Study and distribuition of rabies virus in non neuronal organs in bats sent to laboratory diagnosis in Pasteur Institute

Abstract

Bats are considered important reservoirs of rabies virus, which is paramount in the study of the pathogenesis of this zoonosis disease, through the use of sensitive systems. The presence of viral antigen in these species shows that non-neuronal viral spread is efficient in different organs that participate effectively in the elimination of rabies virus, such as, salivary glands and bladder. This study aimed to investigate the presence of rabies virus in samples of bats submitted for laboratory diagnosis, as well as, to study the pathogenesis of the disease through the use of laboratory animals. 3,930 routine diagnostic specimens of bats were processed during the period between January 2011 and May 2012 by direct immunofluorescence (DIF) and viral isolation on murine neuroblastoma cells (VICC) techniques. 58 samples were diagnosed rabies positive from 37 bats in 2011 and 21 samples were diagnosis rabies positive in 2012, representing a positivity rate of 1.80%. We randomly selected 28 bats from rabies positive which were submitted to collect organs for preparation of inoculum in the proportion to the ratio of 1:10 for salivary glands and tongues, and 1:20 for bladders, which were inoculated in volume of 0.03 mL by the intracerebral route in post-weaning Swiss mice (21 days old and weighing 11g and 14g). Clinical observation was performed during 30 days and the presence of the virus was verified by the DIF technique in diseased and dead animals. 60.7%, 50% and 42.8% of animals selected for the study were rabies positive by viral isolation in the salivary glands, tongue and bladder, respectively. The minimum incubation period was seven days and maximum incubation period varied between 17 and 21 days. The present study demonstrated the presence of rabies virus in non-neuronal organs (salivary gland, bladder and tongue) in 67.8% rabies positive animals in central nervous system (CNS).The detection of rabies virus in non-neuronal organs by DIF and virus isolation has been observed in several studies. For studies of pathogenesis of rabies in bats, these results demonstrate that the use of mice is still a good alternative. Due to lack to use CNS in routine practice in bats for reasons of poor preservation of the specimen, it may be necessary to use nonneuronal organs in order to obtain the positive rabies diagnosis.