Evaluation of Direct Rapid Immunohistochemistry Test for Rabies Diagnosis in the Brain of Slaughtered Dogs in Northern Nigeria

Abstract

Aim: To compare the ability of the direct rapid immunohistochemistry test (DRIT) and the gold standard test, luorescent antibody test, (FAT) to detect rabies virus antigen in the brains of slaughtered dogs from Niger State in the northern region of Nigeria. Study Design: Cross sectional. Place and Duration: Department of Veterinary Public Health, Ahmadu Bello University, Zaria,  Nigeria and Rabies Program, Centers for Disease Control and Prevention(CDC), Atlanta, GA, USA, between January, 2012 and February, 2013. Methodology: Four hundred and seventy one (471) dog brain samples were collected through the occipital foramen from dogs destined for human consumption at five dog slaughter points in Niger State during January and July 2012.  Samples were tested by FAT in July, 2012, then the FAT and DRIT were repeated in January, 2013 simultaneously and independently to detect rabies virus antigens. Results: Of the 471 slaughtered dogs, the same 3 (0.64%) had rabies virus antigens in their brains using both tests. There was absolute agreement between the two tests employed, and all the positive samples had 4+/4+ antigen distribution and the color intensity of the viral antigen. Conclusion: Detection of rabies viral antigens in slaughtered dogs may pose a serious public health risk, particularly for the dog butchers during purchase, shipment, slaughter and processing periods. The DRIT showed absolute agreement with the standard (FAT), yet does not require an electric incubator and an expensive fluorescence microscope, and thus could be a less expensive alternative test for the detection of rabies virus antigen in slaughtered dogs. It is recommended therefore, to use of DRIT for field surveillance of rabies virus antigen in the brain of slaughtered dogs, particularly in the developing countries where fluorescence microscopy is not readily available due to its prohibitive cost.