mansoni, S. haematobium and S. japonicum), WHO (1990). The disease leads to serious physical, social and economic disability and, together with the other major parasitic diseases, can seriously weaken the productive capacity of the developing countries (WHO, 1990). In communities

18 with high prevalence and intensity of infection, there is a wide range of clinical manifestation. The majority of infected people suffering minor but unpleasant symptoms like blood in the urine or stools, occasional diarrhea and abdominal pain (Rollinson & Johnston, 1996). Schistosomiasis is a primary disease of children in most endemic areas. Detection of schistosomes' ova in urine and stool is definitive diagnosis of an active infection. The numbers of infected people decrease after adolescence coupled with the development of resistance (Rollinson & Johnsten, 1996). In urinary schistosomiasis, various malfunctions result from blocked of urinary and kidney ducts. In the intestinal schistosomiasis, the venous drainage of the liver would be blocked, leading to compensatory increase arterial flow. This results in portal hypertension and enlargement of the liver and spleen. Severe complication usually follows after years of silent or mildly asymptomatic infection. Moreover, an association between schistosomiasis and cancer has been identified (Rollinson & Johnsten 1996; Shiff et al., 2005 & Bushra et al., 2005). 2.6 Bilharzia Epidemiology: Epidemiology of human encompasses the definitive human host, the intermediate snail host, all stages of the life cycle of the parasite, their relationship with the two hosts and the development of Schistosoma disease. The processes of transmission are necessarily complicated and subject to considerable variations due to many factors influencing the common environment, the bionomics of intermediate host and the behavioural patterns of the definitive host (Jordan & Webbe, 1982). Transmission of schistosomiasis usually occurs in waterbodies such as bonds, lakes, and canals. Transmission increasing in irrigation and water conservation schemes in many parts of Africa (Christensen. et al., 1986; Daffalla & Suleiman 1988). To provide favourable conditions for Schistosoma transmission (Coracha et al., 1992), inadequate water-supply result in an intensive use of snail infested natural or man-made freshwater habitats (MacDonlad, 1965; Mott & Cline, 1980; Teklehaimanot & Fletcher, 1990). A study on epidemiology of human Bilharzia aims to provide information on place

19 and time of transmission and on prevalence and intensity of infection in definitive host population (Rollinson & Johnston, 1996).

2.6.1 Incidence of Infection: Epidemiological parameters related to infection in man such as water-contact patterns, snail-host population and their infection rate are essential in any comprehensive epidemiological study. Common indices in measurements of human schistosomiasis comprise the prevalence, intensity and incidence of infection. The human parameters of infection are usually calculated for specific groups of population e.g. gender, occupational, educational level, ethnicity, age- class, recreational habits or other sociological factors.

2.6.2 Prevalence of Infection: Prevalence denotes to the percentage of individuals that are infected in the population at a given point of time.

Prevalence (%) = Number Infected X 100 Number Examined

It gives a measure of transmission over a long period of time but because it is a point measure, it does not discriminate between current and past transmission. The prevalence of infection is determined by past incidence and rates of loss on infection. The rate of establishment of new infection may exceed the rate of loss of infection under condition of intensive transmission, thus the prevalence increases. In contrast, under less intensive transmission conditions, loss of infection may exceed establishment of new infection resulting in declining prevalence of infection. A significant reduction in prevalence of infection in human population a result of reduced / blocked transmission induced by control measures other than chemotherapy, is a long lasting process (Ahmed, 1998). In

20 prevalence analysis it is useful to present data of subgroups by standardized categories e.g. age-classes and gender. Both parameters normally rise to a peak normally in the 10 - 20 years age-group followed by a decline in older age- groups (Omer et al., 1976; Abd El Wahab et al., 1980; Bartholomew et al., 1981; king et al., 1982, Dennis et al., 1983; Klumpp & Webbe 1987, Chandiwana et al., 1988). A low stability in transmission may occur as a result of extensive human migration, breakdown of long-lasting effective control or introduction of transmission into pervasively schistosome free areas. The fact that older age- groups have less frequent water contact, together with a slowly developing resistance to re-infection, could be responsible for low infection level in older age-groups of the population (Jordan & Webb 1982). Generally differences in local geographical and geological and climate conditions (Jordan et al., 1980 a & b; Christensen et al., 1983) or differences in the socioeconomic status, human water-contact activities and presence of piped water (Costa et al., 1987) would explain the heterogeneity in intensity of transmission among villages in a given endemic area. Man-made water bodies result in changing the distribution pattern of schistosomiasis like the change from basin to perennial irrigation in Egypt (Mobbark, 1982) and the construction of Gezira-Managil schemes with extensive irrigation system in Sudan (Amin et al., 1982, Babiker 1987). The best examples of utilizing the prevalence figures are those of the evaluation of the sensitivity of the diagnostic technique (Gryseel & Polderman, 1991) as well for the control assessment (Jordan, 1978).

2.6.3 Intensity of Infection: Measurement of the intensity of infection (worm burden) in infected individuals is very important, it expressed as a number of ova excreted in urine and/or faeces. It considered being associated with the worm burden and the deposition of eggs in tissues (Mott, 1987). In young infection a correlation exists between number of ova excreted and morbidity suffered from present and/or later developing

Schistosoma disease. Ova output provides valuable information for epidemiological situation especially from young age-groups (Christensen et al., 1987). Intensity of infection is used for efficacy of control measure on the level of transmission. In snail control programmes, it is necessary to distinguish between changes in a cohort (same individuals) and changed in an index group (different individuals) as stressed by Jordan (1998).

2.6.3.1 Arithmetic Means: Intensity of infection is normally calculated as the mean of intensity for each of specific subgroups (age, sex, ethnicity, etc.) Ova count may be given as an arithmetic mean, which is computed by dividing the total number of ova counted (x) by the number of individual infected (n).

Arithmetic Mean = ∑ (x) n

2.6.3.2 Geometric Means: The non-random distribution of intensity of infection in population, with most individuals harbouring relatively high infection and a few harbouring very heavy infections suggests that the use of the arithmetic means results in an exaggerated overall intensity of infection in the population. It is therefore, more appropriate to calculate geometric means of ova excreted when working at the population level. The geometric mean is calculated by obtaining the anti-logarithm of the logarithm of the ova counted (log x) divided by the number of individuals examined (n).

Geometric Mean = Anti Log ∑ (Log X) (n)

2.6.3.3 Distribution of Eggs Output: Means of intensity of infection, measured by size of ova excreted, in younger age – class, normally exceed that found among old age – group. Within each age- group few individuals harbour heavy infection and the majority is relatively lightly infected. This is mainly due to differences in water contact behaviour (Dalton & Pole 1978; Costa et al., 1978 & Chandiwana, 1987). Individual differences in the immunological capacity between children may also be a contributory factor. Barreto (1978) states that the higher proportion of the population harbouring heavy infections is usually associated with a high prevalence of infection. Transmission of ova count data for purpose of distribution of egg and standardizing comparison of large numbers of persons my be done by (log), (log + 1), or any other transformation procedure. Geometric mean egg-output of infected individuals in community varies according to sensitivity of parasitological technique used such as formal-either technique using 10 gram of faeces. The lowest egg-count can be only one egg per gram (epg). In contrast, in the 20-mg thick smear technique, the results are multiplied by a factor of 50 to convert it to an egg per gram basis (Jordan & Webbe, 1982).

2.6.4 Incidence of Infection: The main importance of incidence studies has been in the monitory of control programmes aimed at reducing transmission where the reduction in the incidence is a measure of effectiveness. The incidence rate defined as the proportion of initially uninfected subjects, who become infected during a given period of time, usually expressed as the percentage per year. Although an easily understood idea, in practice the incidence rate can be difficult to measure (Scott et al., 1982; Goll et al., 1984). The most convenient study group for determination of children cured from infection by drug treatment. Use of uninfected and / or-non treated

23 children results in an underestimation of incidence rates. Their status as initially non-infected reflects a less than average a mount of risky water-contact. The number of children converting from negative to positive ova execrators is expressed as a percentage of original number of non-infected children.

Incidence (%) = Number of positive at second observations X 100 Number of negative at first observation

The approach of using incidence data based on the apparent rate of re-infection after treatment has been contested on the ground that is difficult to differentiate between an unsuccessful chemotherapy and a re-infection (Jordan & Webbe, 1982). Later on, Chandiwana (1988) concluded that the host factors like the water-contact behaviour and innate or acquired immunity were probably different for different individuals. He suggested that incidence studies should include individuals from both treated and untreated groups as the two groups together are more likely to represent unbiased samples. In the same year, this conclusion was supported by Kvalsvigs and Becker (1988), who studies the water-contact behaviour among children in South Africa.

2.6.5 Variation in prevalence and intensity of Infection: Although fundamentally different measurement, prevalence and intensity are related: prevalence rise with increasing intensity to an upper limit of 100% but intensity has no theoretical upper limit. It is now accepted that rising intensity is accompanied by an increased risk of developing morbidity and disease, pathology of urogenital tract; hepatomegaly and heptosplenomegaly, as reported by Word Health Organization (1998).However, severe pathology can occur in light infections and does not develop in all heavy infections, as stressed by Sturrock,(2001). Both prevalence and intensity of infection usually show variation with age

(Jordan, 1972) the peaks of both prevalence and intensity of infection are usually seen in the second decade of life. After that both the prevalence and intensity of infection usually show a downward trend (Wilkins, 1977; Mott, 1982; Chandiwana et al., 1988).this decline is generally more pronounced in S. haematobium than in S. mansoni. But in S. mansoni the decline in intensity is usually more marked than the decline in prevalence ( Jordan and Webbe, 1982).the pattern of decline in prevalence and intensity of infection in older age groups depends on local transmission conditions and the schistosomes species (Christensen et al., 1987).in areas of low transmission stability the pattern of prevalence and intensity of infection with age are more differ due to extensive human migration, also the older age groups have levels of low infection, this mainly due to their less frequent water contact.

Visitations may affected by sociocultural fabric of the community, so in some communities females are fairly confined and restricted in their activities, females usually show a considerable lower prevalence and intensity of infection compared to males. This has been reported from Uganda (Ongom & Bardy, 1972) South Africa (Schutte et al., 1977), Egypt (King et al., 1982) and in Ghana (Klump & Webbe, 1987). in other communities where the females are more active than males, the intensities of infection in females more than of males ( White et al., 1982) in Sierra Leone, (Dennis et al., 1983) in Liberia. In communities with less pronounced sex differences in patterns of water contact, prevalence and intensity of infection may be similar in both males and females this was shown in Egypt (Farooq et al., 1966), Gambia (Wilkins et al., 1984) and Zimbabwe (Taylor & Makura, 1985). Within an endemic area there is usually considerable variation in the prevalence and intensity of schistosome infection over relatively short distance. In urban communities there may be variation in prevalence between different districts of the same town related to variation in socioeconomic status and the provision of piped water (Lima ecosta et al., 1985).

2.6.6 Stability of egg output: The stability of ova output of S-mansoni described to be stable in many 7 endemic areas for up to two years. Brazil (Barreto, 1978). St.Lucia (cook, 1974) and Venezuela (Scott, 1938). The variation between consecutive S. mansoni Ova examination of the same specimen was considerable (Wood stock 1971; Teesdale & Amin, 1976) even through the distribution of Ova is random (Wood Stock, 1971). Wide variation in S. Japonicum Ova counts from the same specimen was reported (Blas, 1970).

2.6.7 Distribution of infected snails in the field: One of the paradoxes in schistosomiasis is the discrepancy between the often- high infection rates obtained in the laboratory and the low over all rates observed in field populations of highly susceptible snails in endemic areas. The possible reasons for this discrepancy were discussed by Sturrock et al., (1979). They suggested the following reasons: (a) Different biotic and biotic factors affect dispersal of miracidia and their ability to locate snails in the field site. (b) Physical and chemical factors affect miracidial behavior and survival, as well a penetration and development of parasite within the snails. (c) The time large due to penetration period. (d) The frequency of self-cures and differential death rate among infected and uninfected snails. A critical factor is the infection pressure in particular field site. Although the commonly held view of continuous contamination with excreta from infected individuals may some times be valid, most field. 2.6.8 Cercarial productivity: The distribution of cercariae in water bodies affected by the distribution of infected snails in the same habitat large number of cercariae released by infected

26 snails are often diluted, especial in habitats with flowing water. Originally, rather tedious and lengthy annual exposures were the means for field studies of cercariae distribution and behavior (Sturrock 1986). Using various types of cercariometric apparatus, it is possible to filter cercariae directly from water samples. (Rewan 1957 & 1957, Sandt 1973 a & b; Theron 1976; Prentice, 1985; Blumenthal & Jewsbury 1986; Wilkins et al., 1987) these methods are too sophisticated for routine control programs but can be useful research tool (Theron 1986) cercariometry gave results paralleling those from animal exposures in a comparative field trails (Prentice & Ouma 1984), it showed reasonable correlation with snail sampling in defecting active transmission sites. It is clear that neither cercariae nor their intermediate hosts are evenly or randomly distributed in space or time. The aggregated focal distribution of snail habitats and transmission sites are of considerable importance and play a major part in producing the clumped non-random distribution of schistosomiasis commonly found within the definitive host (Theron, 1986). Knowledge of Cercarial rate in individual habitats and the area as a whole, but also in relation to seasonal population changes, pattern and degree of cercarial production; factors which influence cercariae; and of susceptibility of the snail to infection and the affects of such infection upon it, are necessary to understand the transmission dynamics Webbe, (1965). Madsen Per comm. (1994), Gryseels per.comm. (1995)& Mc. Clelland (1972) working in Tanzania, reported that the small pools in which B. (ph) nastus, products and Biomphalaria spp. Occur were likely to contain S. haematobium and S. mansoni Cercariae from mid-morning until late evening, and possible longer. He mentioned that use of such place for bathing and domestic water supplies during this period would involve greater risk of exposure to infection than when used in early morning. However, he stated that in streams, it is likely that most S. mansoni Cercariae would be swept a way by mid-afternoon, and that use of water in early morning and evening would less risk than its use in the mid of the day. Cercarial production is a function of many

27 biotic and a biotic factors (Webbe 1965) of which the most important is the species of schistosome under study. Productivity also depends on the host- parasite compatibility (Niemann & Lewis, 1990). Cercarial production varies widely among the different human schistosomes and is, to some extent, related to the size of intermediate hosts (Niemann & Lewis, 1990). The number of Miracidia, to which a snail is exposed, also determines the eventual cercarial output. Increasing the number of miracidia per snail generally increases Cercarial output. Laboratory studies suggested that light is the main stimulus for shedding, through temperature may play a minor role (Jordan & Webbe 1982). Peak cercarial shedding S. mansoni occur in the morning and is brief that of S. haematobium (Mc Clelland 1965). Field observations at flowing habitats, from which cercariae are carried by current, confirm this pattern, but cercariae at accumulate in habitats without any flow and densities remain high well into the night (Barbosa et al., 1954; Rowan 1965, Maldonado, 1959, Pitchford & Visser 1965 & 1966; Prentice & Ouma 1984).

2.6.8.1 Cercarial dynamics: Although there have been few studding on the dynamics of Cercarial embryos of S. mansoni mono-miracidial infections, shown that these intrinsic reproductive variations were due to renewal of Cercarial generations in the sporocyst to the synchronism of their development (Cheng & Bier, 1972; Theron, 1981). In pluri- miracidial infections, the periodicity of Cercarial production is visibly altered following resynchronization in the development of the sporocyst (Theron 1986). Variations in Cercarial production result from the different demographic strategies that the parasite uses depending on the snail in which it develops and on the environmental conditions. The aim of these strategies is to ensure an optimal but reasonable exploitation of the biotic capacity of the host environment (Theron 1986).

2.6.8.2 Daily rhythmicity of schistosome cercariae: Shedding Pattern of Cercariae: The Cercariae leave the snail following a daily rhythm unique to each schistosome species. These rhythms are generally Circadian (One emergence peak/24hr), or more rarely ultradian (two emission peaks/124hr) maximum shedding of S. mansoni (Pitch ford et al., 1969) and S. haematobium (Nojima & Sato, 1982) Cercariae occurs during the photophase. Only S. margrerbowiei Cercariae (Pitchford & Dutoit, 1976) shows strict ultradian type of emission rhythm, with a peak early in the morning and another one late in the year (Pitchford et al., 1969). The periodicity of S. mansoni Cercariae in Puerto Rico (Rowan 1968) and of S. mansoni and S. mattheei Cercariae in Transvaal (Pitchford & visser, 1972) had been demonstrated. The activity of various schistosome Cercariae under outdoor conditions was described (Pitchford & Visser 1976); but so far, there have been no long-term investigations. The influence of seasonal changes on the incubation periods of S. mansoni and S. haematobium (Pitchford, 1966) is considerable, and it is likely that these and other changes influence the shedding pattern of Cercariae in nature.

2.6.8.3 Effects of infection upon snail: Mc Clelland (1972) found that the number of S. haematobium and S. mansoni Cercariae produced and the duration of infection vary widely, but that the general level of output of individual snail on a single day rarely exceeds 2000 S. haematobium and 1500 S. mansoni Cercariae. Fluctuations between 200 and 500 S.haematobium Cercariae, from one day to next, are common. The pattern of output of S. mansoni Cercariae does not differ greatly from that of S. haematobium, but the total number of Cercariae produced and the daily averages are lower (e.g. one snail examined for 19 days produced 25.863 Cercariae with daily average output of 1.361, while another examined for 19 days

29 shed 397 Cercariae with daily average output of 20 Cercariae) (Pitchford et al., 1969). It was shown that S. haematobium infections in B. (ph) nasutus products were only terminated by the snail’s death. This was also true of experimentally infected B. Sudanica tanganyicensis but in some other experiments snail occasionally became spontaneously cured (Pitchford et al., 1969). A high mortality of snails occurs as a result of infection, but Gordon et al., (1934) considered that the effect was small. Infected snails do not appear to survive for long periods. A relative absence of Cercarial infections was noted in “very old’ snails compared to those three to nine methods old (Niemann & Lewis, 1990) the effect of parasitism on snails density was difficult to assess. High Cercarial infection rates frequency occurs immediately before complete drying of the habitats with a high mortality of snails of all age groups (Madsen per Comm., 1995). The observations by Barbosa (1963) suggested that infected snails are rapidly killed under natural conditions, probably as a result of infection, but he failed to determine the life-span of naturally infected snails since the date in which the snails become infected was not known.

