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CHORIORETINAL INFLAMMATORY DISEASES - Infectious Causes

Ocular Toxocariasis

Toxocariasis is an infectious parasitic disease caused by the larvae of the nematodes Toxocara canis and Toxocara cati, which are worms inhabiting the intestines of their hosts. Toxocariasis is a worldwide infection and humans are incidental hosts in which aberrant infection occurs because the parasites cannot completely mature.

The usual mode of infection is eating contaminated soil (geophagia) via the hands, or uncooked food. Children who have close contact with dogs (puppies) are at great risk of infection.

The disease is typically unilateral and most often seen in children, though many cases in adults have been reported. Symptoms include decreased visual acuity but the initial clinical manifestation may be strabismus or leukocoria.

There are three main forms of ocular...

Toxocariasis is an infectious parasitic disease caused by the larvae of the nematodes Toxocara canis and Toxocara cati, which are worms inhabiting the intestines of their hosts. Toxocariasis is a worldwide infection and humans are incidental hosts in which aberrant infection occurs because the parasites cannot completely mature.

The usual mode of infection is eating contaminated soil (geophagia) via the hands, or uncooked food. Children who have close contact with dogs (puppies) are at great risk of infection.

The disease is typically unilateral and most often seen in children, though many cases in adults have been reported. Symptoms include decreased visual acuity but the initial clinical manifestation may be strabismus or leukocoria.

There are three main forms of ocular toxocariasis:

  • Peripheral granuloma
  • Posterior pole granuloma
  • Chronic endophthalmitis

The granuloma is usually yellowish white and 1-2 disc diameter in size, where the larva is encysted. A common finding is a radial fold of the retina extending from the perypheral granuloma to the optic disc. Vitritis may be mild to severe and patients may present with hypopyon.

Complications include macular heterotopia, epiretinal membranes, tractional retinal detachment, ciliary body detachment with hypotony, cataract, secondary glaucoma and phthisis bulbi.

The diagnosis is based on the clinical picture and serologic confirmation of specific IgG and IgM antibodies using ELISA. Other methods are detection of specific anti-toxocara IgG by Western-blot, specific IgE, and intraocular fluid PCR analysis. Patients with visceral larva migrans have leukocytosis and hypereosinophilia, while in patients with ocular toxocariasis they are usually absent.

Differential Diagnosis

  • Diseases with leukocoria:
  • Retinoblastoma
  • Coats’ disease
  • Retinopathy of prematurity
  • Persistent hyperplastic primary vitreous
  • Familial exudative vitreoretinopathy
  • Toxoplasmosis
  • Pars planitis
  • Endogenous endophthalmitis
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Clinical Cases