Follow-up of the 1977 Georgia Outbreak of Toxoplasmosis

Abstract

In 1977, an outbreak of toxoplasmosis occurred among 37 persons associated with exposure to an indoor horse arena. Cat feces containing the organism were most likely stirred up when horses ran on the dirt floor, and were inhaled or ingested by riders and observers. After 25 or more years, we attempted to locate persons from the outbreak and offer them an eye examination. Of the 37 persons in the outbreak, 18 (49%) were located; four had died, and the remaining 14 agreed to an examination. Among the 14 persons examined, three (21%) were found to have lesions typical of toxoplasmic retinochoroiditis. If these three persons were the only ones with ocular disease among the 37 persons in the outbreak, the disease rate would still be high (8%). As a result of exposure to Toxoplasma gondii during this outbreak, a relatively high percentage of persons developed ocular disease.

Figure 1.

A chorioretinal lesion, consistent with an inactive toxoplasmic retinochoroidal scar, in the right eye of a person infected by Toxoplasma gondii 26 years earlier during an epidemic. Other than being more pigmented, the scar appears to be unchanged from its appearance 4 years after infection in 1981, as documented by Akstein and others.