Pinworm Blatticola blattae infection and survival of starving German cockroach Blattella germanica.

The German cockroach Blattella germanica is commonly infected with the pinworm Blatticola blattae. To determine the effect of pinworm infection on cockroach survival, we artificially altered the pinworm infection status of cockroaches and determined the number of survival days under no-feeding conditions, with and without opportunities for fecal feeding. Four lines of the German cockroach (Wn, Wp, Nn, and Np groups) were used in the experiment. Wp and Np were pinworm-infected lines. Wn and Nn were pinworm-free lines. The 50% survival days of cockroaches in the absence of opportunities for fecal feeding were not significantly different in Wp (3.45 days) vs Wn (3.27), and in Np (4.60) vs Nn (4.48). In contrast, in the presence of fecal feeding, the 50% survival times for the pinworm-infected Wp (4.04) and Np (6.65) were significantly longer than those for the pinworm-free Wn (2.77) and Nn (5.46). The number of survival days without feeding was significantly higher in the pinworm-infected group given the opportunity to eat feces than in the non-infected group. These results suggest that pinworm infection of cockroaches during starvation, in association with fecal feeding, may be associated with longer survival.

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.

Effects of anthelmintics on the pinworm Blatticola blattae in laboratory-reared German cockroaches Blattella germanica.

The efficacy of pyrantel pamoate, pyrvinium pamoate, ivermectin, and piperazine citrate against pinworm in cockroach was evaluated. Laboratory-reared German cockroaches naturally infected with Blatticola blattae were treated with the anthelmintics and necropsied at 3 to 35 days after treatment. Ivermectin at over 5 ppm and piperazine citrate at over 2000 ppm killed all the treated cockroaches. Pinworms were still detected in cockroaches given lower concentration of the aforementioned drugs. Administration of pyrantel pamoate (100-1000 ppm) and pyrvinium pamoate (2000 ppm) did not kill the cockroaches, and no pinworms were detected at 3 and 17 days after treatment. Thus, pyrantel pamoate and pyrvinium pamoate were found to be effective for deworming B. blattae in the German cockroaches, without causing mortality for the host. Our results showed that anthelmintics selection is essential for eradication of pinworms in cockroaches because of the toxicity for the host such as ivermectin or piperazine citrate. This is the first report of piperazine citrate toxicity in cockroaches.