Studies on the brain salivary glands and saliva of mice experimentally infected with street rabies virus.
Creators: name: Beauregard, Michel.
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 1964
Subjects: subject: Biology, Animal Physiology.

description: The objective of this investigation was to compare the sensitivity of the intra-cranial and intra-muscular routes of inoculation of street rabies virus. This was done by determining the time of appearance of Negri bodies and/or infectivity in the brain and salivary glands of experimentally infected Swiss white mice, individual groups of five mice inoculated by either of these routes were sacrificed at daily intervals until they died of the infection. Brain and salivary glands from each mouse were examined by three methods: (a) standard impression smear technique, (b) mouse infectivity test, and (c) flourescent antibody technique. When obtainable, saliva samples were also examined by the mouse invectivity test. Out of 60 mice injected by the intra-cranial route, 38 showed Negri bodies when brains were examined by the standard impression smear technique; in one mouse they were detected as early as the fifth post-inoculation day. The salivary glands failed to show Negrigenesis when examined by this method. The presence of infectivity was demonstrated in the brain of 43 mice and preceded by one day the appearance of Negri bodies. Only three mice were found to excrete virus in salivary glands: the first an the eighth, the second on the ninth and the third on the tenth post-inoculation day. Saliva from the second of these three mice proved infectious. Rabies viral antigen was revealed by the fluorescent antibody technique in the brain of all five mice sacrificed on the second post-inoculation day, in that of two of the five killed on the third post-inoculation day and in that of every mouse thereafter. This method, like the direct smear examination, did not detect evidence of infection in any of the salivary glands. The lower sensitivity of the intra-muscular route of injection was evidenced by the late appearance and the marked irregularity of both lesions and infectivity in the 125 mice thus inoculated. Only 19 developed Negrigenesis in the brain; the earliest by the 10th post-inoculation day. Thirty-three mouse brains proved to harbour virus by the mouse infectivity test. The appearance of infectivity did not precede that of Negri bodies in the brain tissue. Only four mice excreted virus in salivary glands. Two saliva samples exhibited infectivity. The fluorescent antibody technique detected rabies viral antigen in 16 Negri-positive and 20 Negri-negative brains, seven of the latter being also non-infective for mice. Four brains found to contain virus were missed by this technique, although three of the fur disclosed Negrigenesis. Positive results were obtained by the fluorescent antibody technique with all mouse-infective salivary glands. Among field brain specimens from 100 domestic and wild animals, 11 revealed evidence of infection by the standard impression smear technique, 54 by the mouse infectivity test and 50 by the fluorescent antibody technique. The results of these studies indicate that the intra-cranial route of inoculation ins more sensitive than the intra-muscular one for the rapid detection of street rabies virus infection in Swiss white mice. Brain also proved to be the most satisfactory tissue for this purpose. Of the methods employed, the standard impression smear technique was found the least sensitive. In contrast to what was observed in experimental mice, the mouse infectivity test appeared more sensitive than the fluorescent antibody technique for the examination of field brain specimens.