Skin specimen as an alternative to brain tissue for post mortem rabies diagnosis in animals to scale up animal rabies surveillance

BackgroundDetection of the virus or some of its specific components using WHO and OIE recommended standard laboratory tests is the only way to get a reliable diagnosis of rabies. Brain tissue is the preferred specimen for post-mortem diagnosis of rabies in both humans and animals. Higher biosecurity requirements, skill and transportation facilities required for collection and transport of brain or whole carcass to the laboratory is one of the reasons for the poor rabies surveillance in animals. Point of care testing with simple, reliable and easy to operate devices would be an ideal approach for providing rapid results. MethodsThe study evaluated diagnostic performance of two reference tests, DFAT and RTPCR on skin specimen, to assess its suitability as an alternative of brain tissue for post mortem rabies diagnosis in animals. Brain tissue and skin sample belonging to different species of animals (n=90) collected at necropsy were compared using Fluorescent Antibody Test and RT PCR, internationally approved methods for rabies diagnosis. ResultsValidation of RT-PCR on skin and DFAT on skin in comparison with DFAT on brain as gold standard gave a sensitivity of 98% (95% CI:94.1-100) and 80% (95% CI:71.8-88.2) respectively. Specificity was 100% in both tests. ConclusionThe findings highlight the potential of skin specimen for improving rabies surveillance in animals especially in resource poor countries. Author SummaryThe present study was undertaken to define a reliable protocol for diagnosing animal rabies using skin specimen, a superficial tissue sample which is collected in a non-invasive manner for post-mortem diagnosis. Our aim was to design a protocol to replace the classical post-mortem diagnostic method that uses brain biopsy with an ultimate target of stepping up rabies surveillance in animals. Brain tissue and skin sample belonging to different species of animals collected at necropsy were compared using Fluorescent Antibody Test and RT PCR, internationally approved methods for rabies diagnosis. The study established that RT PCR on skin specimen is rapid, sensitive and specific, opening its potential as an ideal rabies surveillance tool overcoming the logistical challenges of carcass transportation to reference laboratories and alleviating biosafety concerns associated with brain collection. The study highlights the potential of skin specimen for improving rabies surveillance in animals especially in resource poor countries.