Toxocariasis

Toxocariasis is a zoonotic helminth infection caused by larvae of Toxocara canis (dog roundworm) and T. cati (cat roundworm), acquired by ingestion of embryonated eggs from contaminated soil or by eating undercooked meat of paratenic hosts.

• Seroprevalence is high worldwide (up to 30 to 90% in some tropical settings), particularly in children with pica, geophagia, and exposure to puppies.
• Larvae do not mature in humans but migrate through tissues.
• Syndromes: visceral larva migrans, ocular larva migrans, covert (common) toxocariasis, and neurotoxocariasis.

• Visceral larva migrans (children 1 to 5 years): fever, cough, wheeze, hepatomegaly, abdominal pain, and marked eosinophilia.
• Ocular larva migrans (older children, usually unilateral): leucocoria, strabismus, reduced vision from granuloma, vitritis, and retinal detachment, without eosinophilia.
• Covert toxocariasis: non-specific symptoms (weakness, abdominal pain, headache, cough).
• Neurotoxocariasis (rare): eosinophilic meningitis, myelitis, encephalitis, and epilepsy.

• Serology: Toxocara excretory secretory antigen ELISA (serum; confirm with Western blot); intraocular fluid antibody levels for ocular disease.
• Blood: eosinophilia (up to 30 to 50% in visceral disease), raised IgE, and hypergammaglobulinaemia.
• Imaging: ultrasound or CT shows hypodense liver lesions; fundoscopy and OCT for ocular disease.
• Exclude other helminthiasis (strongyloidiasis, ascariasis, schistosomiasis, hookworm), retinoblastoma (leucocoria), and tuberculosis.

• Visceral and covert disease: albendazole 400 mg twice daily (10 to 15 mg/kg/day in children) for 5 days, or mebendazole 100 to 200 mg twice daily for 5 days.
• Ocular disease: albendazole 400 mg twice daily for 2 to 4 weeks with oral prednisolone 0.5 to 1 mg/kg/day (to prevent inflammatory reaction to dying larvae), periocular or intravitreal steroids, and vitreoretinal surgery for tractional detachment.
• Neurotoxocariasis: albendazole 400 mg twice daily for 14 to 28 days with prednisolone 0.5 to 1 mg/kg/day, antiepileptic therapy.
• Antihistamines or bronchodilators for allergic manifestations.
• Prevention: deworm dogs and cats, hand hygiene, cover sandpits, control pica.