THE STUDY OF FACTORS CONTRIBUTING TO MALARIA OCCURRENCE IN SRI TOY SUB-DISTRICT: CASE STUDIES OF MALARIA PATIENTS

Thanatcha Thaithanasarn1*, Siriporn Chuathao1, Phuriphat Teeralux2, Taksin Tinmeung3 and Amornrat Anuwatnonthakate1,4

1 Public Health, School of Health Science, Mae Fah Luang University, Chiang Rai, Thailand 2 Mae Suai Public Health Office, Chiang Rai, Thailand 3 Sri Toy Health Promoting Hospital, Chiang Rai, Thailand 4Center of Excellence for the Hill tribe Health Research, Mae Fah Luang University, Chiang Rai, Thailand *e-mail : [email protected]

______Abstract Background: Malaria is major public health problem in tropical and subtropical areas of the world. In Thailand, malaria remains high prevalence in the forest areas along the mountainous border. This qualitative study aimed to examine how the factors contributing to an occurrence of malaria in Sri Toy sub-district, Mea Suai district, Chiang Rai province.

Methods: A qualitative method including in-depth interviews and focus group discussion technique was conducted. Ten participants were recruited from propulsive sampling. Data were obtained from non-participant observation and medical record. Semi-structure questions guideline adopted from Office of Disease Prevention and Control 7, UbonRatchathani were used for collecting data.. The data was verify by the triangulation method and interpretation by the content analysis.

Results: The malaria patients were Thai male and Muser, 83.4% were aged 15-44 years old, and all were agriculturist. They had basic knowledge about malaria and experience with malaria influence on their malaria preventive behavior. Moreover, most of them had self- medication before seek medical treatment. The majority of patient living in three villages including Ayiko, Mai Mae Yang Min, and Phaya Kong Dee. In three villages which ongoing of malaria transmission located near the forest and small stream which were ideal for malaria vectors and malaria transmission. The structure of dwelling in the villages has been influenced from culture and economic reason.

Conclusion: The factors contributing to malaria occurrence in Sri Toy sub-district are villages located near forest and small stream, uncontrolled migration of students from border area of Thai-Myanmar. ______Keywords : malaria, factors

Rational and Background Malaria is a life-threatening disease and remains a major public health problem in many tropical and subtropical areas of the world. Malaria caused by parasites belonging to the genus Plasmodium. The four human Plasmodium species transmitted from person to person are Plasmodium falciparum, P. vivax, P. ovaleand P. malariae, of which P. falciparum and P. vivax are the most prevalent and P. falciparum the most dangerous. In addition, human infections with the simian malaria parasite P. knowlesi are being reported from the forested

