The protection against goat abortion by the anti-brucella primary vaccination, the challenge of revaccination

Abstract

Goat brucellosis, by Brucella melitensis, is a zoonotic-endemic disease in eight provinces of Argentina.
The National Animal Health Service (SENASA) urged the local governments to set up a control program
that involves a conjunctival Rev-1 vaccination, every two years, of all goat populations independent of
the age and sex of the animals. The vaccine posse the restriction not to be applied in pregnant goats
because occasionally induce abortion. Practical evidence of herds vaccination, not validated by controlled
experiences, showed that with revaccination pregnant goats did not abort, but were protected against
it and even with further vaccinations. Therefore, the objective of the trial was to assess the effect of
conjunctival Rev-1 vaccination of pre-immunized goats when were revaccinated during the higher
susceptibility period to the abortion. Twenty-two, brucellosis-free Boer goats were randomly assigned
to either yellow or red groups, according to the colour of the ear tag (gA n=11; gR n= 11). The natural
mating lasted 60 days and the pregnancy percentage was 82 (gA) and 91 % (gR), respectively. The gA
received two vaccine doses, at 20 days pre-mating and at 95 days from the beginning of mating, whereas
gR received just one dose at 98 days of the beginning of mating. Blood samples were taken at six-time
points to assess the immune response and microbiology samples were also taken at birth/abortus and
five days thereafter. The microbiology samples were cultured at both Farrell and CITA medium, and every
colony morphologically compatible with Brucella was validated by PCR (Multiplex PCR, Bruce-ladder).
All the goats were serologically positive at 14 days post-inoculation, but the gR maintained a significant
(p<0,05) number of goats positive at 100 days post-birth/abortus. The gA goats gave birth on time and
the vaginal swabs were bacteriology negative at both parturition and five days thereafter, whereas the
vaginal swabs of the gR were positive at both times. In conclusion, the pre-mating vacination against
brucellosis prevented significantly (p<0,0001) both the abortion and the infections of the goats when
they were revaccinated with the vaccine strain during the gestation.