Experimental Ocular Syphilis and Neurosyphilis.

The challenge in clinical syphilis to-day is the detection of the disease in the sero-negative patient. The magnitude of this problem is evident when one considers that over 100 cases of ocular syphilis and neurosyphilis have been encountered in this institution within the past year (Smith, 1964; Smith and Moore, 1964; Smith and Taylor, 1965). Ofparamount importance is the fact that the majority of these patients were non-reactive to the standard reagin tests for syphilis. Diagnosis was established by the following criteria: (1) history of infection and inadequate treatment; (2) clinical signs of the disease-as optic atrophy, pupillary changes, and the like-and (3) reactive Treponemapallidum immobilization (TPI) and/or fluorescent treponemal antibody absorbed (FTAABS) tests on the peripheral blood (Deacon, Falcone, and Harris, 1957; Deacon, Freeman, and Harris, 1960; Deacon and Hunter, 1962). A combined clinical and experimental study was therefore undertaken in collaboration with the Venereal Disease Research Laboratory of the US Public Health Service in Atlanta, Georgia. The purposes of this project were as follows: (1) to study sero-negative syphilis, both in the human and in the experimental animal; (2) to investigate primary neurosyphilis (induced by injecting T. pallidum directly into the subarachnoid space in the primate); (3) to study ocular syphilis and neurosyphilis in the rabbit and monkey-using more recent clinical techniques (such as fluorescein fundus photography), and correlated with both standard reagin tests (VDRL) and more exacting (TPI and FTA-ABS) serological methods; (4) to attempt recovery of virulent T. pallidum from sero-negative patients and