2.6.8.4 Factors influencing shedding patterns: There are many important factors influencing shedding patterns such as photoperiods and thermo periods. In version of photoperiod leads to an immediate inversion of Cercarial rhythm (Glaudel & Etges 1973 a &b) absence of photoperiod at constant temperature induces desynchronization of the rhythm (Valle et al., 1973). Alteration in length of light and dark phase after the rhythm (Naira & Sato 1982). Thermoperiod alone synchronizes emission rhythm in these absence of photoperiod (Valle et al., 1973) but its role seem less important than of light. The modes of action of external synchronizers, and in particular photoperiod, are still unknown. It is not yet certain whether light acts directly on the parasite or on the snail. Some recent crossbreeding experiments between S. mansoni of different chronobiologies points to a direct response of the parasite

(Theron & Combes 1983) they suggested also that sporocyst could play an active part in Cercarial release (Theron & Fournier, 1982). Biotic factors, influencing emission rhythm, in particular those linked to snail-host, are not so well known. No precise correlation was established between the species or genus of the snails and the emission rhythm of Cercariae (Knifeman & Lewis, 1990).

2.6.8.5 Ecological and Genetic aspects of cercarial rhythm: Human schistosomes have a diurnal emission rhythm. Cercarial emission rhythm is closely correlated with periods of activity of the most permissive host. S.rhodaini, which infects wild rodents, has a nocturnal emission. The ultradian rhythm of S. margrerbowiei, emission peaks at dawn and dusk, is perfectly adopted to the antelopes coming to water pools early in the morning and late in the evening (Pitchford & Dutoit 1976) this variability of emission rhythm, documented at the interspecific level, was recently observed at interaspeific level by the discovery of chronobiological polymorphism in population of S. mansoni from single endemic area (Theron 1985). In Brazil, the position of schistosome Cercarial emission peak vary over interval of nine hours from one individual to another, between 10.00 and 19.00, depending on the S. mansoni population considered. Three chrono-biological phenotypes were described. On early shedding pattern (average peak between 11.00 and 12.00 am), an intermediate shedding pattern (average peak between 13.00 and 15.00 p.m.) and a late shedding pattern (average peak between 16.00 and 17.00pm) the phenotypes of the late pattern are particularly frequent in S. mansoni and the reservoir host Rattus rattus shows high levels of infection. Schistosomes with early chrono- biology are mainly found where man is the primary host. In areas where both man and rat support the parasite, the frequency of the intermediate phenotypes is particularly high (Theron, 1984) genetic control of Cercarial rhythm emission was demonstrated for S. mansoni by experimental cross-bedding the early and phenotypes. Where the early and late parents are of the same geographical origin,

the F1 schistosome is characterized by an intermediate emission rhythm. When the parents are from different geographical origin, F1schistosome have a rhythm characterized by two-emission peak (Theron & Combes, 1983).

2.6.9 Human water contact pattern: Transmission of schistosomiasis depends on human behavior related to water- contact activities as well as KAP i.e. information, health beliefs and perceptions learned early in life. Many disease conditions are strongly linked to people’s life styles including occupation and living conditions and are aggregated by ignorance and poverty. The human water-contact behavior plays a central role in the distribution and transmission of schistosomiasis in the poor tropical communities. The elucidation of the pattern of exposure to contaminated waterbodies is essential for a better understanding of the epidemiology of the disease, hence a real and meaningful control (Jordan, & Webbe, 1982, Wilkins, 1987). In fact many researchers handled the aforementioned water-related aspects with especial emphasis on transmission pressure, in Egypt (Farooq & Mallah 1966; Dalton 1976; Kvalsvig & Beache, 1989; Kloss et al., 1990; El Kholy et al., 1990; Chandiwana & Wood-house 1991; Lima-e Costa, 1991; Ahmed 1998 and El Tash, 2000). Human water contact behavior plays a decisive role in the distribution of the disease in population. Combined with parasitological and clinical observation it contributes to better understanding of schistosomal disease in the human population. It is usually classified as domestic, recreational, occupational and personal (WHO, 1990). Although the distribution of contacts varies for each area, but the most common contacts are similar in the average of time e.g. laundry contacts varied from 31 minutes in Egypt, to 59 minutes in St Lucia to 76 minutes in Puerto Rico. Other activities were of short duration per contact. Swimming; 22 minutes in Egypt and

St. Lucia, bathing and playing; 15 and 32 minutes for Puerto Rico compared with 25 minutes for St Lucia and 16 minutes for recreational activities in Ghana. Domestic contacts vary from place to place and from day to day. Farooq and Mallah (1966) stated that the religious practices can be important reasons for water contact as in the ritual washing five times a day before prayers, require for Muslims. Fenwick (1981) showed that in the Sudan, privacy is an important consideration in the selection of the site for defecation and the contact of water is therefore reduced. Patterns of personal and occupational contact obviously differ in different endemic areas, but domestic and recreational contact pattern is normally similar. In general 60% to 70% of all water contacts and 70% to 95% of total duration of water contacts may be categorized as either domestic or recreational (Christensen 1987 & Per Comm., 1995).

2.6.10 Schistosomiasis control: Chemotherapy is playing and will continue to play an important role in the strategy of schistosomiasis control. Population passed chemotherapy has been able to reduce dramatically the prevalence, intensity and severity of the disease in the short time in areas of high endemicity (WHO, 1998). Treatment strategies of the disease have been transformed by the introduction of Praziquantel. The drug is generally effective against all species of parasite in a single dose. Even when complete immediate cure is not obtained, egg counts in urine or faeces are considerably reduced, however, without an integrated control program, re-infection quickly follow and treatment must be sustained (Rollinson & Johnson 1996) Environmental control involves modification of environment of the snail host of the parasite. Making the environment less favorable for snails may provide some degree of control. Only one synthetic molluscicide (Niclosamide) is currently available in the market and is expensive a potentially cost effective alternative is the use of plant extracts that show locally in some

33 endemic area of Africa. The best candidate, so far identified, is endued the Ethiopian local name for phytolacca dodecandra(Mott ,1987) Biological control is based on the introduction of natural enemies of snails predators and competitors or by the introduction of snail’s pathogens or against Laval stages of the parasite. (Ferguson, 1978; McCullough, 1981; WHO 1985; Madsen, 1990). Laval stages of schistosome parasite (miracidia and cercariae) could be controlled by mosquito larvae, Planaria, Oligochaet, Annelida, Daphnia pulex as well as filter feeder snails. Many predators have suggested as biocontrol agents of Biomphalaria and Bulinus snail species (Madsen, 1990; Abdul Magid, 2000; Afifi, 2003) such as fish (Daffalla 1973), water beetles, bugs and dragonfly nymphs. (Afifi, 2003). The biological agents should be found in large quantities to get arid of the snails and so they need certain precaution and care to protect them from others and make the conditions favorable for their survival (Ahmed, 2003). In various part of the world many experience was gained from numerous successful control programmes in reducing transmission and controlling morbidity, Venezuela and Brazil (Costa et al., 1987) Egypt (King et al., 1982, Mobarak 1982) Tunisia (Jordan 1982), Iran (Jordan 1977) the Philippines (Tanaka 1983) China (Lewart, 1984) and Sudan (BNHP, 1985-1990) which is aimed at control of the major water and irrigation associated diseases. Usually as a result of an integrated approach. However, despite much progress, schistosomiasis remains a serious problem in many part of the world (WHO, 1980). In the initial absence of any antischistosomal drugs, early control efforts focused on the elimination of snails. Periodic drying of Egyptian irrigation canals merely duplicated catastrophes which snails were already used to in their natural habitats. Snail numbers dropped briefly but the survivors soon replaced any losses. Transmission was, at best, merely interrupted. Chemical control was hampered because the water to be treated was that used by people for domestic and agricultural purposes. Copper sulphate was the only `safe' chemical readily available. Highly effective in the laboratory, it was far less effective in the field,

34 but remained in use well into the 1950s.

Educating rural populations to prevent human contamination of, and exposure to, potential transmission sites has little chance of success without provision of safe water supplies and acceptable means of excreta disposal. It was rapidly concluded in Egypt that such provisions and their maintenance would be impossibly expensive in rural areas. This remains the situation, today, in countries with endemic schistosomiasis (apart from the very few which have achieved political and economic stability so that everyone can afford to improve their living conditions). Greater progress was possible in stable urban centers where such measures were cost effective and had many other potential benefits. At the end of the First World War, the chance discovery of the antischistosomal properties of Tartar Emetic against all three major schistosomes infecting humans raised hopes of therapeutic interventions using antimonial drugs (McCullough, 1981; Christopherson, 1918).Long courses of painful injections and serious side effects meant that they were really suitable only for treating patients in hospital. When used in the 1920s for outpatients to try to prevent Egyptian labourers introducing S. haematobium during the construction of the new Sudanese irrigation schemes, mortality was estimated at 3 per 1,000 patients treated. Between the two World Wars, community control of schistosomiasis was attempted in various places based mainly on the combined use of the two imperfect weapons available: copper sulphate and antimonial drugs, supplemented in some cases by provision of safe water and sanitation. Occasional successes were claimed in Egypt but follow-up studies showed them to be ephemeral as, for example, at the Dakhla Oasis (Khalil, et al., 1938). Far from decreasing, the number of people exposed to schistosomiasis was, if anything, increasing. Its distribution was spreading as the number of habitats available for the intermediate hosts was extended by water development projects such as dams, irrigation schemes, river navigation improvements and impedance of drainage associated with the growing construction of roads.

2.6.10.1 Planning control programmes:

When snail control for schistosomiasis began in earnest in the 1950s and 1960s the tactic aim was to eradicate the snail and hence , ultimately , the parasites; a process that might take one or more decades, only qualitative egg counting technique , were available and success, if any, as judged primarily by reductions in prevalence (and incidence) of schistosomiasis in human populations, twenty years later, when effective drugs came into use , the prevailing view was that they would succeed ,when molluscicides had failed in eradicating schistosomiasis by attacking the parasites, assessment was still based mostly on qualitative criteria although quantitative egg count were available by them, rapid and dramatic prevalence drops after chemotherapy and quantitative measurements if used confirmed that, drugs had more rapid effects than snail control (Cook et al., 1977). Only gradually was it realized that it would be no easier to eradicate worms than snails, just as the goal of snail control had shifted from eradication to management of snail populations to suppress transmission , so, too, did the goal of chemotherapy change; from eradicating worms to suppressing their numbers to a level where they would no longer be of public hearth significance in the population ( WHO, 1985 ).Reducing the over all community worm burden should reduce the numbers of heavily infected people likely to develop disease. To select the most appropriate control strategy for an area required some frame work (WHO, 1993). One such was based on a combination of age-prevalence and age- intensity curves. Although there are differences in detail between the different human schistosomes, a generalized picture shows that over all prevalence rises to a peak in school children in the second decade of life before dropping to a some what lower level in older age groups ( Ross et al., 2000) plotting prevalence of heavy infection ( >400 epg or > 1000 epg for intestinal schistosomiasis; >50> 200 eggs /10ml for urinary schistosomiasis) gives a similar curve below than of total prevalence in each group the proportion of heavy infection is greatest at, or

36 immediately after, the overall prevalence peak in school children, in older groups, heavy infections are relatively lower than the total prevalence, this figure suggests several control strategies, the simplest approach is mass chemotherapy treating every body in a known , endemic community with a curative dose of praziquantel this was impossible in most endemic areas, if only because of the high cost of praziquantel at the time. Alternatives included targeted chemotherapy treating only infected subjects after examining every one in the community to diagnose those infected; selective targeted chemotherapy, treating only those subjects with heavy infections (also needing diagnosis) and selective, targeted chemotherapy, treating subjects in defined, high risk groups( e.g. school children) with mass treatment ( or targeted or selective, targeted chemotherapy with diagnosis ). Other factors affect the choice of strategy including the overall prevalence and intensity in a community, the nature and accessibility of its members, the proportion of the children who regularly attend school, where transmission occurs and if it is seasonal (and, if so, if it varies in intensity from year to year).

2.6.10 Schistosomiasis biological control:

An alternative method used in the control of snail vectors is the use of predatory organisms or competitors which can control the expansion of the snail population and eventually eliminate the snails from the breeding site. Biological control has been undertaken principally with snails such as Pomacea haustrum (Milward de Andrade 1972) in Brazil and Marisa cornuarietis (Ruiz-Tiben et al., 1969) in Puerto Rico. In the north - east of Brazil a B. straminea strain resistant to S. mansoni has been used to combat B. glabrata (Barbosa et al., 1975). Another snail used as a competitor is Helisoma duryi (Abdallah & Nars, 1973). Fishes used for biological control against vectors and hosts of tropical diseases, and in the field of the mosquito control it has been well known for more than 100 years and the most widely know are Gambusia affinis (the “mosquito fish”), and

Poecilia reticulata (the “guppy”). A great number of other fish species, prey on mosquito larvae. For example, for the countries of the Eastern Mediterranean Region, including Somalia and Sudan, and extending eastward to Pakistan, WHO (1981) lists 34 species. A number of fish species such as Tilapia melanopleura, Astronotus ocellatus, have been used to control snails (Milward de Andrade & Antunes 1969; Motta & Gouvea 1971, Feitosa & Milward de Andrade1986 ) and aquatic birds such as ducks (Michelson 1957), chelonian (Coelho et al., 1975) have also been employed as snail predators. In addition, a number of other types of predators such as mosquito larvae and other diverse insects have also been described as larvae of Lapyridae, Dytiscide and dragon flies (Webbe and Jordan, 1966; Afifi, 2003; Berg, 1964). In the laboratory a small leeche, Helobdella triserialis lineata and ostracods crustacia have been found to be good snail predators (Sohn & Hornicker 1972, Guimar et al., 1983). In the field, however, these animals are found in snail breeding sites in an ecological equilibrium with the snails. Some aquatic plants such as Characeae have been used to combat snails vectors (Renno, 1958). The pathological action of bacteria such as Bacillus pinotti against B. glabrata has also been studied (Texera & Vicente Scorza 1954). In biocontrol agents, more research is required in order to identify the feasibility of introducing organisms of potential value in the field to different geographic area. There is also a need for an evaluation of the possible effects of competitors on schistosome transmission (Madsen, 1992), to getting rid and eradication of snails, the biological agents should be found in large quantities with suitable conditions for their survival (Ahmed, 2003).

2.6.11 Schistosomiasis in Sudan: Schistosomiasis is considered to be one of the major public health problems in the Sudan. The disease is endemic in almost all region of the country, and in recent year has increased in distribution and prevalence as a result of progressive expansion in water resource development and of increased population movement

(Blue Nile health project Annual Report 1981). Political and economic contact with Egypt and thus the thousand of pilgrims from West Africa Passing through the country to and from Mecca introduced and spread the transmission of schistosomiasis in Sudan Archibald (1933). Belford (1904) found 17% of the children in Khartoum primary school suffering from urinary schistosomiasis. A new area in the history schistosomiasis in Sudan began in 1925 with opening of Gezira scheme in Gezira State where schistosomiasis was particularly unknown except for a few sporadic cases in vicinity of the Blue Nile. The Egyptian labourers with schistosomiasis should either be treated before being allowed to enter the Sudan or else is send back to Egypt. Spence (1924). In 1925 a decision to prohibit entry of infected Egyptian labourers was made. Management were then made either to project or treat, at Wadi Halfa quarantine station, all infected labourer going to Sudan similarly, all persons coming from the west of White Nile were examined for S. haematbium at Kosti or Dueim and those found positive were detained to treatment. Between the year 1928 and 1933 protective quarantine station at Wadi Halfa, Kosti and Dueim carried out useful survey work and registered an average S. haematobium infection rate of 17.5%. Annual surveys during years 1926 –1927 suggested that the infection rate with S. haematobium was generally less than 1%. S. mansoni was not detected in stools but may have been looked. A survey conducted by Stephenson (1947) between 1942/1945 revealed some alarming figures. The average of S .haematobium infection was found to be 21% in adults and 45% in children. Greany (1952) found that Bulinus and Biomphalaria snails equally common in all canals in density closely related to weed growth. S. mansoni infection rate in Biomphalaria was twenty times that of S.haematobium in Bulinus (2.1% compared to 0.06%). He examined 80.000 inhabitants (about 2.5% of the Gezira population at that time) and he reported that S. haematobium and S. mansoni were equally prevalent in 10-15 years old children. El Nagar (1958) reported the success of a large control could begin in Gezira irrigated scheme that covered all canals in the

39 scheme that time. The methods adopted were: snail’s habitat destruction by removal of weed from the canals, destruction of snail by copper sulphate, prevention of snail re-invasion by mean of mechanical traps and chemical barriers and treatment of infected persons using antimony based drugs. The results indicated that the campaign was successful and implemented in other irrigated schemes, however, that campaign was the only trail carried out an a large scale to control the disease in Gezira irrigated scheme for every long period. In (1971) a Bilharzia project was established in Gezira scheme with the long-term objective to control the disease. Amin (1972) found that the infection rate of S. haematobium was less than 1% in villages of northern Gezira. He found the infection rate of S. mansoni in the same area to be 25% by direct faecal smears and the following year by the stool digestion technique he found a prevalence of 60%. In 1974 a routine snail control regimen was introduced which consisted of five aerial sprays with the molluscicide N-trityl morpholine over the main, major and minor canals in the most northerly 80.000 feddan (1 feddan = 1.04 acres) of the Gezira Scheme (Amin & Fenwick 1975 & 1977). The regimen was continued for three years and its effects were regularly monitored by. (a) Surveillance and sampling of snails. (b)Parasitological examination in pre-school children and school children. The results suggested that the objective of keeping the minor canal virtually snail free had been achieved. But the incidence data gave equivocal results since in some villages, there was evidence that transmission was as high as in near by untreated area (Amin et al., 1982). The Blue Nile Health project (BNHP) was established in 1979. The 10 year project was aimed at control of major water and irrigation associated diseases in agricultural communities along the Blue Nile River in Sudan. Twenty-eight villages were randomly selected from different agricultural groups of Gezira schemes for monitoring. The first epidemiological survey showed that schistosomiasis prevalence was 51% with arrange from 30% to 70%. The exceptions were villages on the edges of the scheme situated close to the main

