Evaluation of different immunogens against bovine tuberculosis based on presence of lesions at necropsy

Abstract

THE OBJECTIVE OF THIS WORK WAS TO COMPARE THE DEGREE OF PROTECTION GIVEN BY THREE IMMUNOGENS AGAINST BOVINE TUBERCULOSIS IN HEIFERS, BASED ON THE PRESENCE OF LESIONS AT NECROPSY, AFTER CHALLENGE WITH A PATHOGENIC M. BOVIS STRAIN. TWENTY-FOUR TUBERCULOSIS FREE HEIFERS WERE DIVIDED INTO FOUR GROUPS: GROUP 1 WAS VACCINATED WITH M. BOVIS CULTURE FILTRATE PROTEIN EXTRACT (CFPE); GROUP 2 WITH CFPE PLUS INTERFERON-GAMMA (IFN-γ); GROUP 3 WITH BACILLUS CALMETTE-GUERIN (BCG) AND GROUP 4 REMAINED AS CONTROL. AT SIX MONTHS POST-VACCINATION ALL ANIMALS WERE CHALLENGED WITH A FIELD STRAIN OF M. BOVIS AND AFTER SIX MONTHS THEY WERE SLAUGHTERED AND THE PRESENCE OF LESIONS WAS EVALUATED. AT NECROPSY, THE LYMPH NODES LOOKED LIKE ABSCESSES AND HISTOPATHOLOGY SHOWED PYOGRANULOMATOUS LYMPHADENITIS. ALL THE ANIMALS OF THE CONTROL GROUP HAD TUBERCULOSIS LESIONS AND THIS WAS THE GROUP WITH THE HIGHEST NUMBER OF LESIONS, 66.6% OF THEM BEING SEVERE. SEVERAL ANIMALS OF THE THREE IMMUNIZED GROUPS DID NOT SHOW ANY LESIONS, AND ONLY MODERATE LESIONS WERE OBSERVED IN THE OTHERS. NONE OF THE VACCINATION PROTOCOLS GAVE 100% PROTECTION, SINCE LESIONS WERE OBSERVED IN ALL THE GROUPS. NEVERTHELESS, IT IS EVIDENT THAT DIFFERENT DEGREES OF PROTECTION WERE OBTAINED IN THE VACCINATED GROUPS, AS SHOWN BY THE ABSENCE OR DECREASE IN SEVERITY OF LESIONS; THIS REDUCTION BEING GREATER IN THE GROUP VACCINATED WITH BCG. IT WAS CONCLUDED THAT BCG WAS THE IMMUNOGEN THAT GAVE BETTER RESULTS; THEREFORE, IT COULD BE USED FOR TUBERCULOSIS CONTROL IN HIGH PREVALENCE AREAS.