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Individual study: Combined aerial- and ground-baiting with a de-wormer is successful in the control of small fox tapeworm Echinococcus multilocularis in red foxes Vulpes vulpes, Starnberg district, Bayern, Germany

Published source details

König A., Romig T., Janko C., Hildenbrand R., Holzhofer E., Kotulski Y., Ludt C., Merli M., Eggenhofer S., Thoma D., Vilsmeier J. & Zannantonio D. (2008) Integrated-baiting concept against Echinococcus multilocularis in foxes is successful in southern Bavaria, Germany. European Journal of Wildlife Research, 54, 439-447


As a result of a successful rabies immunization campaign, in the 1990s densities of red fox Vulpes vulpes across central Europe have increased. In Bavaria (Bayern), southern Germany, densities are now 2-3 times higher than in the 1980s, and they have colonized urban areas. A high proportion of foxes are infested with the small fox tapeworm Echinococcus multilocularis. In humans, this tapeworm can cause the severe infection (alveolar echinococcosis); human cases are rare but incidences are increasing. There is no human vaccine, thus infection risk can only be reduced through preventative measures. A reduction of the fox population to a level that would prevent an epidemic is impracticable, and given the low risk, even if achievable, it might be considered unacceptable. This study therefore investigated the efficacy of reducing tapeworm infestation in foxes over a large area through a combination of aerial- and ground-baiting, using bait laced with the de-wormer, praziquantel. The aim was to reduce infestation rates to a point where the tapeworm development cycle was interrupted, thus avoiding rapid re-infestation as observed in some previous control attempts.

Study area: The Starnberg district (451 km²) was selected as the study area. Data prior to the experiment indicated that average small fox tapeworm infestation rate of foxes in the district was 51%.

Experimental design: Baiting took place in 2002/2003. Of the 17 communities (sub-divisions) within Starnberg, 10 (totaling 213 km²) were subject to baiting (standard fox bait (Droncit™), each piece laced with 50 mg of praziquantel) and seven served as control areas (no bait distributed).

Baiting methods: Baiting by aircraft was carried out over forests, open countryside and farmland; bait was also distributed around 100 fox dens in rural and recreational areas. Aerial baiting over urban areas is not permitted, therefore bait was laid by hand (mainly in gardens).

Baiting interval: Worming does not result in immunization, thus bait must be distributed repeatedly, and at a frequency shorter than the development cycle of the tapeworm; approximately 3-4 weeks in the intermediate hosts (mice) and 35 days in foxes. Bait was therefore distributed once every 4 weeks.

De-worming success: To measure success, tapeworm infestation rates were recorded in fox carcasses supplied by local hunters from August through winter (this was to ensure that young foxes were old enough to eat mice and that no young foxes killed at their den were brought in). Individuals killed on roads were also collected for diagnosis.

Pre-baiting infestation prevalence was 35% (22–50%). During the 12 months subsequent to first 4-month baiting period, only one fox (n=100) was infested with E.multilocularis. No significant change occurred in the unbaited control areas. The observed decline was far higher than in previous control attempts, likely due to the increased bait distribution, baiting density and baiting frequency, and the inclusion of urban areas in the baiting programme.

The results suggest that a cost-effective medium-term preventative public health measure has been achieved, whilst avoiding the need for reductions in fox populations.

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