Pathological and molecular diagnosis of rabies in clinically suspected food animals using different diagnostic tests

Introduction - Rabies is a fatal viral disease of the nervous system caused by a RNA virus, which belongs to the genus lyssavirus of the family Rhabdoviridae. Rabies can affect all mammals including humans. It is a serious veterinary and public health problem in Jordan and many other countries around the world. Therefore, early diagnosis with highly sensitive and specific tests will reduce unnecessary prophylaxis and treatment. Aim - The aim of this present study was to diagnose rabies in the clinically suspected cows, donkeys, horses and goats in Jordan by using different diagnostic tests and to compare the results of these tests. Materials and methods - During the years 2012-2013, a total of 11 brain samples were collected from different food animal species (5 cows, 3 donkeys, 1 horse and 2 goats) that were provided by the Vaccine and Sera Department / Al-Basheer central hospital in Amman / Jordan. Clinically, rabies was suspected in these animals. These brain tissues were examined by fluorescent antibody test (FAT), histopathology, immunohistochemistry (IHC) and reverse transcriptase polymerase chain reaction (RT-PCR). Results and discussion - The results showed that 55%, 45%, 82% and 91% of 11 brain tissues were positive for rabies by FAT, histopathology, IHC and RT-PCR respectively. The results of 5 animals out of 11 (45.5%) were consistent in all diagnostic tests where 4 (80%) of them were rabies positive. Two cases were rabies negative by FAT and proven to be rabies positive by the other tests. None of the examined clinically rabies cases was only detected by FAT. No significant difference was found when comparing between any two diagnostic tests. Conclusions - Although FAT is considered the primary standard confirming test that is used to distinguish rabies encephalitis from other viral encephalitidis, these results do emphasize the importance of conducting more than FAT to diagnose rabies in animals.