WORMS VS BACTERIA: Investigating Whether Soil Transmitted Helminths Protect Against Diarrhea Inducing Bacteria in Rural Populations of Ranomafana, Madagascar

Abstract

Parasitic gut worms have been found to have therapeutic potential as protective agents against autoimmune diseases. This investigation explores the possibility that soil-transmitted helminths (STH) may also confer some level of protection against diarrheal inducing bacteria (DB). Diarrheal disease is one of the leading causes of morbidity and mortality among the global poor. In Madagascar, it is the leading cause of death. Helminths have numerous immune and microbiome modulating effects, including reducing inflammation and increasing mucus production, which could possibly reduce if not inhibit the ability of diarrhea causing pathogens to colonize and establish themselves within the gut. This thesis examines the association between the infection prevalence of STH and DB using data collected from a cross-sectional study of populations living near Ranomafana National Park, Madagascar. Stool samples and survey information pertaining to demographic and socio-economic variables were collected for all participants. Stool samples were examined for the presence of STH eggs while PCR analysis was run to detect virulence markers for Shigella sp., Salmonella sp. and Yersinia enterocolitica. Sex, age, latrine access, water treatment technique and wealth were all found to be significantly associated with at least one of the investigated STH/DBs, though no single variable was significantly associated with all six. The results of this analysis did not support the hypothesis that STH protect against DBs. On the contrary, people infected with either Ascaris lumbricoides (aOR = 2.87, p = 0.003) or Trichuris Trichiur (aOR = 2.93, p =0.009) were significantly more likely to be infected with Shigella sp. than those that were not infected with these worms. This suggests that, at least in some cases, STH infection increases susceptibility to diarrhea inducing pathogens.