Molecular Detection of Rabies from Milk

Background: Outward spread of rabies virus from the CNS leads to infection of almost all organs and have been reported in various secretions and excretions viz. saliva, urine, CSF, tears (corneal smear). Although transmission of rabies virus from consuming unpasteurized milk from an infected animal is theoretically possible, no human or animal has ever been reported to develop rabies via this route. Neither there had been any practical proof of making claim about shedding of rabies virus in milk. This work aimed to identify the presence of rabies virus in unpasteurized raw milk from naturally-infected animals that were confirmed positive for rabies by FAT on brain tissue.

Method: Out of total 25 animals showing clinical signs of rabies, milk sample was obtained from 17 lactating animals. Brief history was recorded and an attempt was made by employing advanced molecular approach TaqMan real time PCR on milk samples with an aim to detect the presence of rabies viral RNA. Confirmatory diagnosis of rabies was made by applying immunofluorescence techniques on brain tissue after death of an animal.

Results: The present finding depicts the presence of rabies viral RNA in 4/17(23.52%) milk sample with a sensitivity of 60% when compared with FAT applied on brain tissue.

Conclusion: A complete perusal of literature revealed that there had not been a single reported study to detect the presence of rabies viral RNA in milk samples. Although with this study it is now proved practically that rabies viral RNA can be found in milk samples from lactating animals however the infectivity of unpasteurized raw milk needs to be evaluated.