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regions South-East Asia [1-3]. The parasites are spread to people through the bites of infected female Anopheles mosquitoes, called "malaria vectors" which bite mainly between dusk and dawn [4-5]. There is available treatment for malaria and artemisinin-based combination therapy (ACT) is the best available treatment for malaria, particularly for P. falciparum malaria. Early diagnosis and treatment of malaria can prevents deaths and reduces disease because it also contributes to reducing malaria transmission. In 2014, global financing for malaria control increased from an estimated US$ 960 million in 2005 to US$ 2.5 billion because of vector control is the main way to prevent and reduce malaria transmission. Two forms of vector control are insecticide-treated mosquito nets (ITNs) and indoor residual spraying (IRF). If coverage of vector control interventions within a specific area is high enough, then a measure of protection will be conferred across the community [1][3]. However, appropriate infrastructure and community participation were required to reduce the burden of malaria [6]. Despite being preventable and treatable, malaria continues to have a devastating impact on people’s health and livelihoods around the world. Young children under the age of 5 years old, pregnant women, refugees, non-immune travelers from malaria-free areas are particularly vulnerable to the disease when they become infected. According to the latest available data, about 3.2 billion people were at risk of the disease in 97 countries, territories and areas in 2015, and an estimated 214 million cases of malaria occurred worldwide (range: 149 million–303 million) leading to 438,000 malaria deaths (range: 263,000–635,000) Most cases and deaths in 2015 are estimated to have occurred in the WHO African Region, followed by the WHO South-East Asia Region [7][1][3]. In 2011, 2.1 million confirmed malaria cases and 1819 malaria deaths were reported in the WHO South-East Asia Region reported in the Region [8]. Malaria is still one of the important infectious disease in Thailand, despite decades of successful control programs and dramatic reductions in morbidity and mortality. In 2015, 15,446 malaria cases were reported. One third of cases were foreign national (24.65%) and more than half were Thais (75.35%). The number of patients are lower than the same period of recent year about 50.37% [9-10]. However, malaria remains high prevalence in local clusters, and the forest areas along the mountainous border are the places most affected due to logging, agriculture, road construction and other economic activities along Thailand’s border areas attract people especially hilltribes and migrant workers [11-14]. In Chiang Rai province, 164 malaria cases were reported in surveillance system in 2015. There have many hilltribes and migrant workers, moreover, many areas in Chiang Rai were classified intomalarial transmission area. Sritoy sub-district, Mae Suai district was one of malaria endemic area and classify as the periodic transmission area (A2) [15]. Despite the malaria control program including insecticide-treated nets (ITNs) and indoor residual spraying (IRS) was attempt to reduce and control malaria transmission in this area, malaria cases were reported continuous every years. In 2015, all of malaria cases in Sri Toy sub-district were hilltribes and the morbidity rate was 1.1 per 1,000 population [16]. Nevertheless, the morbidity rate remain higher than the expectation of national malaria control and elimination strategy of Thailand (2011-2016) which Annual Parasite Incidence (API) per 1000 mid‐year population among Thai andnon Thai M1 migrants should reduce to 0.2 per 1000 population by the year 2016 [17]. In spite of many research has studies about the associated factors of malaria, however, no study had been conducting to describes the underlying factors of malaria occurrence in Sri Toy sub- district. In order to understand the underlying reasons for occurrence of malaria in Sri Toy sub- district, the aim of this study were to examine how the factors contributing to an occurrence of malaria in Sri Toy sub-district. We used a qualitative study for describes the underlying

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factors for occurrence of malaria. The benefit of this study could help to design the appropriate malaria control program in Sri Toy sub-district.

Materials and methods Study design and population Aqualitative method including in-depth interviews and focus group discussion technique was conducted in Sri Toy sub-district, Mae Suai district, Chiang Rai, Thailand.Purposive sampling was used to select the subjects and 10 participants were recruited. Inclusion criteria were malaria patients age 15 and above which reported in surveillance system in Sri Toy sub-district during 1 January to 31 December 2015, representative of malaria patient in household present with more than three cases in the past 5 years during 2011 to 2015, recurrent malaria patient age 15 and above in the past 5 years during 2011 to 2015 and related people who responsibility with malaria in Sri Toy sub- district including health worker and malaria village health volunteers.

Data collection Data wereobtained from In-depth interviews eight persons, focus group discussion 3 persons, non-participant observation and medical record. Interview was conducted only after the inform consent was obtained from participants. The instruments used in this study were tape recorder, field note and semi-structure questions guideline. Semi-structure questions guidelinewas adopted from Office of Disease Prevention and Control Region 7, UbonRatchathani, Ministry of Public Health. The guideline compose of open-end questions for 3 specific groups in the study.The first is the semi-structured questions guideline for malaria patients contained questions aboutgeneral information of patients (age, gender, marital status, educational level, religious, history of malaria treatment), socioeconomic, culture, knowledge attitude and behavior related to malaria.The second is the semi-structured questions guideline for health worker contained questions aboutactivities related to malaria, malaria control and prevention program, and factors related to malaria occurrence.The third is the semi-structured questions guideline for malaria village volunteer contained questions about knowledge toward malaria, responsibility, and factors related to malaria occurrence.

Data analysis Methodological triangulation was used to cross verification of data. Content analysis was used to analyses and categorize the data for describe how the factors contributing to an occurrence of malaria in Sri Toy sub-district.

Ethical consideration This study was approved by school of Health Science research committee, Mae Fah Luang University, Thailand (Approval No. 3/2558).

