Enzootic bovine leukosis: prevalence of seric antibodies on dairy cows breed at Bahia and comparison between results of ELISA tests and ágar gel immunodiffusion tests

Abstract

The prevalence of infection by the Enzootic Bovine Leukosis virus was determined in dairy cows breed in five micro-regions of Bahia State, comparing the efficiency of three serodiagnostic tests for the detection of antibodies anti Enzootic Bovine Leukosis virus: ELISA test, AGID Immunodiffusion test / gp 51 from foreign origin and AGID Immunodiffusion test / gp 51 produced by the Institute of Technology of Paraná - TECPAR. Seven hundred and ninety-six dairy cattle , from 13 bovine flocks were used. The infection for VLB was detected in every flock, with an prevalence of 41,0%, showing an individual flock value variation between 6,3% (4/64) and 65,8% (25/38). The animals were stratified in six age groups: a) 2 - 6 months; b) 7 - 12 months; c) 13 - 24 months; d) 25 - 48 months; e) 49 - 72 months; f) more than 72 months of age, observing that the indexes of infection in the mentioned groups were 8,8%; 16,9%; 17,7%; 50,8%; 54,4% and 56,5% respectively, showing these indexes increased significantly with age. Were used 434 serum samples were used to evaluate the comparative efficiency of the three serodiagnostic tests, considering ELISA as the standard test. In the comparison between ELISA and IDGA test with antigen of foreign origin, were found a sensibility of 85% and specificity of 80%; a positive predictive value (PPV) of 63% and a negative predictive value (NPV) of 93%, with an agreement index of 81%. Comparatively to the ELISA results, IDGA test with antigen of national origin presented a sensibility of 82%, specificity of 93%, PPV of 79% and NPV of 93%, with an agreement index of 85%. The overall results of these studies suggest that IDGA test with antigen of national origin is sufficiently efficient to its use.