Effects of drug therapy on Toxoplasma cysts in an animal model of acute and chronic disease.
OBJECTIVE
To evaluate the effects of drug therapy on the clinical course of acute acquired Toxoplasma retinochoroiditis and on the number of Toxoplasma cysts present in the brain and ocular tissues in the hamster animal model.


METHODS
The Syrian golden hamster animal model of Toxoplasma retinochoroiditis was used. In acute disease, systemically administered atovaquone was compared with conventional therapies (pyrimethamine combined with sulfadiazine; clindamycin; and spiramycin). The clinical course of the ocular disease was determined with retinal examination and photography of the fundus. The number of Toxoplasma cysts remaining after treatment was evaluated in aliquots of brain homogenate and in retinal tissue. The effect of atovaquone on cerebral Toxoplasma cyst count was also studied in chronic disease.


RESULTS
None of the drugs administered altered the course of the acute disease, judged by clinical examination. Atovaquone alone significantly reduced the number of cerebral Toxoplasma cysts after acute disease. Atovaquone also significantly reduced the cerebral Toxoplasma cyst count in chronic disease.


CONCLUSIONS
Tissue cysts are believed to be responsible for reactivation of Toxoplasma retinochoroiditis. Atovaquone has the potential to reduce the risk of recurrent disease.
Gormley
P D
PD
Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom.
Pavesio
C E
CE
Minnasian
D
D
Lightman
S
S
D000208:Acute Disease; D000818:Animals; D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D053626:Atovaquone; D001921:Brain / Q000469:parasitology; D002825:Chorioretinitis / Q000188:drug therapy* / Q000469:parasitology / Q000473:pathology; D002908:Chronic Disease; D006224:Cricetinae; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination / Q000494:pharmacology; D005260:Female; D008647:Mesocricetus; D009285:Naphthoquinones / Q000494:pharmacology*; D012160:Retina / Q000469:parasitology; D014122:Toxoplasma / Q000302:isolation & purification; D016781:Toxoplasmosis, Cerebral / Q000188:drug therapy* / Q000469:parasitology / Q000473:pathology; D014126:Toxoplasmosis, Ocular / Q000188:drug therapy* / Q000469:parasitology / Q000473:pathology
D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D009285:Naphthoquinones; D053626:Atovaquone