Purpose. These studies were undertaken to establish an animal model fo
r use in studies of ocular toxoplasmosis. An animal model is needed to
examine the development, progression, and resolution of ocular Toxopl
asma infections and to study the effects on the disease of currently u
sed and experimental therapies. Methods. Cysts of the ME 49 strain of
Toxoplasma gondii were injected intraperitoneally into each of 60 gold
en hamsters. The hamsters' eyes were examined before inoculation and a
t intervals after inoculation, and fundus photographs were taken. Hist
ologic sections were analyzed and photographed to document the ocular
effects of the infection. Results. Retinochoroiditis was found in bath
eyes of all hamsters within 2 to 3 weeks of inoculation. The disease
resolved spontaneously without treatment and was quiescent in most cas
es at 12 weeks after inoculation. The animals remained in good general
health, and those tested had high antibody titers to Toxoplasma (1:25
6 to 1:32,000) at 6 months after the infection. The discovery of cysts
and lesions in the retina confirmed the diagnosis. Conclusions. Altho
ugh the lesions were not identical to those of human disease, this ani
mal model of ocular toxoplasmosis offers several advantages: reproduci
bility, short incubation time, spontaneous resolution without treatmen
t, consistent production of cysts, and ease of inoculation intraperito
neally without intraocular injection.