Studies on growth and distribution of Angiostrongylus cantonensis larvae in Ampullarium canaliculatus.

The intramolluscan development of Angiostrongylus cantonensis larvae in Ampullarium canaliculatus, a fresh-water migrant snail which multiplies in tremendous rate in Taiwan, was followed for 28 consecutive days in this study. The snails were infected with first stage larvae of A. cantonensis and groups of three snails were sacrificed daily to study various larval stages in different organs. A. cantonensis larvae were found in all snails examined. During the first four days, they were obtained only from the digestive tract. Mouth is thus suggested as the primary route of natural infection. The first molt was observed on the fifth day of infection, and the second molt, the 12th day. Molting occurred in almost all kinds of organs examined. Studies on tissue tropism showed that the predilection site of A. cantonensis in this freshwater snail was headfoot region. Relatively few larvae were found in visceral organs including liver, heart, and ovary. Most parasites, 62.1%, recovered on the 28th day of infection were third-stage larvae.

Studies on taeniasis in Taiwan. V. Field trial on evaluation of therapeutic efficacy of mebendazole and praziquantel against taeniasis.

Taeniasis is a major public health problem among the aboriginal populations on Taiwan, and is highly prevalent and wide spread in the mountain areas of 10 Counties. Over 27,000 cases of tapeworm infection are estimated influencing the health and economy in the endemic areas. A treatment of taeniasis with mebendazole and praziquantel followed by a re-treatment with atabrine has been done in the field trial, and confirmed that praziquantel is highly effective agent against tapeworm infection, but mebendazole is not. Based upon experiments reported here praziquantel in a single dose of 150 mg, and 450 mg are highly effective against taeniasis and hymenolepiasis respectively.