Visceral Larva Migrans

Essentials of Diagnosis

• Principally seen in young children

• Most infections are asymptomatic

• Liver and lungs most commonly involved organs

• CNS infection is rare

• Ocular larva migrans is distinct syndrome that occurs in children older than is typical for visceral larva migrans

General Considerations

• Caused by the dog roundworm Toxocara canis or by the cat roundworm Toxocara cati

• Rarely, Baylisascaris procyonis, a roundworm of raccoons, causes visceral larva migrans in humans

• Humans are infected after ingestion of eggs in material contaminated by dog or other feces

• With T canis, infection is spread principally by puppies and lactating females, and the eggs must be on the ground for several weeks before they are infectious

• After ingestion by humans, larvae migrate to various tissues but cannot complete their life cycle

Symptoms and Signs

• Most infections are asymptomatic

• Cough, fever, wheezing

• Hepatomegaly, splenomegaly

• Lymphadenopathy

• Pulmonary infiltrates

• Eosinophilia

• Involvement of the CNS can occur rarely, leading to eosinophilic meningitis and other abnormalities

• Ocular larva migrans presents with

  • Visual deficits

  • Pain

  • Retinal mass, which can be confused with retinoblastoma

• Manifestations of B procyonis infection, although rare, are typically similar but more severe than those with T canis

Differential Diagnosis

• Acute HIV infection

• Infectious mononucleosis

• Lymphoma

• Malaria

• Ascariasis

• Chagas disease

• Retinoblastoma

Laboratory Tests

• Blood tests may show eosinophilia in patient with hepatomegaly or other signs of disease

• Serologic tests may be helpful

• ELISA against a group of excreted antigens has shown good sensitivity and specificity

• Molecular assays can identify specific pathogens

Diagnostic Procedures

• Diagnosis is confirmed by identification of larvae in a biopsy of infected tissue, usually performed when other diseases are suspected

Medications

• Most patients recover without specific therapy

• Antihelminthics or corticosteroids may be considered in severe cases

• Although no drugs have been proved to be effective, the following have been used

  • Albendazole

  • Mebendazole

  • Diethylcarbamazine

  • Ivermectin

• Albendazole (400 mg twice daily for 5 days) has been recommended as treatment of choice

Prevention

• Disease in humans is best prevented by periodic treatment of puppies, kittens, and nursing dog and cat mothers, starting at 2 weeks postpartum, repeating at weekly intervals for 3 weeks and then every 6 months

• Prevent defecation by dogs and cats in areas where children play

Prognosis

• Symptoms of the acute infection may persist for months but generally clear within 1–2 years

• The ultimate outcome is usually good, but permanent neuropsychological deficits have been seen

• Partial or total permanent visual impairment is rare

When to Refer

• Patients whose disease is progressive despite therapy

• All patients with ocular toxocariasis

When to Admit

• Progressive respiratory disease

• Patients with CNS involvement or carditis