Among mammals, female apes bear a heavy burden with regard to reproduction, as it takes many months of gestation and years of lactation to ensure their offspring survive to an age of self-sufficiency. Energetic investment in reproduction is predicted to create deficits in other costly functions like immunity, with potential to impact the short and long-term health of reproductive females. Among the great apes, wild chimpanzee females offer an interesting comparative model to the human condition. Chimpanzees share a most recent common ancestor with humans, many genetic and physiological traits, and inhabit environments hypothesized to be similar in ecological and sociological constraints typical of most of human evolutionary history. The goal of this project was to provide novel data addressing costs of reproduction in wild chimpanzees of Kibale National Park, Uganda, and to determine whether high reproductive effort presented a trade-off with immune function that produced immune deficits and increased disease.

The study was conducted on wild chimpanzees at two, long-term chimpanzee research sites in Kibale National Park, Uganda, where non-invasive methods were used to collect urine and fecal samples to assess host physiology, genetics, and infection status. Hormone profiles of body condition and energy availability were produced using radio- and enzyme immunoassays for C-peptide of insulin and cortisol, respectively. Direct and next-generation DNA sequencing was performed to obtain genotypes for two, critical host genes that play a role in both adaptive and innate immunity and are relevant to the pathogens commonly found in wild chimpanzee communities. Assessments of chimpanzee host gastro-intestinal helminth and protozoan infection, performed via light microscopy, were employed as a proxy for immune function. These biomarkers reflecting host body condition, genetics, and infection profiles were combined with more than 30 years of demographic data on age and reproduction to examine the short and long-term impacts of reproductive effort on chimpanzee health.

Results from this study have 1) characterized the parasite and pathogen environment of wild chimpanzees at Kibale National Park, Uganda, including isolating biological and ecological factors leading to increased levels of infection in individual chimpanzees 2) provided robust assessment of individual female chimpanzee biology, including outlining constraints on and trade-offs between necessary and energetically taxing processes like reproduction and immunity, and, 3) revealed relationships between genotypes and phenotypes and the incidence and extent of parasitic infection and disease. Insights gained from this study fill a critical gap in our understanding of patterns of disease across the life course of apes, particularly in the context of reproductive effort, and the project provides a comparative dataset for exploration of differences and similarities in life history parameters between humans and other non-human primates.

This training grant provided the doctoral student, a member of two under-represented groups in STEM, the necessary research funds to carry out a highly interdisciplinary study requiring data collection across the fields of primatology, parasitology, endocrinology, and immunogenetics, at four academic institutions, including University of New Mexico, Stanford University, University of Wisconsin – Madison, and Washington University in St. Louis. This preparation has provided expert level knowledge in biomarker generation, including the generation of hormone, genetic, and immunological and parasitological data relevant to assessing host physiology and health, as well as skills in bioinformatics, statistical analyses, and management of large and complex datasets.

Broader impact initiatives associated with this project have provided educational opportunities to more than 800 K-12 students in the U.S.A. and Uganda in the form of classroom engagements and community projects covering topics related to primatology, parasitology, and human and non-human primate health. Seven students at the University of Wisconsin - Madison, including four undergraduates and three veterinary medicine students, were trained in parasitology and microscopy. Two undergraduates from the University of Wisconsin – Madison were mentored in independent research projects.

Last Modified: 07/19/2019
Modified by: Sarah R Phillips-Garcia