Effects of carcase decomposition on rabies virus infectivity and detection

Carcases received for rabies diagnosis are occasionally decomposed due to delays in finding, submitting or storing them. Positive diagnostic results from such samples are reliable but negative results may be invalid. Previous studies assessed the effect of decomposition on rabies detection using excised brains. To better reflect decomposition in the field, intact infected mouse carcases were stored at three temperatures for up to 70 days. The brains were then removed and tested using routine rabies diagnostic assays. Rabies virus was isolated using the Rabies Tissue Culture Inoculation Test (RTCIT) on days 18, 3 and 3 at 4°C, 25°C and 35°C, respectively. The Fluorescent Antibody Test (FAT) detected viral antigen on days 36, 12 and 3, whilst a rabies specific Hemi-nested RT-PCR detected viral RNA on days 70, 48 and 48 at 4°C, 25°C and 35°C, respectively. These findings suggest the persistence of infectious rabies virus in carcases left for 18 days at cold temperatures (4°C) and up to 3 days in temperatures reaching 35°C. The detection of viral RNA from a carcase decomposing at 35°C for 48 days supports the use of molecular assays to accompany OIE-prescribed rabies diagnostic tests particularly when decomposed samples are likely to be submitted. Count=199.