Results Participant characteristics The ratio of male to female of participants are approximately 9:1 and belong to the Muser (80%), Akha (10%) ethnic groups and Thai (10%), respectively. Malaria patients in this study were Thai male and hill tribes, most of them being Muser (83.3%) and Akha (17.7%). The majority of patients were aged 15-44 years (83.4%). The educational level were uneducated (33.3%), primary education (33.3%) and secondary

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education (33.3%). The religious was Buddhist (50%) and Christian (50%). The majority of patient is living in Ayiko village (50.0), Mai Mae Yang Min village (33.3%), and Phaya Kong Dee village (16.7%), respectively. Family size was less than or equal to 4 persons (66.7%) and more than 4 persons (33.3%) (Table 1).

Table 1 Participant characteristics

Participant characteristics Number Percentage

Key informants(n=10) Malaria village volunteer 3 30 Public Health Officer 1 10 People who have experience with malaria 6 60 People who have experience with malaria (n=6) Sex Male 6 100 Female 0 0 Nationality Thai 6 100 Ethnic groups Muser 5 83.3 Akha 1 17.7 Age (years) 15-44 5 83.4 ≥ 45 1 16.6 Education level Uneducated 2 33.3 Primary school 2 33.3 Secondary school 2 33.3 Religion Buddhist 3 50.0 Christian 3 50.0 Marital status Single 2 33.3 Marriage 4 66.7 Villages which ongoing of malaria transmission Moo.6 Paya Kong Dee 1 16.7 Moo.9 Ayiko 3 50.0 Moo.11 Mai Mae Yang Min 2 33.3 Family size (number of family member) ≤ 4 4 66.7 > 4 2 33.3

Most of malaria patients seek treatment at Mae Suai hospital, only one seek treatment at Malaria clinic at Mea Phrik sub-district because they worried about working time that lose if they admitted to the hospital and they know about their symptoms are likely to be malaria because of experience to see other people in their village with malaria. Most of them were self-medication to relief their symptoms including fever, chill and myalgia before going to seek treatment. The patient infected with Plasmodium vivax (83.3%) and mixed infection of Plasmodium vivax and Plasmodium falciparum (17.7%). Moreover, most of them have the

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history of family member having malaria and forest stay or working near forest prior being sick.

The biophysical environment

Figure2settlement patternin villages Figure1 small stream in villages

Figure3dwelling in the villages

Three villages which ongoing of malaria transmission in Sri-Toy sub-district including Phaya Kong Dee village, Ayiko village and Mai Mae Yang Min village were far from Mae Suai district around 20, 17 and 22 kilometers, respectively. These villages located near the forest and small stream with slow moving water. Moreover, they have many area of deforestation for agricultural propose, average temperature about eighteen to thirty-four degree Celsius and have rainfall during the rainy season. These foregoing conditions are favorable breeding condition for Anopheles mosquitoes which are forest inhabiting mosquitoes. Dwellings in the villages are dispersed settlement pattern. Most of houses built with walls of bamboo or wooden planks without the window. Housing types are related to hilltribes culture and economic reason because it easy to movement to new arable land for farming. All of malaria patients in this study living in permanent houses divided into one-story houses and stilt houses with shady space under the house for storage and animal husbandry such as chickens, pigs and dogs. Their house built with bamboo walls, wooden plank and brick were 50.0, 33.0 and 17.7 percentages, respectively. House thatch with concrete roof tile andtin roof 67.7 and 33.3 percentages, respectively (Table 2).This type of house cannot prevent mosquitoes into their house because of many small spaces around the house. This biophysical environment

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allows mosquitoes circulate freely and facilitate expose of people to Anopheles mosquitoes on daily basis.

