westermani

Paragonimus westermani is a parasitic trematode in the family Paragonimidae and one of several species known as lung flukes. It is commonly called the Asian lung fluke and is a major cause of paragonimiasis in humans and other mammals. The species name westermani honors a person with the surname Westerman in its taxonomic naming.

Life cycle and transmission: Eggs are excreted in sputum and reach freshwater, where they hatch into miracidia that infect freshwater snails. After development, cercariae are released and encyst as metacercariae in crustaceans such as crabs and crayfish. Humans acquire infection by ingesting raw or undercooked crustaceans containing metacercariae. In the intestine, metacercariae excyst and migrate through the peritoneal cavity and diaphragm to the lungs, where they mature into adult flukes. Eggs produced by adults are shed in sputum and may reach other tissues in ectopic infections.

Clinical features: Many infections are asymptomatic initially. When symptoms occur, they typically include chronic cough, chest pain, recurrent pneumonia, fever, and hemoptysis. Ectopic migration can involve the brain, spinal cord, or skin, causing neurological or cutaneous symptoms.

Diagnosis and treatment: Diagnosis relies on finding eggs in sputum or, less reliably, in stool; serologic tests and imaging support the diagnosis. Praziquantel is the drug of choice; alternative regimens include triclabendazole or bithionol in some settings. With appropriate therapy, outcomes are generally favorable.

Epidemiology and prevention: Paragonimus westermani is most common in East and Southeast Asia, with sporadic cases elsewhere. Prevention centers on avoiding raw or undercooked freshwater crustaceans and ensuring thorough cooking; public health measures focus on identifying and treating infected individuals and reducing transmission.