Nematode uveitis

Toxocariasis (nematodal) uveitis

See also Nematode chapter in Microbiology section

• Toxocara canis is the commonest nematode infection
• Puppies are the definitive hosts
• Ova excreted in faeces and then ingested
• Develop into larvae which invade gut wall
• Spread haematogenously to liver, lung, brain, heart and eye
• Larval death causes intense inflammatory reaction

Ophthalmic features

• Diffuse chronic endophthalmitis in young patient

  • White eye with chronic anterior uveitis, PS, vitritis, snowbanking, macular oedema

• Posterior pole granuloma: yellow-white granuloma at the macular with retinal traction

• Peripheral granuloma: asymptomatic until causes retinal traction, dragged optic disc

• Systemic features: fever, pneumonitis, bronchospasm

Tests

• Clinical diagnosis mainly
• ELISA for serum antibodies
• B-scan USS

Management

• Systemic or periocular corticosteroids: based on severity/extent of inflammation
• Antihelminthics: thiabendazole: may worsen ocular inflammation as the nematodes die so generally not used
• Vitrectomy if needed

Onchocerciasis

• River blindness
• Filarial nematode Onchocerca volvulus
• Spread by blackfly vector (Simulium): larvae mature into adult worms and produce subcutaneous nodules
• Ocular disease: sclerosing keratitis (opaque apron over inferior cornea), chorioretinitis, sclerosis of retinal vessels, optic neuritis and optic atrophy
• Histology from skin nodules can confirm diagnosis
• Management: ivermectin