Reciprocal Influence of Concomitant Infections

The influence which one infection may have upon the manifestations of another has been investigated in a number of conditions in connection with a general study of the factors concerned in determining the course and outcome of disease processes. In the case of syphilis and vaccinia of the rabbit, the result of simultaneous inoculations of Tr. pallidum and vaccine virus has been studied. Other experiments have dealt with the syphilitic reaction in rabbits immune to vaccine virus, and conversely, with the vaccine reaction in rabbits infected with Tr. pallidum.

The Nichol's strain of Tr. pallidum and the Noguchi strain of vaccine virus were used; groups of 5 or 10 male rabbits were employed for each series. The syphilitic tissue emulsion was injected in one testicle or intracutaneously on the sheath; the inoculation of vaccine virus was made on the shaved skin of the body by rubbing the infected tissue emulsion into scarified areas, and by intracutaneous injection. In other groups, the syphilitic and vaccine virus emulsions were both injected in the same testicle. Control series of rabbits were inoculated with each of these materials.

The observation period varied from 3 to 5 months. An essential requirement of the work was the frequent examination of the rabbits in order that the syphilitic process in the several groups could be compared. The features of this infection which are especially important for such comparisons are illustrated by the following examples: the incubation period, character and duration of the primary and metastatic orchitis, the occurrence of scrota1 edema, the time of development of generalized lesions, their distribution, number and duration, and the initiation of latency, that is when all manifestations of the disease have healed.