Freshwater Snails Identification, Distribution, their Infection with Cercariae and the Influence of the Associated Factors in Sememo Locality, Adi Quala Sub Zone, Debub Region, State of Eritrea (2018) Asmerom ZerisenayGebrezgabherTeweldemedhn B.Sc (Honours) of Science in Public Health, Asmara College of Health Sciences (June 2015) A Dissertation Submitted to the University of Gezira in Partial Fulfillment of the Requirements for the Degree of Master of Science in Medical Entomology and Vector Control Blue Nile National Institute for Communicable Diseases University of Gezira August,2018 1 Freshwater Snails Identification, Distribution, their Infection with Cercariae and the Influence of the Associated Factors in Sememo Locality, Adi Quala Sub Zone, Debub Region, State of Eritrea (2018) Asmerom Zerisenay Gebrezgabher Teweldemedhn Supervision Committee: Name Position Signature Prof. Bakri Yousif Mohamed Nour Main Supervisor ----------------------- Dr. Lana Mohmmed Elamin Co-supervisor ------------------------- Date: August, 2018 2 Freshwater Snails Identification, Distribution, their Infection with Cercariae and the Influence of the Associated Factors in Sememo Locality, Adi Quala Sub Zone, Debub Region, State of Eritrea (2018) Asmerom Zerisenay Gebrezgabher Teweldemedhin Examination Committee: Name Position Signature Prof. Bari Yousif Mohamed Nour Chairperson ------------------- Dr.Usama Abdalla Elsharief Ibrahim External Examiner -------------------- Dr.Albadwi Abdelbagi Talha Internal Examiner ---------------------- Date of Examination: 12 / 8 /2018 3 DEDICATION I have dedicated this dissertation paper; To my families, parents, wife, kids & friends To everyone who motivated and supported me To everyone who was there when I was in need To everyone who supported, helped and stood beside me To all of you, my immense appreciation 4 ACKNOWLEDGMENT I would like to express my deep gratitude to my main supervisor Dr. Bakri nour and Co-supervisor Dr. Lana Mohmmed Elamin for their valuable advices and comments throughout this study. My immense gratitude is also due to my lovely families, parents, friends and specially to my lovely wife, miss Saron Teklebrhan, for her continuous & endless motivation during conducting of this dissertation paper. I would like to thank all the Blue Nile Institute staff especially the Laboratory head staz Arwa Osman for her continuous comments and corrections. My thanks due to Mr.Eyasu Habte for his great contribution in statistical analysis and Dr. Araya Birhane; director of communicable diseases in the ministry of health, Dr. Eyob Azeria; head of department of Public health, for their valuable comments & corrections and sustainable motivation & guidance. I would also like to thank to the ministry of health, South region branch, for their transportation, financial and material support during the data collection period of the study and for all the regional entomology staff for their great commitment in data collection & all the Laboratory works. At last I want to thank, to everyone I might forgot who helped me and encouraged me, to all of you, I extend my deep gratitude. 5 Freshwater Snails Identification, Distribution, their Infection with Cercariae and the Influence of the Associated Factors in Sememo Locality, Adi Quala Sub Zone, Debub Region, State of Eritrea (2018) Asmerom Zerisenay Gebrezgabher Teweldemedhin Abstract Fresh water snails are well-known intermediate hosts for the transmission of different types of Vector borne diseases. They harbor and transmit various types of trematode worms causing illness for mammals either man or animal, such as schistosomiasis, fascioliasis, paragonimiasis and clonorchiasis. Across sectional study was conducted in Sememo canal (Jan- June 2018) to explore the present snail species and their relation with trematode infection, with observation on environmental factors affecting them. Three surveys at different environmental conditions were conducted, first in January, the second in March and the third in June. A total of 4721 freshwater snails were collected from the study site with overall species prevalence Bulinus trancatus 80 (1.7%), Biomphalaria pfeifferi 3116 (66%) and Lymnaea natalensis 1524 (32.3%). The overall density in the three surveys was (9%), (59%), and (32%) respectively. Snails were screened for trematode cercariae under artificial light; two species were shed different trematode cercariae with infection rate in the three surveys 0 (0%), 43.77%, and 63.56% respectively. Three cercariae morphotypes were shed; Longi-furcate apharengeate monostome cercaria (LPM), undescribed furcocercous type-3 and virgulate xiphidio cercariae. A list of recommendations were made, since the planning of snail control reassures and evaluate their impact, knowledge of their ecology, population trends and dynamism are essential requirement towards understanding disease transmission and control 6 التوزيع والعوامل المؤثرة ﻷنواع القواقع الحلزونية في المياه العذبة وتحديد مدى إصابتها بالسركاريا في محلية سيميو،بمنطقة ديبوب،إريتريا)2018( أسميروم زريساني جيبريزجابهر ملخص الدراسة 7 Table of Contents Content Pap Dedication………………………………………………………………………………… e iV Acknowledgement ………………….