Prevalence of enteric bacterial parasites with respect to anthropogenic factors among commensal rhesus macaques in Dehradun, India

There has been a recent surge in research on primate infectious disease ecology. Two major areas remain relatively unaddressed to date—the prevalence of enteric bacterial parasites and the role of anthropogenic environmental factors in parasite acquisition in commensally living primate populations. In this preliminary assessment, we address both these gaps by assessing the prevalence, and the role of anthropogenic factors in shaping this prevalence, of three enteric bacterial parasites— E . coli O157:H7, Salmonella sp., Shigella sp.—across populations of rhesus macaques ( M. mulatta ) that live commensally with humans in Dehradun, northern India. Across 10-week study period, we collected data on (1) human-macaque behavioral interactions, (2) macaque and human demographic and activity scans, and (3) macaque fecal samples from the environment at four different locations in Dehradun. Biochemical tests and morphology-based confirmations clearly established the presence of all three enteric bacterial parasites in rhesus macaques. Overall prevalence ranged from 2 to 5 %, with Shigella sp. being the most prevalent. Regression analyses linking anthropogenic factors to bacterial prevalence showed a positive association between rates of macaques eating human garbage and E. coli O157:H7 ( β = 0.23, p = 0.083), but a negative association with Salmonella sp. ( β = −0.17, p = 0.026). Rather, the prevalence of Salmonella sp. was positively linked to rates of macaque eating provisioned food ( β = 0.0012, p = 0.058). Finally, we found no relationship between anthropogenic factors and the prevalence of Shigella sp. Our findings establish the prevalence of enteric bacterial parasites in commensal populations of primates and suggest that although anthropogenic factors are linked to bacterial prevalence, the nature of the relationships may depend on the socioecological/foraging strategies of macaques and the food sources that facilitate the environmental survival of particular types of enteric bacteria over others.