Paragonimiasis

Paragonimiasis is a foodborne trematode infection caused by Paragonimus species (P. westermani in Asia, P. africanus and P. uterobilateralis in West and Central Africa, P. kellicotti in North America, P. mexicanus in Latin America), acquired by eating raw or undercooked freshwater crabs or crayfish.

• About 23 million people infected worldwide; endemic in China, Korea, Japan, Philippines, Nigeria, Cameroon, Liberia, Ecuador, and Peru.
• Adult flukes live in pairs in cystic lung lesions; migration may involve brain, abdomen, and skin.
• Frequently misdiagnosed as tuberculosis.

• Pulmonary (most common): chronic cough with rusty or blood tinged sputum (haemoptysis), chest pain, dyspnoea, and pleural effusion, pneumothorax, or empyema.
• Cerebral (1 to 25%): seizures, headache, visual changes, and meningitis, especially in children.
• Abdominal: pain, diarrhoea, and mass lesions; cutaneous migratory nodules (P. skrjabini, P. westermani).
• Eosinophilia, raised IgE.

• Sputum or pleural fluid microscopy for operculated eggs (also in stool); eosinophilic pleural effusion with low glucose and raised LDH.
• Serology (ELISA, Western blot) is sensitive and useful where eggs are absent.
• Chest X-ray and CT: nodules, cysts, cavities, infiltrates, effusions, and pleural thickening; MRI brain for cerebral disease (ring enhancing "soap bubble" lesions).
• Exclude tuberculosis (co-infection common), lung cancer, bacterial pneumonia, lung abscess, and neurocysticercosis.

• Praziquantel 25 mg/kg three times daily for 2 to 3 days (cure above 90%).
• Alternative: triclabendazole 10 mg/kg twice (12 hours apart) or 20 mg/kg single dose; bithionol 30 to 50 mg/kg on alternate days for 10 to 15 doses.
• Cerebral paragonimiasis: praziquantel with corticosteroids (dexamethasone) to control inflammatory response to dying parasites, antiepileptics, and surgery for mass effect.
• Drainage of empyema, management of pneumothorax and haemoptysis (bronchial artery embolisation if massive).
• Prevention: avoid raw or pickled crabs and crayfish, health education, and treatment of sputum positive cases.