When parasites interact: Implications for immunisation efficacy in individuals and populations

Abstract

What happens if individuals are infected with parasites when they are vaccinated? And what happens if an individual in infected by more than one parasite simultaneously? In this dissertation, I explore these two questions through meta-analysis, literature review, and field research. In my first chapter, I present the results of a meta-analysis on parasite-vaccine interactions that was published in Vaccine in 2020, where I find that parasites, in general, tend to interfere with immunisation. In my second chapter, I present on the parasite ecology of wild raccoons, based on two years of field research during which I trapped and sampled raccoons cross-sectionally and longitudinally. I investigate predictors of gastrointestinal nematode infection and burden, and make predictions about whether and how these parasites might be impacting raccoon fitness (body condition and overwinter mortality). In my third chapter, I investigate parasite-vaccine interactions in the context of the ongoing campaign to vaccinate raccoons against rabies in the north-eastern United States. My results suggest that gastrointestinal nematodes are indeed interfering with rabies vaccination in wild raccoons, but that anthelmintic treatment could be a viable option to improve vaccine efficacy.