Bovine brucellosis is a cosmopolitan anthropozoonosis caused by B. abortus, which causes
economic losses to the meat and milk production chain. In order to determine the
seroconversion coefficient attributable to the vaccination of heifers with B. abortus strain B 19, 330 blood serum samples from 110 heifers with three to eight months of age were
analyzed from five properties in the municipality of Araguaína/TO. A randomized trial was
carried out with two groups of heifers, intervention and control, each with 55 animals. Day
zero (D-0) of the experiment was marked from the first blood collection immediately before
vaccination of intervention group heifers. Post-vaccination blood samples were collected on
days 7 (D-7), 14 (D-14) and 21 (D-21). The randomized trial was conducted until D-14, when
the heifers of the control group were vaccinated with strain B-19. The collection of 55 blood
samples in D-21 allowed to repeat the determination of seroconversion on the seventh day
post-vaccination with the control group. All serum samples were submitted to the AAT test.
Statistical analyzes were performed with WinPepi® software (version 11.43) and the
seroconversion coefficient attributable to vaccination was calculated by subtracting the
incidence of seroconversion in the intervention group from that of the control group. In D-7
the seroconversion in the intervention group was 94.55% (95% CI [84.88% to 98.86%]) and
in the control group it was null (95% CI [0.00% to 6.49 %]). In D-14 the seroconversion in the
control group remained null and that of the intervention group was 98.18% (95% CI [90.28%
to 99.95%]). In D-21 the seroconversion in the 55 heifers used in the control group
vaccinated in D-14 was 100% (95% CI [93.51% to 100%]), but without significant difference
(p≤0.05) to the D-7 response of the intervention group. In order to monitor vaccination, FAO
recommends that diagnostic tests be performed using AAT within 2 to 3 weeks post vaccination on random sampling of heifers vaccinated with strain B-19, with 80%
seroconversion as the parameter. The results of this study allow us to recommend to the
SVO that we institute a vaccination audit, with random collection of blood samples from the
seventh day on calves declared as vaccinated with strain B-19, using the AAT test as a
diagnostic test and considering a minimum coefficient of seroconversion of 75%, aiming at
the monitoring of the vaccination process carried out under the technical responsibility of
veterinarians enrolled in the State Programs for the Control and Eradication of Brucellosis
and Tuberculosis.
|
