Diphyllobothriasis

Overview
Diphyllobothriasis is the infection caused by Diphyllobothrium.

Geographic distribution
Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish. Such areas are found in the Northern Hemisphere (Europe, newly independent states of the former Soviet Union (NIS), North America, Asia) (particularly in Japan (because of Sushi or Sashimi)), Uganda, Peru (because of Ceviche) Chile.

Around mid-twentieth in Japan before advancements in refrigeration, many sushi/sashimi connoisseurs suffered great morbidity and mortality from Diphyllobothrium after eating unrefrigerated sashimi. After developments in parasitology, many scientists came to realise that the primary cause for this burden was due to the relatively favourable parasite breeding conditions that raw fish offered.

The disease is rare in the United States, however, it was once more common and was referred to as "Jewish housewife's disease" because Jewish housewives preparing the traditional "gefilte fish" tended to taste the fish before it was cooked.

Clinical features
Diphyllobothriasis can last for decades if untreated. Most infections are asymptomatic. Manifestations may include abdominal discomfort, diarrhea, vomiting and weight loss. Vitamin B12 deficiency with subsequent megaloblastic anemia may occur, but has not for several decades in D. latum infections, possibly because of improved nutrition. In one test, nearly half of the ingested vitamin was absorbed by D. latum in otherwise healthy patients, while 80-100% was absorbed by the worm in patients with anemia. It is not known why anemia occurs in some cases but not others. Massive infections may result in intestinal obstruction. Migration of proglottids can cause cholecystitis or cholangitis.

Females cases are disproportionately reported, most likely due to the higher likelihood for them to be involved in meal preparation, rather than any morphological differences.

Diagnosis
Microscopic identification of eggs in the stool is the basis of specific diagnosis. Eggs are usually numerous and can be demonstrated without concentration techniques. Examination of proglottids passed in the stool is also of diagnostic value.

Diagnostic tool:
 * Microscopy
 * Morphologic comparison with other intestinal parasites

Though it is difficult to identify the eggs or proglottids to the species level, the distinction is of little medical importance because, like most adult tapeworms in the intestine, all members of this genus respond to the same drugs.

Treatment
Praziquantel and niclosamide are historical treatments that should no longer be used as first line therapy in developed countries; they result in destruction and disintegration of the worm which may make it impossible to confirm that the scolex (head of the worm) has been passed (the only way to confirm cure). Praziquantel or niclosamide should only be used in situations when endoscopy is not available or is not possible.

The preferred treatment for all tapeworm infections is injection of diatrizoic acid into the duodenum, which causes the worm to detach and be passed whole.

Prevention
Avoid ingestion of raw freshwater fish. Adequate cooking or freezing of freshwater fish will kill the encysted fish tapeworm larvae. Also, because human feces is an important mechanism for spreading eggs, proper disposal of sewage can cut down on infection of fish and thus of humans.