Paragonimiasis

Essentials of Diagnosis

• Most persons are asymptomatic

• In symptomatic cases, abdominal pain and diarrhea develop 2 days to 2 weeks after infection

• Chronic infection produces pulmonary symptoms and chest pain

• CNS disease presents with seizures, headaches, focal neurologic findings, intracerebral lesions

General Considerations

• Of the eight species of Paragonimus lung flukes that cause human disease, Paragonimus westermani is the most important

• Eggs are released into fresh water, where parasites infect snails, and then cercariae infect crabs and crayfish

• Human infection follows consumption of raw, undercooked, or pickled freshwater shellfish

• Metacercariae then excyst, penetrate into the peritoneum and pass into the lungs, where they mature into adult worms over about 2 months

Demographics

• Paragonimus species are endemic in East Asia, Oceania, West Africa, and South America, where millions of persons are infected

• Infections from Paragonimus kellicotti have occurred in North America, albeit rarely

Symptoms and Signs

• Most persons have moderate worm burdens and are asymptomatic

• In symptomatic cases,

  • Abdominal pain and diarrhea develop 2 days to 2 weeks after infection

  • Then, fever, cough, chest pain, urticaria, and eosinophilia develop

• Acute symptoms may last for several weeks

• Chronic infection can cause

  • Cough productive of brown sputum

  • Hemoptysis

  • Dyspnea

  • Chest pain

• Ectopic infections can cause disease in other organs, most commonly the CNS

• CNS disease can present with

  • Seizures

  • Headaches

  • Focal neurologic findings due to parasite meningitis

  • Intracerebral lesions

Differential Diagnosis

• Tuberculosis

• Mycoplasma pneumoniae infection

• Bacterial pneumonia

• Legionnaires disease (Legionella)

• Amebic lung abscess

Laboratory Tests

• Diagnosis is made by identifying

  • Characteristic eggs in sputum or stool or

  • Worms in biopsied tissue

• Multiple examinations and concentration techniques may be needed

• Serologic tests may be helpful

• An enzyme-linked immunosorbent assay (ELISA) available from the CDC has sensitivity and specificity > 95%

Imaging Studies

• Chest radiographs may show

  • Infiltrates

  • Nodules

  • Cavitary lesions

  • Fibrosis

• Skull radiographs can show clusters of calcified cysts

• CT or MRI can show clusters of ring-enhancing lesions

Medications

• Praziquantel

  • Drug of choice

  • 25 mg/kg orally three times daily for 2 days

  • Use with corticosteroids for cerebral paragonimiasis

• Bithionol and triclabendazole are alternative therapies

Complications

• Bronchitis

• Bronchiectasis

• Bronchopneumonia

• Lung abscess

• Pleural thickening or effusion

Prognosis

• Cure rates of over 90% can be anticipated for praziquantel

When to Refer

• All patients should be referred to a clinician with expertise in the diagnosis and management of this disease

When to Admit

• Patients with presumed or confirmed CNS infection