Table 2 Environmental characteristics Environment Number Percentage Villages which ongoing of malaria transmission in 2015 (n=12) Yes 3 25.0 No 9 75.0 Environment of villages which ongoing of malaria transmission (n=3) Settlement pattern Disperse 3 100.0 Housing condition of malaria patients (n=6) Types of house Permanent 6 100.0 Housing condition One-story houses 3 50.0 Stilt houses 3 50.0 Types of roof Tile 4 67.7 Tin 2 33.3 Types of wall Brick 1 17.7 Wooden plant 3 50.0 Bamboos 2 33.3 Bedroom(rooms) 1 3 50.0 2 3 50.0 Windows(pane) 0 5 83.3 4 1 16.7

Socioeconomic In this villages, men responsible for heavy work such as slashing and burning and women are responsible for household chores, child care, feeding the pigs, weeding, and harvesting because of gender role in their hilltribes culture which more respect to women. In three villages, main occupation of people is agriculturalist, especially, rice cultivation, corn, longan tree andrubber tree. Most of this occupation earn yearly income which not enough forexpenses because they necessary to save some of income for invest in the next year. This economic reason force them to search other jobs for earn extra money. For example, daily hiring in other area and wild food selling due to their forest related lifestyle which is not only people in this village, it also attractive people from other area into the forest in the village. In addition to migration for work, this area also have children from other area including border area between Thai-Myanmar come to study at WiangPhaWittaya school because this school is boarding school with no charge of tuition and other expense. During their return home at the end of semester, some of them got malaria infection from their hometown and come to school again at first semester which leading to cause malaria problem in Sri Toy sub-district. In 2010, malaria epidemic was occurred in Phaya Kong Dee village, Ayiko village with more

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than one hundred cases cause by children infected with malaria from border area during return home come into these villages. Moreover, there have closer relationship between neighbors and their relatives. At dusk time of day, they have gathered at their outdoor meeting place which increase risk to contact with Anopheles mosquitoes.

Knowledge, attitude and behavior related to malaria Knowledge about malaria of malaria patients in this study in overview found that the patient know that malaria transmitted by mosquitoes feeding at night time, however, they cannot identify types of mosquito. Only one of malaria patient can told that malaria transmitted by bitten of Anopheles mosquitoes and other one told that malaria transmitted by bitten ofAedes mosquitoes. Malaria is characterized by fever with chill in short duration every day at the same time, myalgia and can curable with specific medicine. If not promptly treated, they thought malaria infection can become death. Moreover, they know that use of bed net, insect repellent and wear protective cloths can prevent mosquitoes bite. Although, they know how to protect themselves from malaria infection, have positive attitude toward malaria prevention and have willingness to participate in malaria prevention and control program but they think that it is responsibility of health promoting hospital to provide protective resources for malaria such as bed nets. Behavior related to malaria among malaria patients found that most of them having activity related to the forest which increased risk of malaria infection. However, after have experience with malaria most of them sleep under bed net, one of them do not because they complain aboutuncomfortableand difficult to breathing but he was volunteered to be the indoor residual spraying personnel. All of them use insect repellant and making fire at night to scavenge the mosquitoes. If staying overnight in forests, they usually wear protective cloths and use insect repellant both of chemical and traditional, that is, water soak with lemongrass. However, they do not sleep under bed net during stay overnight in forests because they complain about uncomfortablebut they making fire or other mosquito prevention methods for scavenge the mosquitoes instead use of bed net.

The cultural environment Their cultures have systems of health beliefs to explain about how to manage their illness. They belief that loss of their appetite is the first sign of illness and if ignore, it will progress to weak of the body, become extremely tired and finally they become illness. However, they have folk medicine to manage with the illness that mixed with the biomedicine in the present. Ya Duplant is one of folk medicine which use to manage their illness. They use branch of Ya Duplant, then slice it into thin piece and dry in the sun until they are wrinkled and dry. Then boil it with the water and drink it for help to increase the appetite and make them healthy. However, Ya Duplant cannot use to manage fever. Most of them tell that, they use antipyretic drug for manage fever. If the fever not relief within 3-4 days, they will find another way to relief they symptoms such as go to private clinic and hospital. During the period of time that they use self-medication for relief their symptoms it increased risk for malaria transmission.