Khartoum/ wad Medani road which had a low prevalence (< 15%) (BNHP 1981). Omer and Amin 1972 found prevalence ranging from 15 to 17% in school children in Kober Khartoum north. In Kennana sugar scheme in White Nile a prevalence of 12% was reported after a few years of operation (Amin 1978). Elhussien 1989 found in Umm Hani village, south of Kosti, the prevalence of urinary schistosomiasis was to be 53% among school children and some adults. Schistosoma haematobium were demonstrated in EL Duem and Kosti province (2.6 and 2.8% prevalence respectively) Ahmed 1994. In Kordofan west Sudan Eltom (1976) found prevalence of 12% among school children. Deadfall and Suleiman 1988 reported that among school children 8.5% in Kadugli, 29.5% in Eldallang, 35.8% in Rahad and 32.7% in Um Ruwaba. In the Road Elias (1992) found 30.3% of S. haematobium among 5 villages while Abdalatif (1994) reported 25.8% prevalence of S. haematobium in Elobied. In east of Sudan there are a few foci of transmission in Chasm Algebra (Omer 1987). Schistosomiasis has been demonstrated to be endemic in New Halfa (Abdaljalil 1980). Daffalla (1984) found prevalence over 40%. In Elsayal agriculture. Scheme River Nile Musa reported S. haematobium prevalence to be 11.5%. In Gunaid sugar cane scheme (Ahmed 1998 & El Tash 2000) reported the prevalence of S-mansoni was more than 72% among the community of the agricultural labourer, while S. haematobium was less than 1%. In the Sudan the disease become endemic in all irrigation agricultural schemes especially the sugar cane schemes such as El Rehab, Kennana, Asalaya, ElGunaid Sennar and New Halfa (El Tash, 2000; Ahmed et al., 2002, Ahmed, 2005). The recent situation of schistosomiasis in the Sudan was shown in the table. As conducted within the collaborative links of schistosomiasis research laboratory (University of Khartoum) with the national schistosomiasis control program (Federal Ministry of Health)

2.6.12 Intermediate host in Sudan: The distributions of snail intermediate host of schistosomiasis were studied

41 through snail survey or epidemiological studies in different parts of the country during different periods. Archibald (1933) described the distribution of Bulinus for skolu as occurring in the Blue Nile and Spring of Nuba Mountains in south Kordofan State. As for the occurrence of B. Alexandria and B. pfeifferi in the Blue Nile B. biossyi, B. pfeifferi in the White Nile. In Barber region in North province, Buchanan (1937) described the occurrence of Biomphalaria. Stephenson (1947) reported both Bulinus and Biomphalaria in Gezira State. Greany (1952) also described B. truncatus, B. looses, B. forskalii, B. africanus, B. Alexandria in different canals in Gezira scheme. Malek (1958) found B.(P) uganae exists in the southern states, white Nile state and the west of Sudan. He found that B. pfeifferi are existing in all the states of Sudan except the Red Sea State., B. Sudanica was reported in southern state and also near Kosti and Jebel Aulia (Malek 1958, William & Hunter 1968 Saeed (1992) stated that Bul. truncatus Bul.ugangae, Bul. forSkulii, Bul. Sudanica an Bio. Alexandrina in the White Nile area. Manjing, B.K (1978) reported B. pfeifferi in all Gezira canals. The irrigation system in Gezira- Managil scheme provides favorable conditions for the breading of the snail intermediate host and hence the schistosome transmission (Madsen et al 1988) Hilali 1992 described B. Pfeiffer in Managil agricultural scheme and also found B. pfeifferi Bull. Forskolii in Khartoum state (Hilali 1996). Ahmed (1998) reported B. pfeifferi, Bull. Truncatus in Gunied sugar cane scheme canals.

Table (1) Recent situation of schistosomiasis in the Sudan (2000-2005)

Intensity Agricultural Scheme Type of infection Date of Prevalence GMEC(G (or state) survey (%) m or 10 ml) Gezira & Managil intestinal 2000 56 81.2 Gezira & Managil intestinal 2001 53 37.8 Gezira & Managil intestinal 2005 84 83.8 Gezira (Camps) intestinal 2001 74.2 171.9 Gezira (Camps) Intestinal 2004 55.7 125.7 White Nile (Villages) Urinary 2002 48.9 123.3 Blue Nile (Villages) Urinary 2001 50.4 83.9 Kordofan (North) Urinary 2002 51 * * Kordofan (Nuba Mountains) Urinary 2000 48 112. 3 Kordofan (Nuba Mountains) Urinary 2000 42 112.3 Kordofan(Nuba Mountains) Urinary 2003 43 123.4 Darfur (Jebel Mara) Intestinal 2004 23.3 85.5 Sennar (Villages) Urinary 2002 45.2 112.7 Rahad (North) Intestinal 2002 76 * * Gadarif (Camps) Intestinal 2001 93 * * New Halfa (Villages) Intestinal 2002 32 * * New Halfa (Villages) Intestinal 2004 24.3 85.7 New Halfa (Camps) Intestinal 2002 57.5 75.2 New Halfa (Camps) Intestinal 2004 50.5 213.2 Gunaid (Villages) Intestinal 2000 56.4 155.6 Gunaid (Camps) Intestinal 2000 77.2 167.2 Khartoum (Kiryab) Urinary 2000 46.3 77.9 Khartoum (Kiryab) Urinary 2002 48.3 51.1 Khartoum (Kiryab) Urinary 2005 46.5 66.8 Khartoum (Kuku) Urinary 2002 50.4 337.3 Khartoum (Faki Hashim) Urinary 2000 41.6 76.3 River Nile (Villages) Urinary 2002 51.2 571.2 River Nile (Villages) Urinary 2003 5.1 46.1 Unity State (South-Rubcona) Urinary 2002 39.7 * * * * Intensity of infection NOT monitored in the survey

CHAPTER THREE MATERIALS AND METHODS

3.1 STUDY AREA: 3.1.1 Ownership of the Agricultural Land: In 1963, the Sudanese government habilitated the old Halfa population, in a new ﻩ 20 - ﻩ area layed in El Buttana Valley between 15º - 33º longitudes East and 13 latitudes South, about 400 Kilometers Southeastern Khartoum State, and 67 Kms North Khasm El Gibra Dam. Because of the initiation of the Aswan High Dam, the people of old Halfa lost their lands and villages which were drawn by filling of the dam. Twenty-six constructed villages were especially built for the habilitation of the displaced "Halfaween" ethnic group. Later on, at least one camp associated each of the aforementioned villages, where the camps were populated by different ethnicities. To be fair with the dislocated villagers, the Sudanese government committed to compensate them the equivalent area at the newly proposed site instead of their original land in the North. Each displaced family allowed to own an agricultural land, 5 - 20 feddans (I feddans = 1.04 acre), at New Halfa. In addition, another 5 - 15 feddans were distributed to each family for cultivation via the agricultural rotational system (cotton, wheat and Sudanese bean).

3.1.2 Climate: New Halfa is situated in the arid and semi-arid climatic conditions, where the rainfall quantitatively varying from the special and temporal point of view, 250 - 500 mm. The rainfall in the area commences with the blowing of most southwesterly winds, which spread over the whole area then decrease from South to North. The rainy season extend from mid June to September with an average annual

44 rainfall of 410 mm. July and August are the wettest months receiving about two thirds of annual rainfall; August with an average rainfall of 14 mm is the peak of rainfalls season .

In fact, the aridity of the study area is aggravated by precipitation quantities due to average high maximum temperature, relatively low humidity and often storms (Sudan Town Planning Development, STPD, 1979). The climate of the study area could be categorized into three clear seasons: the rainy season (June to October), cold winter (November - February) and hot summer (March - May). In New Halfa, the temperature is high during the summer period, moderate during the rainy season and low during wintertime. January is the coldest month in the year, where the mean temperature of 25º C, with the minimum temperature of 16º C. On the other side, May is the hottest month of the year with a mean temperature of 33 Cº while the mean daily maximum temperature of 42º C.

Taking the wind into consideration, two clear-cut seasons are characterized by their respective prevailing air streams, the dry dust Northeastern wind in winter and the moist Southwestern wind in summer (Mohamed et al., 1994).

The type of soil in the area is heavy clay and deep cracked soil, where the clay rate ranges between 40 - 65%. The natural vegetation cover is characterized by thorny trees, which are resistant to drought conditions and seasonal weeds that usually disappear after the end of the rainy season. In addition there are groups of perennial shrubs as reported by Mohamed (1994). 3.1.3 New Halfa Agricultural Scheme (NHAS): The scheme is considered to be the second largest agricultural scheme in the Sudan after the Gezira irrigation scheme. The total area of the NHAS is estimated to be around 345,000 feddans, cultivated by rotational system.

The NHAS is supplied by gravity irrigation from Khasm El Gibra Dam through two main canals and thirteen subsidiary minor canals. The scheme was initiated in 1964, just one year after the displacement of the "Halfaween" group.

The New Halfa sugar cane scheme covers an area of about 40,000 feddans, cultivated by sprouts of sugarcane and harvested at age of 10-16 months. The scheme is a complex unit including agricultural farms and industrial components of sugar processing. The maximum operational capacity of the sugar factory is 4,000 tons per day; 60,000 tons per year.

The factory largely contributes to the development of environment health and preventive health in the whole scheme. Furthermore, the scheme provides clean drinking water and offers necessary facilities like electricity supply and transport. In addition, it participates in improving the living standards through encouraging and supporting the cooperative societies. The basic educational services in the scheme include two secondary school (one for boys and the other for girls), eight Primary schools, a class of industrial apprentice ship, a number of Quranic schools and kinder gratins.

The inhabitants of the scheme's villages are belonging to a broad spectrum of different ethnic groups, where the Nubians from North Sudan represent the bulk of the population. The remaining inhabitants belong to ethnicities from West Sudan; Kordofan and Darfur Sates, including Baggara, Nuba, Zaghawa, Tama and Fur. Ethnicities from East Sudan include Hadandawa, Bani Amir, Shukryia and Rashayida, while the south-rooted groups are very few. Most of the non- Nubians inhabitants work as farmers or agricultural labourers in the scheme.

3.2 METHDOLOGY AND ORGANIZATION OF THE STUDY: 3.2.1 Preparatory Phase:

3.2.1.1 Ethical Considerations: The basic information was collected from different sources including the Local Councils, New Halfa Administration, schools headmasters as well as health committees. An ethical clearance was obtained from the Federal Ministry of Health and furtherly confirmed by Kassala State Ministry of Health. Many meetings were arranged with the Sheikhs, social leaders and village committees. In these meetings the overall and specific objectives of the study were clearly explained and their consent and cooperation were requested in all segments of the investigation. All candidates who improved microscopically to be infected were treated under medical supervision.

3.2.1.2 Villages Selection and Geographical Recognition: Out of twenty six residential sites in the scheme, four were randomly selected for the study, two villages and two permanent camps. Detailed maps of each of the selected study villages and camps were prepared. In such maps, the houses were plotted and numbered, while bridges, roads, schools, water-supply systems and waterbodies were indicated. In addition, comprehensive demographic data were obtained including the names, age-group, gender, occupational category, education level ethnicity, source of drinking water, method of excreta disposal, access of electricity, number of rooms and type of building as a questionnaire from householders. The information collected was coded from computer data entry and statistical analyses.

.Mountain

.Halfa city

.Atbra River

.Agricultural land

.Rail way

.National road

.Canals

.Boarders .Villages

.Study areas .Forests

Map (1): The general Landscape of New Halfa scheme

Village {12}

Water

container

Plotted

houses

Mosque

Dispensary

School

Road

Canal

Agricultura

Village {16} l land

Map (2): Main Geographical Features of the study area, Village (12) & Village (16) in New Halfa scheme

3.2.1.3 Sample Size Determination and Randomization: For determination of the reasonable sample size without overburdening the surveys, the local experience for the primary estimates was utilized. Based on the fact that no control operation was conducted for schistosomiasis in the scheme, 50% of the inhabitants were expected to be infected. In conformity of the above, and via exploiting the epi-info programme (epidemiological information package) the needed sample size was decided. The sample size for the conduction of a sounding epidemiological survey was at least 120 individuals i.e. around 40 households in each village. In fact, for considering the dropout more samples were included in the survey, 25% of the villagers, every 4th household was selected. In each of the selected two villages, all school children of the mixed school were included in the study.

3.2.2 Intervention Phase: 3.2.2.1 Parasitological Surveys: The parasitological surveys were conducted at 12-months apart to determine the prevalence and intensity of schistosomiasis among the randomly selected villagers and campers. School children in the Basic Schools of the villages and camps were included in the two parasitological surveys. Teacher prepared lists of all pupils and gave each a serial number.

3.2.2.1.1 Collection of Urine and Stool Samples: Containers with lids and universal bottles with screw tops for stool and urine sample with the serial number and the first name of each candidate in the selected households were distributed. Concerning the villagers, the faecal and urine samples were collected in early morning in the second day. Regarding the school children, the sample containers and bottles were distributed in the same way, but collected one-hour after their distribution. A field laboratory was established at the football club in each of the four surveyed residential site, where the Clubs'

Councils show high cooperation throughout the surveys. At the end of the microscopic diagnosis, those who did not give excreta samples were revisited the next day to persuade them for samples collection. All microscopically ensured infected samples were given Praziquantel, single dose 40 mg/Kg. BW, under medical supervision. 3.2.2.1.2 Utilized Diagnostic Techniques: 3.2.2.1.2.1 Urine Samples Examination: Urine samples were examined by utilizing the simple centrifugation/sedimentation method to determine the presence or the absence of S. haematobium ova. In the aforementioned, 10 milliliters of the collected urine was placed into each of three centrifuge tubes. The prepared tubes were left for 30 minutes to allow the precipitation of the urine deposit, if any. Then after, the supernatant was discarded and the deposit of each tube was placed onto a clean slide, which was covered with a cover-slip and examined under a binocular microscope. The visualized ova were systematically counted and the average of the three prepared slides was manipulated. Thus, the results were recorded as the number of eggs per 10 milliliters of urine, which designated as the intensity of infection.

3.2.2.1.2.2 Faecal Samples Examination: Stool samples were examined by exploiting the modified Kato technique (Teesdale & Amin, 1976). In such technique, only one gram of the collected faecal sample was taken and pressed through the standardized sieve with small meshes. The sieved stool sample was calibrated via small disposal syringe, which estimated to hold only 25 milligram of the sieved faecal sample. The sieved calibrated faeces then pressed out onto a clean glass-slide, and the process was repeated three times, hence, 3 slides from each sieved stool sample were prepared. Each prepared slide was then covered with another clear slide to form a "sandwich" and a gentle pressure was applied with a finger until the faecal matter

51 spread to cover an area of 20-25 mm in diameter. The prepared slides were then immediately examined under a binocular microscope.

An average of the egg-counts on the slides was taken and multiplied by 40 for manipulation of the egg-counts per a gram of faeces. The obtained results were expressed as egg per gram of faeces, epg.

Plate (1): Laboratory Examination of Faecal samples

3.2.2.2 Adopted tools for reduction of Schistosomiasis: 3.2.2.2.1 Chemotherapy Approach: All candidates who ensured microscopically to have the infection were treated by the subscribed dose of Praziquantel i.e. a single dose 40 mg/Kg. body weight, under medical supervision.

3.2.2.2.2 Health Education and Community Participation Approach: The outcomes of the KAP survey in this investigation were highly utilized in the entry point and formatting of the adopted and conducted health education programme. The main components of the programme were based on intensive talks to the inhabitants of each of the surveyed residential sites. The talks were substantially supported by utilizing audiovisual media and coloured posters. The designed message concentrated on the transmission mode of the disease, symptoms, complications, and preventive measures and control tools. The talks highlighted the role of the community participation along the way of combating the notorious disease. Such talks were conducted at the sport clubs, schools and the mosques, based on the taste of choice of the inhabitants. Considering the KAP of the surveyed communities, the talks were repeated in each residential site; on gender basis i.e. males were separated from the females.

Plate (2): Health Education Lecture in a Basic- school in New Halfa

3.2.2.2.3 Latrines for Excreta Disposal: The two surveyed villages are enjoying the presence of siphon latrines for excreta disposable, but not the two camps. Thus, digging and usage of the VIP (ventilated improved pits) were highly encouraged in the two camps. The health committee actively influenced to achieve the proposed system of excreta disposal. In fact, many latrines were built and used on "relative" basis, hence urinating and defecating frequencies were declined around waterbodies.

3.2.3 Second Survey: The second parasitological survey was conducted 12-monthes spaced with the first one. It is very important to state that the adopted approaches in the first survey were just replicated in the second one. Guided by "no survey without services" considerable number of the non-selected candidates were examined and treated but not included in the survey findings.

3.2.4 Water-contacts Observations: The waterbodies around El Gamhouria camp and Village 16 were selected for the monitory of the population's water-contact activities. The monitory commenced around sunrise (7:00 AM, Sudan Standard Time) to around sunset (7:00 PM). The water-contact observations were conducted once a week for three months, July- October. The main technique of observation was based on the naked eyes while parking at a suitable place near some water-contact sites. The essential collected information was the approximate age-class, gender and the duration, type and level of exposure. For convenience, the types of activities were recorded in numerical from to represent the type of contact as follows: 1= bathing, 2= swimming, 3= paddling, 4= fishing, 5= washing stocks, 6= crossing canal, 7= collecting & drinking water, 8= washing extremities, 9=washing clothes and utensils.

These activities were further categorized as: (i) Important water contact activities were a considerable bodily exposure for a relatively long duration was observed e.g. bathing, swimming, paddling, fishing and washing stocks in canals water. (ii) Relatively unimportant water contact activities which involved limited duration and minimal exposure e.g. crossing the canals, water drinking and collection, washing extremities and washing clothes, utensils.

3.2.5 Laboratory Experimental Designs: 3.2.5.1 Snails Collection: Using a standardized scoop that made of metal frame 30 cm x 30 cm on which lined by gauze of one millimeter mesh. The frame was soldered to along metal bar to act as a handle (Plate). Only Biomphalaria pfeifferi snails were collected from the waterbodies around the selected villages and camps, and then lined by vegetation cover in small plastic bowls. The snail’s containers were transported to University of Kassala, Zoology Laboratory, for maintenance and breeding of the snails.

