Prevalence of Blatticola blattae (Thelastomatidae) in German cockroaches Blattella germanica in Japan

A survey for nematode infection in German cockroaches captured in restaurants in various areas of Japan as well as the laboratory-bred colony was carried out. The nematodes were then identified morphologically and molecularly. Of the 320 German cockroaches collected at 79 restaurants in 26 prefectures in Japan, 66.6% (213/320) were found to be parasitized by a single species of pinworm in the hindgut. The mean number of pinworms per cockroach was less than 1.6. Of the three laboratory-bred lines of cockroaches examined, 2 lines (NIID and NK) were found to be infected with a single species of nematode. The prevalence was 93.0% (40/43) and 84.8% (39/46), respectively. The other laboratory line (WAT) was found to be free of the nematode infection. The nematode detected in this study was identified as Blatticola blattae. This is the first report of B. blattae infection in German cockroaches in Japan. Our study showed that B. blattae is distributed all over Japan together with its host Blattella germanica. An experimental infection with B. blattae in nematode-free cockroach by contaminating the rearing environment with infected-cockroach feces showed that once the environment of the cockroach is contaminated with B. blattae eggs, the pinworm infection could spread easily.