Vaccination against bovine brucellosis.

Area of Science:

• Veterinary immunology
• Bacteriology
• Animal health

Background:

• Brucella abortus strain 19 vaccination is standard for cattle, but persistent serological reactions hinder eradication programs.
• Alternative vaccination strategies are needed for flexible application across all cattle ages, enabling cessation of calfhood vaccination.

Purpose of the Study:

• To investigate modifications of strain 19 vaccination to reduce serological interference.
• To identify effective vaccination methods applicable to all cattle ages for improved brucellosis control.

Main Methods:

• Experiments involved vaccinating calves at 1 month with strain 19, followed by a booster or vaccinating pregnant cows with reduced doses.
• Immunity and serological responses were assessed in cattle vaccinated at different ages and with varying doses.

Main Results:

• Vaccination at 1 month reduced serological response but yielded unsatisfactory immunity; a booster improved it.
• Reduced doses in pregnant cows offered better immunity than calfhood vaccination, with lower uterine infection rates at 3 x 10^8 c.f.u.
• Vaccinating mature heifers with 3 x 10^8 c.f.u. provided comparable immunity with reduced serological responses in most animals.

Conclusions:

• Modified strain 19 vaccination protocols, including early vaccination with boosters or reduced doses in specific cattle groups, can enhance brucellosis control.
• Further research is needed to optimize dosage and timing to balance immunity and minimize serological interference for cattle eradication programs.