Epidemiology

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Metagonimiasis is found mostly in the Far East, Siberia, Manchuria, the Balkan states, Israel and Spain. The parasite requires freshwater species of fish and snails to carry out its lifecycle. Therefore, it is prevalent in communities and populations that rely on polluted streams and rivers. In Korea, M. yokogawai is the most common of intestinal trematodes identified in  in humans. There, most streams on the Eastern and Southern coast are endemic foci for the fluke.

 

Countries with M. yokogawai - Endemic Foci (in pink): China, Taiwan, Korea, Indonesia, Philippines, Israel, The Former Soviet Union, Spain, Israel, Egypt.

 

Because of difficulty in diagnosis, it is hard to definitively establish morbidity rates for metagonimiasis based on clinical observations. However, a survey in 1981 in The Republic of Korea found that at least 450,000 people (1.2% of Korea's population) had M. yokogawai eggs in their feces. In communities living next to rivers that run along the Eastern and Southern coasts, they recorded infection rates of up to 20%. (Cho, SY; Kang, SY; Lee, SB. "Metagonimiasis in Korea").

Also, with increased travel and migration, there have been incidents of M. yokogawai infections imported into the United States by travelers from endemic regions. One such case was identified in 1978 in a young American one and a half years after she had returned from traveling in Asia. She had suffered from intermittent diarrhea ever since her trip. M. yokogawai eggs were found in her feces. (Goldsmith, RS. "Chronic Diarrhea in Returning Travelers: Intestinal Parasitic Infection with the Fluke Metagonimus yokogawai").

Physicians in the US are advised to consider M. yokogawai and other similar intestinal fluke infections as a possible cause of persistent diarrhea in travelers returning from endemic areas abroad.