Endemic areas are mainly concentrated in Asia, particularly in China (including Taiwan), Korea, and Japan. It is also endemic in several places in Europe, in particular the Balkan region and Spain. The former USSR, western India, Indonesia, and the Philippines also contain endemic areas. Scattered human cases have been known to occur in non-endemic regions, such as in the United States, through the importation of infected fish for human consumption.
There are about 650,000 cases of metagonimiasis worldwide, mostly in China, Korea, and Japan. In 1999, it was estimated that there were 500,000 cases of M. yokogawai infection in Korea alone. Over 40 million people worldwide are infected with any food-borne trematode. Food-borne trematodiases are most prevalent in remote rural areas among school-age children, low-wage earners, and women of child-bearing age.
Although specific numbers are unavailable, there are indications that trematode infections in general have been increasing in the past few years. This is believed to be because of an increasing production of fish and shellfish in unhygienic fish ponds, as well as an increase in the popularity of raw, undercooked, or insufficiently processed food in many parts of the world. This is further exacerbated by increased international travel. More than 10% of the world population is potentially at risk for acquiring a food-borne trematode infection.
Public Health Implications
Because of centuries-old traditions of eating raw or insufficiently cooked food, unsanitary defecation practices, and the use of "night soil" (human excrement used as fertilizer) in many endemic areas, it is difficult to change the lifestyles of at-risk populations to decrease their risk of acquiring a metagonimiasis infection. In addition, there are many zoonotic reservoirs for M. yokogawai such as dogs, cats, pigs, and others that ensure that the parasite does not die out.
General factors that increase risk of intestinal fluke diseases include:
Socio-economic risk factors for intestinal fluke diseases include:
What Can Be Done?
Increased awareness efforts (for both the public and public health authorities) can yield substantial results, especially in very endemic areas. Teaching people about the dangers and risk factors and presenting alternatives is very important. Some suggestions for decreasing personal risk might include:
In non-endemic areas, it is also important to inform the public about the potential of acquiring a food-borne infection such as metagonimiasis. Suggestions for decreasing risk in non-endemic areas might include:
Make sure the public knows to report any symptoms to local public health authorities (this will help establish a more accurate picture of the spread of the disease, including incidence and prevalence).