High prevalence of Echinococcus multilocularis in urban red foxes (Vulpes vulpes) and voles (Arvicola terrestris) in the city of Zürich, Switzerland

Abstract

Over a period of 26 months from January 1996 to February 1998, 388 foxes from the city of Zürich, Switzerland, were examined for intestinal infections with Echinococcus multilocularis and other helminths. The prevalence of E. multilocularis in foxes sampled during winter increased significantly from 47% in the urban to 67% in the adjacent recreational area, whereas prevalence rates of other helminths were similar in both areas. Seasonal differences in the prevalence of E. multilocularis were only found in urban subadult male foxes which were significantly less frequently infected in summer than in winter. The distribution of the Echinococcus biomass, as expressed by worm numbers per fox was overdispersed in 133 infected foxes randomly sampled in winter. Ten of these foxes (8%) were infected with more than 10,000 specimens and carried 72% of the total biomass of E. multilocularis (398,653 worms). Prevalences did not differ significantly in these foxes in regard to age and sex but worm burdens were significantly higher in subadult foxes as compared with adult foxes. In voles (Arvicola terrestris) trapped in a city park of Zürich, E. multilocularis metacestodes were identified by morphological examination and by PCR. The prevalence was 20% among 60 rodents in 1997 and 9% among 75 rodents in 1998. Protoscoleces occurred in 2 of the cases from 1997. The possible risk for human infection is discussed with respect to the established urban E. multilocularis cycle.

Infection of red foxes with Echinococcus multilocularis in western Switzerland

“…This may be due to parasite-induced host immunity to reinfection. This phenomenom was also observed in other studies (Hofer et al, 2004) and was also seen in dogs infected with E. granulosus (Torgerson et al, 2004).…”

Infection of foxes byEchinococcocus multilocularisin urban and suburban areas of Nancy, France: influence of feeding habits and environment

“…The same trend was observed in Switzerland: Zürich (Hegglin et al, 2007;Hofer et al, 2000) and Geneva (Fischer et al, 2005). The first report of an urban cycle for E. multilocularis concerned the city of Zürich.…”

“…The analysis of the effect of urbanisation level, year, season, age class and sex have shown that urbanisation only explained fox infection. Other studies have revealed a seasonal prevalence in an urban area with higher rate in winter for young males (Hofer et al, 2000) and more pronounced variation along the urbanisation gradient in juveniles foxes than in adult foxes (Hegglin et al, 2007). In our study urban positive cases were juveniles males.…”

Canine echinococcosis in Kyrgyzstan: Using prevalence data adjusted for measurement error to develop transmission dynamics models

“…The infection pressures reported for E. multilocularis assume that infection pressure is constant throughout the year which is unlikely. In Switzerland for example, differences in prevalences have been suggested between foxes sampled in the winter and the summer (Hofer et al, 2000;Stieger et al, 2002;Hegglin et al, 2007). Studies are being undertaken to resolve the issues of seasonal transmission in Kyrgyzstan.…”