3.2.5.2 Breeding and Screening of Snails: The collected Biomphalaria pfeifferi snails were washed several times with clean water to remove the attached dirt and mud. Two days post-collection, the snails were screened for their infection with any trematoda. In the screen technique, a group of few snails (10 - 20) were immersed in half filled small beakers, 100 ml. The prepared beakers were put under artificial illumination from 7:00 AM for two to three hours. After the exposure period, the water in each of the beakers was examined with a hand lens for any trematoda cercariae, where all infected snails were isolated in different aquaria.

Only un-infected Biomphalaria pfeifferi snails were put in biologically balanced aquaria, containing 10 liters of artificially hard water (0.104 gm of Ca Cl2 and 26 gm of Mg SO4. H2O) per liter of a 48-hours stored tape water. The prepared aquaria were maintained at room temperature (25º-35º C) and kept under fluorescent light for 12-hours daily. The snails were feet daily on boiled dried lettuce or chard, local names (Khass or Thalig). Water was added to the aquaria, daily to replace the loss by evaporation. Water in the aquaria was changed once a week, egg-masses of the snail were collected on polythene sheets and transferred to new aquaria for hatching. Thus, only the first generation of Biom. Pfeifferi was utilized in all sets of the laboratory experimental designs.

Plate (3): Snail scooping from the canalization system

3.2.5.3 Miracidial Harvest and Snails Infection: Stool samples were collected from patients with high egg-counts from New Halfa villages and camps. The faecal samples were combined and macerated with few drops of water until they became mushy. The material was then introduced into several urine flasks. Then cold water (10 º - 15º C) was added to the material in the urine flasks, which was left to settle. The supernatant was changed several times, with cold water, until it was clear, the sediments containing the ova was then stored in the refrigerator for maximum of 5 days for use as required. For infection of snails, the stored sediment was transferred by Pasteur pipette to Petri dishes, which were placed under fluorescent light for 4 hours to stimulate hatching of the miracidia (Plates). Fifty snails of 6-weeks old Biom. Pfeifferi were placed individually into the haemagglutination plate chambers containing 1-2 ml of freshwater. The emerged miracidia were picked up from the Petri dishes under a dissecting microscope, using a Pasteur pipette, to infect the snails. Each snail was exposed individually to four S. mansoni miracidia, as described by Ahmed (1998), the plates were then covered with a polythene sheet and left under artificial illumination at room temperature (30º - 35º C) overnight to ensure miracidial penetration. After the exposure period, the snails were transferred and kept in small plastic aquaria for 4-5 weeks until cercarial shedding was commenced

Plate (5): Laboratory Infection of bred snails

3.2.5.4 Cercariae Preparation and Enumeration: Groups of 10-20 laboratory infected Biom. Pfeifferi were placed in a small beaker and washed to remove faecal and food remains. About 25 ml of warm water was added to the snails and placed under artificial light from 10:00 AM to 1:00 PM, for enhancing the cercarial shedding. After the nominated interval, the snails were removed and returned to their aquaria. Five samples, 50 microlitres each, of the cercarial suspension in the beaker, were taken by a Finn pipette into small Petri-dishes. Drops of lugol’s iodine were added to kill and stain the cercariae, which were counted under a dissecting microscope.

The average of the observed cercariae in the 5 samples was calculated. Then the total number of cercariae in the whole suspension was calculated as follows: Cercariae in 50 micrometers X 20 X Volume of suspension in milliliters

3.2.5.6 Data Handling and Statistical Analysis: Data analysis was carried out by using microcomputer and the STATISTIX and Epi-info statistical packages. Chi-squared test was utilized to determine the level of significance in the differences of infection in the prevalence rates. The student t-test used for detection of any significant differences in the intensity of infection. One-way ANOVA was adopted for other independent of more than two levels, and to calculate the mean of snails' density.

CHAPTER FOUR SCHISTOSOMIASIS INFECTION PARAMETERS

The response rate of the selected samples was 100%, where 562 individuals were cooperated by providing the requested faecal and urine samples. During the first survey, not a single urine sample was found to be infected with S. haematobium ova. Thus in the second survey no trial for urine examination and all tabulated results presented here refers only to intestinal schistosomiasis only.

4.1 Villagers Epidemiological Surveys: • 4.1.1 Infection Parameter by Residential Sites: Table (2), Figure (1 & 2) verifies the overall prevalence and intensity of S. mansoni in four residential sites at New Half Scheme. In the first survey, the overall prevalence and geometric mean egg-count of S. mansoni were 41.8% and 79.4 epg, respectively. The prevalence rates among the residents of Gamhoria and Masna camps were very high and almost equi-distributed, 59.2% and 55.8%, respectively. Likewise, the infection rates of the villagers from Village (12) and (16) were moderate and also equi-distributed, 29.8% and 30%, respectively. The statistical analysis suggested that the variations in the infection rates of the four residential sites were of significant level, (P < 0.05).

Considering the worm burden, expressed in eggs excreted, the surveyed residential sites could be arranged in the following descending manner: El Masna (100.0), El Gamhoria (79.4) Village 16 (50.1), and Village 12 (50.1) epg. The deep analysis via Scheffe test suggested that the significant variations in intensity of infection were attributed to El Masna camp, (P < 0.05).

In the second survey, the overall infection rate and intensity were 35.5% and 50.1epg, respectively. Taking the prevalence in mind, still the two camps significantly outnumbered those of the two villages, (P < 0.05). Almost the same ascending pattern indicated above, was observed in the findings of the second survey, but the figures were insignificantly skewed to the lowest grates.

Table (2): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2002-2004)

Number Intensity of eggs (Per One Gram) Residential Site Examined Prevalence Log of egg load GEM±C Frequency (%) (%) (X ± SD) (X ± SD) First Survey (2002):

• Village (12) 161 (28.5) 29.8 1.7± 0.2 50.1 ± 1.6

• Village (16) 156 (27.7) 30.0 1.7 ± 0.2 50.1 ± 1.6

• Gamhoria Camp 125 (22.5) 59.2 1.9 ± 0.2 79.4 ± 1.6

• Masna Camp 120(21.3) 55.8 2.0 ± 0.3 100.0 ± 2.0 Total 562(100.0) 41.8 1.9 ± 0.3 79.4 ± 2.0 Statistical significance P < 0.05 P < 0.001

Second Survey (2004):

• Village (12) 161 (28.5) 15.3 1.6 ± 0.1 39.8 ± 1.2

• Village (16) 156 (27.7) 33 1.6 ± 0.3 39.8 ± 2.0

• Gamhoria Camp 125 (22.5) 52 1.7 ± 0.1 50.1± 1.2

• Masna Camp 120 (21.3) 48.3 1.8 ± 0.1 63.1 ± 1.2 Total 562 (100.0) 35.5 1.7 ± 0.2 50.1 ± 1.6 Statistical significance P < 0.05 P < 0.05

Prevalence (%) 100 Intensity (GMEC/gm) 90 80 70 60 50 40 30 20 10

Prevalence(%) &Prevalence(%) Intensity (GMEC/gm) 0 Village 12 Village 16 Gamhoria camp Masna camp Surveyed villages & Camps (2002)

Figure (1): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2002)

Prevalence (%) 70 Intensity (GMEC/gm)

Prevalence (%)Prevalence & Intesity (GMEC/gm) 10

0 Village 12 Village 16 Gamhoria Masna camp camp Survayed Villages & Camps (2004)

Figure (2): Overall Prevalence and intensity of S. mansoni in four residential sites, New Half Scheme, (2004)

4.1.2 Infection Parameter by Gender:

Table (3), Figure (3) shows the overall prevalence and intensity of S. mansoni in the four investigated residential sites, in the two surveys by Gender. Concerning the prevalence and intensity of S. mansoni infection in the first survey, the males significantly outnumbered the females, 45.6%, 100.0 epg and 30.4%, 50.1epg respectively, (P < 0.05). In conjunction with the above, the finding of the overall infection rate and intensity in the second survey ensured a significant proportionate of the infection among the males compared to the females, 43.7%, 79.4epg, and 27.0%, 39.8epg respectively, (P < 0.05).

Table (3): Overall Prevalence and intensity of S. mansoni Infection among the surveyed samples from New Half Scheme, by Gender (2002-2004)

Number Intensity of eggs (Per One Gram) Gender Examined Prevalence Log of egg load GEMC Frequency (%) (%) (X ± SD) (X ± SD) First Survey (2002):

• Males 322 (57.2) 45.6 2.0 ± 0.5 100.0 ± 3.2 • Females 240 (42.8) 30.4 1.7 ± 0.2 50.1 ± 1.6 Total 562 (100.0) 41.8 1.9 ± 0.3 79.4 ± 2.0 Statistical significance P < 0.05 P < 0.001

Second Survey (2004): • Males 322 (57.2) 43.7 1.9 ± 0.2 79.4 ± 1.6 • Females 240 (42.7) 27.0 1.6 ± 0.2 39.8 ± 1.6 Total 562 (100.0) 35.5 1.7 ± 0.2 50.1 ± 1.6 Statistical significance P < 0.05 P < 0.05

Prevalence(%)

100 Intensity (GMEC/gm)

20 Prevalences (%)Prevalences & Intensity (GMEC/gm)

0 Males Females By Gender (2002)

Prevalence(%) 80 Intensity (GMEC/gm)

Prevalence (%) & Intesity (GMEC/gm) & (%) Prevalence 0 Males Females By Gender (2004)

Figure (3): Overall Prevalence and intensity of S. mansoni Infection among the surveyed samples from New Half Scheme, by Gender (2002-2004)

4.1.3 Prevalence and Intensity by Age-groups:

Table (4), Figure (4) illustrates the overall prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by age-groups. The prevalence rates gradually increased to peak (57.4%) at the age-group (15- 19) years, then also gradually declined and remained almost high throughout the age-classes of the young adults, (25 – 44) years. Again the infection pattern was further declined throughout the rest of the age-groups. The statistical analysis of the infection rates suggested a significant variation among the categorized age- classes, of the villagers (P < 0.05). Almost the same trends were observed concerning the worm burden, expressed in the secreted eggs, with only one crucial observation, three peaks. The first peak was observed in the age-class (10 - 19 years), the second one was among the age-group (30 - 39 years), while the third was monitored among the age-class (55 - 59 years). Like above, the statistical differences of the eggs excreted was judged to be of significant value, (P < 0.05).

Table (4): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by age-groups

Number Intensity of eggs Age-groups Examined Prevalence (Per One Gram) Frequency (%) (Years) % Log of egg load GEMC (X ± SD) (X ± SD) • 05 – 09 57(10) 42.1 1.4 ± 0.2 25.1 ± 1.5

• 10 – 14 99(17.6) 55.5 2.0 ± 0.3 125.1 ± 1.9 • 15 – 19 47(8.9) 57.4 2.2 ± 0.2 158.4 ± 1.5 • 20 – 24 37(6) 48.9 1.7 ± 0.6 50.1 ± 4.0 • 25 – 29 50(8) 34.0 1.3 ± 0.1 20.0 ± 1.2 • 30 – 34 31(5.5) 41.9 1.9 ± 0.5 79.4 ± 3.1 • 35 – 39 37(6) 37.9 2.0 ± 0.2 100.0 ± 1.5 • 40 – 44 40(7) 40.0 1.6 ± 0.4 39.8 ± 2.1 • 45 – 49 42(7.5) 28.5 1.8 ± 0.5 63.1 ± 3.1 • 50 – 54 38(6.7) 23.6 1.4 ± 0.2 25.1 ± 1.5 • 55 – 59 19(3) 21.0 2.1 ± 0.2 125.8 ± 1.5 • ≥ 60 59(10.5) 30.5 1.2 ± 0.2 15.8 ± 2.2 • Total 562(100) 41.8 1.9 ± 0.3 79.4 ± 2.0 Statistical significance P < 0.05 P < 0.05

Prevalence(%) 160 Intensity(GMEC/gm) 140 120 100 80 60 40 20 0 s s s s s s s s s ars r r r r r r r r r e ea ea ea ea ea ea yea ears .9y 4y 9y 4y 9y 4y 9y 4 0y

Prevalence (%) & Intensity (GMEC/gm) & Intensity (%) Prevalence 1 1 2 - - - - 2 - 3 - 3 - 44yea - 49yea - 5 6 - 0 0 5 ≤ .5 1 1 0 5 0 5 0 5 0 0 2 2 3 3 4 4 5 55 - 59years BY Age-groups

Figure (4): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by age-groups

4.1.4 Prevalence and Intensity by Ethnicity: Table (5), figure (5) presents the overall prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Ethnicity. The finding indicated that the western-rooted villager has the lion-share of the prevalence and intensity of the infection, 62.9% and 100.0 egg per gram, respectively, (P < 0.001). The infection parameters among the other surveyed ethnicities, northern and eastern, were almost equi-distributed.

Table (5): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Ethnicity

Number Prevalence % Intensity of eggs (Per One Gram) Ethnicity Examined Log of egg load GEMC Frequency (%) (X ± SD) (X ± SD) • Northerns 286 (50.8) 30.0 1.3 ± 0.3 20.3 ± 2.0 • Easterns 127(22.7) 30.2 1.4 ± 0.3 25.1 ± 2.0 • Westerns 149 (26.5) 62.9 2.0 ± 0.3 100.0 ± 2.0 • Total 562 41.8 1.9 ± 0.3 79.4 ± 2.0 Statistical significance P < 0.001 P < 0.001

Prevalence(%) 100 Intensity(GMEC/gm) 90 80 70 60 50 40 30 20 10

Prevalence (%) Intensity & (GMEC/gm) 0 Northern Eastern Westen By Ethnic- groups

Figure (5): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Ethnicity

4.1.5 Prevalence and Intensity by Occupation: Table (6), Figure (6) verifies the o0verall prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by occupation. The high infected occupants could be arranged in the following descending order: farmers (65%), labourers (53.8%), students (50%) and free work (43.4%). These followed by the moderately infected occupants that could be ordered as follows: the government employee (36.5%), house women (30.7%), no work (30%), animal breeders (19.3%) and the merchants (15.3%). The statistical analysis of the findings suggested a significant variation among the villagers, based on their occupation, (P < 0.05). Regarding the intensity of infection, surprisingly, the merchants significantly postured the worm burden (158.4 epg), followed by the labourers (125.7 epg), farmers (100.0 epg). The worm burden among those of no work and the animal breeders were almost equi-distributed, 79.4 epg, and 79.4 epg, respectively. The least suffering in terms of the eggs excreted were the and free work (63.1 epg), the government employee (31.5 epg), the house women (31.5 epg), and surprisingly the students (40.1 epg). The statistical variations of the excreted eggs by different occupants were found to be of a significant rate (P < 0.05).

Table (6): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Occupation

Number Intensity of eggs (Per One Gram) Occupational Examined Prevalence Log of egg load GEMC Frequency Category (%) (X ± SD) (X ± SD) (%)

• No Work 40(7) 30.0 1.9 ± 0.2 79.4 ± 1.5 • Farmers 40(7) 65.0 2.0 ± 0.4 100.0 ± 2.5 • G. Employee 52(9) 36.5 1.5 ± 0.1 31.5 ± 1.2 • Merchants 13(4.3) 15.3 2.2 ± 0.4 158.4 ± 2.5 • Labourers 52(9) 53.8 2.1± 0.3 125.7 ± 2.1 • Students 212(37.7) 50.0 1.6 ± 0.3 40.1 ± 2.1 • House Women 114(20) 30.7 1.5 ± 0.2 31.5 ± 1.5 • Free Work 23(4) 43.4 1.8 ± 0.1 63.1 ± 1.2 • Animal Breeders 16(2) 19.3 1.9 ± 0.3 79.5 ± 2.1 • Total 562 41.8 1.9 ± 0.3 79.4 ± 1.9 Statistical significance P < 0.001 P < 0.001

160 Prevalence(%) Intensity(GMEC/gm)

140

120

100

40 Prevalence (%) Intensity(GMEC/gm) 20

0 No works Farmers G.Employee Merchant Labourers Students H.Women Freework Animal Breeders By occupations

Figure (6): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Occupation

4.1.6 Prevalence and Intensity by Socioeconomic Status: 4.1.6.1 Water-supply Accessibility: Table (7), Figure (7) illustrates the overall prevalence and intensity of S. mansoni infection among the surveyed villagers accessibility of the water supply. The villagers who had no source of clean water-supply were 80%, and 57.3% of them were infected with a high worm burden of 79.4 epg. On the other hand, the 20% of the villagers had access to clean water, where 30.6% were infected with intensity of 63.1 epg. Although the variation of the prevalence rates between the two categories was significant (P < 0.05), but not the intensity of infection.

Table (7): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Water Supply

Number Prevalence Intensity of eggs (Per One Gram) Water Supply Examined (%) Log of egg load GEMC Frequency (%) (X ± SD) (X ± SD) • Accessible 49 (20) 30.6 1.8 ± 0.3 63.1 ± 2.0 • Not accessible 196 (80) 57.3 1.9 ± 0.3 79.4 ± 2.0 • Total 245 41.8 1.7 ± 0.3 50.1 ± 2.0 Statistical significance P < 0.001 P > ± 0.001

Prevalence(%) 80 Intensity(GMEC/gm) 70 60 50 40 30 20 10

Prevalence (%) & Intesity (GMEC/gm) & Intesity (%) Prevalence 0 Accessible Not accessible By water -supply

Figure (7): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Water Supply

4.1.6.2 Excreta Disposal System:

Table (8), Figure (8) verifies the overall prevalence and intensity of S. mansoni infection among the surveyed villagers accessibility of latrines. Fortunately more than three-quarters (76.6%) of the surveyed villagers hadn’t access to excreta disposal system. It seems that the access to latrine had no influential effects on the infection parameters since the two measures were almost similar.

