Anthelmintic Baiting of Foxes against Urban Contamination with Echinococcus multilocularis

recent years, increases in the urban fox population have been observed in many countries of the Northern Hemisphere. As a result, Echinococcus multilocularis has entered the urban environment. Because of a possible increased risk for alveolar echinococcosis, intervention strategies need to be evaluated. In Zürich, Switzerland, 50 praziquantel-containing baits per km 2 were distributed monthly in six 1-km 2 bait areas and one 6-km 2 bait area from April 2000 through October 2001. The proportion of E. multilocularis coproantigen–positive fox fecal samples collected remained unchanged in six control areas but decreased significantly in the 1-km 2 bait areas (from 38.6% to 5.5%) and in the 6-km 2 bait area (from 66.7% to 1.8%). E. multilocularis prevalence in the intermediate host Arvicola terrestris also decreased significantly in baited areas. This controlled baiting study shows that a pronounced reduction of E. multilocularis egg contamination is feasible in urban areas where the organism is highly endemic. T he zoonotic tapeworm Echinococcus multilocularis is typically perpetuated in a wild life cycle, which includes foxes (genera Vulpes and Alopex) as definitive hosts and various rodent species as intermediate hosts (1). In addition, eggs are accidentally ingested by humans; the metacestodes enter mainly the liver and cause alveolar echinococcosis, a severe, sometimes fatal disease if left untreated (2,3). Few studies have been performed on the epidemiology of alveolar echinococcosis. Risk factors for alveolar echinococcosis may include occupational and behavioral activities. However, hunters, trappers, and persons working with fur were not at increased risk for alveolar echinococcosis in South Dakota (4). Data from Europe have indicated that farming activities increase the risk for infection (5,6). Contamination of the rural environment with E. multilocularis connected with farming activities was indirectly demonstrated by high prevalences of alveo-lar echinococcosis in sows kept indoors but fed with grass (7). Areas with high water vole (Arvicola terrestris) densities yielded a 10-fold higher risk for human alveolar echinococcosis compared with areas with low densities of this important intermediate host (8). In an area where the organism is highly endemic, up to 39% of A. terrestris and up to 7% of dogs with free access to rodents were infected with E. multilocularis (9), and persons who have kept dogs around dwellings were at higher risk for alveolar echinococcosis on St. Lawrence Island, Alaska (10). Red foxes (Vulpes vulpes) are likely to be the most important final host in many regions (11). In the past …