VARIATIONS IN THE PREVALENCE OF ANTIBODY TO BRUCELLA INFECTION IN CATTLE BY FARM, AREA AND DISTRICT IN KENYA

Variations in the sere-prevalence of antibody to brucella infection by cow, farm and area factors were investigated for three contrasting di stricts in Kenya: Samburu, an arid and pastoral area; Kiambu, a tropic al highland area; and Kilifi, a typical tropical coastal area. Cattle were selected by a two-stage cluster sampling procedure and visited on ce between August 1991 and 1992. Schall's algorithm, a statistical mod el suitable for multi-level analysis was used. Using this model, older age, free grazing and large herd size (greater than or equal to 31) w ere associated with higher seroprevalence. Also, significant farm-to-f arm, area-to-area and district-to-district variations were estimated. The patterns of high risk districts and areas seen were consistent wit h known animal husbandry and movement risk factors, but the larger tha n expected farm-to-farm variation within high risk areas and districts could not be explained. Thus, a multi-level method provided additiona l information beyond conventional analyses of sere-prevalence data.