Experimental infection of Opisthorchis viverrini cercariae to the cyprinid fish, Barbonymus gonionotus.

Opisthorchis viverrini is an important public health problem, a major cause of cholangiocarcinoma in the Greater Mekong subregion including Lao PDR, Cambodia, Vietnam and Thailand. Humans acquire the infection by consumption of raw, fermented or partially cooked freshwater cyprinid fish containing infective metacercariae. This study examined the effect of cercarial infection dosage (25-200 cercariae), age (1-60 day) and size (1-24mm) of Barbonymus gonionotus fish on infection success of O. viverrini cercariae. Additionally, the site of cyst formation of O. viverrini cercariae and subsequent development to the metacercariae was examined. The result showed that cercarial infection dose (F4,95=8.52, P<0.001) age (P<0.001, ƛLR(2)=954.72) and size (P<0.001, ƛLR(2)=1204.84) were significantly associated with number of O. viverrini metacercariae recovery with in every additional fish age, the O. viverrini metacercarial recovery rate increased by 5.4% (P<0.001). Most metacercariae were found in the body of the fish (81.4%). We concluded that O. viverrini cercarial infection dosage, and age and size of fish were important determinants for a successful infection to fish.