THE DETERMINANTS OF HELMINTH INFECTION IN BABOONS
Intestinal parasitic helminths are common in wild primate populations [1, 2] and can impose a significant burden on their host’s fitness. Numerous factors can affect the prevalence and diversity of intestinal parasites in natural populations including environmental factors [3, 4], the host’s behavior and genetics [5, 6]. How these different factors interact in natural populations remains unclear. This is in all probability due to the fact that previous studies have seldom looked at the prevalence and diversity of parasitic helminths in the same species but in different habitats over periods longer than a one year. I am proposing to conduct a comprehensive analysis of helminth prevalence and diversity in wild non-human primates (NHP), specifically baboons (genus Papio) in Ethiopia. Papio sp. are common and widespread in Ethiopia and can be found in a wide variety of habitats that range from arid dessert regions to rain forests. Their unique distribution across varied topographies affords a rare opportunity to examine the role of the environment on parasitic infestation.
I will test the hypothesis that ecological conditions constitute the major determinant of helminth infestation in baboons in Ethiopia. To achieve this goal I will assess the prevalence and diversity of intestinal helminths in populations of baboons that differ (1) by their ecology, (2) by their genetic composition and (3) by their behavior. I will first perform this analysis on the baboon hybrid zone in Awash National Park because the baboon populations in Awash have been extensively studied for the past 50 years [7, 8] and a vast amount of data on the ecology, behavior and genetic composition of the troops is readily available.
The analysis of troops will be extended to olive baboons (Papio anubis) across the entire Ethiopian range of the species. I will compare the prevalence and diversity of helminths in olive baboons inhabiting three main habitats: rain forests, in savannahs and semi-dessert. This study will be performed using a combination of microscopic and molecular techniques to insure the most detailed survey possible. The data collected will be analyzed using an ecological niche modeling approach to rigorously assess the relationship between the environment and the distribution of baboon parasites.
While parasite surveys provide useful information they do not inform about the long-term interaction of intestinal parasites and their hosts. We will examine this issue by comparing the molecular evolution of genes involved in parasite resistance between two species with different ecologies and different levels of parasitic infestation: the olive baboon, which is a savannah baboon, and the hamadryas baboon, which is a dessert baboon. Preliminary analyses suggest that olive baboons carry a greater abundance and diversity of helminth intestinal parasites than hamadryas, possibly because the hamadryas’ habitat is less favorable to the survival of helminth eggs. I will test if this difference in infestation has left a genetic signature on the genome of these two species. To this end, I will amplify and sequence a large number of helminth resistance genes in these two species and assess if selection is acting more strongly on these genes in olive baboons than in hamadryas baboons.