Toxocariasis
Toxocariasis is human infection with the dog or cat roundworm Toxocara canis or Toxocara cati, acquired by ingesting embryonated eggs, producing visceral larva migrans with hepatic, pulmonary, and eosinophilic disease or ocular larva migrans mimicking retinoblastoma. Diagnosis rests on compatible exposure and clinical findings plus Toxocara-specific serology, and treatment combines an antihelminthic with corticosteroids for organ-threatening inflammation.
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What this article covers
- Overview
Aberrant human infection with a dog/cat roundworm: toxocariasis follows ingestion of Toxocara canis or Toxocara cati eggs; humans are an accidental, dead-end (paratenic) host, so larvae migrate…
- Epidemiology
Fecal-oral transmission from contaminated soil: infection follows ingestion of embryonated Toxocara eggs shed in dog or cat feces that have contaminated soil, sandboxes, or unwashed produce.
- Risk factors
Pica and geophagia: deliberate soil or dirt ingestion in toddlers is the single strongest behavioral risk factor for heavy VLM.
- Pathophysiology
Ingested eggs hatch in the small intestine: larvae penetrate the intestinal wall and enter the portal circulation rather than maturing into adult worms, distinguishing toxocariasis from helminths…
- Clinical features
Asymptomatic infection is most common: many patients, particularly with light exposure, have no symptoms and are identified only through incidental eosinophilia or serology.
- Differential diagnosis
Retinoblastoma (for OLM): the most dangerous mimic in a child with leukocoria or a white retinal mass; distinguished by calcification pattern on imaging and absence of Toxocara serology/exposure…
- Diagnosis
Confirmed by a compatible clinical syndrome plus positive Toxocara-specific serology in the correct exposure context: because humans are a dead-end host, stool ova-and-parasite examination is always…
- Management
Assess severity and organ involvement first: mild, asymptomatic, or minimally symptomatic infection with isolated eosinophilia may be observed or treated with an antihelminthic alone…
- Complications
Vision loss from ocular larva migrans: retinal granuloma, traction retinal detachment, or macular scarring can cause permanent unilateral visual impairment, particularly if diagnosis or steroid control of inflammation is delayed.
- Prognosis
Excellent in most VLM: because larvae cannot mature or reproduce in humans, most visceral disease resolves with treatment and supportive care, and even untreated mild disease is often self-limited.
- Prevention
Routine veterinary deworming of puppies and kittens: treating young animals starting at 2 to 3 weeks of age and repeating on a veterinary schedule reduces environmental egg shedding, the principal source of human exposure.
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