Bovine brucellosis serum agglutination test prevalence and breed disposition according to prevalent management systems in the Lake Victoria zone of Tanzania

A total of 13078 cattle 8 months of age and older belonging to 558 units in the Lake Victoria zone of Tanzania were screened for brucellosis using the serum agglutination test (SAT). This exercise was executed as a Tanzanian Agriculture Ministry's directive for screening all adult bovines in the country reared under controlled grazing and receiving good veterinary supervision and inputs so that brucellosis control measures could be instituted. In this category two types of management systems were encountered: Dairy, comprising 15 units totalling 3626 Exotic (Friesian and Ayrshire) and Grade (Zebu and Exotic) crosses, and Ranch, comprising two units totalling 6756 mainly dual-purpose Mpwapwa (MPW) animals. These three animal types have much higher milk production potential than the indigenous Tanganyika shorthorn Zebu (TSZ). This latter beef type is reared under local management system and owned wholly by subsistence stock owners practising uncontrolled communal grazing and having little or no veterinary supervision and inputs. However, TSZ animals from 541 farm units totalling 2705 members were also screened from the east and south sub-zones because of their close proximity to the Dairy/Ranch units and also the Serengeti Wildlife National Park. This exercise revealed an overall prevalence rate of 10.8%. There was moreover a significant difference in the seroprevalence rates among the management systems (P < 0.001). The lowest prevalence rate (4.3%) was found in the Local management system, with Dairy intermediate (6.3%) and Ranch highest (15.8%). There was also significant variation in prevalence rates between TSZ and Grade animals, and between MPW and Exotic animals (P < 0.001).