Westward Spread of Echinococcus multilocularis in Foxes, France, 2005–2010

Benoît Combes¹, Sébastien Comte, Vincent Raton, Francis Raoul, Franck Boué, Gérald Umhang, Stéphanie Favier, Charlotte Dunoyer, Natacha Woronoff, and Patrick Giraudoux¹

Author affiliations: Author affiliations: Entente for the Control of Zoonoses, Nancy, France (B. Combes, S. Comte, V. Raton, S. Favier); University of Franche-Comté/National Center for Scientific Research, Besançon, France (F. Raoul, P. Giraudoux); Institut Universitaire de France, Paris (P. Giraudoux); French Agency for Food, Environmental and Occupational Health and Safety, Nancy (F. Boué, G. Umhang); National Game Federation, Issy-les-Moulineaux, France (C. Dunoyer); Departmental Veterinary Laboratories Manager Association, Besançon (N. Woronoff)

Abstract

During 2005–2010, we investigated Echinococcus multilocularis infection within fox populations in a large area in France. The parasite is much more widely distributed than hitherto thought, spreading west, with a much higher prevalence than previously reported. The parasite also is present in the large conurbation of Paris.

Echinococcus multilocularis is the causative agent of the parasitic zoonosis alveolar echinococcosis. The adult stage of this cestode is found mostly in the digestive tract of the red fox (Vulpes vulpes) (1). Parasite eggs, expelled in feces, are the only external living stage of the parasite life cycle. Once ingested by small mammals, they migrate to the liver and proliferate, forming protoscolices in multivesicular cysts. The life cycle is completed when a definitive host (usually canid) preys on an infected intermediate host (mostly rodent). Epidemiologic studies indicate that humans can be infected by eating raw vegetables contaminated by infected fox or dog feces or by direct contact with an infected fox or dog (2). Despite the low incidence of human alveolar echinococcosis in Europe (0.02–0.18 cases/100,000 inhabitants [3]) the zoonotic potential of the fox tapeworm, in terms of persistence and pathogenicity, poses a major parasitic threat to human health in nontropical regions (4).
Three main trends have been reported in the past decade in Europe. First, E. multilocularis prevalence has increased in foxes within areas to which it is known to be endemic (5), seemingly linked with the increase of fox population densities in Germany and Switzerland (6). Second, the geographic distribution of E. multilocularis in foxes has extended toward southern, northern, and eastern countries where it had not previously been detected; the most recent are northern Italy (7); Svalbard, Norway (8); and Sweden in 2011 (9). Third, the geographic distribution of echinococcosis has extended toward Russia and neighboring countries (10), including the Baltic states.