Incidence of reactive VDRL tests in the normal rabbit.

Serology of normal primates.

“…Rabbits are most commonly employed in this research, but approximately 25 per cent. of normal rabbits show at least a weakly reactive serum reagin (VDRL) test (Pannu, Rosenberg, Israel, and Smith, 1967). Furthermore, rabbits are susceptible to an endemic treponemal infection with T. cuniculi which cannot be morphologically or serologically differentiated from T. pallidum (Smith and Pesetsky, 1967).…”

Serological tests for syphilis in healthy rabbits.

“…Even so, most manifest infections would have been noted during routine treponemal research procedures. Pannu, Rosenberg, Israel, and Smith (1967), examining 149 animals from a commercial rabbitry near Miami, found 10 per cent. to be reactive and 30 per cent.…”

Recovery of spirochagetes in the monkey by passive transfer from human late sero-negative syphilis.

“…This is because rabbits are known to harbour an endemic venereal disease known as benign venereal spirochaetosis, due to Treponema cuniculi, an organism which is morphologically, serologically, and pathologically indistinguishable from Treponema pallidum (Smith and Pesetsky, 1967). Indeed, one out of four normal rabbits purchased on the open market will show a reactive or weakly reactive VDRL serum test, even when no clinical signs of disease are present (Pannu, Rosenberg, Israel, and Smith, 1967). Therefore, if one had inoculated a rabbit with a specimen from a patient, and had later demonstrated the presence of spirochaetes, it would have been difficult to decide whether the organism was Treponema cuniculi.…”