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.