Abstract
Eight hundred fifty nine serum samples were collected randomly from housed and free-ranged camels, aged from less than 1 to more than 20 years in 4 parts of Riyadh Region, Saudi Arabia. Serological testing for Brucella antibodies was performed using Rose Bengal plate agglutination (RBPT), standard tube agglutination (STAT), competitive enzyme-linked immunosorbent assay (c-ELISA) and complement fixation (CFT) tests. Polymerase chain reaction (PCR) was used to confirm serologically positive samples and identify the causative agent.
The results showed variation between different tests, with only 16 samples (1.86%) being positive by RBPT, 27 samples (3.14%) by STAT and 26 (3.03%) by c-ELISA. The STAT, however, revealed predominantly low titres, limiting its reliability as a screening test for chronically infected and carrier camels. CFT was positive in 34 samples (similar to 4%) including all of those shown to be positive by other tests. Positive sera were further confirmed by PCR, which revealed Brucella abortus as the causative agent.
The highest percentage of serologically positive camels was recorded in Wadi Al-Dawasir in the southern part and the lowest in the western part of Riyadh region. All serologically positive camels were females. The prevalence of infection was twice as high in housed than in free-ranged camels and the majority of positive cases were recorded in the age group 5-10 years. Differences in prevalence were observed between different local breeds, with highest prevalence in the Shu'l camels. All serologically positive camels were clinically normal at the time of sampling.
Based on these results, we recommend c-ELISA as screeing test, CFT as a confirmatory test and application of PCR for determining the species of brucella infecting the camels.