[Spontaneous infection of Hymenolepis nana in hamsters (author's transl)]

Hymenolepis nana (von Siebold, 1852), the dwarf tapeworm causing hymenolepiasis, has been reported to be the common intestinal cestode of rodents and man throughout the world. The authors found spontaneously occurred hymenolepiasis in conventional laboratory hamsters with mass and heavy infections. Some individuals were infected with as many as 188 to 290 worms and in addition, numerous cysticercoids were found in the intestinal villi from the same hamsters. According to the early investigations it is said that there are two ways of infection to rodents. In this study the authors considered a natural autoinfection is to be the case because cysticercoids and immature worms were abundant in the intestines of hamsters. The infection rate of the hamsters was 15% as 6 hamsters were found infected out of 40. All the cases of the heavily infected hamsters showed showed loss of weight and some of them died. Particular damage of the intestinal mucosa was not seen by post-mortem examinations, however, chronic inflammation and destruction of intestinal mucosa caused by the worms observed microscopically (the given pictures). Heavy infection of Hymenolepis nana occurred spontaneously in hamsters has rarely been found in Japan. The case reported here seems to be very peculiar one.