Validation of a Rapid Rabies Diagnostic Tool for Field Surveillance in Developing Countries

Abstract

BackgroundOne root cause of the neglect of rabies is the lack of adequate diagnostic tests in the context of low income countries. A rapid, performance friendly and low cost method to detect rabies virus (RABV) in brain samples will contribute positively to surveillance and consequently to accurate data reporting, which is presently missing in the majority of rabies endemic countries.Methodology/Principal findingsWe evaluated a rapid immunodiagnostic test (RIDT) in comparison with the standard fluorescent antibody test (FAT) and confirmed the detection of the viral RNA by real time reverse transcription polymerase chain reaction (RT-qPCR). Our analysis is a multicentre approach to validate the performance of the RIDT in both a field laboratory (N’Djamena, Chad) and an international reference laboratory (Institut Pasteur, Paris, France). In the field laboratory, 48 samples from dogs were tested and in the reference laboratory setting, a total of 73 samples was tested, representing a wide diversity of RABV in terms of animal species tested (13 different species), geographical origin of isolates with special emphasis on Africa, and different phylogenetic clades. Under reference laboratory conditions, specificity was 93.3% and sensitivity was 95.3% compared to the gold standard FAT test. Under field laboratory conditions, the RIDT yielded a higher reliability than the FAT test particularly on fresh and decomposed samples. Viral RNA was later extracted directly from the test filter paper and further used successfully for sequencing and genotyping.Conclusion/SignificanceThe RIDT shows excellent performance qualities both in regard to user friendliness and reliability of the result. In addition, the test cassettes can be used as a vehicle to ship viral RNA to reference laboratories for further laboratory confirmation of the diagnosis and for epidemiological investigations using nucleotide sequencing. The potential for satisfactory use in remote locations is therefore very high to improve the global knowledge of rabies epidemiology. However, we suggest some changes to the protocol, as well as careful further validation, before promotion and wider use.

Surveillance to Establish Elimination of Transmission and Freedom from Dog-mediated Rabies

“…Storage in Tanzania and during shipments was not ideal for preservation, therefore samples were tested using a real-time PCR assay 23,24 , as the gold standard OIE tests FAT and RTCIT in particular are sensitive to degradation 25 . More recently samples were also tested in the field using rapid diagnostic tests (RDTs, Bionote, Korea) 26,27 .…”

An inter-laboratory trial as a tool to increase rabies diagnostic capabilities of Sub-Saharan African Veterinary laboratories

“…Indeed, the vaccine protection for LYSVs belonging to phylogroups 2 and 3 is still under debate [36]. In this context, molecular protocols also have the advantage of early inactivation of diagnostic samples following immersion in lysis buffer or using tools like LFDs [37] [38] or FTA cards [39] which both allow the preservation of viral nucleic acid and inactivate the virus [38] [40]. In addition, sample typing will eventually provide important information on the source of the rabies case to local stakeholders.…”

Situation of Rabies in the Republic of Chad

“…The said test is easy to perform and does not need a cold chain in the field. Its utility in the field was proved [26]. Apparently, the test works well because all the samples tested have all been positive for the direct immunofluorescence test.…”