Discussion Malaria remain one of public health problem in tropical and subtropical areas especially, forests area having stream nearby. Despite malaria control and prevention program was attempt to reduce disease in this area but malaria cases were reported every year. This studyaimed to examine how the factors contributing to an occurrence of malaria in Sri Toy sub-district from the people having experience with malaria and key informants which familiarto malaria problem in this area for understanding about factors contributing to

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malaria in Sri Toy sub-district. The environment of area which ongoing of malaria transmission in Sri-Toy sub-district cover with forest, nearly to stream and have area with deforestation for agricultural purpose. Most of dwelling built with the natural product especially bamboo and wooden plank. These finding are similar to many previous studies which malaria is commonly a jungle disease, requiring a stream nearby. Because of this condition is the favorable breeding site for Anopheles mosquitoes [18-24]. And the expansion of deforestation or farming activities contributes to alterations in the local ecosystem including temperature, sunlight, humidity and vegetation because it can effect in mosquitoes breeding behavior. These result may increase malaria transmission in that region [25-26].And house structure especially bamboo was indeed identified as associated risk factor with malaria [20]. Especially, ethnic groups settle down in village cover with forest and living in house made from natural products. This way of life exposes them to a higher risk of malaria infection [27]. However, this result of this study shows that Sri Toy sub-district is non border area but malaria is remaining problem. These finding are contrast with previous study that malaria was mainly located along Thailand’s borders [20]. Becausein many recent years, malaria problem in Sri Toy sub-district due to migration of people, especially, children from other area come to study at boarding school in this area. In 2010, malaria epidemic was occurred which cause by import malaria students from Myanmar border area return home during end of semester. Whichpresence of migration led to failure in primary prevention and control of malaria infections [24].Malaria patients in this study were Thai male. There are hill tribes with the highest education level are secondary school and main occupation is agriculturalist. Most of them have additional jobs such as wild food selling due to their income not enough and have culture about gender roles, men responsible to do heavy work. Therefore, men has forest related activities more than women.Moreover, patients in this study having history of forest relate activities prior being sick. These finding are similar to many previous studies that malaria cases was highly restricted to the male adults because men were more likely than women to work in the jungle [23] and education and ethnicity were increase risk to the disease [36]. Normally, human behavior is influenced by social, cultural, economic, and political factor which is clearly related to health, including the risk for infectious diseases like malaria [29]. Economic circumstances forcing human-vector contact [18] because it negatively associated with malaria [30-31]. Poverty is one of the major motivations for people to seek more resources to get the money from the forests that forces them to be exposed to malaria [29][32][23]. This study reveal that people have self-medication before seeking treatment at hospital and they have closer relationshipin villages leading to gather at dusk for meeting, which agreed with previous studies that self-medication before seeking medical treatment at hospital and outdoor stay increase risk of malaria transmission [23][33][28]. After patient have experience with malaria and increase knowledge about malaria transmission, most of patient concern and change their preventive behavior which agreed with previous study that knowledge about malaria transmission have positive effect on usage of mosquito nets and chemoprophylaxis,negatively on the habit of sleeping outdoor [32].

Conclusion Malaria problem is embed in Sri Toy sub-district because this area which ongoing of malaria transmission have favorable environment for malaria vectors breeding site combination with forest related lifestyles of people in villages. These conditions increased risk of human vector contact, especially, men have more risk due to working conditions. Moreover, malaria in this area become problem as a result of uncontrolled migration,

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especially, in way of children from the other areaborder area of Thai-Myanmar come to study in this area.

Limitation and suggestion The limitations of this study were this finding cannot generalize to whole population and other setting and short period of data collecting time effect to rapport building between researchers and participants. However, the result could help to design the appropriate malaria control and prevention program or other strategy to reduce malaria occurrence in Sri Toy sub-district.

Acknowledgement The authors wish to thank all of participants and staffs in Sri Toy health promoting hospital. We are grateful to Mae Suai hospital and Sri Toy sub-district administrative organization for support. In particular, we would like to thank all professors inPublic Health major, school of health science at Mae FahLuang University for their advices.

