The impact of introduced hosts on parasite transmission: opisthorchiid infections in American mink (Neovison vison)

Ellie Sherrard-Smith,Jo Cable,Elizabeth A Chadwick

doi:10.1007/s10530-014-0709-y

Abstract

Introduced animals may be considered at an advantage over native competitors because they have escaped natural parasites. In some cases however, generalist parasites in a novel environment can use introduced species as an alternative or reservoir host. This can change the dynamics of parasite populations, with implications for epidemiology. The key factor determining the impact of an alternative host is its ability to maintain a reproductively successful parasite and contribute to the transmission potential of that parasite. The digenean Pseudamphistomum truncatum is found in native otters Lutra lutra in Britain and has been reported in introduced American mink Neovison vison. To investigate whether introduced mink are competent hosts and to ask how mink compare with otters as hosts, we compared parasite prevalence, intensity and fecundity between the two host species in a region where both are common. Although prevalence was not statistically different between otters and mink (48 %, n = 27, compared to 33 %, n = 21 respectively), mean parasite intensity was higher in mink (253 ± 145 standard error parasites/infected host, compared to 46 ± 18 in otters). Parasite fecundity was lower in mink (mean egg count/parasite/host = 622 ± 64) than in otters (1,204 ± 108), and this difference was not confounded by host or parasite size or by intraspecific competition among parasites. Assuming the parasite eggs are equally viable from otters or mink, mink are not only a competent host for P. truncatum, but because of the higher parasite intensity in mink, they can potentially spread c.3 times as many parasite eggs to intermediate hosts, than otters. The naturalisation of mink to new habitats may therefore contribute to trematode infections in native fauna.

Highlights

The role of invading hosts as reservoirs for infectious disease can have severe, negative impacts on native hosts (Bonhoeffer et al 1996; Halliwell and Macdonald 1996; Daszak et al 2000; Macdonald and Harrington 2003; Bonesi and Palazon 2007)
There was a significant difference in parasite fecundity between otters and mink with otters having slightly more eggs per parasite than mink
The introduced mink were infected to a higher intensity than native otters, and otters harboured parasites with a higher in utero egg count than the introduced mink, once intensity of infection was taken into account the total potential contribution of parasite eggs released by mink is greater than that of native otters

Summary

Introduction

The role of invading hosts as reservoirs for infectious disease can have severe, negative impacts on native hosts (Bonhoeffer et al 1996; Halliwell and Macdonald 1996; Daszak et al 2000; Macdonald and Harrington 2003; Bonesi and Palazon 2007). The introduction of a non-native species that is a competent host for a native parasite can cause an increase in disease, a process termed ‘parasite spillback’ (Kelly et al 2009). Parasites are reported to do better within a native rather than an introduced host—with higher parasite species richness and higher abundance recorded in native host populations The traits associated with parasite fitness such as parasite abundance can, on occasion, be higher in introduced host species (Kennedy et al 1991; Rauque et al 2003)

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