Paragonimose

Paragonimose, or paragonimiasis, is a human parasitic infection caused by lung flukes of the genus Paragonimus. The most common species affecting humans include Paragonimus westermani in Asia and Paragonimus kellicotti in North America. The disease is acquired by ingestion of metacercariae in undercooked freshwater crustaceans, such as crabs or crayfish.

Infection begins when metacercariae are released in the small intestine, migrate through the peritoneal cavity and diaphragm, and reach the lungs where they mature into adult flukes. Eggs produced by the adults are deposited in lung tissue and reach the airways, being expelled in sputum or swallowed and excreted in stool, thus continuing the life cycle.

Pulmonary disease is the most common manifestation and typically presents with chronic cough, chest pain, and hemoptysis. Fever, night sweats, and weight loss may occur. Extrapulmonary paragonimiasis can involve the brain, skin, or other organs, leading to neurologic symptoms or subcutaneous nodules depending on the site of migration and egg deposition.

Diagnosis relies on a combination of exposure history, clinical and radiologic findings, and laboratory tests. Imaging may reveal focal infiltrates or nodules in the lungs. Eosinophilia is common. Demonstration of Paragonimus eggs in sputum or stool supports diagnosis, though eggs may be difficult to find. Serologic tests, such as ELISA, can aid in diagnosis, particularly when stool examination is negative.

Treatment is with praziquantel, typically 25 mg/kg three times daily for 2–3 days. Alternative regimens include triclabendazole. Most patients respond well to therapy, though chronic infection can cause lasting lung damage.

Prevention centers on avoiding raw or undercooked freshwater crustaceans and implementing public health measures in endemic regions to reduce transmission.