Ocular Toxoplasmosis

Ocular toxoplasmosis is a potentially blinding necrotizing retinitis that may have a prolonged and relapsing course. Human toxoplasmosis may occur as either a congenital or an acquainted form. It can be acquainted in humans by:

  1. ingestions of undercooked, infected meat containing toxoplasma cysts,
  2. ingestion of the oocyst form from contaminated hands or food,
  3. inoculation of tachyzoites through a break in skin,
  4. drinking of raw milk,
  5. blood transfusion or organ transplantation,
  6. transplacental transmission.

The major routes of transmission are the ingestion of contaminated foods, accidental contamination of hands from disposing of cat feces and transplancental transmission of infection from mother to fetus during gestation.

Clinical findings most often seen as presenting signs include focal retinitis involving the inner layers of the retina with a whitish, fluffy lesion with surrounding edema. An overlying vitreitis is often present. Acute lesions are classically adjacent to an old inactive scar.

The treatment decision is made on the basis of the nature and location of the lesion. It includes Pyremethamin, Sulfadiazene, Prednisone, Folenic acid with monitoring of WBC and platelet count every two weeks if the fovea is threatened. If the fovea is not threatened, the inflammatory lesion is benign and self limiting and no treatment is generally given.