Fasciola hepatica: Infection Status of Freshwater Snails Collected from Gangwon-do (Province), Korea

The sheep liver fluke, Fasciola hepatica, is primarily a zoonotic parasite that causes liver infection in cattle and sheep, and occasionally in humans.Freshwater snails are the first intermediate host, and humans are infected mainly by ingesting raw aquatic plants contaminated with the metacercariae [1,2].F. hepatica infection in snails has traditionally been evaluated by microscopy; however, this method is time-consuming and laborious [2].In addition, microscopic investigation of snails for F. hepatica larvae has low diagnostic sensitivity [3].Thus, various molecular approaches have been used to identify Fasciola sp.infectons [3][4][5][6][7][8][9].F. hepatica is distributed mainly in Europe, America, and Oceania [1,2].The prevalence of F. hepatica infection was high in cattle before 2000 in Korea [10].There were also several human F. hepatica infection cases [6].However, little information is available regarding the prevalence of F. hepatica infection in Korea.Therefore, to obtain basic information regarding F. hepatica infection in snail intermediate host in freshwater environments in Korea, we collected freshwater snails from Gangwon-do (Province) and evaluated F. hepatica contamination by PCR.Freshwater lymnaeid snails were collected at Hoenggye-ri (upper stream) and Suha-ri (lower stream) of Song-cheon (stream) in Daegwalnyeong-myeon, Pyeongchang-gun in Gangwon-do (Province) near large cattle or sheep farms in August 2015 (Fig. 1).A total of 402 samples were collected and examined for the presence of the F. hepatica ITS-2 gene by PCR.Briefly, genomic DNA was extracted from the whole snail body using a G-DEX™ genomic DNA extraction kit (iNtRON Biotechnology, Seoul, Korea) according to the manufacturer's instructions.Genomic DNA isolated from an adult F. hepatica worm (kindly provided by Prof. Sung-Jong Hong, Chung-Ang University) and adult Fasciola gigantica worm (kindly provided by Prof. Keeseon S. Eom, Chungbuk National University) were used as positive controls.The sequences of the primers used were as follows: F. hepatica ITS-2, forward; GTTATAAACTAT-