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

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.

Assessing the invasion potential of non-native branchiobdellidans: experimental studies of survival, reproduction and competition

“…okadai or other co-occurring symbionts. Overall, this study contributes towards understanding the symbiotic fauna of invasive non-native signal crayfish, and demonstrates the need to consider such cointroduced organisms as a "hidden cost" of biological invasion (Sherrard-Smith et al, 2014).…”

Helminths of mustelids with overlapping ecological niches: Eurasian otter Lutra lutra (Linnaeus, 1758), American mink Neovison vison Schreber, 1777, and European polecat Mustela putorius Linnaeus, 1758

“…The study of parasites related to the N. vison invasion in new regions is important due to possibility of introduction of new parasites to endemic host and transfer of endemic parasites to a new host. The impact of the introduced N. vison on parasite transmission has been studied (e.g., Ivanov and Semenova, 2000; Sherrard-Smith et al, 2015a; Martínez-Rondán et al, 2017).…”

Spatial and seasonal factors are key determinants in the aggregation of helminths in their definitive hosts: Pseudamphistomum truncatum in otters (Lutra lutra)

“…The life cycle of P. truncatum includes two intermediate hosts; both Bithynia snails and cyprinid fish are highly abundant in freshwater environments in the UK and across Europe so there is potential for the maintenance of this parasite regardless of any intervention to protect the definitive host. A potential reason behind the recent identification of P. truncatum might be the establishment of mink (Neovison vison) -a second viable definitive host -increasing the abundance of P. truncatum (Sherrard-Smith et al, 2014). The likelihood of encountering a definitive host will be associated with parasite aggregation, abundance and fecundity in intermediate hosts and careful consideration of these patterns in earlier life stages is needed to complement our understanding of distributions in the definitive hosts.…”