BRUCELLOSIS SURVEILLANCE AND CONTROL IN ZIMBABWE - BACTERIOLOGICAL AND SEROLOGICAL INVESTIGATION IN DAIRY-HERD

Brucellosis in dairy cattle is endemic in Zimbabwe. The prevalence con tinues to be monitored intensively. Only milk and serum samples are ro utinely screened. Attempts to culture Brucella spp. from clinical spec imens are seldom made. Consequently, incidence of various Brucella spp , within Zimbabwe is virtually unknown, despite the high serepositivit y reported, This information is paramount in understanding the transmi ssion cycle and is also significant to public health; particularly as B. melitensis infects humans more often than do the other brucellae. T his paper describes the results of bacteriological and serological inv estigations of brucellosis in a dairy from near Bulawayo. The said far m was selected for the present pilot study because of the high inciden ce of reported abortion. The milk ring test was employed to test the b ulk pooled milk samples once a month for 14 months. The test was recor ded highly positive on all 14 occasions. To locate reactors, milk samp les from 36 individual cows were similarly tested. Of these, 21 (almos t 59%) were found to be reacting positively. One hundred and seventy-s even animals were marked for serotesting. Of these, 40 (approximately 25%) showed quite high serum titres (> 1:360) in both the STT and the Rosebengal test. The farmer was advised to havet all abortions fully i nvestigated. However, all the clinical material from cases of abortion , except one, were received in an advanced state of putrefaction. From this, Brucella was isolated on culture from stomach contents and coty ledons. The isolates from both the sites were characterized in detail, employing dye inhibition, phagetyping; the oxidative metabolic test a nd agglutination with monospecific sera. Both the isolates belonged to B. abortus biovar I, which was confirmed by the Central Veterinary Re search Laboratory, Weybridge. The significance of isolation and the ne ed to intensify similar studies have been discussed.