Evaluation of efficacy of some serological tests used for diagnosis of brucellosis in cattle in Egypt using latent class analysis

Abstract

In this study serum samples were collected from 4 different groups of cattle, Group I (non-vaccinated Brucella infected group), Group II (Vaccinated Brucella infected group), Group III (Non-vaccinated Brucella free group) and Group IV (vaccinated Brucella free group). These samples were subjected to the different serological tests including Rose Bengal plate antigen test, Tube Agglutination test, Rivanol test, Indirect Enzyme Linked Immunosorbent Assay and Competitive Enzyme Linked Immunosorbent Assay. Statistical analysis of the obtained results in different cattle groups was carried out using Latent Class Analysis (Lem model). The prevalence of brucellosis was 6.4%, the sensitivity of RBPT was 96.1% while its specificity was 99.3%, the sensitivity of Rivanol test was 85% while its specificity was 100%, the sensitivity of Indirect Enzyme Linked Immunosorbent assay was 100% while its specificity was 98.3 % and the sensitivity of Competitive Enzyme Linked Immunosorbent assay was 97.1% while its specificity was 100%. The results proved that, the most sensitive test was Indirect Enzyme Linked Immunosorbent assay while the most specific test was Competitive Enzyme Linked Immunosorbent assay. This study therefore, recommends the use of Indirect Enzyme Linked Immunosorbent assay as a screening test and Competitive Enzyme Linked Immunosorbent assay as a confirmatory test. Bacteriological examination was carried out on supramammary lymph nodes and spleen of some slaughtered seropositive cattle, the rate of isolation was 25% from non-vaccinated infected group and 10% from vaccinated infected group. Brucella melitensis biovar3 was recovered only from supramammary lymph nodes.

Keywords: Brucellosis, Cattle, Sensitivity, Serology, Specificity, Latent Class Analysis