Table (8): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by latrine accessibility

Number Prevalence Intensity of eggs (Per One Gram) Accessibility Examined (%) Log of egg load GEMC Frequency (%) (X ± SD) (X ± SD) • accessible 57(23.4) 56.6 1.8 ± 0.3 63.1 ± 2.0 • Not Accessible 188 (76.6) 59.5 2.0 ± 0.3 100.0 ± 2.0 Total 245 (100.0) 57.2 1.9 ± 0.3 79.4 ± 2.0 Statistical significance P > 0.001 P > 0.001

100 Prevalence(%) Intensity(GMEC/gm) 90 80 70 60 50 40 30 20 10 Prevalence(%) & Intensity (GMEC/gm) & Intensity Prevalence(%) 0 Accessible Not Accessible By accessibility to latrine

Figure (8): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by latrine accessibility

4.1.6.3 Number of Rooms: Table (9), Figure (9) illustrates the overall prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by number of rooms. The number of rooms as a socioeconomic parameter was inversely related to prevalence of infection. The infection rates of the villagers who had one, two and three rooms were 60%, 58.8% & 52.7%, respectively. While those of four and five rooms were 28.6% & 25.5%, respectively. The verified general trend was also monitored in the intensity of infection, excluding the group of "three rooms". The differences of the two infection parameters, based on the number of rooms, were found to be of significant score, (P < 0.05).

Table (9): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Number of Rooms

Examined Intensity of eggs (Per One Number of Samples Prevalence Gram) Rooms Frequency (%) (%) Log of egg load GMEC (X ± SD) (X ± SD) • One Room 35(14) 60.0 1.9 ± 0.4 79.4 ± 2.5 • Two Rooms 36(15) 58.8 1.9 ± 0.2 79.4 ± 1.6 • Three Rooms 75(30.5) 52.7 2.0 ± 0.2 100.0 ± 1.6 • Four Rooms 91(37.5) 28.6 1.8 ± 0.2 63.1 ± 1.6 • Five Rooms 8(3) 25.0 1.8 ± 0.3 63.1 ± 2.0 Total 245 45.2 1.9 ± 0.3 79.4 ± 1.9 Statistical significance P < 0.05 P < ± 0.05

Prevalence(%) 100 Intensity(GMEC/gm) 90 80 70 60 50 40 30 20 10 Prevalence(%)Intensity(GMEC/gm) & 0 One Two Three Four Five Room Rooms Rooms Rooms Rooms By number of rooms

Figure (9): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by Number of Rooms

4.1.6.4 Quality of Building: Table (10), Figure (10) presents the overall prevalence and intensity of S. mansoni infection among the villagers by type of building. It seems that the infection rates were significantly inversed the quality of building, (P < 0.05), where those who had the thatched (59.3%), the mud brick (53.2%) while those of the red brick (29.8%). On the other hand, the egg-counts had no consistent pattern to the villagers' quality of building as well as no significant variation was detected.

Table (10): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by quality of building

Quality Number Prevalence Intensity of eggs (Per Gram) of Examined (%) Log of egg load GMEC Building Frequency (%) (X ± S± D) (X ± SD) • Grass Thatched 97(39.5) 59.3 1.8 ± 0.1 63.1 ± 1.2 • Mud Brick 68(27.2) 53.2 1.8 ± 0.2 63.1 ± 1.6 • Red Brick 80(32) 29.8 1.5 ± 0.2 31.5 ± 1.6 Total 245 40.6 1.7 ± 0.2 50.1 ± 1.6 Statistical significance P < 0.05 P > 0.05

prevalenc(%) 70 Intensity(GMEC/gm)

10 Prevalence (%) & Intensity (GMEC/gm) 0 Grass Mud Brick Red Brick Thatched By type of building

Figure (10): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by quality of building

4.1.6.5 History of infection: Table (11), Figure (11) presents the overall prevalence and intensity of S. mansoni infection among the surveyed villagers by history of infection. More than four-fifth (84.5%) had the history of infection, where 38.7% of them were still suffering the infection, 85.2 epg. On the other hand, very few (16.6%) had no history of infection, but 6.7% of them were microscopically proved to be infected with 56.5 epg. The statistical analysis ensured significant variations of the infection rates and the worm burden between the two categories, (P < 0.05).

Table (11) Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by history of infection

Previous Infection Number Examined Prevalence Intensity (Frequency %) (%) (GMEC- epg) • Yes 207 (84.5) 38.7 85.2±2.6

• No 38 (16.5) 6.7 56.5±1.8

Total 245 (100) 29.5 70.6±1.8

Statistical Significance P < 0.05 P < 0.05

4.1.6.6 Awareness of Bilharzia and its snails: Table (12), Figure (12, 13) shows the overall infection parameters of S. mansoni infection among the villagers by awareness of Bilharzia and snails. General speaking, it seem that the awareness level of both the disease and its snails had an inverse relation to the infection rates. It worse to mention that the villagers who know much about Bilharzia and its snails were found free from the infection, although very few. The variation of the prevalence rates among the different categories, based on Bilharzia awareness, was found to be statistical significant, (P < 0.05). On the other hand, the intensity of infection has no fixed pattern to the awareness level of the villagers to the intermediate hosts.

Prevalence(%) 90 Intensity(GMEC/gm) 80 70 60 50 40 30 20 10 Prevalence (%) Intensity(GMEC/gm) & 0 Yes No By history of infection

Figure (11): Overall Prevalence and intensity of S. mansoni infection among the surveyed samples from New Half Scheme, by history of infection

Table (12): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Bilharzia and snails

Awareness Level Number Examined Prevalence Intensity (Frequency %) (%) (GMEC- epg) Bilharzia Awareness:

• Nothing 50 (20.4) 35.0 34.6±1.8

• Very few 148 (64.4) 59.4 57.4±2.7

• Moderate 28 (11.4) 8.6 121±3.4

• Much 9 (3.8) 0.0 0

Total 245 (100) 29.5 70.6±1.8

Statistical Significance P < 0.05 P < 0.05

Snails Awareness:

• Nothing 164 (66) 39.4 57.6±3.4

• Very few 40 (16.2) 56.5 85.2±1.3

• Moderate 34 (14.4) 20.2 68.5±1.2

• Much 8 (3.4) 0.0 0

Total 245 (100) 29.5 70.6±1.8 Statistical Significance P < 0.05 P < 0.05

140 Prevalence(%) Intensity(GMEC/mg) 120

100

20 Prevalence (%) & Intensity (GMEC/gm) &Intensity (%) Prevalence 0 Nothing Very few Modrate Much By awereness of Bilharzia

Figure (12): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Bilharzia

140 Prevalence(%) Intensity(GMEC/mg) 120

100

20 Prevalence (%) & Intensity (GMEC/gm) &Intensity (%) Prevalence 0 Nothing Very few Modrate Much By awareness of Bilharzia

Figure (13): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by awareness of Snails

4.1.6.7 Water-contact Activities: Table (13), Figure (14) presents the overall infection parameters of S. mansoni infection among the villagers by their water contacts. More than three-fifth (61.1%) of the villagers used to contact surrounding contaminated waterbodies, where 37.2% of them were infected with high egg-counts, 100.0epg. More than one-quarter of the villagers (29.3%) reported that "rarely" they contact the waterbodies, where 24.5% of them were infected with high egg-counts, 79.4%. Although 10.6% of the villagers reported that they "never" had any water- contact activities, but still of 10.5% of them were infected, with 50.2 epg. The statistical analysis of the infection rates and the worm burden, based on the villagers' water contacts, were found significant, (P < 0.05).

Table (13): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by water contacts

Water contact Number Examined Prevalence Intensity activities (Frequency %) (%) (GMEC- epg) • Usually 150 (61.1) 37.2 100.0± 2.5

• Rarely 72 (29.3) 24.5 79.4± 1.8

• Never 23 (10.6) 10.5 50.2± 1.5

Total 245 (100) 29.5 70.6± 1.8

Statistical Significance P < 0.05 P < 0.05

Prevalence(%) 100 Intensity(GMEC/mg) 90 80 70 60 50 40

(%) &(%) Intensity (GMEC/gm) 30 20 10 Prevalence Prevalence 0 Usually Rarely Never By water -contact

Figure (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by water contacts

4.1.6.8 Water-contact Categories: It seems that only the occupation and swimming were the most crucial water contact activities influencing the infection pressure, Table (14), Figure (14). Being an agricultural area 80% of the villagers had the occupational water contacts, for watering their farms, where 36.3% of them were infected with high egg-counts, 63.4 epg. Although swimming as a water-contact activity practiced only by 10%, where 16.7% were significantly suffering the infection, 109.6 epg. Based on the categories of water-contacts, the variation of the prevalence and intensity were ensured to be of significant score, (P < 0.05)

Table (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by categories of water contacts

Categories of Number Examined Prevalence Intensity Water Contact (Frequency %) (%) (GMEC-epg) • Fetching 3 (1.2) 0.0 0

• Swimming 30 (10.0) 16.7 109.6±1.6

• Paddling 2 (1.2) 0.0 0

• Bathing 9 (4.2) 0.0 0

• Laundry 5 (2.6) 0.0 0

• Occupational 196 (80.0) 36.3 63.4± 1.7

Total 245 (100.0) 29.5 70.6± 1.8

Statistical Significance P < 0.05 P < 0.05

120 Prevalence(%) Intensity9GMEC/mg)

100

0 Prevalence (%) & Intesity (GMEC/gm) & Intesity (%) Prevalence Fetching Swmming Paddling bathing Laundary Occupational Catigories of water-contact activities

Figure (14): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by categories of water contacts

4.1.6.9 Educational level: Table (15), Figure (15) illustrates the overall infection parameters of S. mansoni infection among the villagers educational level. The findings highlighted that the educational level had no effects on the two infection parameters, although they slightly inversed the educational level.

Table (15): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by educational level

Examined Intensity of eggs (Per One Gram) Educational Samples Prevalence Level Frequency (%) Log of egg load GEMC (%) (X ± SD) (X ± SD) • Illiterate 132 (23.4) 39.8 2.0 ± 0.3 100.0± 2.0 • Basic School 267 (47.5) 50.5 2.0± 0.3 100.0± 2.0 • Intermediate 40 (7.6) 39.5 1.8± 0.3 63.1± 2.0 • Secondary 101 (18) 38.7 1.8± 0.3 63.1± 2.0 • University 21 (3.5) 32.8 1.7± 0.2 50.1± 2.0 Total 562 41.8 1.9± 0.3 79.4± 2.0 Statistical significance P > 0.001 P < 0.001

Prevalence(%) 100 Intensity(GMEC/gm) 90

80 70

50 40

10 Prevalence (%) & Intensity (GMEC/gm) & Intensity (%) Prevalence 0 Illitrate Basic Intermedate Secondary Univeristy By educational level

Figure (15): Overall infection parameters of S. mansoni infection among the villagers of New Half Scheme, by educational level

4.1.6.10 Proportion of infection and worm burden by level of infection: The distribution of S. mansoni egg-outputs among the villagers by the level of infection verified in Table (16) and Figure (16). The survey ensures that 39.2% of the infected children were lightly infected with an average of intensity of 54.3 eggs per gram. The survey classified 12.0% of the infected villagers as bee moderately infected with an average of worm burden of 159.5 eggs per gram. On the extreme, 0.4%, of the villagers were suffering the highest intensity of worm burden, 580.2 eggs per gram. The analysis of the findings pointed that the level of infection among the villagers varied significantly, (P < 0.05).

Table (16): Distribution of S. mansoni egg-outputs among villagers in New Half Scheme, by level of infection (Based on WHO, 2005)

Number Intensity of eggs (Per One Gram) Level of Infection Examined Prevalence Frequency (%) (%) Log of egg load GEM±C (X ± SD) (X ± SD) First Survey (2002):

• Light Infection 145(62) 39.2 1.7 ± 0.3 50.1 ± 2.0 • Moderate Infection 70(29) 12.0 2.2 ± 0.3 158.4 ± 2.0 • Heavy Infection 20(9) 0.4 2.7 ± 0.4 501.2 ± 2.5 Statistical significance P < 0.05 P < 0.001

Second Survey (2004):

• Light Infection 127(62) 27.3 1.6 ± 0.2 39.8 ± 1.6

• Moderate Infection 63(32) 8.6 2.1 ± 0.3 125.8 ± 2.4

• Heavy Infection 14(6) 0.3 2.6 ± 0.4 398.2 ± 2.5 Statistical significance P < 0.05 P < 0.05

Prevalence( %) 600 Intensity (GMEC/gm )

500

400

300

200

100

Prevalence (%) Intensity & (GMEC/gm) 0 Light Moderate Heavy Egg output by level of infection among villagers

Figure (16): Distribution of S. mansoni egg-outputs among villagers in New Half Scheme, by level of infection (Based on WHO, 2005)

4.1.7 Reduction in infection Parameters: 4.1.7.1 Reduction in Prevalence Rates among villagers: Tables (17, 18 & 19) indicate the overall and genderized reduction rate in prevalence of S. mansoni infections among the villagers from 2002 to 2004. The overall reduction among the villagers, due to interventional programme, was 62.2%. In fact, the reductions among the males and the female were almost equi- distributed, 65.4% and 60.2%, respectively.

Table (17): Overall reduction rate in prevalence of S. mansoni among the villagers in New Halfa Scheme (2002 - 2004 )

Variable Pre-intervention Post-intervention

Total Villagers: • Negative 327 468 • Positive 235 94 • Total 562 562

A = Prevalence before chemotherapy = 235/562 = 41.8% B = Prevalence after chemotherapy = 94/562 = 16.2% Ø = Reduction in prevalence = (a - b)/a = 62.2%

Table (18): Overall reduction rate in prevalence of S. mansoni among the male villagers in New Halfa Scheme

Variable Pre-intervention Post-intervention

Villagers Males: • Negative 160 267 • Positive 162 55 • Total 322 322

Like above: A = 162/322 = 50.3% B = 55/322 = 17.5%

Ø = = 65.4%

Table (19): Overall reduction rate in prevalence of S. mansoni among the female villagers in New Halfa Scheme

Variable Pre-intervention Post-intervention

Villagers Females: • Negative 167 211 • Positive 73 29 • Total 240 240

Like above: A= 73/240 = 30.4% B = 29/240 = 12.1% Ø = = 60.2%

4.1.7.2 Residential reduction in Prevalence Rates: Table (20) Figure (17) verifies the overall reduction rate in prevalence of S. mansoni infections among the villagers and campers from 2002 to 2004. The surveyed study areas could be arranged in a descending manner as follow: Gamhoria camp (75.3%), Village 12 (52.3%), Masna camp (50.2%) and Village 16 (45.3%).

Table (20): Residential reduction of S. mansoni infection among the surveyed villages and camps of New Halfa scheme (2002 – 2004)

Residential Site Number infected Number infected Reduction Rate (Prevalence - 2002) (Prevalence - 2004) (%) • Village (16) 55 (30.4) 22 (13.2) 45.3 • Village (12) 49 (29.8) 23 (15.3) 52.2 • Gamhoria camp 72 (59.2) 17 (12.4) 75.3 • Masna camp 67 (55.8) 24 (18.3) 50.2 Total 243 (41.8) 89 (16.2) 62.2

Prevalence(%)2002 80 Prevalence(%)2004 70 Reduction

30 20

Reduction in Prevalence( 2002-2004) Prevalence( in Reduction 0 Village(16) Village(12) Gamhoria Masna Camp Camp Surveyed villages & camps

Figure (17): Residential reduction of S. mansoni infection among the surveyed villages and camps of New Halfa scheme (2002 – 2004)

4.2 Villagers Epidemiological Surveys: • 4.2.1 Infection Parameter by Residential Sites: The response rate of the school children in the first parasitological survey was 95% (2420 out of 2531 children), where all cooperated by providing urine and faecal samples. Table (21) and Figure (18),(19) verify the overall infection of S. mansoni infection among school children in some selected residential sites in New Half Scheme. The overall infection rate was found 54.6%, while the overall intensity of infection was 80.6 eggs per gram. In the first survey the infection rate of S. mansoni among school children of villages (12) and (16) were significantly higher than those monitored among the villagers, 42.1% & 55.5%, (P < 0.05). Concerning the camps' situation, the infection rates among the school children of Gamhoria camp and El Masnaa camp slightly overrode those of the villagers, 59.2% and 55.8% compared to 57.4% and 53.3%, respectively. The variation of the infection rate among the school children was not significant, based on their residential settlement. Regarding the worm burden, expressed I eggs excreted, surprisingly, those of the villagers were overnumbered the monitored figures of the school children, in all study areas. The findings suggested that the residential differences in the excreted eggs by the school children were of significant value, (P < 0.05).

Table (21): Overall infection parameters of S. mansoni infection among school children in some selected residential sites in New Half Scheme

Number Intensity of eggs (Per One Gram) School Village Examined Prevalence Log of egg load GEM±C Frequency (%) (X ± SD) (X ± SD) (%) First Survey (2002):

• Village (12) 274 (11.3) 42.1 1.8 ± 0.2 63.1 + 1.6 • Village (16) 424 (17.5) 55.5 1.8 ± 0.3 63.1 + 2.2 • Gamhoria Camp 866 (35.7) 57.4 2.0 ± 0.2 100.0 + 1.9 • Masna Camp 854 (35.2) 53.3 2.1 ± 0.2 125.1 + 1.1 Total 2420 54.6 1.9 ± 0.3 80.6 + 2.0 Statistical significance P > 0.05 P < 0.05 Second Survey (2004):

• Village (12) 274 (11.3) 9.0% 1.7 ± 0.3 50.1 + 2.0

• Village (16) school 424 (17.5) 11.2% 1.7 ± 0.4 50.1 + 2.5 • Gamhoria Camp 866 (35.7) 12.4% 1.8 ± 0.4 63.1 + 2.5 • Masna Camp 854 (35.2) 20.6% 1.8 ± 0.3 63.1+ 2.0 Total 2420 14.3% 1.7 ± 0.3 56.2 + 2.1 Statistical significance P > 0.05 P > 0.05

Prevalence() (%) 140 Intensity(GMEC/gm)

120

100

20 Prevalence (%) Intensity (GMEC/gm)

0 Village(12) Village(16) G.Camp M.Camp Selected schoolchildren in villages & camps (2002)

Figures (18) (19): Overall infection parameters of S. mansoni infection among school children in some selected residential sites in New Half Scheme (2002-2004)

Prevalence() (%) 70 Intensity(GMEC/gm)

10 Prevalence (%) Intensity & (GMEC/gm)

0 Village(12) Village(16) G.Camp M.Camp Selected schoolchildren in villages & camps (2004)

4.2.2 Overall Prevalence and Intensity by Gender: Table (22), Figure (20) illustrates the overall infection of S. mansoni infection among school children in New Half Scheme, by gender. Regarding the prevalence of infection in the first survey, the males significantly overrode the females, 74.7% & 36.4%, (P < 0.05), but not in the worm burden, 82.3 & 78.2 eggs per gram.

