Hideharu Tsukada

Preliminary study of the role of red foxes in Echinococcus multilocularis transmission in the urban area of Sapporo, Japan

In order to assess the infection risk of alveolar echinococcosis among urban residents of Sapporo, the capital of Hokkaido, Japan, a survey was conducted on fox distribution in the urban area and on the prevalence of Echinococcus multilocularis among the foxes. The fox distribution, evaluated from fox footprints left on the snow in parks and woodlands, and from locations of fox carcasses recorded by the Sapporo municipality, was concentrated along the border of the urban area and in the southwestern part of the city, facing the mountain. Fox faeces were collected around active fox dens, and analysed by a coproantigen detection assay and parasite egg examination for the Echinococcus infection. Thirty-three out of 155 faeces were coproantigen positive. Coproantigen-positive faeces were collected from 11 den sites (57.9% of total den sites), and all except 1 were located in the urban fringe. A high intensity of taeniid eggs (> 100 eggs per 0.5 g) containing faeces were also collected in the 3 sites of them. Although Echinococcus infection in rodents was not observed from the necropsy of 23 rodents captured around active fox dens, arvicolid rodents, a suitable intermediate host for E. multilocularis, were captured in the urban fringe. Therefore, the urban fringe offers suitable conditions in which the life-cycle of E. multilocularis could be maintained. Prompt measures to control echinococcus infection should be taken, even in urban areas.

Potential remedy against Echinococcus multilocularis in wild red foxes using baits with anthelmintic distributed around fox breeding dens in Hokkaido, Japan

The effect of bait-delivered anthelmintic to reduce the prevalence of Echinococcus multilocularis in wild red foxes was evaluated in Koshimizu, in the eastern part of Hokkaido, Japan. The study area (200 km2) was divided into baited and non-baited sections. The anthelmintic baits were distributed around fox den sites in the baited section every month for 13 months. After 1 year of the anthelmintic bait distribution, the prevalence of E. multilocularis in foxes, evaluated either by the parasite egg examination (from 27.1 to 5.6%) or coproantigen ELISA (from 59.6 to 29.7%), decreased in the baited section contrasting to that in the non-baited section (parasite egg: from 18.8 to 24.2%; ELISA: from 41.9 to 45.8%). The prevalence of E. multilocularis in grey red-backed vole Clethrionomys rufocanus, caught around fox dens, born after bait distribution also decreased and was significantly lower than that in non-baited section. However, within the study periods, the coproantigen-positive rate in fox faeces sporadically increased, while egg-positive rate constantly decreased. Since coproantigen ELISA can detect pre-patent infection, this observation indicates that reinfection pressure in the baited section was still high even after the 13 months of anthelmintic bait distribution. Therefore, the bait distribution longer than our study period is required for the efficient control of E. multilocularis in wild red fox population.

Coproantigen survey for Echinococcus multilocularis prevalence of red foxes in Hokkaido, Japan

An epidemiological survey was conducted on the seasonal variation of Echinococcus multilocularis prevalence in red foxes from 1997 to 1998, using a monoclonal antibody-based detection of the tapeworm coproantigen. Thirty-six breeding dens of reproductive fox families were identified in the endemic area of Koshimizu, eastern Hokkaido, Japan. Fecal samples from each site were examined by coproantigen detection assay and fecal egg examination. Whereas the prevalence of coproantigen positive feces showed no seasonal fluctuation (51.6-66.7%), variation was found in the prevalence of egg positive feces in which a higher prevalence was observed in the summer and winter (31.1 and 38.7%) than spring and autumn (13.3 and 13.5%). Significant differences were observed between juveniles and adult foxes in both examinations. Samples from juvenile foxes gave higher coproantigen positive results and taeniid egg intensity. Those results suggest more juveniles infected with the cestode than adults in the same period. The practical use of coproantigen assay as a survey tool and factors which affect the prevalence and host age-related difference are discussed.

A division between foraging range and territory related to food distribution in the red fox

Spatial organization of the red fox (Vulpes vulpes schrencki) was investigated on the basis of seasonal food distribution in the Shiretoko National Park, Hokkaido from 1992 to 1994. Four periods were recorded pertaining to the distribution of 2 kinds of food resources: human food and spawning salmonid carcasses. The home range utilizations of radio-collared foxes were compared for the periods. In the periods when food was not spatially concentrated, resident foxes were territorial, showing exclusive distribution of home ranges between families, defense against intruding foxes at the edge of home ranges, and site specific dominance over intruding foxes. In contrast, during periods when food distribution was concentrated, home ranges overlapped. In the latter periods, foxes made round trips of up to 8 km from their territories to the localized concentration of food, the distance that foxes can travel within a day. This suggests that red foxes in this area have unique foraging ranges that include some seasonally available food outside their territories, and that these ranges depend on fluctuating food distribution caused by humans.

Monitoring of Echinococcus multilocularis infection in red foxes in Shiretoko, Japan, by coproantigen detection

The study was conducted to evaluate a mAb-based coproantigen detection assay for monitoring fox prevalence of Echinococcus multilocularis infections in the Shiretoko National Park in Hokkaido, Japan. Eight fox families, each consisting of 2-4 adults and their pups, were selected because their territories have been determined. Faeces of each family (total n = 537) were collected monthly from April to October, 1994. Detection of coproantigen and taeniid eggs was recognized in 58 and 27 faeces, respectively, but mostly restricted in 1 family, in which coproantigen ELISA OD values had dual peaks, one in June and the other in October, whereas taeniid eggs were detected only from April to July. Fox pup faeces (n = 51) collected around the dens used by the positive family were all coproantigen and taeniid egg negative except for 1 faeces. These results suggest that the prevalence and infection pressure in the study area were low and the infected family terminated the infection in the summer and acquired a new one in the early autumn, 1994. This monitoring method for fox infection will be a practical management tool for E. multilocularis infection, especially at the tourist spots in Hokkaido where close contact of fox with humans is frequently observed.

Depredation of Concentrated Feed by Wild Mammals at a Stock Farm in Japan

Concentrated feed, which contains high levels of digestible nutrients, is widely used as a food source for fattening cattle in Japan. However, it is also a valuable food resource for wild animals. Wild animals such as crows (Kitazaki and Tanida 1996; Nagano et al. 1998), raccoon dogs (Nyctereutes procyonoides) (Murakami and Arata 1998), and Asiatic black bears (Ursus thibetanus) (Maruyama 2003) steal feeds from cattle farms. In the US and UK, wild animals cause economic losses from depredation of cattle feed (Palmer 1976; Johnson and Timm 1987), and sometimes disease transmission (Garnett et al. 2002; Daniels et al. 2003; Palmer et al. 2004). Furthermore, high nutrition cattle feeds may improve the pest’s nutritive status leading to increase of pest populations. Nevertheless, there are few reports on depredation of cattle feed by wild animals. There is no information about which species are more attracted by the concentrated feed than others. Identifying which species steal cattle feed is valuable for developing countermeasures. In this study, the depredation of concentrated feed on a stock farm by wild mammals was investigated to identify which species steal the concentrated feed, and to establish daily and seasonal patterns of depredation.