Schlüsselwörter
(Deutsch)
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Tiergesundheit, Epidemiologie, Echinococcus multilocularis, Zoonosen, Siedlungsraum, Infektionsdruck, Surveillance, Dispersion, Fuchs, Zwischenwirt, Endwirt, Kotsampling-Methode
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Kurzbeschreibung
(Deutsch)
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Seit dem Abklingen der Tollwut haben die Fuchsbestände in der Schweiz, und insbesondere im Siedlungsraum, markant zugenommen. Wie Ergebnisse aus dem NF-Projekt Nr. 31-47031.96 zeigen, sind bis zu 64% der Füchse am Stadtrand und knapp 20% der Füchse im Stadtzentrum von Zürich mit E. multilocularis befallen. Auch ca. ein Viertel der untersuchten Wühlmäuse aus einer Parkanlage waren mit E. multilocularis infiziert, was auf eine aussergewöhnlich hohe Kontamination dieser öffentlichen Anlage mit Eiern dieses Parasiten hinweist. Somit ist ein urbaner Zyklus des Parasiten zwischen Nagern und Endwirten Fuchs, Hund und Katze möglich.
Im vorliegenden Projekt sollen deshalb Möglichkeiten zur Beeinflussung des Echinokokkose-Zyklus erprobt werden. Durch das Ausbringen von mit Praziquantel versehenen Ködern soll die Möglichkeit einer langfristigen Entwurmung der urbanen Fuchspopulation getestet werden. Auch andere Massnahmen, wie der bereits laufende, intensive Abschuss in einem Teilgebiet der Stadt oder das Einzäunen von kritischen Flächen (Schrebergärten, Badeanstalten, etc.) sollen geprüft werden. In einem Kosten-Nutzen Modell sollen die verschiedenen Massnahmen und die Möglichkeiten keine Massnahmen zu ergreifen einander gegenüber gestellt werden.
Als weitere Resultate werden ein besseres Verständnis des E. multilocularis-Zyklus im urbanen Lebensraum und eine praxisorientierte Transekt-Samplin-Methode von Fuchslosung zur Surveillance des Infektionsdruckes im Siedlungsgebiet erwartet.
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Abstract
(Englisch)
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background and objectives
In several European countries a distinct increase of red fox (Vulpes vulpes) populations has been observed in recent years, particularly in urban areas. As a result, foxes now live in close vicinity to humans and their pets in many European cities. Sylvatic rabies has not yet been eradicated in Europe. Furthermore the small fox tapeworm Echinococcus multilocularis, the aetiological agent of the severe human liver disease alveolar echinococcosis (AE), is widespread in European fox populations. Consequently there is a serious concern about emerging zoonotic risks caused by the current fox population dynamics.
The aims of this project were (a) to quantify the infection pressure with E. multilocularis eggs in urban areas (b) to determine E. multilocularis prevalence in different urban intermediate hosts, (c) to investigate factors affecting the dynamics of an urban cycle of E. multilocularis, (d) to test how urban foxes can be reached with baits, if the application of rabies vaccine or anthelmintics were necessary, and (d) to evaluate an intervention strategy based on the delivery of anthelmintic-containing fox baits in order to reduce the infection pressure with E. multilocularis eggs in urban areas.
methods
In the framework of this project (a) 604 fox faeces were collected in the field and investigated for E. multilocularis with an coproantigen sandwich-ELISA, (b) 1155 rodents were trapped and necropsied for the identification of intermediate host species, (c) 252 baits were surveyed with automatic camera traps, and (d) an anthelmintic intervention was tested by the monthly distribution of 50 praziquantel-containing baits per km2 in six 1-km2 bait areas and one 6-km2 bait area. The effect of anthelmintic baiting was tested by investigating collected fox faeces for coproantigens of E. multilocularis and by determining the parasites of water voles (Arvicola terrestris) trapped in baited and non baited areas.
results and discussion
Of fox faeces investigated, 26% were positive for E. multilocularis on coproantigen ELISA. The proportion of fox faeces positive for E. multilocularis antigens decreased significantly from periurban areas towards more central urban areas. The highest prevalence of E. multilocularis in intermediate hosts was detected in A. terrestris (9.1%). In nine of ten trapping areas along the city border E. multilocularis infected A. terrestris were recorded. Of 252 baits surveyed with camera traps 36% disappeared within 3 days. Foxes took 48% of the removed baits. However baits were also consumed by hedgehogs, snails, dogs and rodents.
Baiting had a distinct effect on the proportions of E. multilocularis coproantigen-positive fox faecal samples. These decreased significantly in the 1-km2 bait areas from 38.6% to 5.5%, and in the 6-km2 bait area from 66.7% to 1.8%. E. multilocularis prevalence in the intermediate host, A. terrestris, also decreased significantly. The baiting study demonstrated that a reduction of urban E. multilocularis infection pressure by the distribution of anthelmintic-containing fox baits is feasible. The decision for an intervention remains, however, a political, ecological and economic issue. Further risk analyses and cost-benefit evaluations are therefore recommended.
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Publikationen / Ergebnisse
(Englisch)
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Steiger, C., Hegglin, D., Schwarzenbach, G., Mathis, A., Deplazes, P. (2002): Spatial and temporal aspects of urban transmission of Echinococcus multilocularis. Parasitology 124, 631-640.
Deplazes, P., Eckert, J. (2001): Veterinary aspects of alveolar echinococcosis - a zoonosis of public helath significance. Veterinary Parasitology 98, 65-87.
Gloor, S., Bontadina, F., Hegglin, D., Deplazes, P., Breitenmoser, U. (2001): The rise of urban fox populations in Switzerland. Mammalian Biology 66, 155-164.
Dip, R., Steiger, C., Deplazes, P., Hegglin, D., Müller, U., Dafflon, O., Koch, H. Naegeli, H. (2001): Comparison of Heavy Metal Concentrations in Tissues of Red Foxes from Adjacent Urban, Suburban, and Rural Areas. Arch. Environ. Contam. Toxicol 40. 551-556.
Hegglin D., Ward, P., Deplazes, P. (2003): Anthelmintic baiting of foxes against urban contamination with Echinococcus multiocularis. Emerging Infectious Diseases 9, 1266-1272
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