Metagonimiasis is a disease caused by an intestinal trematode, most commonly Metagonimus yokagawai, but sometimes by M. takashii or M. miyatai.

When present in large numbers, can cause chronic intermittent diarrhea, nausea, and vague abdominal pains.

Occasionally, flukes invade the mucosa and eggs deposited in tissue may gain access to circulation.

An additional study examining karyotype data on the three disease-causing agents also supported the nomination of M. miyatai as a separate species.

Transmission requires two intermediate hosts, the first of which is snails, most commonly of species Semisucospira libertina, Semiculcospira coreana, and Thiara granifera.

Definitive hosts include humans and various fish-eating mammals, primarily dogs, cats, and pigs.

The presence of heterophyid infection in humans is generally caused by a lack of host specificity by the parasites, as seen in the many non-human reservoirs for metagonimiasis.

The egg also has a very slight opercular shoulder, marking the line of cleavage between the shell and operculum, an "escape hatch" for the miracidium.

Diagnosis may be difficult because the egg-laying capacity of heterophyids is limited, and therefore sedimentation concentration procedures may be needed to demonstrate eggs in lighter infections.

It is important to ask where the person may have contracted the disease, find out if they have been to en endemic area, and check for signs and symptoms that would lead to metagonimiasis.

This could potentially be problematic and not as effective as hoped as many of the people affected by metagonimiasis eat raw or pickled fish as part of a traditional, long-seated dietary practice.

Praziquantel is a Praziniozoquinoline derivative that alters the calcium flux through the parasite tectum and causes muscular paralysis and detachment of the fluke.

Praziquantel has some side effects but they are generally relatively mild and transient and a review of evidence shows it overall a well-tolerated drug.

Possible side effects include abdominal pain, allergy, diarrhea, headache, liver problems, nausea or vomiting, exacerbation of porphyries, pruritus, rash, somnolence, vertigo, or dizziness.

In fact, in 2002, the World Health Organization recommended the use of Praziquantel in pregnant and lactating women, though controlled trials are still needed to verify this.

A 1978 study also looked at the efficacy of several drugs on metagonimiasis infection, including bithionol, niclosamide, nicoflan, and Praziquantel.

M. yokagawai infections are found mostly around the large and small streams where sweetfish live and have been identified as endemic foci.

M. miyatai and M. takahashii are prevalent along the upper reaches of the big rivers where minnows and carps are caught for eating raw.

Metagonimiasis is also common in Japan, with 10-15% prevalence rates in populations bordering major rivers and 150,000 estimated infected.

Food-borne trematodes are most common in rural areas where traditional food habits are more preserved and raw freshwater fishes are incorporated into the diet.

Both clonorchiasis and metagonimiasis have become infections of higher social classes in Hong Kong and Japan, owing to their frequent consumption of raw fish.

Chai, Jong-Yil et al. "An epidemiological study of metagonimiasis along the upper reaches of the Namham River."

Chi, Je G. et al. "Intestinal Pathology in Human Metagonimiasis with Ultrastructural Observation of Parasites."

Han, In-Soo et al. "An Epidemiologic Study on Clonorchiasis and Metagonimiasis in Riverside Areas in Korea."

Lee, Jin-Ju, et al. "Decrease of Metagonimus yokogawai Endemicity along the Tamjin River Basin."

Lee, Gye-Sung et al. "Epidemiological study of clonorchiasis and metagonimiasis along the Geum-gang in Okcheon-gun, Korea."

Lee, Seoung Cheol et al. "Antigenti c protein fractions of Metagonimus yokogawai reacting with patient sera."

Lee, Soo-ung et al. "Sequence comparisons of 28S ribosomal DNA and mitochondrial cytochrome c oxidase subunit I of Metgonimus yokogawai, M. takahashii, and M.

Lee, Soo-ung et al. "A cytogenetic study on human intestinal trematodes of the genus Metagonimus in Korea."

Yamada, Shoko Merrit et al. "A Case of Metagonimiasis Complicated with Multiple Intracerbral Hemorrhages and Diabetes Mellitus."