Meeting Abstract

S6.6  Wednesday, Jan. 5  Ecological consequences of parasite-parasite interactions and the role of host immunity EZENWA, V.O.*; ETIENNE, R.S.; JOLLES, A.E.; University of Georgia; University of Groningen; Oregon State University vezenwa@uga.edu

Accumulating evidence suggests that parasite-parasite interactions can be a powerful force shaping the spread of infectious diseases. In particular, immune-mediated interactions between co-occurring parasites may modify both individual and population-level patterns of disease. For example, nematodes are widespread macroparasites of wildlife that can bias the host immune response towards a T helper type 2 (Th2) over a type 1 (Th1) response impairing the host’s ability to control concurrent microparasitic infections. Although key immunological mechanisms driving interactions between nematodes and intracellular microparasites have been described, the ecological consequences of these interactions are still poorly understood. We developed a two-parasite, one-host disease dynamic model to explore the consequences of nematode-induced immune suppression on bovine tuberculosis (TB) invasion success in African buffalo (Syncerus caffer). Our model, parameterized with empirical data from a free-ranging population of buffalo in Hluhluwe-iMfolozi Park, South Africa, showed that nematode-induced immune suppression can alter the basic reproductive number (R₀) of TB, facilitating the invasion of TB into the buffalo population. To better understand the generality of this finding, we compared model-derived estimates of the magnitude of immune suppression necessary for nematode-driven TB facilitation against data generated from a longitudinal antihelminthic treatment experiment in a second buffalo population from Kruger National Park. Our study highlights the importance of parasite-parasite interactions in shaping the distribution and spread of infectious diseases in the wild, and reveals a key role of host immune function in this ecological process.