Diphyllobothriidae

Diphyllobothriidae is a family of parasitic tapeworms in the class Cestoda that infect vertebrate hosts, including birds, mammals, and fish. The best known human parasite in this family is Diphyllobothrium latum, commonly called the fish tapeworm. Members of Diphyllobothriidae are classified as pseudophyllidean cestodes, typically characterized by a scolex with two shallow bothria (grooves) for attachment rather than a rostellum with hooks.

Life cycle and morphology: Adult tapeworms inhabit the small intestine of their final hosts and produce proglottids containing eggs. Eggs are operculated and released in feces, where they hatch into free-swimming coracidia in water. Coracidia are eaten by freshwater crustaceans (copepods), where the parasite develops into a procercoid; subsequently, second intermediate hosts such as fish acquire plerocercoid larvae in their tissues. Humans and other mammals become infected by consuming raw or undercooked fish containing plerocercoids, which mature into adults in the intestine. The infection is called diphyllobothriasis.

Clinical presentation and diagnosis: Infections are often mild or asymptomatic, but heavy infections can cause abdominal discomfort, diarrhea, weight loss, and sometimes B12 deficiency leading to megaloblastic anemia. Diagnosis primarily relies on detection of operculated eggs or attached proglottids in stool, with molecular tools used for species confirmation.

Treatment and prevention: Praziquantel is the preferred therapy; niclosamide is an alternative. Prevention focuses on proper fish handling: thoroughly cooking fish or freezing it at appropriate temperatures to kill larvae. Public health measures emphasize surveillance and education in endemic regions.

Epidemiology: Diphyllobothriidae infections occur worldwide where raw or undercooked freshwater fish is consumed, with Diphyllobothrium latum being the most commonly implicated human species in many regions.