Control of Brucella melitensis infection in a large camel herd in Saudi Arabia using antibiotherapy and vaccination with Rev. 1 vaccine.

The authors describe an attempt to control Brucella melitensis infection in a large camel herd in Saudi Arabia. Sera from the entire herd (2,536) were examined by the Rose Bengal and standard United States of America buffered plate agglutination tests. The overall Brucella seroprevalence was 8%. Milk samples from the 120 seropositive milking camels were cultured on Brucella-selective media. B. melitensis biovars 1, 2 and 3 were isolated from 41 camels (34%). Seropositive camels (202) were treated for the first time with a combination of long-acting oxytetracycline (OTC) at a dose of 25 mg/kg administered intramuscularly (i.m.) every 2 days for 30 days and streptomycin at 25 mg/kg i.m. every 2 days for 16 days. In addition, milking camels were given OTC-intramammary infusion at a rate of 10 ml/teat every 2 days for 8 days. This regimen was found to be effective in eliminating the shedding of Brucella organisms by camels, with no relapse. Moreover, all treated camels became seronegative within 16 months after treatment. Seronegative camels (2,331) were vaccinated for the first time with the B. melitensis Rev. 1 strain vaccine, as follows: a) 175 young camels (aged three months to one year) were each inoculated subcutaneously with a full dose (1-2 x 10(9) viable organisms in 1 ml). Brucella antibody titres between 1:50 and 1:200 were detected 2-4 weeks post-vaccination. Brucella antibodies decreased gradually until the animals became seronegative 8 months after vaccination. b) 2,156 camels aged more than one year were each inoculated subcutaneously with a reduced dose (1-2 x 10(6) viable organisms in 1 ml). Antibody titres measured 2-4 weeks post-vaccination varied from 1:25 to 1:200. The titres decreased gradually, until the animals became seronegative 3 months post-vaccination. No Brucella organisms were recovered from repeated udder secretion samples from all vaccinated milking camels, and no abortions were recorded among pregnant vaccinated camels.