1) The molluscicidal effect of 10 agricultural chemicals which are commonly usedby farmers in Saitama Prefecture was tested experimentally against A. ollula in the laboratory. The snails were made to contact with chemical solution for 48 hrs. at 23-25°C, then transferred to new containers with fresh water. The death rate was observed after 1 more hr.
LC₅₀ value of Saturn emulsion (Benthiocarb 50%), Saturn-S granule (Benthiocarb 7%, Simetryne 1.5%), MO emulsion (CNP 20%), NIP emulsion (NIP 25%), Sumithion emulsion (MEP 50%), Baysid emulsion (MPP 50%), Disiston granule (Ethylthiometon 5%), Bassa emulsion (BPMC 50%), Kitasin-Pemulsion (IBP 4%), and Lime nitrogen granule (CaNCN 21%) were 13.0, 92.5, 24.8, more than 50, 16.5, 13.5, more than 500, more than 50, more than 50 and 360 ppm. respectively, all figures were far larger than the doses in practical use for each chemicals. So it can not be expected that these chemicals would be effective against the snail in the ordinally practice.
2) Themolluscicidal effect of Lime nitrogen granule was also investigated with the snail in the paddy field where this fertilizer had been applied at an ordinally dose that is 2 Kg per are., 5 days prier to the test. The snails were introduced into the paddy and the mortality rate was observed 1, 2 and 3days after the introduction. The mortality rates of the snails at each day were 7.5%, 11.0% and 12.9% respectively. In the untreated field these figures were 7.0%, 14.9% and 4.4%.
It was concluded that Lime nitrogen granule was not effective against the snail at the ordinally dose for the use for fertilizer.

A dermatitis of unknowns etiology has occurred among the farmers working in paddy fields in some districts of Kagoshima Prefecture, such as Ibusuki, Hiyoshi, Oura, Makizono and Minami-tane.
In order to acertain the cause of the disease, the epidemiological investigations have been made since1975.
The dermatitis occurrs from March to July when rice-planting and weeding are on and is characterized by erythemato- papulo-vesicular eruptions accompanied with severe itching. The chief symptoms are observed on the parts exposed to water, especially on forearms and lower legs.
The research for snail intermediate hosts was carried out in the paddy fields where the dermatitis originated.
As a result, two species of apharyngeal furcocercous cercariae were obtained from the fresh water snails, Polypylis hemisphaerula and Austropeplea ollula. The cercaria from P. hemisphaerula resembled to that of Gigantobilharzia sturniae in shape and size, and the other one from A. ollula was identified as species belonging to the genus Trichobilharzia and was regarded the same species as described in Saitama Prefecture by the authors.
An experimental infection with the cercaria belonging to the genus Trichobilharzia was performed. A few drops of water containing10cercariae were placed on the forearm. The cercariae invaded into the skin and produced a dermatitis quite similar to that prevailing in the endemic areas.
Therefore, it was concluded that the etiological agent were the cercariae of two different avian schistosomes, namely, G. sturniae and Trichobilharzia sp.

A dermatitis of unknown etiology has occurred among the farmers working in paddyfields in some districts of Tokushima Prefecture, such as Anan, Kainan and Komatsujima.
The dermatitis occurs from March to May when rice-planting and weeding are on and is characterized by erythemato-papulo-vesicular eruptions accompanied with severe itching. The chief symptoms are observed on the parts exposed to water, especially on forearms and lower legs. The results of the epidemiologicaland clinical observations indicated that the dermatitis was due to the invasion of cercariae of an avian schistosome.
The investigation for snail intermediate hosts was carried out in the paddy fields where the dermatitis occurred.
Cercariae of apharyngeal furcocercous type were detected from the fresh water snails (Austropeplea ollula) which were collected most abundantly from the paddy fields during the season of occurence of the dermatitis.
The cercaria wasidentified as species belonging to the genus Trichobilharzia and was regarded as the same species as so far described in Saitama Prefecture by Suzuki et al (1973).
An experimental infection with the cercaria was performed. A few drops of watercontaining cercariae was placed on the fore-arm of. a voluntor. The cercariae invaded into the skin and produced a dermatitis quite similar to that prevailing in the endemic areas.
Therefore, it was concluded that theetiological agent was the cercaria of a species of an avian schistosome.