Development of Rapid Immunohistochemical Test (dRIT) in the evaluation of suspect rabies tissue samples A direct Rapid Immunohistochemical Test (dRIT) for the postmortem detection of rabies virus antigen in brain smears has been developed [8] . Using a cocktail of highly concentrated and purified biotinylated monoclonal antibodies, rabies antigen can be detected by direct staining of fresh brain impressions within 1 hour. This test employs anti-rabies monoclonal antibodies specific for the nucleoprotein, a viral protein produced in abundance during productive infection. The FAT is based on antibodies specific for the same protein but, being conjugated to fluorescein isothiocyanate, requires a fluorescent microscope to visualise any specific antibody bound to viral protein within the test sample [2] . In contrast, the new Box 1. Key Learning Points dRIT antibody cocktail is biotinylated such that following a short incubation with a streptavidin-peroxidase complex, antibody-antigen binding complexes can be visualised through the addition of the substrate, 3-amino-9-ethylcarbazol. Performed on brain tissues, the dRIT has proven as sensitive as the FAT for fresh specimens [9, 10] . Brain impressions stained using the dRIT technique can be read within one hour and the antibody cocktail used has been shown to detect classical rabies virus strains (genotype 1) that have been assessed [11] . Currently, the FAT is routinely used to detect virus antigen in badly decomposed sample material. For the purpose of testing samples in the developing world where suitable cold storage for samples is often unavailable, this factor is important in the development of new tests. This obstacle has been overcome through evaluating sample preservation in phosphate buffered 50% glycerol at a range of temperatures for different time periods prior to testing for virus antigen. Glycerol saline solutions have been previously recognised as suitable storage media for tissue samples in the absence of cold storage [12] (Box 2). Using the dRIT in field studies in Tanzania, viral antigen could be detected in samples after considerable time periods post collection regardless of the regimen of glycerol preservative used [11] . Applications of the dRIT to analyse field samples in other rabies endemic regions have also proven highly successful. Field trials in Chad sought to study the dRIT in direct comparison to the FAT to attempt to confirm previous studies as to the incidence of rabies within a district known to be endemic. In this study, results between the two tests were 100% in agreement [9] and the only issue regarding use of the dRIT over the FAT was the need for the dRIT kit to be stored refrigerated prior to use. The dRIT will enable developing countries to perform routine rabies surveillance at greatly reduced cost and without the need for prohibitively expensive microscopic equipment along with the expertise and financial input needed to maintain them. The cost effectiveness of the dRIT will allow knowledge and technology transfer to areas of the developing world that currently are unable to diagnose rabies cases.