Migratory behaviour predicts greater parasite diversity in ungulates

Long-distance animal movements can increase exposure to diverse parasites, but can also reduce infection risk through escape from contaminated habitats or culling of infected individuals. These mechanisms have been demonstrated within and between populations in single-host/single-parasite interactions, but how long-distance movement behaviours shape parasite diversity and prevalence across host taxa is largely unknown. Using a comparative approach, we analyse the parasite communities of 93 migratory, nomadic and resident ungulate species. We find that migrants have higher parasite species richness than residents or nomads, even after considering other factors known to influence parasite diversity, such as body size and host geographical range area. Further analyses support a novel ‘environmental tracking’ hypothesis, whereby migration allows parasites to experience environments favourable to transmission year-round. In addition, the social aggregation and large group sizes that facilitate migration might increase infection risk for migrants. By contrast, we find little support for previously proposed hypotheses, including migratory escape and culling, in explaining the relationship between host movement and parasitism in mammals at this cross-species scale. Our findings, which support mechanistic links between long-distance movement and increased parasite richness at the species level, could help predict the effects of future environmental change on parasitism in migratory animals.

See full text at: https://doi.org/10.1098/rspb.2018.0089

Teitelbaum, C.S., Huang, S., Hall, R.J. & Altizer, S. (2018). Migratory behaviour predicts greater parasite diversity in ungulates. Proceedings of the Royal Society B: Biological Sciences, 285(1875), 1-8.

You know nothing, John Snow.

Cholera affects an estimated 3 to 5 thousand people in Westeros each year. Its spatial distribution is largely characterized by sporadic outbreaks following the onset of Winter. The common dogma in Cholera epidemiology is that transmission spreads through water sources contaminated with the bacterium \textit{Vibrio cholerae}. However, we used species distribution modeling to demonstrate that the incidence of Cholera cases has no association with the distance to any water sources (Sunset Sea, Narrow Sea, Trident, or either Fork). Thus, the original insight gained from famous epidemiologist, John Snow, in the 1800’s is brought into question.

See full text at: http://mvevans89.github.io/docs/targaryen2018.pdf

Targaryen, Daenerys M.D (2018). You know nothing, John Snow. Proceedings of the Royal Society of Westeros, 12:1-3.

UPDATE: April fool!