Paragonimus westermani

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iParagonimus westermani

Egg of P. westermani

Scientific classification

Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Trematoda
Subclass:	Digenea
Order:	not available
Family:	not available
Genus:	Paragonimus

Species

Paragonimus westermani

Paragonimus westermani is the taxonomic name of an important lung fluke. It is endemic to Asia. Oncomelania snails are essential to this worm's life cycle. The infection of P. westermani is a serious disease.

The eggs of P. westermani range in size from 68µm-118µm x 39µm-67µm. They are yellow-brown, ovoidal or elongated, with a thick shell, and often asymmetrical with one end slightly flattened. At the large end, the operculum is visible.

Paragonimiasis is a disease caused by parasites called flukes, most commonly Paragonimus westermani. There are other Paragonimus species that can cause disease in humans. The major forms of disease are pulmonary (lung) and extrapulmonary (outside of the lung, such as in the abdomen or brain).

Lung fluke infection can be a serious illness in humans, but it is not transmitted from person-to-person. Symptoms of lung fluke infection can include cough, difficulty breathing, diarrhea, abdominal pain, fever and hives. The parasite, Paragonimus, can migrate from the lungs to other organs, and infection can last for years. Medication is available to treat the infection.

When Paragonimus eggs hatch in fresh water, the miracidium enters different snails and develops into cercaria, which infect freshwater crabs and crayfish, where they form cysts in gills and muscles. When freshwater crabs are eaten raw, the parasite penetrates the gut wall, migrates through the abdominal cavity and passes the diaphragm, where it develops into adult worms. The classical symptoms of a fully developed infection is bloody sputum in which Paragonimus eggs can be demonstrated, and Paragonimus is, therefore, an important differential diagnosis to tuberculosis. In the migratory phase, elevated eosinophils and IgE are common. Diagnosis can be aided by detection of specific antibodies. The treatment of choice is praziquantel.