A survey of metacercariae in cyprinoid fish in Nakhon Ratchasima, northeast Thailand.

Metacercariae were recovered from freshwater fish taken from a stream in Lum Cha Muak, Nakhon Ratchasima Province, northeast Thailand during the year 2000. Seventy-nine cyprinoid fish comprising 3 species (52 Puntius leiacanthus, 22 Cyclocheilichthys armatus, and 5 Hampla dispar) were collected. The prevalence of infection with metacercariae was 51.9%. Only two genera of metacercariae were found: Haplochinae spp and Heterophyidae spp. Haplochinae metacercariae were found in all 3 species of fish, giving rates of infection of 95.5%, 20% and 1.9% for Puntius leiacanthus, Cyclocheilichthys armatus and Hampla dispar respectively. Heterophyidae metacercariae were found only in Puntius leiacanthus, whose infection rate was 30.77%. There were fish intected at the rate of 3.8% with unclassified metacercariae. Interestingly, no fish infected with Opisthorchis viverrini metacercariae were found, which is at odds with previous reports from Thailand in which a higher infection rate was given. This is the first report of fish infected with Haplorchinae spp in Thailand.

A survey of trematode cercariae in Bithynia goniomphalos in northeast Thailand.

A survey of trematode larvae in the fresh water snail, Bithynia goniomphalos in the main water reservoir of Huai Thalaeng district, Nakhon Ratchasima Province, Thailand, was conducted. The study site is in an area with a high prevalence of Opisthorchis viverrini infection. Malacological samplings were made during the year 2000 to study the prevalence and intensity of infection. Parasitological examinations of 527 live snails were performed at the Veterinary Parasitology Laboratory, Chulalongkorn University. Of the 527 snails, only 16 (3.04%) were found to be infected with cercariae. Of these 16 snails, 75% were infected with Amphistome cercariae, 6.25% with Armatae cercariae and 18.75% with Virgulate cercariae. Most infected snails (75%) had a density of infection of less than 100 cercariae/snail. No snail was infected with cercariae of Opisthorchis spp. This snail was, therefore, unlikely to be the intermediate host of Opisthorchis viverrini in the main water reservior of Huai Thalaeng district.