References 1. World Health Organization (WHO). Fact sheets: Malaria January 2015. 2016 http://www.who.int/mediacentre/factsheets/fs094/en/

2. World Health Organization (WHO). Guidelines for the treatment of malaria-Third Edition. 2015. http://apps.who.int/iris/bitstream/10665/162441/1/9789241549 127_eng.pdf

3. World Health Organization (WHO). Document centre: world malaria report December 2015. 2015. http://www.who.int/malaria/publications/world-malaria-report- 2015/report/en/

4. Centers for disease control and prevention (CDC). Global Health - Division of Parasitic Diseases and Malaria: Anopheles Mosquitoes. 2015. http://www.cdc.gov/malaria/about /biology/mosquitoes/

5. World Health Organization (WHO). Fact sheets: Malaria January 2016. 2016 http://www.who.int/mediacentre/factsheets/fs094/en/

6. World Health Organization (WHO). Global malaria control and elimination: report of a technical review. 2008. http://apps.who.int/iris/bitstream/10665/4 3903/1/9789241596756_eng.pdf

7. World Health Organization (WHO). Areas of work: Global Technical Strategy for Malaria 2016–2030. 2016. http://www.who.int/malaria/areas/global_technical _strategy/en/

8. World Health Organization (WHO). Malaria: WHO calls for strengthening malaria elimination strategy, says 3.2 billion people still at risk. 2015. http://www.searo.who.int/entity/malaria/en/

9. Chareonviriyaphap T, Bangs MJ, Ratanatham S. Status of malaria in Thailand. Southeast Asian J Trop Med Public Health. 2000;31(2):225-37. http://www.ncbi.nlm.nih.gov/pubmed/11127318

64

10. สานักโรคติดต่อน าโดยแมลง กรมควบคุมโรค. สถานการณ์โรคไข้มาลาเรียรายสัปดาห์ปี 2558-2559 ค้นหาเมื่อ 16 กุมภาพันธ์ 2559 จากhttp://www.thaivbd.org/n/home

11. Markwardt R, Sorosjinda-Nunthawarasilp P, Saisang V. Human activities contributing to a malaria outbreak in Thong PhaPhum district, Kanchanaburi, Thailand. Vector Control Programs Burapha University. 2008;39(1): 10-18. http://www.tm.mahidol.ac.th/seameo/2008-39-suppl-1/03_2007.pdf

12. Suwonkerd W, Ritthison W, Ngo C.T, Tainchum K, Bangs M.C, Chareonviriyaphap T. Vector Biology and Malaria Transmission in Southeast Asia. Anopheles mosquitoes - New insights into malaria vectors. 2013; 273-325. http://cdn.intechopen.com/pdfs- wm/45385.pdf

13. Pichainarong N, Chaveepojnkamjorn W. Malaria infection and life-style factors among hilltribes along the Thai-Myanmar border area, northern Thailand. Southeast Asian J Trop Med Public Health. 2004;35(4):834-9. http://www.ncbi.nlm.nih.gov/pubmed/15916 077

14. Chaveepojnkamjorn W, Pichainarong N. Behavioral Factors and Malaria Infection among the Migrant Population, Chiang Rai Province. J Med Assoc Thai. 2005; 88 (9): 1293-301. http://ns2.ph.mahidol.ac.th/phklb/knowledgefiles/behavioral_factors_and_malaria_infect ion_among_the_2005.pdf

15. สานักโรคติดต่อน าโดยแมลง กรมควบคุมโรค.ค่มู อื แนวทางการดา เนินงานและการประเมนิ ผลการป้องกนั และควบคุมโรคตดิ ต่อน า โดยแมลง ระดับอ าเภอปี 2555. ค้นหาเมื่อ 16 กุมภาพันธ์ 2559 จาก http://www.thaivbd.org/uploads/upload/Documents /l31.pdf

16. โรงพยาบาลส่งเสริมสุขภาพต าบลศรีถ้อย. สถานะสุขภาพ ปี 2558 ค้นหาเมื่อ 16 กุมภาพันธ์ 2559 จากJava health center information systems

17. Bureau of vector-borne disease, Department of disease control. National Strategic Plan for Malaria Control and Elimination in Thailand2011-2016. 2011.http://static1.1.sqspcdn.com/static/f/471029/25389167/1409611865417/thailand_na tional_strategic_plan_2011-2016.pdf?token=WpWUeLCguSTjPWu8YG 6xbNzPt5E%3D 18. Renard A.S. Malaria and mobility in Thailand. Social Science & Medicine. 1993;37(9):1147-1154. http://www.sciencedirect.com/science/article/pii /02 77953693902542

