Sandra Gloor

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

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.

The diet of urban foxes (Vulpes vulpes) and the availability of anthropogenic food in the city of Zurich, Switzerland

Summary The diet of urban foxes and the availability of anthropogenic food were studied in the city of Zurich, Switzerland. A stomach analysis of 402 foxes, which were shot or found dead between January 1996 and March 1998, showed a broad variety in the diet of urban foxes, with a dominance of scavenged meat, other scavenge and cultivated fruit and crops. More than half of an average stomach content was anthropogenic. The proportion of anthropogenic food was increased in stomachs from the city centre – mainly due to the increasing proportion of scavenged meat – compared with stomachs from the periurban area. Significant seasonal variations in the diet were found for invertebrates, birds and for cultivated fruit and crops, which were all most frequently consumed in summer. A written survey among the inhabitants of three municipal districts showed that 85% of the households provided anthropogenic food which was accessible to foxes. This food supply consisted of three quarters of rubbish and compost, completed by fruit and berries and, to a lesser extent, food provisions for pets, birds, and other wild animals. In contrast, the anthropogenic food supply of allotment gardens mainly consisted of berries, completed by fruit, compost and birdseed. The anthropogenic food supply in public areas was determined by transects. The overall food supply of households, allotment gardens and public areas would be sufficient to feed a much higher number of foxes than currently present. This overabundance of food resources could explain the continual increase of urban population densities. A possible further exploitation of anthropogenic food sources is discussed considering its specific characteristics and the necessary behavioural adaptations.

BAITING RED FOXES IN AN URBAN AREA: A CAMERA TRAP STUDY

Abstract Baiting red foxes (Vulpes vulpes) is an established method of vaccinating foxes against rabies in rural environments. Furthermore, anthelmintic baiting has been demonstrated to reduce the prevalence of the zoonotic tapeworm Echinococcus multilocularis in foxes. The recent invasion of foxes into urban areas on continental Europe represents a considerable health risk that calls for the evaluation of baiting strategies adapted to the urban environment. We investigated bait uptake by urban foxes using camera traps in Zurich, Switzerland. Baits with and without the anthelmintic praziquantel were placed in several arrangements (exposed, covered, buried), at different locations (fox dens, compost heaps, fox tracks) and in different seasons (early summer, summer, winter). Ninety-one of 252 baits (36%) disappeared within 3 days. Most of the baits consumed near cameras were consumed by foxes (44 of 91). The remaining baits were consumed by hedgehogs (Erinaceus europaeus), snails (Arion sp.), dogs, rodents (Apodemus sp.), and unidentified animals. Bait uptake by foxes was significantly higher during summer than winter (P = 0.022), and foxes accepted baits most frequently at fox dens during early summer (52.8%). Burying baits reduced bait removal by species other than foxes (P < 0.01). For rabies control in urban areas, avoiding contact of nontarget species with the rabies vaccine is particularly important. Greater selection of the fox population can be achieved by distributing baits in winter, burying baits, and choosing sites that are less accessible to non-target species. However, with anthelmintic treatment, uptake by nontarget species is of lesser importance; hence, the effort to bury the bait is unnecessary.

Survey of public knowledge about Echinococcus multilocularis in four European countries: Need for proactive information

BackgroundPublic information about prevention of zoonoses should be based on the perceived problem by the public and should be adapted to regional circumstances. Growing fox populations have led to increasing concern about human alveolar echinococcosis, which is caused by the fox tapeworm Echinococcus multilocularis. In order to plan information campaigns, public knowledge about this zoonotic tapeworm was assessed.MethodsBy means of representative telephone interviews (N = 2041), a survey of public knowledge about the risk and the prevention of alveolar echinococcosis was carried out in the Czech Republic, France, Germany and Switzerland in 2004.ResultsFor all five questions, significant country-specific differences were found. Fewer people had heard of E. multilocularis in the Czech Republic (14%) and France (18%) compared to Germany (63%) and Switzerland (70%). The same effect has been observed when only high endemic regions were considered (Czech Republic: 20%, France: 17%, Germany: 77%, Switzerland: 61%). In France 17% of people who knew the parasite felt themselves reasonably informed. In the other countries, the majority felt themselves reasonably informed (54–60%). The percentage that perceived E. multilocularis as a high risk ranged from 12% (Switzerland) to 43% (France). In some countries promising measures as deworming dogs (Czech Republic, Switzerland) were not recognized as prevention options.ConclusionOur results and the actual epidemiological circumstances of AE call for proactive information programs. This communication should enable the public to achieve realistic risk perception, give clear information on how people can minimize their infection risk, and prevent exaggerated reactions and anxiety.