Pathological, immunological and molecular diagnosis of rabies in clinically suspected animals of different species using four detection techniques in Jordan

A total of 29 brain tissue samples (BTS) were examined for rabies infection by different diagnostic techniques. None of the examined brain tissues were presented as a whole intact brain. Twenty-seven brain tissue samples from various animal species - dog (13 cases), cat (one case), fox (one case), pig (one case), cow (three cases), sheep (two cases), goat (one case), camel (one case), horse (one case) and donkey (three cases) - were provided by the Vaccine and Sera Department/Al-Bashir Central Hospital in Amman/Jordan from July 2009 up to May 2010. All these samples were frozen at -20°C, for a period of time and then fixed in 10% formalin after being tested for rabies virus by fluorescence antibody test (FAT). The results showed that 21 (77.77%) of 27 BTS were positive for rabies by FAT. Seventeen samples (58.62%) of 29 were positive by histopathology, 2 (6.90%) were positive by histopathology, immunohistochemistry (IHC) and of those which were fixed for 24h only, and 21 (72.42%) were positive using RT-PCR assay. Five of 29 BTS had no pathological lesions, 17 had Negri bodies and the remaining had non-suppurative encephalitis and necrosis. Thirteen BTS that were diagnosed positive by FAT were also positive by RT-PCR and histopathology, but negative by IHC. Four BTS that were positive by FAT were negative by histopathology, IHC and RT-PCR. Also, 3 BTS (cases 19, 22, and 25) that were negative by FAT were positive by RT-PCR and negative by IHC. One of these was negative, while two were positive by histopathology. Therefore, definitive diagnosis of rabies under these conditions in Jordan needs one or more other diagnostic tests in addition to FAT. Also, freezing and prolonged formalin fixation of BTS is not suitable for the detection of rabies virus antigen using IHC.