Uso do ELISA no diagnóstico e controle da leucose enzoótica e da tuberculose dos bovinos

Abstract

Enzootic Bovine Leukosis (EBL) and Bovine Tuberculosis (BT) are infectious diseases that cause great losses to the dairy industry due to the discard of animals, carcasses condemnation and veterinary services. The aim with this work was to evaluate the performance of a commercial imported (IDEXX®) enzyme linked immunoassay kits (ELISA) on the diagnosis and control of EBL and BT in dairy cattle naturally infected raised in the state of Pernambuco. The ELISA has being tested for assisting the diagnosis of both diseases, with the purpose of increasing the results sensitivity. While the efforts aim progressively to replacement of the agar gel immunodiffusion (AGID) for a more sensitive technique on the EBL diagnosis, about the BT the technique could be used in conjunction with the tuberculin test for the detection of animals at different stages of the immune response to the etiological agent. Blood serum samples from 327 dairy herds in the state of Pernambuco were subjected to AGID and commercial imported ELISA CHEKIT-leucosis-serum, produced by IDEXX® laboratory, for the diagnosis of EBL. 25 samples that resulted inconclusive to one or both tests were discarded. 302 samples were examined, resulting positive 24.1% (73/302) in the AGID and 45% (136/302) in the ELISA. The lack of agreement between the diagnostic methods was probably due to the high sensitivity of ELISA, which detects antibodies even in situations with low serum levels. The ELISA in relation to the AGID, considered the standard technique, had a sensitivity of 98.6%, specificity of 72% and Kappa 0.55. About the TB diagnosis, 379 cattle were tested for cervical compared test (CCT) and had blood serum samples examined for identification of anti-Mycobacterium bovis antibodies throught the ELISA kit IDEXX® M. bovis Ab Test. From the 379 cattle examined, 16 (4.2%) were positive to CCT and 10 (2.6%) to ELISA. The results associated to tuberculosis, with the simultaneous use of both tests, would allow the discard of 26 infected cattle and not 16, if the CCT had been used alone, resulting in remaining 10 potentially infected cattle and disseminators of the disease. It is concluded that the ELISA is relevant in the control and eradication of EBL and BT, its application on EBL diagnosis may replace the AGID, as well as in the TB, together with the tuberculin skin test.