Dissertation Research: Within-host seasonal drivers of pathogen dynamics in a fruit bat reservoir

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Diseases often follow regular patterns: there is commonly a flu season, for example, and regular cycles in the occurrence of measles and chicken pox are well known. Explanations usually involve patterns of host (human) movement and contact. This project will examine how other factors such as seasonal changes in host status (nutritional or reproductive status, for example) influence the spread of disease. The research focuses on bats, which are known or suspected hosts and reservoirs for a number of diseases. Understanding more about host tolerance to disease will be critical to predicting and preventing new infectious diseases. Results will improve understanding of disease risk and spread, with direct consequences for human health. The researchers will continue to work with scientists in Madagascar, contributing to human and wildlife health and conservation in that country. The award will advance the education and training of a doctoral student, supporting her to develop a new measure of host condition and improved models for disease dynamics. The doctoral student will develop a course in modeling disease dynamics and will continue to engage undergraduate students in the research. The researchers hypothesize that seasonal fluctuations in adipose tissue underlie a host's strategy of pathogen tolerance versus resistance for a diverse suite of viral, bacterial, and protozoan infections. Adipose tissues may mediate pathogen-induced intracellular damage and promote repair by regulating processes of intracellular autophagy. This regulation would promote host tolerance to infection. During resource-scarce winters, reductions in adiposity could lead to declining function in autophagic processes, allowing for accumulation of intracellular pathogen-induced damage that necessitates immune resistance. The researchers will test these hypotheses using serum samples collected during an 18-month field study of pathogen dynamics in three endemic fruit bats in Madagascar. They will conduct enzyme-immunoassays for leptin, a neuroendocrine signaling hormone secreted by adipose tissue, in serum samples of each individual bat in the dataset to quantify adiposity. Data on adiposity will be used to parameterize a new, within-host model exploring adipose tissue contributions to pathogen damage control. Although seasonal contact patterns often capture epidemic dynamics in human infections, they are insufficient to explain pathogen persistence, and the observed seasonality of disease transmission, in a number of important wildlife hosts, including bats.