19. Renard A.S. Population movement, socio-economic behavior and the transmission of malaria in northern Thailand. The Southeast Asian Journal of Tropical Medicine and Public Health.1986;17(3):396-405. http://europepmc.org/ abstract/med/2951857

20. Panvisava S. (2001). Poverty and malaria: a study in a Thai-Myanmar border area. Southeast Asian J Trop Med Public Health, 32(3):608-14. http://www.ncbi .nlm.nih.gov/pubmed/11944725

65

21. Myint L, Ye H. (1991). Study of the malaria situation in forested foothill and nearby plain areas of Myanmar. Southeast Asian J Trop Med Public Health, 22(4), 509-14. http://www.ncbi.nlm.nih.gov/pubmed/1840316

22. Erhart A, Ngo DT, Phan VK, Ta TT, Van OC, Speybroeck N, et al. (2005). Epidemiology of forest malaria in central Vietnam: a large scale cross-sectional survey. Malar J. http://www.ncbi.nlm.nih.gov/pubmed/16336671

23. Chaveepojnkamjorn W, Pichainarong N. Malaria infection among the migrant population along the Thai-Myanmar border area. Southeast Asian J Trop Med Public Health. 2004;35(1):48-52. http://www.ncbi.nlm.nih.gov/pubmed/ 15272744

24. Chaveepojnkamjorn W, Pichainarong N. Behavioral Factors and Malaria Infection among the Migrant Population, Chiang Rai Province. J Med Assoc Thai. 2005; 88 (9): 1293-301. http://ns2.ph.mahidol.ac.th/phklb/knowledgefiles/behavioral_factors_an d_malaria_infection_among_the_2005.pdf

25. Walsh JF, Molyneux DH, Birley MH. (1993). Deforestation: effects on vector-borne disease. Parasitology. http://www.ncbi.nlm.nih.gov/pubmed/8488073

26. Global council. Linkages between Malaria and Agriculture. 2012.http://www.gbchealth.org/linkages-between-malaria-and-agriculture/

27. Thang N.D, Erhart A, Speybroeck N, Hung K.X, Thuan L.K, Hung C.T. Malaria in central Vietnam: analysis of risk factors by multivariate analysis and classification tree models. Malaria Journal. 2008. https://malariajournal.Biomed central.com/articles/10.1186/1475-2875-7-28

28. Fungladda W, Sornmani S, Klongkamnuankarn K, Hungsapruek T. Sociodemographic and behavioural factors associated with hospital malaria patients in Kanchanaburi, Thailand. The Journal of Tropical Medicine and Hygiene. 1987;90(5):233-237.

29. Heggenhougen H. K, Hackethal V, Vivex P, Spielman A. (2003). The behavioural and social aspects of malaria and its control. Social, Economic and Behavioural (SEB) Research, 03(1): 1-228. http://cdrwww.who.int/tdr/publications/documen ts/seb_malaria.pdf

30. Somi MF, Butler JR, Vahid F, Njau J, Kachur SP, Abdulla S. (2007). Is there evidence for dual causation between malaria and socioeconomic status? Findings from rural Tanzania. Am J Trop MedHyg, 77(6):1020-7. http://www.ncbi.nlm.nih.gov/pubmed/18165515

31. Krefis AC, Schwarz NG, Nkrumah B, Acquah S, Loag W, Sarpong N. (2010). Principal component analysis of socioeconomic factors and their association with malaria in children from the Ashanti Region, Ghana. Malar J. http://www.ncbi. nlm.nih.gov/pubmed/20626839

66

32. Hongvivatana T, Leerapan P, Chaiteeranuwatsiri M. (1985). Knowledge perception and behavior of malaria. Center For Health Policy Studies Mahidol University, 1-121. http://www.ircwash.org/sites/default/files/245.3-85KN-2388.pdf

33. Inchana W, Kamchoo K, Wetasin K. Factors Associated with Malaria Infection in VibhavadiDistrict,SuratThani Province, Southern Thailand. J Trop Med Parasitol. 2013;36:49-57. http://www.tm.mahidol.ac.th/tropmed-parasitology/201 3-36-2/36-2- 2013-e1-Factors-Associated-with-Malaria-p-49-57.pdf

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