PubMed1984
Of the intestinal trematode infections in Korea, metagonimiasis is the most important under public health aspects. In a nationwide survey in 1981, at least 450,000 people (1.2%) were found infected. The endemic areas are scattered along rivers which run to the southern and eastern coast, where more than 20% of villagers are commonly infected. The snail hosts of Metagonimus yokogawai are either Semisulcospira spp. or Koreanomelania spp. The fish hosts are sweetfish (Plecoglossus altivelis) and many species of cyprinid fish, of which the former is the more important source of infection. Dog, cat and rat are found naturally infected in endemic areas. Sweetfish frequently have more than 10,000 metacercariae in their muscles. In autumn, the metacercarial burden reaches its zenith, when the fish is sweetest. Eating only one raw sweetfish may result in severe abdominal pain, prostration and watery diarrhoea, However, in endemic areas, many egg discharging cases rarely suffer from diarrhoea and abdominal pain. The symptoms seem mainly to depend on the degree of infection. But also duration of infection seems to be a factor which determines the intensity of symptoms. In experimental infection of cat or dog, juvenile worms thrive into crypts of Lieberkühn in the jejunum for about 5 days. Thereafter, the adults move to the intervillous space and destroy the enterocytes. Adults rarely reach the submucosa or lymphatic tissues. In rather heavy infection, mucosal damage such as villi fusion, villi shortening, slight hypertrophy of crypts, goblet cell depletion, inflammatory cell infiltration and shortening of microvilli were observed. These pathologic findings regress within 4 weeks of infection though adult worms still live in the mucosa.