Epidemiology of bovine babesiosis and anaplasmosis in Zambia.

The serological prevalence of bovine babesiosis and anaplasmosis in the traditional farming sector of six provinces of Zambia was determined using the indirect fluorescent antibody test (IFAT) for babesiosis and the card agglutination test (CAT) for anaplasmosis. Antibodies to Babesia bigemina occurred throughout the country whereas the prevalence of B. bovis followed the distribution of its tick vector Boophilus microplus which is limited to the north-eastern part of the country. Low numbers of B. bovis serologically positive cattle were demonstrated in central and southern Province. Anaplasma spp. occurred throughout Zambia but the overall percentages of positive sera were low ranging between 14.7% and 38.6% using the CAT. Two hundred sera were retested for anaplasmosis using an enzyme-linked immunosorbent assay (ELISA). Sero-prevalence rates were 1.5 to 2.3-fold greater with the ELISA than with the card agglutination test.

Prevalence of trypanosomiasis in cattle in south-west Zambia.

A trypanosomiasis survey was conducted in South-West Zambia. From a total of 3,346 cattle sampled 342 cattle showed a positive trypanosomiasis parasitaemia. During the survey trypanosome species and PCV values were also recorded. With simple statistical analysis populations with higher and lower prevalence rates were differentiated. The results indicated that the Kwando River Basin Tsetse Fly Belt and the Kafue River Basin Tsetse Fly Belt infested a larger area than originally assumed and that a link-up between both belts occurred or will occur in the near future.

Continuing presence of rinderpest virus as a threat in East Africa, 1983-1985.

The re-emergence of rinderpest virus in East Africa in 1979 caused widespread outbreaks of disease and subclinical infection throughout the region until mid-1983. Subsequent massive emergency vaccination campaigns have been successful in eliminating clinical rinderpest from Tanzania and preventing its spread southwards. Unfortunately the virus is still endemic in north-eastern Uganda and has recently caused epidemic outbreaks with high mortality in cattle in that country. In Kenya, buffaloes (Syncerus caffer) in and around the Masai Mara game reserve have developed antibodies to rinderpest virus as recently as late 1984. Although there have been no outbreaks of clinical disease in Tanzania or Kenya from April 1983 to the end of 1985 this serological evidence plus the increasing incidence of clinical outbreaks in Uganda indicate that rinderpest virus still threatens East Africa. The substantial aid which has been provided to the region for rinderpest control must be maintained.

Theileria taurotragi in Zambia.

Theileria sp. (Bwengwa) of low virulence was isolated by feeding R. appendiculatus ticks collected from the field on a susceptible calf and subsequently transmitted between cattle by R. appendiculatus ticks- Theileria sp. (Bwengwa) was shown to be T. taurotragi on parasitological, clinical and serological grounds. T. taurotragi is the fourth Theileria sp. shown to be present in Zambia.

Leptospiral and brucellar titers in frozen bovine sera after 20 years of storage.

Generally good agreement was obtained between the rankings of sera titers when originally tested (T1), and those of the same sera 20 years later (T2). At the later time, the majority of samples (88%) were in, or within 1 dilution factor of their classification at T1. Test results for Brucella abortus and Leptospira interrogans var pomona antibodies demonstrated that original titers, in the upper-lower limits of 20 to 50, had decreased over a wide range (20% to 90%), and the later tests show that the greater the original titer, the greater the proportional decrease. Thus, titers of 20,000 at T1 had decreased by 49% to 99% and those of 200,000, by 95% to 99.8%. Variations in T2 test results were noted between some samples which had given identical results at T1. A decrease in titer over time has been demonstrated. An estimate of the expected half-lives of sera of differing initial Leptospira antibody titers is that for each unit increase in log10 of the initial titer, the half-life is reduced by about 50%. The heterogeneity of the immune response is postulated as the reason for this variation.