Efficacy of anthelmintic baiting of foxes against Echinococcus multilocularis in northern Japan.

Field application of anthelmintic baits against Echinococcus multilocularis in red foxes (Vulpes vulpes) was conducted on Nemuro Peninsula at the eastern edge of Hokkaido, Japan. The total study area was 412 km(2), of which 135 km(2) were used for bait distribution. Commercial baits containing 50mg praziquantel were distributed by car along roads outside towns and villages in a density of 15/km(2). Additional baits were distributed around fox breeding dens. Baiting was done from November 1999 to January 2006 at an average frequency of 4.3 distribution rounds per years (in total 27 rounds). Prevalence in foxes collected in the baiting and non-baiting areas were determined by necropsy. Base prevalence (before baiting) was 49.4% (CI95%: 43.7-55.0) in the baiting area and 70.5% (CI95%: 60.2-79.2) in the non-baiting area. During the first and second half of the baiting period, the prevalence in the baited area changed to 26.2% (CI95%: 14.4-42.3) and later to 15.8% (CI95%: 7.9-28.4), but remained at a high level in the neighboring non-baited area with 60.4% (CI95%: 45.3-73.9) and 65.0% (CI95%: 40.9-83.7). Our data show, that significant prevalence reduction (but not elimination) of E. multilocularis in foxes can be achieved by this method under epidemiological conditions, which are fundamentally different from those in Europe where most previous studies have been done.