Distribuição do vírus rábico no sistema nervoso central em ruminantes naturalmente infectados

Abstract

With the aim to study the distribution of lesions the rabies virus in spontaneous cases of rabies in ruminants and to determine the efficiency of the direct fluorescent antibody test (DFA), mouse inoculation (MI) and presence of Negri bodies in the diagnosis of the disease, 48 cases of the rabies were examined. Samples of frontal, temporal, parietal and occipital cerebral cortex, hippocampus, thalamus, rostral and caudal colliculi, cerebellum, pons, medulla oblongata, basal nuclei and sections of the cervical, thoracic and lumbar spinal cord were examined. Of the 48 samples examined all were positive on DFA and MI, and in 30 (62.5%) Negri bodies were observed. However there were differences in the results of the three tests among different regions of the central nervous system. In the samples of the cerebral cortex in 38 cattle, the frequency of inclusion bodies was low (11-37%), and so was the positivity to DFA and MI (60-80%). In contrast, all samples of thalamus, pons and spinal cord were positive to DFA and MI. In other regions of the brain stem, positivity to these tests varied between 60% and 96.7%. On histologic examination, the major frequency of Negri bodies (88.2%) was observed in the cerebellum. In eight sheep the DFA and MI tests were positive in all sections of the CNS examined and Negri bodies were found in three sheep. Only two goats were examined; both were positive in DFA and MI tests and in one Negri bodies were found. These results suggest that the recommendations of the Brazilian Technical Manual for Rabies of Herbivores is adequate for rabies diagnosis, because their recommendations include the histologic study and the examination of cerebellum, and sections of the brainstem with high positivity to DFA and MI tests. However, a better recommendation is to send for DFA and MI half of the brain cut longitudinally and samples of the spinal cord, which will permit to examine one or two sections, and if those are negative to get back to the material and examine the rest of the sections. In contrast, to collect samples of the brain or half brain can be inappropriate for the diagnosis of other diseases of the CNS, for which the study of the whole fixed brain is necessary to recognize the symmetry or distribution of lesions. In these situations by the results obtained here, it can be recommended to send different sections of the spinal cord for DIF and MI tests and to fix the whole brain for gross and histologic examinations.

Cattle rabies: the effect of clinical evolution, viral genetic lineage, and viral load on the severity of histological lesions

“…Moreover, a bovine that died after a clinical course of 6 days in the current study had NBs only in the cerebellum. NBs developed more often in the cerebellum of cattle from the current study corroborating the findings from others (Langohr et al 2003, Silva et al 2010. However, in one bovine NBs were found only in the trigeminal ganglion.…”

Influence of euthanasia, the intensity of inflammatory lesion and viral load in the laboratory diagnosis of rabies in cattle

“…Regarding the distribution of the lesion, the cerebellum was the best area for visualizing the corpuscle, similar to what was described by Wisser et al (2020), Silva et al (2010) and Langohr et al (2003). It is known that rabies does not infect all brain structures equally, thus varying the presence of NB with the analyzed area and thus compromising the diagnosis efficiency.…”

In situ histopathological and immunohistochemical characterization of rabies in the brains of naturally infected equines and bovines

“…Studies have shown that the incubation period of the virus from herbivore samples inoculated in mice varies from 7 to 13 days (Silva et al, 2010;Achkar et al, 2010). Here, the virus was isolated in 75% of the samples, and the incubation period varied from 7 to 14 days.…”