Seroprevalence of Echinococcus spp. and Toxocara spp. in Invasive Non-native American Mink

Abstract

Invasive non-native species can become reservoirs of zoonotic pathogens and cause their spread during colonization, increasing the risk of zoonoses transmission to both wild hosts and humans. American mink (Neovison vison) are considered an important invasive mammal species responsible for carrying endoparasites. The aim of our study was to evaluate the role of feral American mink as a possible transmission vector of Echinococcus spp. and Toxocara spp. in wildlife. We analysed the frequency of American mink exposure to both parasites, the spatial distribution in Poland, and the variability over time on the basis of specific antibody presence using ELISA and Western blot. Alimentary tract analyses revealed that American mink do not serve as definitive hosts for these parasites. Altogether, 1100 American mink were examined. The average seropositivity for American mink was 14.2% for echinococcosis and 21.7% for toxocarosis; dual-seropositivity was detected in only 6.0%. Seroprevalence of both parasites differed between study sites and significantly increased over time in Toxocara spp. Thus, our study revealed that free-living American mink are exposed to parasites and likely to be involved in the maintenance of both Echinococcus spp. and Toxocara spp. in the wild as paratenic hosts.

Keywords: Echinococcosis; Invasive species; Paratenic host; Seroprevalence; Toxocarosis; Zoonoses.

Figure 1

Comparison of the occurrence of echinococcosis in various hosts in Poland: a seroprevalence in the American mink (this study); b prevalence in the red fox (Karamon et al. 2014); c number of human cases per million inhabitants (data on inhabitant numbers in provinces were taken from the Central Statistical Office of Poland) (Nahorski et al. 2013). Study sites are marked with black dots: WMNP—Warta Mouth National Park, GR—Gwda River, DNP—Drawa National Park, SNP—Słowiński National Park, VR—Vistula River, BNP—Biebrza National Park, NNP—Narew National Park. Seroprevalence of American mink for each studied province is given; in the case of data being made available from two study sites located in one province, the mean value is provided (a). Provinces marked with grey colour indicate places where the highest prevalence of echinococcosis was stated; for red fox above 25% (b) and for humans above 2 human cases per million inhabitants (c).

Figure 2

Echinococcus spp. and Toxocara spp. seropositivity of American mink. Optical density (OD) value of ELISA performed for: a individuals negative for Echinococcus spp.—Neg1, individuals negative for Echinococcus spp. but positive for Toxocara spp.—Neg2, individuals positive for Echinococcus spp. but negative for Toxocara spp.—Pos1, individuals positive for both parasites (mixed infection)—Pos2; b individuals negative for Toxocara spp.—Neg1, individuals negative for Toxocara spp. but positive for Echinococcus spp.—Neg2, individuals positive for Toxocara spp. but negative for Echinococcus spp.—Pos1, individuals positive for both parasites (mixed infection)—Pos2; c proportion of American mink seropositive for Echinococcus spp., Toxocara spp., and both parasites (dual infection) in Poland (n = 1100).

Figure 3

The seroprevalence of Echinococcus spp. and Toxocara spp. in American mink, accompanied by 95% CIs, in relation to: a, b study site; c, d year of American mink death; and e, f sex as predicted by the generalized linear models (GLM). F—female, M—male. Rug plots along the x axis show the data distribution.

Figure 4

Western blot analysis of: aEchinococcus-specific IgG antibodies in selected American mink samples. The lines represent: 1–28—selected American mink samples ELISA-positive for Echinococcus, PC—positive E. multilocularis control dog serum, NC—negative control dog serum. bToxocara-specific IgG antibodies in selected American mink samples. The lines represent: 1–28—selected American mink samples ELISA-positive for Toxocara, PC—positive T. canis control dog serum, NC—negative control dog serum.