Effectiveness of Rose Bengal test and fluorescence polarization assay in the diagnosis of Brucella spp. Infections in free range cattle reared in endemic areas in Zambia

Abstract

The effectiveness of Rose Bengal test (RBT) and fluorescence polarization assay (FPA) in diagnosing cattle brucellosis in endemic areas was assessed and RBT and FPA test agreement was compared (n=319). The sensitivity of RBT and FPA in detecting low Brucella titres were evaluated in paired sera (n=34). A logistic regression model was constructed to predict cattle test result in FPA using RBT as the main predictor and incorporating bio-data and animal history. There was 79.3% agreement between the RBT and FPA (Kappa = 0.59; Std error = 0.05; p = 0.000) and a high correspondence between high RBT scores and positive FPA results suggesting that sera with high RBT score may not require confirmation with tests such as competitive-ELISA or CFT. High FPA cut-off points were more likely to miss animals with low antibody titres. The RBT had a reduced ability in detecting low antibody titres compared to the FPA. FPA test interpretation was improved if a priori information, such as sex and age was used. Under the challenging disease surveillance conditions prevailing in rural Africa, field-testing methods that are sensitive and specific, allow single animal contact, low technical skills in data interpretation are suitable.