Comparative assessment of seller's staining test (SST) and direct fluorescent antibody test for rapid and accurate laboratory diagnosis of rabies.

Ishaya S Tekki,Chika I Nwosuh,Sani M Ahmed,Peterside R Kumbish,Clement L Jonah,Philip A Okewole,Zhakum N Ponfa,David Shamaki

doi:10.4314/ahs.v16i1.16

Abstract

Rabies causes 55, 000 annual human deaths globally and about 10,000 people are exposed annually in Nigeria. Diagnosis of animal rabies in most African countries has been by direct microscopic examination. In Nigeria, the Seller's stain test (SST) was employed until 2009. Before then, both SST and dFAT were used concurrently until the dFAT became the only standard method. This study was designed to assess the sensitivity and specificity of the SST in relation to the 'gold standard' dFAT in diagnosis of rabies in Nigeria. A total of 88 animal specimens submitted to the Rabies National Reference Laboratory, Nigeria were routinely tested for rabies by SST and dFAT. Overall, 65.9% of the specimens were positive for rabies by SST, while 81.8% were positive by dFAT. The sensitivity of SST in relation to the gold standard dFAT was 81.0% (95% CIs; 69.7% - 88.6%), while the specificity was 100% (95% CIs; 76% - 100%). The relatively low sensitivity of the SST observed in this study calls for its replacement with the dFAT for accurate diagnosis of rabies and timely decisions on administration of PEP to prevent untimely deaths of exposed humans.

Highlights

Rabies is a fatal zoonotic disease of mammals caused by a highly neurotropic virus belonging to the Lyssavirus genus, in the family Rhabdoviridae[1]
Touch impression smears of the hippocampus on slides were fixed in chilled acetone and tested for the presence of rabies virus antigens by the direct fluorescent antibody test (dFAT) as described by Dean et al.[21]; using rabies fluorescein isothiocyanate conjugated (FITC) Anti-Rabies Monoclonal Globulin (FDI FUJIREBIO Diagnostic, Inc.), according to manufacturer’s instructions
Fourteen (14) of the 30 samples that tested negative by stain test (SST) were positive by the gold standard dFAT (Table 1)

Summary

Introduction

Rabies is a fatal zoonotic disease of mammals caused by a highly neurotropic virus belonging to the Lyssavirus genus, in the family Rhabdoviridae[1]. Since its first occurrence in the country in humans in 1912 and first laboratory confirmed diagnosis in a dog in 19257, human and animal rabies cases have been recorded in all the regions and ecological zones of Nigeria annually,[8]. Objective: This study was designed to assess the sensitivity and specificity of the SST in relation to the ‘gold standard’ dFAT in diagnosis of rabies in Nigeria. Conclusion:The relatively low sensitivity of the SST observed in this study calls for its replacement with the dFAT for accurate diagnosis of rabies and timely decisions on administration of PEP to prevent untimely deaths of exposed humans. Comparative assessment of seller’s staining test (SST) and direct fluorescent antibody test for rapid and accurate laboratory diagnosis of rabies.

Objectives

Methods

Results

Conclusion