Paragonimus

Epidemiology

• small snails serve as the 1st intermediate host
• freshwater crabs or crayfish serve as 2nd intermediate host & harbor infectious metacercariae
• infection may result from ingestion of raw, undercooked or marinated crustaceans

Pathology

• larvae are released into the stomach, migrate through the intestinal wall & into the peritoneal cavity
• they reach the lungs by penetrating the diaphragm
• maturation takes 5-6 weeks & the worms may live many years
• adults measure 12 by 6 mm
• they are often found in pairs in lung parenchyma of cats, dogs, other carnivores & humans within a fibrous capsule produced by the host
• the capsule communicates with the bronchi through which eggs pass to be excreted in the sputum or feces
• eggs remaining in the lung or other tissues may cause an extensive granulomatous reaction
• worms may develop in ectopic sites, including the peritoneum, subcutaneous tissues & the brain

Clinical manifestations

• related to migration of larvae or by adults in tissue
• onset of lung infection associated with fever/chills
• chronic cough
• abundant mucus production
• episodes of hemoptysis
• pleural effusion

Laboratory

• complet blood count: eosinophilia
• isolation of eggs from
  • feces
  • sputum
  • tissues
• unembryonated eggs
  • measure 80-120 by 45-70 um
  • operculated
  • moderately thick, yellow-brown shell
  • different species of Parogonimus cannot be distinguished on the basis of appearance of eggs
• Paragonimus eggs may be distinguished from those of Diphyllobothrium, Fasciola & Fasciolopsis on the basis of size
• Paragonimus serology

Radiology

• Chest X-ray:
  • nodular shadows, calcifications, patchy infiltrates
  • pleural effusion may be present

Management

• praziquantel 25 mg/kg TID for 2 days

More general terms

• Troglotrematidae

More specific terms

• paragonimiasis
• Paragonimus caliensis
• Paragonimus ecuadoriensis
• Paragonimus kellicotti
• Paragonimus mexicanus
• Paragonimus westermani