Schistosoma mansoni-like infection in Phayao Province, Northern Thailand.

Schistosome ova were found in the serosa of colon mass of a 65-year old Thai woman from Dokkhumtai District, Phayao Province. On the basis of the shape and microscopic appearance of the ova, they probably belonged to those of Schistosoma mansoni complex. In follow-up study, no ova were found by faecal examinations and rectal biopsy. There are evidences suggesting the presence of two distinct mammalian strains in Thailand: Orientobilhorzia harinasutai, a schistosome of water buffalo in Southern region and Tricula bollingi schistosome, a rodent schistosome in Northern region. This case is believed to be the first human schistosome infection with mammalian strain of S. mansoni complex in Thailand.