Efficacy of a killed vaccine (SILIRUM®) in calves challenged with MAP

MUÑOZ M, GARCÍA MARÍN JF, GARCÍA-PARIENTE C, REYES LE, VERNA A, MORENO O, FUERTES M, DOCE J, PUENTES E, GARRIDO J, PÉREZ V

Copenhagen, Denmark

Congreso; 8th International Colloquium on Paratuberculosis; 2005

A killed vaccine against bovine paratuberculosis (SILIRUM®, CZ Veterinaria) was evaluated in calves experimentally challenged with Mycobacterium avium subspecies paratuberculosis (MAP). Ten calves out of 18 were injected subcutaneously when two months old with a single dose of the vaccine. The remaining 8 calves were vaccine controls, injected with PBS. Two months after vaccination 8 and 6 calves (from the vaccinated and control groups respectively) were challenged with 6 doses of 6.9 x 1010 cfu of MAP.Peripheral cellular and humoral immune responses were assessed as well as MAP fecal shedding between 0 and 330 dpv. Three vaccinated and two control calves were slaughtered at 180 dpv and the remaining 13 calves at 330 dpv. Pathologic and bacteriologic evaluation of intestine and lymph nodes samples were completed. The number of granulomas was counted in sections from both locations. No adverse reactions to the vaccine were observed in any of the calves. Humoral responses appeared in vaccinated groups at 90 dpv, whereas cellular responses were detected at 30 dpv, reaching the highest values at 120 dpv. A significant reduction in the number of granulomas present in the tissues was observed in vaccinated calves. These calves showed either no or only focal lesions confined mainly to the lymphoid tissue, except in onecase of the diffuse form of infection. In non-vaccinated control calves, diffuse lesions extended to the intestinal mucosa. In this study the administration of a single dose of SILIRUM® in calves was safe and able to control the progression of disease. Vaccinated calves had fewer lesions, less severe lesions and a lower tissue burden of MAP than unvaccinated calves. Fecal shedding of MAP was not detected in any animal. Key words: Paratuberculosis, calves, vaccination, SILURUM®, experimental study.