STUDIES ON CERCARIAE FROM FRESH WATER SNAILS IN THAILAND

Recent investigations on the human parasite in Thailand revealed that many pathogenic trematodes existed among the inhabitants. Harinasutaet al. (1959) reported heavy endemic areas ofOpisthorchis viverriniin the north and north-east parts of Thailand. Sadun and Maiphoom (1953) investigated the prevalence of Fasciolopsis buskiamong the inhabitants of the central part of Thailand. Vajrasthiraet al. (1958, 1959) detected a new endemic area ofParagonimus westermaniin Saraburi Province, 90 kilometer far from Bangkok City. One case of human schistosomiasis was reported from the southern part of Thailand and identified asSchistosoma japonicumby Chaiyapornet al. (1959) though no intermediate snail host was found. Itoet al. (1962) investigated stray dog parasites in Bangkok, resulting in finding several trematode species such asEchinochasmus japonicus, Haplorchis taichui, Haplorchis yokogawai.Though the faunistic study of cercariae is considered to be an important step in the epidemiological survey of human trematode, no report has been published as yet concerning the cercariae in Thailand.By the reasons above mentioned, many fresh water snails from various parts of Thailand were collected and brought into the laboratory of Faculty of Public Health in Thailand in order to study the parasitic cercariae in the period from 1960 to 1961. Twelve species of cercariae were detected from four species of snails. In this paper, those cercariae are described, five of which were morphologically identified with known species, and the remaining seven were given new names.