Paragonimiasis (lung fluke disease) causes hemoptysis, pneumonia, and pulmonary fibrosis in chronic infections. Humans are infected eating undercooked freshwater crabs or crayfish. The larvae can survive pickling, marinating, and salting. The larvae penetrate the intestines and migrate to the lung.
CASES/YEAR
50 (US); 23,000,000 (Global)
OTHER NAMES
Lung fluke; Pulmonary distomiasis; Paragonimus westermani; P. mexicanus;
INCUBATION
7-12 weeks from ingestion until eggs appear in sputum; [CCDM]
INITIAL SYMPTOMS
Abdominal pain, diarrhea, fever, urticaria, chest pain, and dyspnea; [ID, p. 2381-2]
PRECAUTIONS
Not directly transmitted from person to person because eggs passed in sputum and stool are not embryonated. [CCDM, p. 445]
COMMENTS
EPIDEMIOLOGY:
Humans are infected after eating undercooked freshwater crabs or crayfish containing encysted larvae of this trematode. The larvae can survive pickling, marinating, and salting. [ID, p. 2381-2]
FINDINGS
The larvae penetrate the intestines and migrate to the lung. Eggs can be found in the sputum and stool. Symptoms of chronic infection include hemoptysis, pneumonia, and pulmonary fibrosis. Paragonimus mexicanus is one species that tends to encyst in the central nervous system. Meningitis may occur. Worm cysts are occasionally found in the intestinal walls and peritoneal cavity. [ID, p. 2381-2] Definitive hosts and reservoirs are humans, dogs, cats, swine, and wild carnivores. Paragonimiasis may be misdiagnosed as tuberculosis. Eggs in sputum are destroyed by acid-fast staining. [CCDM, p. 443-5] Marked eosinophilia is present early. Eosinophilia may or may not be present during chronic infection. Urticaria may occur. Subcutaneous nodules (trematode larva migrans) occur, especially with species other than P. westermani. Worms invading the eye can cause uveitis and cranial nerve palsies. Most patients with CNS disease have preceding pulmonary disease. [Guerrant, p. 863-4;, 943; 1015; ] Lung infection may be followed within a year by cerebral infection marked by seizures, paresis, and other neurological symptoms. Cutaneous larva migrans is associated with P. skriabini and other species. [Merck Manual, p. 1722] Eosinophilia and leukocytosis occur in early stages. [Guerrant, p. 864] Eosinophilia of pleural fluid is an important diagnostic clue. Rusty sputum, discolored by eggs, resembles iron filings. [Cecil, p. 2127] Unlike tuberculosis, chronic paragonimiasis is marked by eosinophilia and lacks fever. [PPID, p. 3461]
DIAGNOSTIC
Microscopic exam to identify the eggs in sputum or stool; Note: Acid-fast staining destroys the eggs; [CCDM] EIA and western blot serological tests available; Also, chest x-ray, CT & MRI; [Harrison ID, p. 1039t]
SCOPE
Asia, Africa, and Latin America; Endemic in China (22 million infected); Rare in N. America; Eliminated from Japan; [CCDM] Far East, South Asia, Philippines, West Africa, Central & South America & USA; [PPID, p. 3452t]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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G abdominal pain
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G diarrhea
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G nausea, vomiting
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H eosinophilia
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H leukocytosis
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N confusion, delirium
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N headache
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N lethargy
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N muscle weakness
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N paresthesia
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N seizure
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R chest pain
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R cough
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R dyspnea
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R hemoptysis
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R sputum production
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S skin or subcutaneous nodule
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S urticaria
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S skin lesion, linear or serpiginous
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X cystic or cavitary lesions
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X lung infiltrates
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X pleural effusions
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*brain abscess or lesion
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*cranial neuropathy
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*encephalitis
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*mediastinitis
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*meningitis
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*paralysis
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*pneumonia
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*pneumonitis
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*uveitis
SOURCE
Animal Tissue, Eating Contaminated Food, Eating Contaminated Mollusks or Crustacean
RESERVOIR
Cats, Dogs, Fish and Shellfish, Swine, Human, Wild Animals
RISK FACTORS
- Eat undercooked meat or fish
- Travel to endemic area
TREATMENT
Praziquantel is the drug of choice. [CDC website]
REFERENCES FOR CASES/YEAR
1. (US) Rare in N. America; [CCDM, p. 444] More than a dozen cases from undercooked crayfish have been reported in Mississippi River basin. [PPID, p. 3460] Guesstimate: 50 cases/year;
2. (Global) 56 million suffered and 7000 died from foodborne trematodiases in 2005; [Fact sheets from WHO] 23 million people infected; [Cecil, p. 2127]