ACQUIRED RETINOCHOROIDITIS IN HAMSTERS INOCULATED WITH ME-49 STRAIN TOXOPLASMA

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.