Infection characteristics of Metagonimus species (Digenea: Heterophyidae) metacercariae in fish from major rivers of Korea

Abstract

This article analyzed the infection characteristics of metacercariae of <i>Metagonimus</i> spp. (MsMc) in fish from 9 major water systems in Korea. A total of 19,568 fish in 87 species were examined over a period of 10 years (2011–2020). MsMc were detected in fish from all 44 survey areas in 9 water systems. Most of the surveyed sites showed very low and low infection levels (66.7%), while 33.3% of the areas, such as Tamjin-gang and Seomjin-gang, revealed moderate and high infection levels. High endemicity depends on the abundance of susceptible fish species, especially sweet smelt (<i>Plecoglosus altivelis</i>). The susceptibility index (SI) with MsMc in index fish, Zacco spp., was very low and low levels in 62.0%, moderate in 28.0%, and high in 10.0% regions. The SI was highest in the following order: Yeongam-cheon (283.8), Hoeng-cheon (192.3), Togyo-jeosuji (131.2), Deokcheon-gang (119.1), and Joyang-gang (106.3). The recent infection status of MsMc in <i>P. altivelis</i> was analyzed by the survey localities. In addition, except for <i>P. altivelis</i>, 9 fish species were highly infected with MsMc in some survey areas, including <i>Zacco platypus</i>, <i>Z. koreanus</i>, <i>Z. temminckii</i>, <i>Opsariichthys uncirostris</i>, <i>Rhynchocypris oxycephalus</i>, <i>Carassius auratus</i>, <i>Acheilognathus rhombeus</i>, <i>Onchorhynchus masou</i>, and <i>Tribolodon hakonensis</i>. In Korea, 74 fish species (15 families) are collectively listed as second intermediate hosts of <i>Metagonimus</i> spp. This review provides several novel characteristics of MsMc infection and clarifies the fish species of second intermediate host of <i>Metagonimus</i> spp. in this country.