…..……….………………………….. …………… V Abstract (English) ………………………………………………………………………. Vi Abstract (Arabic)…………...……………………………………………………………. Vii Table of content…………..……….……………………………………………………… Viii List of tables………………..………….……………………………… X List of figures ……………………....………………………………......... Xi List of plates………………………………………………………………… Xii List of appendices……………………………….…………………………… Xiii Abbrevations………………………………………………………………… Xiv … CHAPTER - ONE .............................................................................................................................1 INTRODUCTION .............................................................................................................................1 1.1 BACK GROUND ........................... ………………………………………………………….1 1.2 PROBLEM/TOPIC IDENTIFICATION:…………………………………………… ............3 1.2.1 Justification of the study………………………………………………………… ...........3 1.2.2 Justification of the area……………………………………… .........................................3 1.3 RESEARCH OBJECTIVES; ................... ……………………………………………………4 1.3.1 General Objective ........................ ……………………………………………………4 1.3.2 Specific Objectives: ……………………………………………………………. 4 CHAPTER –TWO……………………………………………………………………… 5 8 LITRATURE REVIEW……………………………………………………………….......... 5 2.1 Global Distribution of scistosomiasis………. ............... ……………………………………..5 2.2 Regional distribution of schistosomiasis; ............................ …………………………………6 2.3 Situation of schistosomiasisin Eritrea ..................... ………………………………………….7 2.4 Major forms and distribution of schistosomes..................... …………………………………9 2.5 Fresh water snails……………………………………………………………………............ 11 2.6 Some Common Fresh water snail species ......................... …………………………………..14 2.7 Snails Vector Population and Infection Studies .......................... ……………………………16 2.8 Environmental factors affecting snails' population: ....................... ………………………….21 2.9 Snail control measures ............... ……………………………………………………………..25 CHAPTER –THREE……………………………………………………………………............. 29 RESEARCH METHODS AND MATERIALS USED………………………………………… 29 3.1: Study Area: ........................ ………………………………………………………………….29 3.2 Study Population:.................... ……………………………………………………………….31 3.3StudyDesign:....................... …………………………………………………………………..31 3.4 Malacological Survey ................. …………………………………………………………….32 3.5 Laboratory work:…………………………………………………………………............ 35 3.6 Data Analysis .............. ……………………………………………………………………….36 CHAPTER-FOUR……………………………………………………………………............... 37 RESULTS AND DISCUSSION……………………………………………………………….. 37 4.1 RESULTS………………………………………………………………………………....... 37 4.1.1; Identification of Snails species ... ………………………………………………………….37 4.1.2; Prevalence Rate in all the Surveys ..................... ………………………………………….37 4.1.3; Snails and their Infectivity Rate .......................... …………………………………………42 4.1.4; Descriptive of environmental factors affecting snails’ population ............................... 51 4.2 DISCUSSION………………………………………………………………………………. 62 CHAPTER-FIVE……………………………………………………………………………….. 68 9 CONCLUSION AND RECOMMENDATION………………………………………………… 68 5.1 CONCLUSION................ ……………………………………………………………………68 5.2 RECOMMENDATION ........................... ……………………………………………………69 REFFERENCE .............................................................................. Error! Bookmark not defined.70 ANEXES ....................................................................................... Error! Bookmark not defined.84 APPENDICES……………………………………………………………………………. 88 LIST OF TABLES Table number and type Page number Table4.1: Snails collected and examined at Sememo locality, Eritrea, Janurary-June 40 2018. Table 4.2: Species examined, infected and their infectivity rate during the three 46 surveys, at Sememo locality, Eritrea, Janurary-May 2018. Table 4.3: Comparison of infectivity rate of the different species within the same 47 surveyduring the study period Table4.4: Comparison of infectivity rate of the same species between the three 48 surveys during the study period Table4.5: Types of Cercariae found; human and non-human cercariae,in Sememo 49 canal during the study period Table4.6; Comparison on number of the different Species within the same 51 Surveyduring the study period Table 4.7: Potential of environmental