Experimental toxoplasmosis of the uveal tract.

Introduction THE histopathological studies of Wilder (1952) on eyes removed on account of intractable iritis of unknown origin suggest that toxoplasmosis may have been the cause in some cases. Following on her work, requests were received for the serological investigation of patients suffering from chronic anterior uveitis of undetermined aetiology. Some of these gave weak positive results in the low titre ranges, but were of doubtful significance since Beverley and Beattie (1952) found, in a survey of normal people, that 74 per cent. were negative or <1: 4, 23 per cent. positive with a titre from 1: 4 to <1: 16, 2 per cent. with a titre from 1: 16 to <1 : 32, 1 per cent. with a titre from 1: 32 to <1 : 64, and none with a titre of 1: 64 or over. In three patients, however, the levels were high: Case 1, 1: 160; Case 2, 1: 64; Case 3, 1: 96. In the first case the eye had been removed before the publication of Wilder's work. The eye removed in the second case was unfortunately promptly fixed for histological examination and animal inoculation tests could not be done. Though pseudocysts could not be found in sections of either of these eyes, structures resembling paired vegetative forms could be seen. Unequivocal proof of the latter's identity is not available since recovery of the parasite by inoculation into animals was not attempted, and at the present time there is no staining procedure which is specific for toxoplasms. In the third case the eye was not removed as the condition slowly improved. The possibility of treatment by desensitization on the lines suggested by Frenkel (1949) was discussed and finally rejected. In view of the possibility of recurrence of the uveitis in this case, and bearing in mind future cases, a series of therapeutic experiments were undertaken, the first group of which is now reported.