Vaccination, a promising method of control
The use of an inactivated vaccine to control the disease offered more promising results. The vaccine Coxevac was used and its effectiveness was proven in the short (1 year) and long term (4 years). No immediate effects were noticed during the first year following vaccination, because the flocks studied had a high percentage of infected animals. However, with routine annual vaccinations it was possible to gradually reduce the infection until its disappearance after four years of vaccination.
The vaccine was beneficial in controlling abortions which, after the first year of vaccination, were significantly reduced (<2%). Q fever is responsible for abortion rates between approximately 6% and 10% of the ewes in an infected flock.
After four years of vaccination, the absence of the infection in the animals did not necessarily mean that the bacteria Coxiella burnetii had been eradicated on the sheep flock, since this bacterium is very persistant in the environment, and it remains present in sheep premises (surfaces, floor, aerosols) for long periods of time. So Neiker-Tecnalia recommends that after an outbreak of Q fever in a sheep flock, vaccination should be implemented for a period of five years at least. It is very important that replacement lambs are immunised against the bacterium when they reach three months of age.
Means of eliminating Coxiella burnetti
Neiker-Tecnalia scientists found that the main Coxiella burnetti shedding routes in sheep are vaginal fluids and faeces; and to a lesser extent, milk. Bacterial shedding through milk is basically concentrated in the first month after lambing, while vaginal and faecal excretion is more prolonged in time. Bacterial excretion favours the generation of contaminated aerosols and
|Contact: Irati Kortabitarte|