As the number of emerging infectious disease events increases globally it is becoming more and more imperative that we consider the parasite community to which the emerging disease enters. A typical wild host is infected with numerous parasites simultaneously – and these parasites can interact resulting in competition or facilitation – just like free-living ecological communities. Recent reviews have emphasized that analytical tools used in community ecology may provide a unique way to investigate entire disease communities within a host (i.e. Johnson et al 2015), including trait-based community ecology which emphasizes the importance of understanding species-level functional traits, allowing for a more mechanistic understanding of the parasite community (Seabloom et al 2015). We employed tools from community ecology to investigate how an invasive and emerging infectious disease (bovine tuberculosis, BTB) may modify parasite infra-communities in African buffalo. We took advantage of a longitudinal study of African buffalo in Kruger National Park, South Africa following 29 buffalo prior to and post BTB infection between 2008-2012, along with 29 age and location matched animals that did not acquire BTB. We collected information on their parasite community, monitoring 17 different parasites every 6 months in each individual. We then evaluated how the host's disease community changed after infection with BTB -using a combination of taxonomic and functional analyses.
We found that animals infected with BTB had altered parasite communities after infection, compared to before, with an increase in parasite species richness that was mirrored by an increase in functional richness, that was not present in animals uninfected with BTB during the same time period. However, this increase in parasite richness was not a random sampling of pathogens in the environment, but was instead directional with the increase driven primarily by directly-transmitted intracellular parasites, represented taxonomically by several bacteria and viruses. These results suggest that BTB alters the host parasite infra-community in predictable ways, and indicate that the effects of BTB on the host may not be limited to direct consequences of infection but also to changes in the host’s parasite community. This points to a new frontier in disease ecology: how do emerging diseases alter existing parasite communities both taxonomically and functionally and what are the consequences for disease transmission and host fitness?