Table (22): Overall Prevalence and intensity of S. mansoni in four residential settlements in New Half Scheme, by children gender

Number Intensity of eggs (Per One Gram) Gender Examined Prevalence Log of egg load GEMC Frequency (%) (%) (X ± SD) (X ± SD) First Survey (2002):

• Males 1116(46.2) 74.7 2.0 ± 0.3 100.0 ± 2.0 • Females 1304(53.8) 36.4 1.9 ± 0.3 79.4 ± 2.0 Total 2420 54.6 1.9 ± 0.3 80.6 + 2.0 Statistical significance P < 0.05 P > 0.05 Second Survey (2004):

• Males 1116(46.2) 16.3 1.7 ± 0.3 64.1± 2.0 • Females 1304(53.8) 12.5 1.6 ± 0.3 50.1 ± 2.0 Total 2420 14.3 1.7 ± 0.3 56.2 ± 2.0 Statistical significance P > 0.05 P > 0.05

Prevalence(%) 100 Intensity (GMEC/gm) 90 80 70 60 50 40 30 20

Prevalence (%) Intensity & (GMEC/gm) 10 0 Males2002 Females2002 Males2004 Females2004 Schoolchildren by gender

Figure (20): Overall Prevalence and intensity of S. mansoni in four residential settlements in New Half Scheme, by children gender

4.2.3 Overall Prevalence and Intensity by age-groups: Table (23), Figure (21) illustrates the overall infection of S. mansoni infection among school children in New Half Scheme, by age-classes. The findings suggested typical graphical fluctuations, where both infection parameters significantly postured at the mid-aged children, 10 - 14 years, (P < 0.05).

Table (23): Overall Prevalence and intensity of S. mansoni infection in four residential settlements in New Half Scheme, by children age-groups

Age group Number Prevalence Intensity of eggs (Per One Gram) (in years) Examined (%) Log of egg load GEMC Frequency (%) (X ± SD) (X ± SD)

05 - 09 701 12.2 1.9 ± 0.3 79.4 ± 2.1

10 - 14 1531 36.2 2.0 ± 0.3 100.0 ± 2.3 < 15 188 6.2 1.7 ± 0.0 63.5 ± 1.1 Total 2420 54.6 1.9 ± 0.3 80.6 + 2.0 Statistical significance P < 0.05 P < 0.05

120 Prevalence(%) Intensity (GMEC/gm) 100

20 Prevalence (%) & Intensity(GMEC/gm) (%) Prevalence

0 0.5-9 Years 10-14Year < 15 Schoolchildren by age-group

Figure (21): Overall Prevalence and intensity of S. mansoni infection in four residential settlements in New Half Scheme, by children age-groups

4.2.4 Proportion of infection and worm burden by level of infection: The distribution of S. mansoni egg-outputs among school children by the level of infection verified in Table (24) and Figure (22). The obtained findings stressed that 36.2% of the infected children were classified as been lightly infected with an average of intensity of 50.1 eggs per gram. On the other side, 18.1% of the infected children were categorized as moderately infected with an average of worm burden of 158.5 eggs per gram. Unfortunately, the survey recapitulate that very few of the infected children, 0.3%, were responsible for the highest proportionate of the worm burden, 501.2 eggs per gram. The statistical analysis suggested a high significant variation among the infected children by level of infection, (P < 0.05)

Table (24): Distribution of S. mansoni egg-outputs among school children in New Half Scheme, by level of infection (Based on WHO, 2005)

Number Intensity of eggs (Per One Gram) Level of Infection Examined Prevalence Log of egg load GEM±C Frequency (%) (X ± SD) (X ± SD) (%) First Survey (2002): • Light Infection * 220(49.6) 36.2 1.7± 0.2 50.1 ± 1.5 • Moderate Infection ** 180(40.3) 18.1 2.2± 0.2 158.5 ± 1.5 • Heavy Infection *** 43(0.006) 0.3 2.7± 0.4 501.2 ± 2.5 Statistical significance P < 0.05 P < 0.001 Second Survey (2004):

• Light Infection * 220(49.6) 9.4 1.7± 0.1 50.1 ± 1.2 • Moderate Infection ** 180(40.3) 4.5 2.2± 0.3 158.5 ± 2.0

• Heavy Infection *** 43(0.006) 0.4 2.6± 0.4 398.2± 2.5 Statistical significance P < 0.05 P < 0.05

100

Light Infection * = (< 100 eggs per gram) Moderate Infection ** = (> 100 but < 400 eggs per gram) Heavy Infection *** = (> 400 eggs per gram)

Prevalence ( % ) Intensity (GMEC/gm) 600

500

400

300

200

100 Prevalence (%) & Intensity (GMEC/gm)

0 Light Moderate Heavy Egg output by level of infection among schoolchildren (2002)

Figure (22): Distribution of S. mansoni egg-outputs among school children in New Half Scheme, by level of infection (Based on WHO, 2005)

4.2.5 Reduction in Prevalence Rates among school children: Tables (25, 26 & 27) show the overall and genderized reduction rate in prevalence of S. mansoni infections among the school children from 2002 to 2004. The overall knockdown of infection among the children was 76.3%. Considering the gender reduction, the infection rates of the males declined by 78.1% while those of the females reduced by 65.6%.

101

Table (25): Overall reduction rate in prevalence of S. mansoni among the villagers in New Halfa Scheme (2002 - 2004 )

Variable Pre-intervention Post-intervention

Total School children: • Negative 1065 2131 • Positive 1355 289 • Total 2420 2420 Like above: A = 1355/2420 = 54.6% B = 289/2420 = 14.3% Ø = = 76.3%

Table (26): Overall reduction rate in prevalence of S. mansoni among the male villagers in New Halfa Scheme

Variable Pre-intervention Post-intervention

Villagers Males: • Negative 298 937 • Positive 818 179 • Total 1116 1116

Like above: A = 818/1116 = 74.7% B = 179/1116 = 16.3% Ø = = 78.1%

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Table (27): Overall reduction rate in prevalence of S. mansoni among the female villagers in New Halfa Scheme

Variable Pre-intervention Post-intervention

Villagers Females: • Negative 730 1135 • Positive 574 169 • Total 1304 1304

Like above: A = 574/1304 = 36.4% B = 169/1304 = 12.5% Ø = = 65.6%

4.2.6 Eggs-output Reduction: Table (28), Figure (23) shows the reduction in eggs-output of S. mansoni infection among the villagers and the school children in New Halfa Scheme, 2002 - 2004. It seems that the reduction of the infection level among both villagers and the school children was directly proportional to the number of the infected candidates. The reduction level among the lightly and moderately infected villagers were statistically significant, (P < 0.05), but not among the heavily infected ones. Such finding was also observed among the school children, 84.5%, 67.4% compared to 25.0%, respectively.

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Table (28): Eggs-output reduction of S. mansoni infection among the surveyed villages and the school children by the level of infection in New Halfa scheme (2002 – 2004)

Villagers: Number infected Number infected Reduction Level of infection (Prevalence %) (Prevalence %) (%) 2002 2004 • Light Infection 155 (39.3) 84 (18.8) 82.2

• Moderate Infection 72 (12.1) 14 (11.1) 62.8

• Heavy Infection 8 (0.4) 6 (0.3) 29.3

Total 235 (41.8) 104 (16.2) 62.7

School Children:

• Light Infection 969 (40.2) 175 (9.5) 84.5

• Moderate Infection 174 (13.2) 150 (4.4) 67.4

• Heavy Infection 92 (0.3) 20 (0.4) 25.0

Total 1335 (54.5) 345 (14.3) 76.3

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Prevalence (%) 2002 Prevalence (%) 2004 90 Reduction 80

40 2002 - 2004) - 2002 30

10 Egg output reduction in Prevalence( Prevalence( in reduction Egg output 0 Light Moderate Heavy Reduction among schoolchildern by level of infection (2002 - 2004)

Figure (23): Eggs-output reduction of S. mansoni infection among the surveyed school children by the level of infection in New Halfa scheme

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4.3 DISCUSSION: The epidemiology of schistosomiasis in man involves the two quantitative measures of parasite, prevalence (occurrence or absence of paired mature female worm) and intensity (abundance of schistosome eggs). Limited size of transmission site (Forsyth & Bradley 1966; Hira & Patel 1981, Koura et al., 1981; Scott et al., 1982, Goal & Wilkins, 1984; Mazurka et al.,. 1985; Babiker 1987, Chandiwana et al., 1988; Hilali 1992), habitat proximity to human settlements (Teklehaimanot & Fletcher 1990), habitat geology and climatic conditions (Abdelwahab et al., 1980, Jordan et al., 1980 a & b; Nordbeck et al., 1982; Christensen et al., 1983; Goal and Wilkins 1984., Bukenyo & Andama 1985; Cheever et al., 1985 a & b; and human activity (Polderman 1979; Polderman et al., 1985; Costa et al., 1987), are factors which affect the epidemiology and transmission of schistosomiasis in any endemic areas.

The overall prevalence and intensity of s.mansoni infection vary markedly among villages and camps in New Halfa scheme, in Village (12) and (16) were moderate and equi-distributed, 29.8% (50.1) epg and 30%, (50.1) epg respectively.

Also the prevalence rates among the residents of El Gamhoria and Masna camps were very high and almost equi-distributed, 59.2 %, (79.4) epg and 55.8%, (100.0) epg respectively. It proved that the proximity to canalization system, the availability of clean adequate water supply and the socio-economic status are the most important factors to determine the intensity of s.mansoni infection in any particular area.

The prevalence and intensity in two camps were very high because they are poor socio-economically. There are no electricity, dispensaries, and latrines and has poor socio-economically. They get water directly from canalization system.

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In New Halfa villages and camps the majority of infected people had light 39.2% or moderate infection 12.0% (1 - 400 epg) and only a very small proportion of the population had heavy infection 0.4%, ( > 400 epg) and 0.3% in the second survey.

The number of heavily infected villagers (> 400 epg) identified in this study were same to those reported by Hilali (1992) and Ahmed (1998), but low if compared to other studies, Warren and Mahmoud (1976) found 30% heavily infected people in the Machakos area, Kenya, and 20% heavy infected people reported in Egypt (Abdelwahab et al., 1980).

These references in prevalence of heavily infected people could be due to the contamination of environment with schistosome eggs and the intensity of population in these areas.

Prevalence and intensity of infection are directly related and usually show similar patterns of variation with age in villages and camp, both increase generally to the age (10 – 20) year’s age groups followed by decline in the elderly and then other increase at the age group > 60 year.

This general pattern was reported from different endemic areas (Abdelwahab et al., 1980, Bartholomew et al., 1981;King et al., 1982; Dennis et al., 1983; Bukenya & Andama 1986; Babiker 1987; Chandiwana et al., 1988, Gryseels 1989; Glad-Nordhi 1989; Butterworth et al., 1989; Teklehaimont & Fletcher: 1990; Simonsen 1990; Tavares-Neto 1991; Lakwo et al., 1991; Ndamba et al., 1991; Diaw et al., 1991; Barreto 1991; Vargas et al., 1991; Kabatereine et al., 1992, Hilali 1992; Marcel-Junior, 1993; Eltom et al., 1993; Ahmed, 1998;).

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The peak in the 60 + year age group was described by Babiker (1987) in Gezira, Hilali (1992) in Managil and Ahmed (1998) in Gunied scheme, it was hypothesized that this increase in the infection rates is related to a reduced immunity in older people.

There was a significant difference in prevalence and intensity of s.mansoni infection between the two Genders, the males significantly outnumbered the females, 45.6%, 100.0 epg and 30.4%, 50.1epg respectively, (P < 0.05).

The differences are mainly due to the activities carried by the males and females in the community of New Halfa. Bringing water from canals is a feminine job, in camps, the females do not swim and rarely wash and bath in the canals, where as the males usually swim, wash and bath in canals, so they are more exposed to cercariae than females.

The agricultural activities in the fields are mainly carried by males, though females usually contribute in picking cotton and harvesting crops. The relationship of prevalence and intensity of s.mansoni infection to genders reported in many endemic areas. The prevalence of schistosomiasis was higher in males then in females, (Farooq et al., 1966; Omer et al., 1976, Puph & Gilles, 1978; king et al., 1982; Klumpp & Webbe 1987; Babiker 1987; Hilali; 1992; Ahmed 1998).

Prevalence and intensity of S. mansoni infection in villages and camps by occupation, suggested that the high infected occupants could be arranged in the following descending order: farmers (65%), labourers (53.8%), students (50%) and free work (43.4%). These followed by the moderately infected occupants that

109 could be ordered as follows: the government employee (36.5%), house women (30.7%), no work (30%), animal breeders (19.3%) and the merchants (15.3%).

The statistical analysis of the findings suggested a significant variation among the villagers, based on their occupation, (P < 0.05).

The cooperation of the villagers in all stages of agricultural activities might be suitable justification of the moderate prevalence and intensity among water unrelated jobs. In villages the intensity of infection among different occupants is relatively less than the intensity of infection among the same occupation in camps; this is probably due to the high socio-economic status of the villages, in addition to the location of the canals a pit far from the villages.

Many disease, include schistosomiasis are result of poor socio-economic conditions. Gordon (1972) states that the effort by the government to improve standard of living of rural population could lead to beneficial and lasting effects on the overall incidence of schistosomiasis.

A lot of studies proved that the prevalence and intensity of schistosomiasis are closely related to socio-economic status in any endemic area. Adequate water supply and sanitary facilities are the most important factors (Farooq et al., 1966, Siongok et al., 1976).

In New Halfa camps the prevalence and the intensity of S.mansoni infection are highly significant among people, the reason for this presumably the lack of water supply and latrine which determines the prevalence of intensity of S.mansoni infection in any community.

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In addition to socio-economical factors such as access of electricity, number of rooms, type of building, education and ethnicity which probably that the combined effect of these factors affect the prevalence and intensity of S.mansoni infection in New Halfa villages and camps. People has less socio-economical status in New Halfa most of them are poor, ignorant and they could not afford to educate their children, so most of the children swimming and playing in the canals, this prove the high prevalence and intensity of infection among poor people.

The ethnic groups are most probably reflecting differences in socio-economic status of these group rather than differences in ethnicity. The northern are the main citizen in the area, they have their own land and most of them are farmers. The eastern and the western people are agricultural laborers; they are poor, and lives in camps or at the fringe of the villages in huts or mud brick houses.

In the first survey the infection rate of S. mansoni among school children of villages (12) and (16) were significantly higher than those monitored among the villagers, 42.1% & 55.5%, (P < 0.05).Concerning the camps' situation, the infection rates among the school children of Gamhoria camp and El Masnaa camp slightly overrode those of the villagers, 59.2% and 55.8% compared to 57.4% and 53.3%, respectively. The variation of the infection rate among the school children was not significant, based on their residential settlement.

Regarding the worm burden, expressed I eggs excreted, surprisingly, those of the villagers were overnumbered the monitored figures of the school children, in all study areas. The findings suggested that the residential differences in the excreted eggs by the school children were of significant value, (P < 0.05).

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Most of the schistosomiasis epidemiological studies, in the Sudan, were done on the school children (BNHP, 1986-1990); Babiker unpublished report 1990; Salim 1996; Ahmed 1998). The school children are well organized, sample can obtained easily and they are the group in the population with the highest risk to infection. The relation between the prevalence rate of S.mansoni infection in the school children and the population in any particular village was plotted against each other. The result indicates a linear relationship, as the prevalence of S.mansoni infection in the school children increases the prevalence among the population increases.

In conclusion the overall prevalence and intensity of S.mansoni infection vary markedly among villages and camps, as well as among Gender and age group in New Halfa. These variations reflect the local variation in the transmission pattern and the intensity of transmission. A control strategy was planned and adopted in the area; it depends on focal control of snails, mass chemotherapy, health education, environmental sanitation and water supply to reduce the transmission of S.mansoni infection in New Halfa scheme.

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CHAPTER FIVE

Micro-ecology of Schistosomiasis

5.1 Seasonal dynamics of macrofaunal form in two canals: Monthly and wise fluctuations were observed between these macrofaunal aquatic forms in the two canals. These up and down were correlated on statistical basis to the equivalent fluctuations of monitored ecological factors e.g. water temperature, water level turbidity and speed. In addition the fluctuations of the intermediate host snails were correlated statistically to the abundant biocontrol agents. The analysis suggested a high significant difference in snails between the three sites, upper, mid and down canal but there are no significant difference between the two canals. The description of the general abundance between the two canals has the same share of the monthly collection of Biomphalaria snail. The analysis of the field finding shown in table (29). Biomphalaria snails were symphonizingly fluctuating monthly. Most voracious biocontrol agents for Biomphalaria snails observed were, the normal water dug, the cyprinus fish ,dragonfly nymph and freshwater- shrimps. All these biocontrol agents were gradually increased to the end of the canal.

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Table (29): The relative abundance of the macro-aquatic forms collected from canals (16 & 12) in New Halfa scheme

Total collection of Aquatic macrofaunal form Macro-aquatic form Canal (16) Canal (12) Biomphalaria snail 862 663 Cyprinus fish 68 72 Water bug 65 66 Dragonfly Nymph 25 59 Freshwater shrimps 108 141 Ecological Factors Canal (16) Canal (12) Water temperature 24.2 24.4 Water level 63.5 61.2 Water turbidity Medium Medium Water speed 1.7 1

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5.1.1 Seasonal dynamics of Biomphlaria pfeifferi: Table (30) and Figure (24) verify the monthly the fluctuation of Biomphalaria pfeifferi snails monitored at canals (16) and (12) of the scheme. In the two canals, there were clear increase rates in the population of the snail that reaches its apex at May, where it suddenly declined to complete disappearance around August- September. At October, the snails' density gradually built-up to peak at May, as mentioned above. The anticipated ups and downs of the monitored snail in the two canals were highly significant, (P < 0.001).

