Rabies virus detection by RT-PCR in decomposed naturally infected brains

The warm climate of Israel and mishandling of the cadavers during transit to the laboratory requires an accurate method for diagnosis of rabies in decomposed tissues. By using the reverse transcriptase polymerase chain reaction (RT-PCR) 10 decomposed brain samples that collected between 1998 and 2000 were diagnosed as negative by direct fluorescent antibody test (FAT), were found positive. Three of the 10 decomposed brains were confirmed as positive by isolation of rabies virus in tissue culture and by mouse inoculation (MIT) while the other seven decomposed samples were found positive only by RT-PCR. Direct sequencing and molecular analysis of a 328bp fragment of the N gene of all the rabies sequences confirmed their geographical origin. These results demonstrated the importance of the RT-PCR in the detection of rabies virus in decomposed naturally infected brains, especially in cases when the sample is not suitable for other laboratory assays. Thus, the RT-PCR can provide a positive diagnosis; however, when a negative result is obtained due to the nature of the decomposed tissue that can be caused by technical reasons and a false negative might be the case.