Eco-epidemiology of diarrheal disease with an emphasis on Cryptosporidium in and around Ranomafana National Park, Madagascar Público
Bodager, Jonathan R (2012)
Abstract
Purpose: Pathogens transmitted between wildlife, livestock, and humans pose a serious threat to human health and wildlife conservation. Although much is known about the basic biology of zoonotic pathogens, the ecology and epidemiology of their transmission between species has received less attention. Likewise, for clinical syndromes such as diarrheal disease, the contribution of novel zoonotic transmission relative to human-to-human transmission on overall disease burden is unknown. This project examined the eco-epidemiology of diarrheal disease in rural Madagascar, with an emphasis on Cryptosporidium, one of the most common diarrhea-causing zoonotic parasitic genera in the world.
Methods: In July and August 2011, 278 fecal samples were collected from humans, livestock, and wildlife from Ambodiaviavy and Ankialo, two communities near Ranomafana National Park, Madagascar. Human subjects (n=135) were surveyed for socio-demographic (sex, age, profession, etc.) and health data (diarrheal illness, medication usage, water usage, etc.). DNA was extracted from samples, screened for Cryptosporidium by 18S PCR of the SSU, rRNA gene and subtyped using RFLP and genomic sequencing. Chi-square tests of association were used to examine relationships among factors from the survey instrument.
Results: A greater number of diarrheal symptoms occurred in Ambodiaviavy than Ankialo (23.1% vs. 4.2%) with 67% of cases younger than 18 years. Other behavioral practices varied across communities, i.e. - drinking boiled water (Ambodiaviavy = 52.3% reporting 'often'; Ankialo = 58.6% reporting 'never'). There were a total of 41 (14.7%) positive Cryptosporidium samples (20.2% from Ambodiaviavy and 12.5% from Ankialo). Species prevalence of Cryptosporidium was: 0.8% of humans, 4.0% lemurs, 33.3% peri-domestic rodents, 29.0% bovine, and 23.5% of porcine (one positive canine, n=1). Subtyping revealed a diverse array of Cryptosporidium species.
Conclusion: Survey data indicates differing behavioral practices between communities that were not linked to increased diarrhea but suggest varying risks of zoonotic transmission across the human-animal interface. One human, infected with C. suis, suggests a potential risk for human-pig transmission in Ankialo, whereas, large numbers of infected cattle in Ambodiaviavy suggest a potential risk for human-cattle transmission. Public health efforts should focus on improving sanitation and hygiene and on rational modifications of daily practices to avoid zoonotic transmission.
Table of Contents
TABLE OF CONTENTS
PageBackground ………………………………………………………………………
1Studying Global Diarrheal Illnesses…………………………………………........
Madagascar………………………………………………………………….................... Cryptosporidium………………………………………………………………................ 1 2 2Project Aims………………………………………………………………………
Objectives………………………………………………………………........................
Relevance to the Field of Environmental Health …………………………....
5 5 6 Methods……………………………………………………………………….......Study Area and Population……………………………………………..................
Survey Instrument………………………………………………………….................
Fecal Sample Collection……………………………………………………...............
Nucleic Acid Extraction……………………………………………...……...............
18s Polymerase Chain Reaction……………………………………...……..........
Restriction Fragment Length Polymorphism………………………...…….....
Genomic Sequencing………………………………………………………................
Ethical Considerations…………………………………………………….................
6 6 6 7 8 9 10 12 12Results ……………………………………………………………………...…..
Descriptive Statistics for All Study Subjects..………………………………...
Comparison of Risk Factors for Diarrhea …………………………………......
Medication Usage Across Communities…………………………………….......
Interaction with Lemur Population………………………………………….........
Analysis of Samples Positive for Cryptosporidium…………………………..
Subtyping of Cryptosporidium Positive Samples………………...………….
12 12 13 15 16 16 18 Discussion…………………………….………………………………………….. 19 Conclusion…………………………………..……………………………………. 24 References………………………………………………………………………… 26 Tables……………………………………………………………………………... 29About this Master's Thesis
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