Table (30): Monthly fluctuation of Biomphlaria pfeifferi snail collected from canals (16) and (12), New Halfa Scheme

Monitory Months Number of collected snails (Frequency - %) (2002) Canal (16) Canal (12) January 2002 96 (11.1) 72 (10.8) February 106 (12.2) 88 (10.2) March 118 (13.6) 92 (13.8) April 132 (15.3) 92 (13.8) May 184 (21.3) 162 (24.4) June 39 (4.5) 41 (6.1) July 15 (1.7) 4 (0.6) August 0.0 0.0 September 0.0 0.0 October 15 (1.7) 10 (1.5) November 45 (5.2) 35 (5.2) December 88 (10.2) 52 (7.8) Total 862 663 Statistical Significance P < 0.001 P < 0.001

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200 canal(12) 180 canal(16) 160 140 120 100 80 60 40

Number of snails Number of 20 0

y y l y y pri a er M Jul b ber A June m bruar March august t cto Januar Fe O Sep NovemberDecember

Monitory Monthes

Figure (24): Monthly fluctuation of Biomphlaria pfeifferi snail collected from canals (16) and (12), New Halfa Scheme

5.1.2 Seasonal dynamics of Cyprinus species fish: Table (31) and Figure (25) illustrate the fluctuations of Cyprinus species fish collected from canals (16) and (12). Like above, in the two canals, there were significant fluctuations of the fish that peak at May, thenafter decreases to non- existence around August. At September, the fish population gradually increased to peak at May, as mentioned above. The statistical analysis suggested that the fluctuations of the fish in the two canals were statistically significant, (P < 0.05).

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Table (31): Monthly fluctuation of Cyprinus species collected from canals (16) and (12), New Halfa Scheme

Monitory Months Number of collected snails (Frequency - %) (2002) Canal (16) Canal (12) January 2002 8 (11.7) 7 (9.7) February 5 (7.3) 8 (11.1) March 8 (11.7) 10 (13.8) April 8 (11.7) 10 (13.8 ) May 10 (147) 15 (20.8) June 3 (44) 5 (6.9) July 0.0 4 (5.5) August 0.0 0.0 September 4 (5.8) 0.0 October 5 (7.3 ) 5 (6.9) November 5(7.3) 7 (9.7) December 7 (10.2) 9 (12.5) Total 68 72 Statistical Significance P < 0.05 P < 0.05

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canal(12) 16 canal(16)

12 10

Number of Cyprinus fish 2

0 r h e er ust b April May Jun July g Marc ctober January au February O ecem Monitary Months Septmber NovembeD

Figure (25): Monthly fluctuation of Cyprinus species collected from canals (16) and (12), New Halfa Scheme

5.1.3 Seasonal dynamics of Waterbug: The fluctuations of the waterbugs that collected from canals (16) and (12) were verified in Table (32) and Figure (26). The waterbug population, in the two canals, declined gradually to undetectable level around July. Thenafter suddenly increased around October after which the insects' population decreased throughout the rest of the year. The analysis of the obtained figures pointed that that the general trends of the arthropod in the two canals were statistically significant, (P < 0.05).

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Table (32): Monthly fluctuation of waterbug collected from canals (16) and (12), New Halfa Scheme

Monitory Months Number of collected snails (Frequency - %) (2002) Canal (16) Canal (12) January 2002 9 (13.8) 8 (12.1) February 8 (12.3) 7 (10.6) March 6 (9.2) 8 (12.1) April 8 (12.3) 8 (12.1) May 4 (6.1) 4 (6.0) June 4 (6.1) 6 (9.0)

July 0.0 0.0 August 4 ( 6.1 ) 0.0 September 10 (15.3) 11 (16.1) October 10 (15.3) 6 (9.0) November 6 (9.2) 4 (6.0) December 4 (6.1) 5 (7.5) Total 65 66 Statistical Significance P < 0.05 P < 0.05

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12 canal(12) canal(16) 10

4 Number of Water-bug of Number 2

y y ril ar rch p ay ne er uar u a July b n A M Ju br M august Ja e Octo F Septmber November Monitory Months December

Figure (26): Monthly fluctuation of waterbug collected from canals (16) and (12), New Halfa Scheme

5.1.4 Seasonal dynamics of Dragonfly Nymphs: The ups and downs of the dragonfly nymph that monitored from canals (16) and (12) were shown in Table (33) and Figure (27). The frequencies of the nymphs, in the two canals, were briefly fluctuated to peak at July, after which they completely disappeared around August-September. The comparisons of the means suggested that the overall fluctuations in the two canals were of statistical significance (P < 0.05).

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Table (33): Monthly fluctuation of dragonfly nymph collected from canals (16) and (12), New Halfa Scheme

Monitory Months Number of collected snails (Frequency - %) (2002) Canal (16) Canal (12) January 2002 3 (12.0) 8 (13.5) February 3 (12.0) 6 (10.1) March 1 (4.0) 5 (8.4) April 3 (12.0) 5 (8.4) May 2 (8.0 ) 7 (3.3) June 1 (4.0) 3 (5.0)

July 6 (32.0) 10 (20.3) August 0.0 0.0 September 0.0 0.0 October 1 (4.0) 6 (10.1) November 2 (8.0) 5 (8.4) December 2 (8.0) 8 (13.5) Total 25 59 Statistical Significance P < 0.05 P < 0.05

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canal(12) 12 canal(16)

2 Number of Dragonfly-Nymph of Number

l r ry ry i ly r a pr ne ust be arch A May Ju Ju g rua M u tm embe a cember Janu Feb ep October ov e S N D Monitory Months

Figure (27): Monthly fluctuation of dragonfly nymph collected from canals (16) and (12), New Halfa Scheme

5.1.5 Seasonal dynamics of Freshwater Shrimps: Table (34) and Figure (28) show the seasonal trends of freshwater shrimps that harvested from the two canals, (16) & (12) of the scheme. Like the Biomphararia snails, the harvested numbers of the shrimps were skewed to the highest grates as well as the general fluctuations. In other words, the shrimp’s peak at May, disappeared around July-August, and then gradually flared-up. The seasonal ups and downs of the shrimps' population were ensured to be of statistical value (P < 0.05).

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Table (34): Monthly fluctuation of freshwater shrimps collected from canals (16) and (12), New Halfa Scheme

Monitory Months Number of collected snails (Frequency - %) (2002) Canal (16) Canal (12) January 2002 8 (7.4) 13 (9.2) February 12 (11.1) 11 (7.8) March 10 (9.2) 13 (9.2) April 10 (9.2) 18 (12.7) May 28 (25.9) 45 (31.8) June 4 (3.7) 6 (4.2)

July 0.0 0.0 August 0.0 0.0 September 7 (3.8) 5 (3.5) October 12 (6.6) 10 (7.0) November 7 (3.8) 7 (4.9) December 10 (9.2) 9 (6.3 Total 108 141 Statistical Significance P < 0.05 P < 0.05

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50 canal(12) canal(16) 45

10 Number water-shrimps of 5

0 r y y e y st e r er r n b Ma Jul u nua arch April Ju a bruary M aug ptmb J e Octobe Fe S Novem December Monitory Months

Figure (28): Monthly fluctuation of freshwater shrimps collected from canals (16) and (12), New Halfa Scheme

5.2 Seasonal fluctuations of some microecological factors: Tables (35 & 36) and present the seasonal ups and downs of water temperature, level, turbidity, speed as well as the percentage of the vegetation cover. Regarding the water temperature, in the two canals, it fluctuates between 15° C (January) and 28° C (May-June). Like temperature, the water level also fluctuates in the two canals: 50 cm (April-May) and 80 cm (August). It seems that the naked eye observations, without utilizing any hydrometric device, result in reporting only the medium level of water turbidity. Likewise, the water speed, although speeded during July-October, but averages around 0.5 cm/second. Regarding the vegetation cover, in the two canals, it gradually increased to peak

124 at September-October, where it declines to the lowest percentage around January- February. The different environmental factors that might affect the presence of macro-faunal forms. Biomphalaria Pfeiffer was found in large number in the canals when the water level is slow to medium flow during the hot season. Almost the large numbers of Biomphalaria snails were found in areas with vegetation cover medium densities .On the other hand, it seemed that Cyprinus, Dragonfly- Nymph, water-Bug and freshwater-Shrimps preferred shallow, low flowing water and medium vegetation cover.

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Table (35): Seasonal fluctuations of some microecological factors monitored in longitudinal surveys of canal (16), New Halfa Scheme

Months Temperature Water level Turbidity Water speed Vegetation (° C) (cm) (cm/sec) Cover (%)

Hot Season: March 25 60 Medium 0.5 35 April 26 50 Medium 0.5 35 May 28 50 Medium 0.5 35 June 28 50 Medium 0.5 40 Rainy Season: July 27 70 Medium 0.7 50 August 27 80 Medium 0.7 60 September 25 70 Medium 0.6 65 October 20 60 Medium 0.6 65 Cold Season: November 19 60 Medium 0.5 60 December 18 60 Medium 0.5 40 January 15 60 Medium 0.5 20 February 18 60 Medium 0.5 20

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Table (36): Seasonal fluctuations of some microecological factors monitored in longitudinal surveys of canal (12), New Halfa Scheme

Months Temperature Water level Turbidity Water speed Vegetation (c◦) (cm) (cm/sec) cover (%)

Hot Season: March 25 60 Medium 0.5 35 April 26 60 Medium 0.5 35 May 28 60 Medium 0.5 40 June 28 50 Medium 0.5 40 Rainy Season: July 27 70 Medium 0.7 50 August 27 80 Medium 0.7 50 September 25 70 Medium 0.6 60 October 20 60 Medium 0.6 65 Cold Season: November 19 60 Medium 0.5 50 December 18 60 Medium 0.5 40 January 15 50 Medium 0.5 30 February 18 50 Medium 0.5 20

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5.3 Water-contact observations: 5.3.1 Results: 5.3.1.1 Prevalence rates in relation to water-contact activities: It was attempted to correlate the prevalence rate of s. mansoni by 5-years age group in New Halfa villages and camps with their contact activities. The results of this observation are summarized in table (37). It is very conspicuous that the prevalence rats as well as the important and the relatively unimportant water contact activities peak in synchrony at age-class 14 - 19 years, regardless of the gender. Precisely, in the nominated age-class, the prevalence among the males was 49.8% and among the females was 30.0%, while the total water contacts 54% and 29%, respectively. Furthermore, it appears that, in both sexes, the total water contacts fluctuate in symphony with those of the prevalence rates i.e. the more water contacts the more prevalence rates.

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Table (37): Genderized frequencies and types of water-contact activates in relation to the proportion of intestinal Bilharzia by age-classes (Village (16) minor canal) Age-group Prevalence Water Contacts (Years) Gender (%) Relatively Important Total Unimportant* # • 05 - 09 M 34.2 14 15 29 F 12.5 15 - 15 • 10 -14 M 35.4 12 18 30 F 18.2 21 4 25 • 15-19 M 49.8 36 18 54 F 30.0 25 5 29 • 20-24 M 27.0 12 11 23 F 12.5 14 - 14 • 25-29 M 13.3 6 9 15 F 19.2 13 - 13 • 30-34 M 32.1 21 7 28 F 10.5 15 2 17 • 35-39 M 30.2 14 4 18 F 11.6 4 2 6 • 40-44 M 27.0 3 1 4 F 15.4 6 - 6 • 45-49 M 20.2. 1 5 6 F 20.0 - - - • ≤ 50 year M 20.5 1 6 7 F 11.2 - 4 5 Total M 50.3 119 94 213 F 30.4 112 22 134 * = Crossing canals, drinking, water collection, washing the extremities and washing clothes/utensils. # = Bathing, swimming, paddling, fishing and washing stocks.

129

Plate (6): Swimming in the canalization system as a recreational water- contact activity

130

60 Males Prevalence(%) Femals Prevalence(%) 50

10 Males & females Pravelence (%) Pravelence & females Males

0 0.5 - 9 Years 10 -14Years 15 -19Years 20 - 24Years 25 - 29Years 30 - 34Years 35 - 39Years 40 - 44Years 45 - 49Years ≥ 50 Age groups

Figure (29): Genderized frequencies and types of water-contact activates in relation to the proportion of intestinal Bilharzia by age-classes (Village (16) minor canal)

5.3.1.2Categories of water-contact activities: Table (38) and figure (30) verify the proportions of important and relatively unimportant water contacts among villagers in waterbodies around Village(16). The monitored water contact could be arranged in the following descending order: Swimming (50.0%), Bathing (25.0%), Paddling (20.0%) and Fishing (5.0%). On the other hand, the relatively unimportant water contacts could be ordered in the following descending manner: water collection (72.0%), washing clothes and utensils (13.0%), crossing waterbodies (10.0%) and washing extremities (5.0%).

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Table (38): Proportions of important and relatively unimportant water- contacts among villagers in waterbodies around Village (16), New Halfa Scheme

Category of water-contacts Percentage (%)

Important Water Contacts: • Swimming 50.0 • Bathing 25.0 • Paddling 20.0 • Fishing 05.0 • Others 0.0 Total 100.0 Unimportant Water Contacts: • Water Fetching 72.0 • Crossing Canals 10.0 • Washing Clothes & Utensils 13.0 • Washing Extremities 05.0 • Others 0.0 Total 100.0

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5.3.1.3 Interval and duration of water contacts: Table (39) and Figure (31) show the frequencies of water contacts of the villagers in waterbodies around Village (16), by interval and duration of exposure. The villagers' water-contacts commenced from early morning to reach it maximum activity at (10 - 01) PM, 54.6%, then gradually declined to complete disappearance at around sun set,( 6 – 7) PM, Sudan Standard Time Regarding the time of exposure, unfortunately, the systematic monitory ensure that the water- contacts of more than 30 minutes represent 54.3%, while those of less than 10 minutes constitute only 10%. The analysis of the obtained findings suggested conspicuous heterogeneity in both the interval and duration of the water-contacts performed by the villagers, (P < 0.05).

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Plate (7): Collecting Water from the canals

134

Important water contact activities Swimming Bathing

Paddling

Fishing

Fishing Paddling 5% 20%

Swimming 50% Bathing 25%

Fe tching Unimportant Water contact activiteis

Washing Clothes

Crossing Washing Extremities Crossing Washing 5% 15% Extremities

Washing Clothes 10% Fetching 70%

Figure (30): Proportions of important and relatively unimportant water- contacts among villagers in waterbodies around Village (16), New Halfa Scheme

135

Plate (8): Washing animals as unimportant water- contact activity

Plate (9): Contamination of water-bodies by urination

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Table (39): Frequencies of water contacts of the villagers in waterbodies around Village (16), by interval and duration of exposure

Interval and Duration Number of monitored candidates Of water contacts (Frequency %) Interval of Water Contacts: (07 - 10) AM 89 (24.0) (10 - 01) PM 182 (54.6) (01 - 03) PM 36 (10.3) (03 - 06) PM 42 (11.1) (06 - 09) PM None Total 347(100.0) Statistical Significance P < 0.05 Duration of Water Contacts: > 30 Minutes 189 (54.3) 10 - 30 Minutes 123 (35.7) < 10 Minutes 35 (10.0) Total 347 (100.0) Statistical Significance P < 0.05

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(0.7-10)AM 60 (10 - 0.1)PM 50 (0.1- 0.3)PM (0.3-0.6)PM 40

10 Frequency(%) 0 (0.7-10)AM (10 - 0.1)PM (0.1- 0.3)PM (0.3-0.6)PM Interval of water contacts

Figure (31):Frequencies of water contacts of the villagers in waterbodies around Village (16), by interval of water contact

Prevalences(%) 70 Intensity(GMEC/gm) 60

10 Pravelence intensity & (GMEC/gm) 0 >30Minutes 10- <10Minutes 30Minutes Duration of exposure

Figure (32): Frequencies of water contacts of the villagers in waterbodies around Village (16), by duration of exposure

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Discussion: In the malacological surveys, "snail as unit of study" the investigation marked the variation on distribution of the intermediate-hosts and their direct infestation in transmission patterns. Thus, the observed finding enhanced that Biomphlaria pfeifferi: is the most abundant intermediate-host of S. masoni in New halfa scheme

Monthly and wise fluctuations were observed between these macrofaunal aquatic forms in the two canals. These up and down were correlated on statistical basis to the equivalent fluctuations of monitored ecological factors e.g. water temperature, water level turbidity and speed. In addition the fluctuations of the intermediate host snails were correlated statistically to the abundant biocontrol agents.

Most voracious biocontrol agents for Biomphalaria snails observed were, the normal water dug, the cyprinus fish ,dragonfly nymph and freshwater- shrimps. All these biocontrol agents were gradually increased to the end of the canal.

In the two canals, there were clear increase rates in the population of the snail that reaches its apex at May, where it suddenly declined to complete disappearance around August-September.

At October, the snails' density gradually built-up to peak at May, as mentioned above. The anticipated ups and downs of the monitored snail in the two canals were highly significant, (P < 0.001).

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There were significant fluctuations of the fish that peak at May, thenafter decreases to non-existence around August. At September, the fish population gradually increased to peak at May, as mentioned above. The statistical analysis suggested that the fluctuations of the fish in the two canals were statistically significant, (P < 0.05).

The waterbug population, in the two canals, declined gradually to undetectable level around July, thenafter suddenly increased around October after which the insects' population decreased throughout the rest of the year.

The analysis of the obtained figures pointed that that the general trends of the arthropod in the two canals were statistically significant, (P < 0.05).

The frequencies of the Dragonfly nymphs, in the two canals, were briefly fluctuated to peak at July, after which they completely disappeared around August-September. The comparisons of the means suggested that the overall fluctuations in the two canals were of statistical significance (P < 0.05).

Like the Biomphararia snails, the shrimp’s peak at May, disappeared around July-August, and then gradually flared-up. The seasonal ups and downs of the shrimps' population were ensured to be of statistical value (P < 0.05).

The analysis suggested a high significant difference in snails between the three sites, upper, mid and down canal but there are no significant difference between the two canals. The description of the general abundance between the two canals has the same share of the monthly collection of Biomphalaria snail. Biomphalaria snails were symphonizingly fluctuating monthly

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Regarding to the Seasonal fluctuations of some microecological factors, the water temperature, in the two canals, it fluctuates between 15° C (January) and 28° C (May-June). Like temperature, the water level also fluctuates in the two canals: 50 cm (April-May) and 80 cm (August). It seems that the naked eye observations, without utilizing any hydrometric device, result in reporting only the medium level of water turbidity. Likewise, the water speed, although speeded during July- October, but averages around 0.5 cm/second. Regarding the vegetation cover, in the two canals, it gradually increased to peak at September-October, where it declines to the lowest percentage around January-February.

