Prevalence of Clonorchis sinensis metacercariae in freshwater fish from three latitudinal regions of the Korean Peninsula

Abstract

A large-scale survey was conducted to investigate the infection status of fresh water fishes with Clonorchis sinensis metacercariae (CsMc) in 3 wide regions, which were tentatively divided by latitudinal levels of the Korean peninsula. A total of 4,071 freshwater fishes were collected from 3 regions, i.e., northern (Gangwon-do: 1,543 fish), middle (Chungcheongbuk-do and Gyeongsangbuk-do: 1,167 fish), and southern areas (Jeollanam-do, Ulsan-si, and Gyeongsangnam-do: 1,361 fish). Each fish was examined by the artificial digestion method from 2003 to 2010. In northern areas, only 11 (0.7%) fish of 2 species, Pungtungia herzi and Squalidus japonicus coreanus from Hantan-gang, Cheolwon-gun, Gangwon-do were infected with av. 2.6 CsMc. In middle areas, 149 (12.8%) fish were infected with av. 164 CsMc. In southern areas, 538 (39.5%) fish were infected with av. 159 CsMc. In the analysis of endemicity in 3 regions with an index fish, P. herzi, 9 (6.2%) of 146 P. herzi from northern areas were infected with av. 2.8 CsMc. In middle areas, 34 (31.8%) of 107 P. herzi were infected with av. 215 CsMc, and in southern areas, 158 (92.9%) of 170 P. herzi were infected with av. 409 CsMc. From these results, it has been confirmed that the infection status of fish with CsMc is obviously different among the 3 latitudinal regions of the Korean peninsula with higher prevalence and burden in southern regions.

Keywords: Clonorchis sinensis; freshwater fish; latitudinal level; metacercaria; prevalence.

Fig. 1

The surveyed areas. The northern area located over 37° North Latitude is comprised of 7 administrative regions of Gangwon-do (① Inje-gun: Soyang-gang, ② Hongcheon-gun: Hongcheon-gang, ③ Cheolwon-gun: Hantan-gang and Hwa-gang, ④ Yanggu-gun: Sooip-cheon, ⑤ Yangyang-gun: Namdae-cheon, ⑥ Youngweol-gun: Dong-gang and ⑦ Samcheok-si: Osip-cheon and Gagok-cheon). The middle area located between 36° and 37° North Latitude is contained 3 regions of Chungcheongbuk-do (⑧ Okcheon-gun: Gum-gang, ⑨ Goisan-gun: Cheong-cheon and ⑩ Daecheong-ho), and 7 regions of Nakdong-gang (⑪ Ahndong-si, ⑫ Sangju-si, ⑬ Bonghwa-gun, ⑭ Yecheon-gun, ⑮ Youngyang-gun, ⑯ Youngdeok-gun and ⑰ Gunwi-gun) in Gyeongsangbuk-do. The southern area located below 36° North Latitude is comprised of 6 administrative regions of Jeollanam-do (⑱ Gokseong-gun: Seomjin-gang, ⑲ Gurye-gun: Seomjin-gang, ⑳ Naju-si: Youngsan-gang, ㉑ Gangjin-gun: Tamjin-gang, ㉒ Jangheung-gun: Tamjin-gang and ㉓ Boseong-gun: Boseong-gang), and ㉔ Ulsan Metropolitan City (Taehwa-gang) and ㉕ Sancheong-gun (Yangcheon-gang) in Gyeongsangnam-do.