2022 Volume 62 Issue 1 Pages 31-37
A soil-transmitted nematode, Strongyloides callosciureus, is an exotic parasite introduced into Japan along with the spread of an invasive host, Pallas’s squirrel Callosciurus erythraeus. The establishment of this parasite has so far been reported from several localities in Shizuoka and Kumamoto Prefectures, but basic information for risk assessment is not fully available in other host-colonized areas. Here, we report the infection status of this parasite in suburban areas (i.e., Yokohama, Yokosuka, Kamakura, and Bando Cities) in the Kanto region, where the host squirrel has already invaded. A total of 124 host individuals, captured in 2016, 2018, and 2019, were examined. Parasite infection was found only in Yokosuka City, with a low prevalence (13.33%) and low mean abundance (0.40 worms per host examined) and mean intensity (3.00 worms per host infected). This suggests that in the examined areas, infections are infrequent or that the parasite itself is absent. In addition, partial sequences of the 18S and 28S rDNA regions, examined for all the parasite individuals, showed the highest homology with S. callosciureus from Hamamatsu City, with values of 99.93% and 100.00%, respectively.