The different environmental factors that might affect the presence of macrofaunal forms. Biomphalaria Pfeiffer was found in large number in the canals when the water level is slow to medium flow during the hot season. Almost the large numbers of Biomphalaria snails were found in areas with vegetation cover medium densities .On the other hand, it seemed that Cyprinus, Dragonfly- Nymph, water-Bug and freshwater-Shrimps preferred shallow, low flowing water and medium vegetation cover.

The observed variation on the selected sampling sites was not significant based on the population density of the snails. It had been reported that seasonal variations in the snails' density are influenced by seasonal fluctuation factors, such as rainfall (Klumpp & Chu, 1977, O'Keefe, 1985) temperature (Demain & Kamal, 1972, Appleton, 1978), where Webbe (1964) stated that both factors act together, as well as a vegetation cover.However, the present finding suggested that the observed role of rainfall and vegetation cover were clearly observed as of influential role rapid production of snails in the study villages and camps.

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The control strategies in the past had been directed toward the molluscan host, the week link in the life parasitic cycle this based on the destruction of the snail habitats through engineering method, which are not economically feasible in many of the afflicted nations, snail control strategies have relied almost exclusively on chemical control molluscicides which are applied through various techniques to the water courses.

The biological control might be the solution after the intervention phase (Chemotherapy for patients and molluscicides for snails) to replace the indiscriminate repetition of chemotherapy or molluscicides application.

Fishes and freshwater shrimps proved to be the most efficient consumer of snail’s egg mass and neonates among the biocontrol agent while the insects (water bug & dragonfly nymph) observed to be voracious in consumption of the neonates rather than egg masses.

In the two canals the snails are abundant with a peak during March to June, while during the rainy season July-October the canals are relatively free from snails probably due to the high slit content in the water at this time. Snails typically start to appear in November.

It is very conspicuous that the prevalence rats as well as the important and the relatively unimportant water contact activities peak in synchrony at age-class 14 - 19 years, regardless of the gender. Precisely, in the nominated age-class, the prevalence among the males was 49.8% and among the females was 30.0%, while the total water contacts 54% and 29%, respectively. Furthermore, it appears that, in both sexes, the total water contacts fluctuate in symphony with those of the prevalence rates i.e. the more water contacts the more prevalence rates.

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The monitored water contact could be arranged in the following descending order: Swimming (50.0%), Bathing (25.0%), Paddling (20.0%) and Fishing (5.0%). On the other hand, the relatively unimportant water contacts could be ordered in the following descending manner: water collection (72.0%), washing clothes and utensils (13.0%), crossing waterbodies (10.0%) and washing extremities (5.0%).

The role of human water contact behavioral studies in the elucidation of the dynamic of schistosomiasis transmission are increasingly being recognized (WHO 1979). Water availability and temperature are the major factors limiting and governing the pattern of water contact (Farooq et al., 1966; Dalton & Pole 1978; Kvalsvig & Schutte 1986; Chandiwana 1987), most activities were for domestic and recreational purposes these results are in agreement with similar studies conducted in other endemic areas (Farooq et al., 1966; Farooq & Mallah 1966; Dalton & Pole 1978; Tayo et al., 1980; Kloos et al., 1983; Chandiwana 1987). Investigations of human water contact activities in natural water bodies are very crucial in determining the essential activities involved (Kloos et al., 1990, Elkholy et al., 1990 Chandiwana & Woodhouse 1991, Lima-e-costa 1991).

Most of water-contact activities performed by the villagers at the very mid-day (10 – 01) PM which represent the diurnal rhythmicity of cercariae and the most risky time for man to aquifer infection. The situation was furtherly aggravated by the fact that more than half of water contacts were of prolonged activities (> 30 minutes), and one third those of unimportant water contact like drinking and washing extremities takes about (10-30 minutes).

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CHAPTER SEVEN DICUSSION AND RECOMMENDATIONS

DISCUSSION: Many part of the world in particularly tropical and subtropical countries which implement the canalization system in irrigation schemes has the tragic side effect of introducing and aggravating schistosomiasis problems. (Greany 1952, Amin 1997, Tayo & Jewsbury 1978, Gilles et al., 1983; El Gaddal 1985)

Schistosomiasis is considering a water-borne disease in agricultural development under irrigation which acts as one of the important habitats for the spread and multiplication of snail vector of schistomiasis.thedisease is recognized as one of 10 tropical diseases of most concern to the World Health Organization (WHO, 2003). ).

In conformity of the above, agriculture sector, in Sudan, plays a pivotal role, for developmental purposes, which were facilitated by the fact that the Nile is the real asset for the country. Thus, many agricultural schemes had been constructed, where the canalization system provided the ideal microhabitats for the snails breeding, and hence dramatic propagation of schistosomiasis. Many sounding epidemiological surveys had been conducted in these agricultural schemes to assess the epidemiological status and the control trials of schistosomiasis (Ahmed, 2005).

Schistosomiasis is both preventable and curable, but unfortunately, it remains a serious public health problem in the endemic countries. Poverty and scarce financial resources go hand in hand with this chronic disease. Endemicity of schistomiasis in any specific area results from the presence of an infected population interacting with water site containing potential snail vector.

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Ecological factors may produce changes in the prevalence, intensity of infection and in morbidity in endemic communities. The contamination of the environment with faecal excrete, the absence of health-education programs, the problem of safe water supply and basic sanitation, the lack of focal snail control, chemotherapy and trained persons due to poor resources, all these factor which contribute to transmission integrated approach was-associated disease are debilitating and seriously reduce the productivity of labourers in poor countries (El Tash 2002 & 2005).

A real and meaningful epidemiological survey (parasitological, malacological and socioeconomical) was crucially needed in New halfa scheme to answer some paramount questions pertaining the whole situation of schistosomiasis.

The study was conducted to confirm of some factors influencing microepidemiological pattern of schistosomaiasis related to the KAP of people and to justified on basis of socioeconomical component and the population’s way of life were strongly linked with the infection parameters e.g. age, sex, occupation, educational level and ethnic group to improve the correlation to prevalence and intensity of infection. Further more, the role of health education and community participation which is important in reduction of infection parameters of schistomiasis.

In addition to human water contact activities to identify which activity is more exposed to infection of schistosomiasis. Laboratory experiments were designed to elucidate the diurnal rythmicity of cercariae and the most risky time for man to require infection. Furthermore, monthly-based malacological surveys were conducted for one- year, with especial emphasis on the snail’s fluctuations, infections and microecological factors influencing sustainability of the intermediate-hosts.

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The successful approach of the targeted community was reflecting the high response rate 100% of the villagers as well as the school children in the two surveys. The finding results reassured that the situation of intestinal schistosomiasis was miserable and desolated, where the overall prevalence of infection among the villager was 41.8% while the intensity was 82.2 epg .On the other side the prevalence rate among the school-children was 54.6% and the intensity was 80.6 (epg), respectively. The results indicated that New Halfa scheme as endemic area was composed of a collection of micro-foci, each with its own specific characteristics. The prevalence rates among the residents of Gamhoria and Masna camps were very high and almost equi-distributed, 59.2% and 55.8%, respectively.

Likewise, the infection rates of the villagers from Village (12) and (16) were moderate and also equi-distributed, 29.8% and 30%, respectively. The statistical analysis suggested that the variations in the infection rates of the four residential sites were of significant level, (P < 0.05).

Considering the worm burden, expressed in eggs excreted, the surveyed residential sites could be arranged in the following descending manner: El Masna (109.1), Village 16 (86.8), Village 12 (85.9) and El Gamhoria (56.2) epg. The deep analysis via Scheffe test suggested that the significant variations in intensity of infection were attributed to El Masna camp, (P < 0.05).

Considerable national surveys attempted to link the age-groups to the two infection parameters (Hilali, 1982; Ahmed, 1998; Ahmed et al., 2002; El Tash, 2000). This link was reported in other affected endemic areas (Bukenya & Andama, 1986; Chandiwana et al., 1988; Teklehaimanot & Fletcher, 1990). There was an ideal symphony in the ups-and-downs pattern of the two infection parameters by age-classes. Ideally, the two infection parameters.

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The prevalence rates gradually increased to peak (57.4%) at the age-group (15- 19) years, then also gradually declined and remained almost high throughout the age-classes of the young adults, (25 – 44) years. Again the infection pattern was further declined throughout the rest of the age-groups.

The statistical analysis of the infection rates suggested a significant variation among the categorized age-classes, of the villagers (P < 0.05). The findings suggested typical graphical fluctuations, where both infection parameters significantly postured at the mid-aged school children, 10 - 14 years, (P < 0.05). Almost the same trends were observed concerning the worm burden, expressed in the secreted eggs, with only one crucial observation, three peaks. The first peak was observed in the age-class (10 - 19 years), the second one was among the age- group (30 - 39 years), while the third was monitored among the age-class (55 - 59 years). Like above, the statistical differences of the eggs excreted was judged to be of significant value, (P < 0.05).

The monitored significant decline in the prevalence and intensity of infection with increasing age might be due to the combined effect of a build-up of the acquired immunity with age and the decline of important water-contacts activities. The study findings support the results obtained from Egypt (Abd el Wahab et al., 1980); Tanzania (McCullough & Magendantz, 1974), Burundi (Gryseels & Nkulikyinka, 1988).

Concerning the prevalence and intensity of S. mansoni infection, the genderized links was investigated in many parts of the country as well as in other endemic countries. In the first survey, the males significantly outnumbered the females, 45.6%, 86.9 epg and 30.4%, 42.1epg respectively, (P < 0.05). In conjunction with the above, the finding of the overall infection rate and intensity in the second survey ensured a significant proportionate of the infection

147 among the males compared to the females, 43.7%, 20.8epg, and 27.0%, 20.0epg respectively, (P < 0.05), this is mainly due to their activities, males being more exposed to highly infested cercariae during swimming, bathing and irrigating field in many communities. g.in Ghana (Klumpp&Webbe,1987), in Egypt(king et al.,1982)in Nigeria(Pugh& Gilles,1978) and (Hilali,1992;Ahmed,1998,2000,2002,2004;El Tash,2000&2005) in Sudan.

In El Rahad Scheme, Hilali (1992) and in Jebel Mara, Zakaria (2002), observed no significant differences in sex-specific prevalence and intensity of Bilharzia infection. Women in New Halfa community did not expose to important water contact activities.

An array of national epidemiological findings illustrated significant variations in the overall prevalence of infection related to different occupational categories. Higher prevalence rate were detected among water-related jobs than among other occupation in Gunied Sugar cane Scheme, as reported by Ahmed (1988); Ahmed et al (2002) and El Tash (2000). In this study the analysis of the prevalence and intensity of S.mansoni infection by occupation reported that farmers (65%), labourers (53.8%), and students (50%) were the high infected occupants. The statistical analysis of the findings suggested a significant variation among the villagers, based on their occupation, (P < 0.05). These finding would be manipulated within the frame of water- contact activities of the different occupants.

The findings highlighted that the educational level had no effects on the two infection parameters, although they slightly inversed the educational level.

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The study pointed out that the personal hygiene is low in the investigated communities, which well reflected in the considerable infection rate of s. mansoni.Low standards of personal hygiene are reflect in low standards of public hygiene, and efforts to raise the latter will have little effect if the former remain low.

S.mansoni. infection in New Halfa scheme are highly significant among villagers with no access to water supply were 80%, and 57.3% of them were infected with a high worm burden of 85.5 epg. On the other hand, the 20% of the villagers access to clean water, where 30.6% were infected with intensity of 70.6 epg.

Three-quarters (76.6%) of the surveyed villagers had no access to excreta disposal system. It seems that the access to latrine had no influential effects on the infection parameters since the two measures were almost similar, (59.5% & 56.6% respectively). In addition to the other socio-economic factors such as access to electricity, number of rooms type of building and ethnicity.

The differences between the ethnic group in village and camps are more probably due to the inferior socio-economic status than ethnicity.

General speaking, it seem that the awareness level of both the disease and its snails had an inverse relation to the infection rates. It worse to mention that the villagers who know much about Bilharzia and its snails were found free from the infection, although very few. The variation of the prevalence rates among the different categories, based on Bilharzia awareness, was found to be statistical significant, (P < 0.05). On the other hand, the intensity of infection has no fixed pattern to the awareness level of the villagers to the intermediate hosts.

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More than three-fifth (61.1%) of the villagers used to contact surrounding contaminated waterbodies, where 37.2% of them were infected with high egg- counts, 83.2 epg.

More than one-quarter of the villagers (29.3%) reported that "rarely" they contact the waterbodies, where 24.5% of them were infected with high egg- counts, 72.3%. Although 10.6% of the villagers reported that they "never" had any water-contact activities, but still of 10.5% of them were infected, with 54.2 epg. The statistical analysis of the infection rates and the worm burden, based on the villagers' water contacts, were found significant, (P < 0.05).

It seems that only the occupation and swimming were the most crucial water contact activities influencing the infection pressure. Being an agricultural area 80% of the villagers had the occupational water contacts, for watering their farms, where 36.3% of them were infected with high egg-counts, 63.4 epg. Although swimming as a water-contact activity practiced only by 10%, where 16.7% were significantly suffering the infection, 109.6 epg. Furthermore, usually during swimming and bathing the candidates automatically urinate, hence leading to contamination of waterbody with Bilharzia eggs. Based on the categories of water-contacts, the variation of the prevalence and intensity were ensured to be of significant score, (P < 0.05)

The survey ensures that 39.2% of the infected villagers were lightly infected with an average of intensity of 54.3 eggs per gram. The survey classified 12.0% of the infected villagers as bee moderately infected with an average of worm burden of 159.5 eggs per gram. On the extreme, 0.4%, of the villagers were suffering the highest intensity of worm burden, 580.2 eggs per gram. The analysis of the findings pointed that the level of infection among the villagers varied significantly, (P < 0.05).

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The health education element is very important in the implementation of control, for both men and women because women have the responsibility for the health in the homes. The process of acquiring better habits can be speeded up utilization of religious messages in mosque and by the education of children in particular. It is essential to prevent the villagers and schoolchildren not to defecate or urinate near water course or canals, because this plays an influential role in the transmission of schistosomiasis.

Health education for children must include high rate of egg elimination and high level of re-infection, as reported by Ahmed (1998 & 2004). VDU films or even colored posters showing how the transmission takes place are more illuminating than task on the radio. Members of health committee e.g. social and political, and religious leaders, in addition to school staff members should actively participated in the process of health education and community participation.

The community participation is very important in any control programme. The community realizes the health problems in the area; it could contribute greatly to the control efforts through self-reliance projects. The community participation help the villagers to help themselves in raising standards of living, participated in control activities, protection water bodies and construction of latrines.

Cooperation of the villagers in the "self-help scheme" would encourage them to nominate the influential people to lead the community for adopting fruitful entry- points and explaining objectives and methodologies.

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The intervention reduced the overall infection parameters among the villagers, due to interventional programme, was 62.2%. In fact, the reductions among the males and the female were almost equi-distributed, 65.4% and 60.2%, respectively. While the overall knockdown of infection among the school children was 76.3%.

Considering the gender reduction, the infection rates of the males declined by 78.1% while those of the females reduced by 65.6%. It seems that the reduction of the infection level among both villagers and the school children was directly proportional to the number of the infected candidates.

Biomphalaria snails were symphonizingly fluctuating monthly. In the two canals, there were clear increase rates in the population of the snail that reaches its apex at May, where it suddenly declined to complete disappearance around August-September. At October, the snails' density gradually built-up to peak at May, as mentioned above. The anticipated ups and downs of the monitored snail in the two canals were highly significant, (P < 0.001).

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There were significant fluctuations of the fish that peak at May, thenafter decreases to non-existence around August. The waterbug population, in the two canals, declined gradually to undetectable level around July, thenafter suddenly increased around October.

The frequencies of the Dragon- fly nymph, in the two canals, were briefly fluctuated to peak at July, after which they completely disappeared around August-September. The shrimp’s peak at May, disappeared around July-August, and then gradually flared-up. The seasonal ups and downs of these biocontrol agents were ensured to be of statistical significance value (P < 0.05).

Regarding the water temperature, in the two canals, it fluctuates between 15° C (January) and 28° C (May-June). The water level also fluctuates in the two canals: 50 cm (April-May) and 80 cm (August). It seems that the naked eye observations, without utilizing any hydrometric device, result in reporting only the medium level of water turbidity.

Likewise, the water speed, although speeded during July-October, but averages around 0.5 cm/second. Regarding the vegetation cover, in the two canals, it gradually increased to peak at September-October, where it declines to the lowest percentage around January-February.

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Recommendations: The aim of Bilharzia control programmes is to knock-down the overall disease parameters and subsequently morbidity, to levels where the disease is no longer considered to be of public health problem.

The transmission pressured schistomiasis in endemic are seriously affected by different determinant factors hence the disease is patchily distributed in location among people such patching mapping was attributed in location among people such patchily distributed to different factors, including the limited size of transmission sites as reported by Scott et al., (1982) Chandiwana et al., (1988) and Hilali (1992).

The habitat proximity to human settlements Tekelhaimanot and Fletcher (1990), the habitat geology and climatic conditions, Christensen et al., (1993) Wilkins (1984) Bukenya and Andama (1986) Cheever et al., 1988 a & b) the role of human activity, Polderman (1979); Polderman et al., (1985) and Costa et al., (1987).

No single control method is likely to break the transmission of these parasites; an integrated approach should be considered an attempt to control schistomiasis. First: Chemotherapy, the mass treatment of all the inhabitant in villages and camps, this strategy must be implemented also at the school age children since

155 the prevalencdecrease. Second: The provision of e\water supply and basic sanitation will help to reduce the contamination of canals with excreta infected with egg of schistosomiasis and reduces human water contact. Third: Snail control declines the possibility of transmission and therefore improve the safety of human water-contact, via chemical application method or by biological control e.g. biocontrol agents of the snails as well as molluscicides of plant origin, like the Neem and Hegleig. Forth: The community participation and health education are very important in any control programme, first to realize the health problem in the area, how, when and why this disease transmitted the community scheduled programme in control measures and curing people and helping them to help themselves. Fifth: The usage of the modified Kato technique is highly advocated in both public and private medical laboratories than any other technique for faecal analysis. Sixth: In the national plan the federal ministry of Health, it is apparent that there is more stress on curative medicine than on prevent one. This situation is unfortunate and is one of the main reasons why the condition of health in the country are unsatisfactory more attention should be paid to the improvement of the environmental sanitation and epidemiological studies.

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