Serological survey of bovine brucellosis in barka and arado breeds (Bos indicus) of western Tigray, Ethiopia.

A cross sectional study was conducted to determine the seroprevalence and associations with potential risk factors of brucellosis in indigenous cattle breeds of Western Tigray zone, North West Ethiopia. A total of 1968 cattle were examined between October 2007 and April 2008. Of these, 1120 cattle were from semi-intensive production system composed mainly of barka breed while 848 cattle were from extensive system with arado breed being predominant. Sera were screened using Rose Bengal Plate Test (RBPT) and positive samples were then confirmed by Complement Fixation Test (CFT). The overall individual animal-level prevalence was 4.9%. Brucellosis seroprevalence was higher in herds reared under semi-intensive production systems. 7.7% and 63.6% prevalence were found at individual- and herd-level in the semi-intensive system, respectively. 1.2% and 3.3% were the figures for the extensive system. Both individual- and herd-level seroprevalence were higher in Mykadra and Bereket towns among all investigated towns. Though the odds ratio for Humera was more than two, seroprevalences across the three districts in the extensive production system were comparable. Herd size, age, sex, and husbandry practices were significantly associated with seropositivity and brucellosis increased the calving interval. Higher risk to infection was found in barka breed than arado in the semi-intensive production system but not in the extensive production system. Breed management systems, but not breed caused breed susceptibility variation. A high prevalence of brucellosis in barka breed in the study area indicates that it might serve as source of infection for others in the region. Hence, screening tests aiming at culling seropositive barka was recommended before distribution to other poverty-prone areas of the region.