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.

Angiostrongylus cantonensis infection in Ampullarius canaliculatus (Lamarck) in Kyushu, Japan.

Ampullarius canaliculatus is a large fresh-water snail of which the original habitat is said to be Argentina. Recently, the snail which grew wild has propagated in various parts of Japan, and is causing damage to aquatic plants by feeding on them. The present study was performed to find out whether the snail can be a suitable intermediate host for Angiostrongylus cantonensis. Natural infection with A. cantonensis was confirmed in the snails collected from 5 different places in 4 hamlets in Okinawa and in those from Ishigaki Island. All snails experimentally infected with first-stage larvae of the parasite showed second-stage and third-stage larvae developing at the time of examination later on. Thus, A. canaliculatus is a suitable intermediate host for A. cantonensis, and, if eaten raw, it can be a potential source of human infection with eosinophilic meningoencephalitis in the endemic areas.

The biology of Angiostrongylus cantonensis larvae in immune rats.

Rats acquired protective immunity to Angiostrongylus cantonensis after a single infection with 50 infective larvae. Immunity was stronger after subsequent infections. Fewer worms were recovered which were shorter and produced fewer progeny after secondary and tertiary infections. However, the growth of A. cantonensis during the early developmental stages in the brain and the ability of the young adult parasites to migrate to the lungs was not affected in the immune host.

Growth and localization of Angiostrongylus cantonensis in the molluscan host, Achatina fulica.

The development of the rat lung worm Angiostrongylus cantonensis within the giant African snail Achatina fulica is reported. In this host, ingested first stage larvae penetrate the intestinal wall into the hemocoel and migrate to the mantle where they undergo two molts and become third stage larvae within 24 days. The mantle, harboring 85% of the total number recovered is the major location of infective larvae. The kidney contains about 11% but few larvae are found in the remaining visceral organs. Host response consists of encapsulation; destruction by means of phagocytosis was not observed.