Seroprevalence of small ruminant brucellosis in selected districts of Afar and Somali pastoral areas of Eastern Ethiopia : the impact of husbandry practice.

SUMMARY A seroprevalence study of small ruminant brucellosis was conducted in two sheep and goat rearing pastoral regions of Ethiopia, namely Afar and Somali, from November 2004 to April 2005. Sera from 2000 sheep and goats were tested by Rose Bengal Plate test (RBPT) and Indirect Enzyme Linked Immuno – Sorbent Assay (I – ELISA). Out of the 2000 sera tested 1.9 % (n = 38) were positive to RBPT and 9.7 % (n = 193) were positive to I – ELISA. This investigation is the first of its type to be performed in small ruminants kept under pastoral production systems. There was statistically highly significant difference (P < 0.001) between the over all seropositivity revealed by RBPT and I – ELISA (Z0.05 = 250 ; 95 % C.I. for the difference between prevalence using I – ELISA and RBPT = 7.69, 7.81). Only fair agreement (Kappa = 31.25 %) was observed between RBPT and I – ELISA for the detection of Brucella antibodies in sera of sheep and goats. Higher prevalence rate (16 %) was found in Afar region (where commingling of animals at communal grazing is the common practice) while lower prevalence (1.9 %) was recorded in Somali region where herding and rangeland utilization is based on clan basis. (X 2 = 117.06 ; P < 0.001). Afar region is about 12 times at risk of infection with Brucella organisms (OR = 11.76 ; C.I : 6.76, 22.11). Brucella antibodies were more prevalent in goats (13.2 % ; C.I : 11.2, 15.3) than in sheep (5.6 % ; C.I : 4.2, 7.3). This difference is statistically significant (X 2 = 32.5 ; P < 0.001 ; OR = 0.392). No difference was observed in prevalence between male and female study animals. The current study revealed higher prevalence of Brucella antibodies (9.7 %) in the absence of Brucella vaccination. This is an indication of the wide spread nature of Brucella infection in the study areas. The Afar region is particularly at high risk of brucellosis. Further epidemiological studies on the distribution and risk factors of brucellosis in the area are warranted.