Evaluation of Fluorescent Antibody Test for Detection of Rabies Virus Antigen in Fresh, Frozen and Formalin-Fixed Brain Tissue Specimens in Suspected Rabid Animals in Ethiopia
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Date
2017-12
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Addis Ababa Universty
Abstract
Background: Rabies is an infectious and preventable viral disease of mammals. It is caused by several Lyssavirus species, a group of negative sense RNA viruses, and most often transmitted through the bite of a rabid animal, commonly dogs. Many diagnostic methods have been used to detect rabies virus antigen. The preferred method for routine diagnosis of rabies in fresh or frozen brain tissues is the fluorescent antibody test.
Objective: The aim of this study was to evaluate fluorescent antibody test for rabies detection in fresh, frozen and formalin-fixed brain tissue specimens in Ethiopia
Methods: The study was carried out on rabies-suspected brains of animals which were collected from March 2017 to July 2017 at Ethiopian Public Health Institute. The detection of rabies antigen was done in brain impressions from three areas of the brain: hippocampus, cerebellum, and brain stem. One portion of each paired specimen was prepared for fresh, frozen and formalin fixed FAT. It was treated with globulin labeled with fluorescein isothiocyanate. Specific aggregates of rabies virus antigen was detected by their fluorescence using a reflected light (incident light) fluorescence microscope.
Results: The sensitivity of fixed brain tissue compared with fresh FAT was 96.9% and specificity was 100%.Frozen specimen gave similar sensitivity and specificity with fresh FAT which was 100%. The association between Formalin fixed tissue sample & Fresh tissue sample when it is done using FAT had p -value 0.257, frozen tissue sample & Fresh tissue sample had p value 1.00 and Formalin fixed tissue sample & frozen tissue sample had p value 0.257 with no significant difference.
Conclusion: Rabies detection in animals can be accomplished from diagnosis of rabies from fixed brain tissues which offers similar sensitivity as detection of rabies in impression smears.
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Rabies, fluorescent antibody test, Ethiopia