gen-positive fecal samples was significantly higher than in the 1-km2 bait areas (mean 66.7%; 95% CI 46.0% to 83.5%; χ2 test: p<0.05). The proportion decreased signifi- cantly to 9.2% (95% CI 3.8% to 18.1%) during summer/autumn 2000, and to 1.8% (95% CI 0.0% to 6.5%) during summer/autumn 2001 (Actus randomization test, p<0.001). This proportion of coproantigen-positive fecal samples did not differ significantly from the final propor- tion of positive fecal samples found in the 1-km2 bait areas. The spatial persistence of the baiting effect was inves- tigated by comparing the prevalence in relation to the dis- tance from the baiting area. In both the bait area center (>250 m inside the bait area) and in the bait area periphery (250 m inside to the border of the bait area), the effect of baiting was very pronounced (Figure 3). For fecal samples collected 0 to 500 m from the next bait area, the effect of baiting was less clear; for those collected >500 m, no sig- nificant effect could be registered. A total of 16 coproantigen-positive fecal samples from bait areas and 55 coproantigen-positive fecal samples from control areas, all collected from July to October 2001, were investigated for the presence of E. multilocularis eggs. PCR analyses revealed significantly fewer fecal samples positive for E. multilocularis eggs (mean 25.0%; 95% CI 7.3% to 52.4%) in bait areas than in control areas (mean 52.7%; 95% CI 38.8% to 66.3%; χ2 test [one-tailed] p<0.05). Prevalence in Intermediate Hosts Of 1,014 A. terrestris, 509 originated from 1-km2 bait areas and 505 from control areas. The stepwise backward logistic regression indicated a significant final model (model χ2=8.4, df=3, p<0.05) showing that anthelmintic baiting, expressed by the interaction between area type and period, on the prevalence of E. multilocularis in A. ter- restris (Wald Statistics 3.7, df 1, p [1-tailed] <0.05) had an Figure 2. Proportions of Echinococcus multilocularis coproanti- gen–positive fox fecal samples and 95% exact binomial confi- dence intervals in the six 1-km2 bait areas, baited monthly with 50 praziquantel-containing baits per km2, and the six unbaited control areas during the experiment. RESEARCH Figure 3. Proportions of Echinococcus multilocularis coproanti- gen–positive fox fecal samples and 95% exact binomial confi- dence intervals obtained at different distances from the border of the 1-km2 bait areas, baited monthly with 50 praziquantel-contain- ing baits per km2, before baiting started (November 1999 to March 2000) and after baiting had taken place for 3 months (July 2000 to October 2001). influence. During the first year of baiting, the prevalence in control and baited areas was similar (Figure 4), but dur- ing autumn 2001 the prevalence in baited areas was signif- icantly lower (mean 2.1%; 95% CI 0.6% to 5.2%) than in control areas (mean 7.3%; 95% CI 4.4% to 11.2%). Independently from their interaction effect, the blocking variables of period and area type also entered the final model but not urban area and season. The results for the 1-km2 bait areas could be confirmed in the 6-km2 bait area. The prevalence of E. multilocularis in 215 A. terrestris was highest from July 1999 to February 2000 before baits were delivered (mean 21.6%; 95% CI 11.3% to 35.3%) and decreased significantly afterwards (χ2=4.54, df=2, p [1-tailed]=0.05). The prevalence was lower from April to November 2000 (mean 14.3%; 95% CI 6.4% to 26.2%) and lowest from July to October 2001 (mean 9.3%; 95% CI 4.5% to 16.4%). Discussion Baiting Strategy and Bait Density The high bait density of 50 baits per km2, combined with a manual bait distribution at sites attractive for foxes, was highly effective. In oral rabies vaccination campaigns, up to 20 baits were usually delivered per km2 (32). Also, in the anthelmintic bait studies in Germany bait densities from 15 to 20 baits per km2 were successfully used (19,20). In contrast to densities in rural habitats, in urban areas, fox densities can easily exceed 10 adult foxes per km2 (23,24). Furthermore, in summer, many adolescent foxes are present. A previous camera trap study conducted Emerging Infectious Diseases • Vol. 9, No. 10, October 2003 1269