PERSISTENSE OF BRUCELLA ABORTUS RB51 VACCINE STRAIN IN MILK OF VACCINATED ADULT CATTLE

Karina Leite Miranda (UFMG); Fernando Padilla Poester (UFMG); Elaine Maria Seles Dorneles (UFMG); Thiago Magalhães Resende (UFMG); Adil Knackfuss Vaz (UDESC); Sandra Maria Ferraz (UDESC); Andrey Pereira Lage (UFMG)

Brucellosis caused by Brucella abortus is a chronic disease of cattle of worldwide economic and public health importance resulting in abortion and infertility. Brucellosis in cattle in Brazil is widespread in the country, although it has an uneven distribution with areas with very low and others with high prevalences of cattle and herd infections. Voluntary vaccination of adult animals with RB51 is approved by MAPA as additional control strategy. The aim of this study was to evaluate the shedding of B. abortus in the milk of cows vaccinated with RB51. Nine cows, vaccinated with S19 as calf and other nine cows, not vaccinated with S19 were used. The animals were vaccinated 30 to 60 days after parturition with 1.3 x 10¹⁰ CFU of B. abortus strain RB51 subcutaneously on day 0 of the experiment. Milk samples were collected on days 1, 2, 3, 4, 7, and weekly up to day 63 after vaccination. The samples were manually collected from all quarters, mixed and stored at -20ºC. Samples were thawed and centrifuged at 2500 x g, for 15 minutes. The skim milk was discarded and the cream and deposit were mixed and immediately spread onto tryptose agar plates with antibiotics (Farrell’s supplement) in duplicates. Moreover, 1 mL of each mixture was inoculated in 9 mL of enrichment media (tryptose broth with Farrell’s sellective supplement) and incubated into 5% CO2 at 37ºC for 5 days, and then inoculated onto tryptose agar with antibiotics. All plates were incubated into 5% CO2 at 37ºC for 9 days. Samples were also tested by genera specific PCR. No B. abortus was isolated from any sample tested. Only one sample, collected on the first day after RB51 vaccination, from a B19-calf vaccinated cow, was positive by PCR. In conclusion the spread of RB51 by milk seems not to be a public health problem. Nevertheless the pasteurization of the milk from cows recently vaccinated with RB51 is highly recommended. Agradecimentos: Fapemig, CNPq, Capes e FEP-MVZ Coordenação financeira.