Influence of Massive and Long Distance Migration on Parasite Epidemiology: Lessons from the Great Wildebeest Migration

Abstract

Very little is known about the influence of massive and long distance migration on parasite epidemiology. Migration can simultaneously minimize exposure to common parasites in their habitats and increase exposure to novel pathogens from new environments and habitats encountered during migration, while physiological stress during long distance movement can lead to immune suppression, which makes migrants vulnerable to parasites. In this paper, we investigated the diversity, prevalence, parasite load, co-infection patterns and predilection sites of adult gastrointestinal helminths in 130 migrating wildebeests and tested for their relation with animal age, sex and migration time (which also could indicate different migration routes), and compared them with the non-migratory wildebeest. Surprisingly, only four parasite species were found, Oesophagostomum columbianum, Haemonchus placei, Calicophoron raja and Moniezia expansa, which were lower than in non-migratory wildebeest reported in the literature. These parasites were generalists, infecting livestock, and suggests that wildebeest and livestock, because of their interaction during migration, have a cross-infection risk. There was a negative relation between parasites diversity, prevalence and intensity of infection, and host age, which suggests that wildebeests acquire protective immunity against these parasites as they get older. Prevalence and intensity of infection were higher among wildebeest crossing the Mara Bridge (early migrants) compared to those crossing the Serena (late migrants), which suggests that early migrants (or migrants originating from different areas) have varying infection intensities. The prevalence and intensity of infection were higher in males compared to females and may be due to ecological, behavioural, or physiological differences between males and females. Our findings compared to those of previous studies suggest that migration may provide a mechanism to minimize exposure of hosts to common parasites through migratory escape, but this result awaits examination of helminths epidemiology of non-migratory wildebeests from areas of migrant origins. The potential parasitic cross-infection between wildebeests and livestock is a real risk to be taken into account in the management of wildebeest migration corridors.

Migratory animals feel the cost of getting sick: A meta‐analysis across species

“…Strikingly, there is little research on the impact of infections on migratory mammals (although this is increasing, e.g. Mijele et al., ; Mysterud, Qviller, Meisingset, & Viljugrein, ), despite the renowned migrations of mammals such as ungulates and whales, and evidence for the transmission of zoonotic pathogens by migratory bats (Leroy et al., ; Ogawa et al., ). Lastly, considering our results here, future studies addressing these questions should ensure statistical power to detect small effect sizes (e.g.…”

“…Strikingly, there is little research on the impact of infections on migratory mammals (although this is increasing, e.g. Mijele et al, 2016;Mysterud, Qviller, Meisingset, & Viljugrein, 2016), despite the renowned migrations of mammals F I G U R E 4 Estimated effect sizes (Fisher's z), standard errors (shaded grey) and 95% confidence intervals (whiskers) extracted from (a) the meta-model predicting the effect of infection intensity on performance trait (Table 4a); and (b) when each trait is modelled separately (Table 4b). Boxplot overlaid with raw data (circles) with the size of the circle proportional to its weight within the model.…”

Migratory hosts can maintain the high‐dose/refuge effect in a structured host‐parasite system: The case of sea lice and salmon

“…The critical role in our model of migration between distinct host populations underscores the importance of migration and population structure for evolution within host/parasite systems. Migration features in parasite dynamics for animal hosts from ungulates to arthropods (Altizer, Bartel, & Han, 2011;Bartel et al, 2011;Folstad et al, 1991;Mijele et al, 2016), and connectivity among structured host-parasite populations can drive evolution of host defences (Møller & Szép, 2011), parasite virulence (Herre, 1993) and even host speciation (Møller & Szép, 2011 (Vilas, Vázquez-Prieto, & Paniagua, 2012), and malarial gene flow, related patterns of antigen diversity and associated selection are likely to affect malaria vaccine design (Barry, Schultz, Buckee, & Reeder, 2009). Building on the known role of pest migration in opposing the evolution of pesticide resistance (Comins, 1977; Huang, Andow, & Buschman, 2011), we have illustrated the role that host migration may play in opposing treatment resistance in parasites.…”

Animal migrations and parasitism: reciprocal effects within a unified framework

“…Juvenile galaxiid fishes that migrate out of rivers and into coastal seas avoid infections by freshwater trematodes at a critical period of their life, whereas congeners that do not migrate incur severe trematode‐induced developmental malformations and mortality (Poulin et al ., 2012). Finally, large‐scale migrations of ungulates have also been linked with escape from areas of high infection risk and movement towards parasite‐free areas (Folstad et al ., 1991; Mijele et al ., 2016).…”