Toxocara canis
Summary
Toxocara canis is a roundworm that causes visceral larva migrans (VLM) in humans, primarily children. Infection occurs through ingestion of embryonated eggs from contaminated soil or fomites. The larvae migrate through various organs causing eosinophilia, hepatomegaly, and potential ocular complications.
Detail
Toxocara canis is an ascarid nematode whose definitive host is dogs. Humans are accidental hosts who become infected by ingesting embryonated eggs from contaminated soil, sandboxes, or fomites. After ingestion, larvae hatch in the small intestine and migrate through the portal circulation to the liver, lungs, and other organs including the CNS and eyes. Unlike in dogs, the larvae cannot complete their life cycle in humans and remain in larval stage, causing chronic inflammation. Clinical manifestations include visceral larva migrans (VLM) with fever, hepatomegaly, splenomegaly, lymphadenopathy, and marked eosinophilia. Ocular larva migrans can cause unilateral vision loss, retinal granulomas, and uveitis. Pulmonary involvement may cause cough and wheezing. Diagnosis is made by ELISA serology, elevated eosinophil count, and clinical presentation. Treatment includes albendazole or mebendazole for systemic disease, with corticosteroids for severe inflammation or ocular involvement.
Sources
- First Aid for the USMLE Step 1
- Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases
- Parasitic Diseases by Guerrant
- CDC Guidelines on Toxocariasis
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