Human intestinal flukes Haplorchris taichui and Haplorchris pumilio in their intermediate hosts, freshwater snails of the families Thiaridae and Pachychilidae, in southern Thailand

Abstract

The intestinal flukes Haplorchis taichui (Nishigori, 1924) and Haplorchis pumilio (Looss, 1899) (family Heterophyidae) are among the most important food-borne parasitic zoonoses found in Southeast Asia. Here, we report on a study of infection rates in freshwater snails of the two Cerithioidean families Thiaridae and Pachychilidae in the south of Thailand. The snails were collected by handpicking and scooping every two months for one year at several locations between January 2008 and September 2009. The snail samples were examined for parasitic infections in the lab by shedding and crushing methods. Parasite infections were found in snails from 13 of 34 sampling sites. Nine species of thiarid snails were collected in this study, viz. Melanoides tuberculatus (Muller, 1774) Melanoides jugicostis (Hanley & Theobald, 1876), Thiara scabra (Muller, 1774), Sermyla riqueti (Grateloup, 1840), Neoradina prasongi (Brandt, 1974) and Tarebia granifera (Lamarck, 1822) as well as in four species of pachychilids, viz. Brotia sp. 1, Brotia sp. 2, Brotia wykoffi and Adamietta housei (Lea, 1856). Among these only the three thiarid species (M. tuberculatus, M. jugicostis and N. prasongi) were found to be infected with the two parasites, while we found no record in pachychilids. The infection rates of H. taichui and H. pumilio were 0.59% (126/21,501) and 0.12% (25/21,501) respectively, with H. taichui found in the three thiarid species M. tuberculatus, M. jugicostis and N. prasongi. The infection rates were 0.96% (89/9,227), 0.11% (1/920) and 7.74% (36/465), respectively. H. pumilio was found in M. tuberculatus only, with an infection rate of 0.27% (25/9,227). (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)