Problems in the Laboratory Diagnosis of Rabies

Abstract

The difficulties in demonstrating Negri bodies arise from 2 sources of error which can be enumerated as inability to differentiate them from other inclusion bodies and cell structures, and inherent deficiencies in the methods of examination. The satisfactory demonstration of Negri bodies does not always fail because of the size. There do occur in rabid animals bodies described by Goodpasture as "lyssa bodies." The lyssa bodies differ from Negri bodies in size and the absence of "Innen-korper." These bodies are described as very small, pink-staining, homogeneous spheres. In membranes containing no unmistakable Negri bodies these bodies are the cause of much confusion in diagnosis, and animal inoculation is the only method by which the diagnosis in such cases can be made. In all doubtful cases of rabies and in Negri-negative cases the author has used mouse injection. Of 354 animals found to be Negri-negative or doubtful, only 310 were rabies-negative by mouse inoculation, giving a failure in microscopic diagnosis of 12.43%. Of particular interest is the result of mouse inoculations with emulsions from 24 specimens, in which small, atypical inclusion bodies were found in the cerebral cortex. In 5 instances the bodies were considered characteristic enough to consider the microscopic examination to be Negri-positive. In only 1 of the 5 was rabies virus demonstrated. The remaining 19 specimens were considered doubtful by microscopic examination. Of these 9 were rabies-positive and 10 were rabies-negative. By microscopic examination of sections and in some smears eosinophilic bodies resembling lyssa bodies and atypical Negri bodies are demonstrated which are not associated in the brain with rabies virus.