Molecular approach for ante-mortem diagnosis of rabies in dogs

Background & objectives: The ante-mortem diagnosis of rabies is of great significance in establishing the status of infection in dogs, especially since they are involved in exposure to human beings. The present study was, therefore, undertaken to elucidate the most appropriate secretion/tissue for reliable diagnosis of rabies in 26 living dogs suspected to be rabid. Methods: In the present study 26 dogs suspected to have rabies were included for ante-mortem diagnosis of rabies in clinical samples of skin and saliva by molecular approach viz. heminested reverse-transcriptase polymerase chain reaction (HnRT-PCR). Skin and saliva samples were collected from 13 dogs each. Results: Of the 13 clinically suspected dogs, fluorescent antibody technique (FAT) confirmed rabies in nine cases of dogs. Of these nine true-positive dogs, eight cases could be confirmed by HnRT-PCR from skin. Of the other 13 dogs clinically suspected for rabies, FAT confirmed rabies in 10 cases. Of these 10 true-positive dogs, rabies was detected ante-mortem by HnRT-PCR from the saliva in seven dogs. Thus, rabies was detected from skin with 90 per cent sensitivity, 100 per cent specificity and 92.85 per cent accuracy. With saliva, rabies was detected with a sensitivity of 76.92 per cent, specificity of 100 per cent and accuracy of 62.50 per cent. The positive predictive values were 100 per cent for both skin and saliva samples while negative predictive values were 80 and 50 per cent, respectively. Interpretation & conclusions: Skin biopsy may be more appropriate clinical sample as compared to saliva for ante-mortem diagnosis of rabies in dogs. HnRT-PCR can be employed for molecular diagnosis of rabies from skin in live dogs.