Development and application of a Bacillus anthracis protective antigen domain-1 in-house ELISA for the detection of anti-protective antigen antibodies in cattle in Zambia

In Zambia, anthrax outbreaks among cattle are reported on nearly an annual basis. Presently, there is a lack of serological assays and information to develop an anthrax management and control strategy. In this study, an indirect enzyme-linked immunosorbent assay (ELISA) based on recombinant protective antigen domain 1 (rPA-D1) of Bacillus anthracis was developed and used to detect anti-PA antibodies in cattle in Zambia. An antigen coating of 10 ng/well and a serum dilution of 1:100 were determined to be the optimal rPA-D1 ELISA titration conditions. The intra- and inter-assay % coefficients of variation were less than 10% and 15%, respectively. The rPA-D1 ELISA could detect seroconversion in the cattle 1 month after anthrax vaccination. In a cross-sectional study conducted in the Western Province, Zambia, 187 serum samples from 8 herds of cattle were screened for anti-PA antibodies using the rPA-D1 ELISA. The seropositive rate of the serum samples was 8%, and the mean anti-PA antibody was 0.358 ELISA units. Additionally, we screened 131 cattle serum samples from Lusaka, which is a nonendemic area, and found no significant association between the antibody levels and sampling area (endemic versus nonendemic area). Conversely, significant differences were observed between the anti-PA antibody levels and herds, anti-PA antibody levels and vaccination status and anti-PA antibody levels and vaccination timing. Collectively, these findings suggest that the rPA-D1 ELISA is a useful tool for the detection of anti-PA antibodies in cattle in Zambia. The low proportion of seropositive sera indicates that there is inadequate cattle vaccination in the Western Province and, in addition to other epidemiological factors, this may precipitate the anthrax outbreak recurrence.

Recent observations on site reactions in cattle to vaccination against contagious bovine pleuropneumonia (CBPP) using T1/44 vaccine in Zambia

Contagious bovine pleuropneumonia (CBPP), a highly infectious and fatal disease of cattle present in many countries in sub-Saharan Africa, is usually controlled by mass vaccinations. However, vaccination against CBPP is known to cause site reactions in a percentage of cattle especially in primary vaccinations. In Zambia, a record of site reactions was kept for seven consecutive years from 2005 to 2011 to establish the level of the problem. In some areas, after 3 years of consecutive vaccination campaigns, immunization could not be implemented for a period of 2 years because of logistical difficulties or owner resistance. Whereas in the three preceding years when animals were vaccinated annually, site reactions were in the range of 6.2%; on resumption of vaccination in the herds that had not been immunized for 2 years, site reactions averaged 21.3%. This data shows that the T1/44 vaccine may cause severe local reactions in cattle if there is any break in annual vaccinations. It is therefore important for authorities to ensure that the cattle at risk of contracting CBPP are regularly vaccinated to avoid discouraging farmers from presenting their animals.

Private sector involvement in the control of contagious bovine pleuropneumonia (CBPP) in the Kazungula district of Zambia benefitted the community and the control strategy

Contagious bovine pleuropneumonia (CBPP) is a disease of economic importance that is widely distributed in sub-Saharan African and contributes significantly to cattle morbidity and mortality. Lack of resources to implement eradication measures has led to the disease becoming endemic in most areas in sub-Saharan Africa where governments have little resources and the majority of the people are poor. Usually, control and eradication of such diseases as CBPP is treated as a public good by governments and to achieve this, governments are usually assisted by nongovernment organisations, bilateral government programmes and international donors. The private sector, which usually is companies that run businesses to make profit, although not very well established in sub-Saharan Africa could play a big role in the eradication of CBPP in the region. This could play a dual role of promoting investment and also eradicate livestock diseases which have proved a menace in the livestock sector. This paper highlights the role played by the private sector in the control of CBPP in Zambia.

Bacteria isolations from broiler and layer chicks in zambia

Chick mortality (CM) is one of the major constraints to the expansion of the poultry industry in Zambia. Of the 2,829 avian disease cases submitted to the national diagnostic laboratory based at the Central Veterinary Research Institute in Lusaka between 1995 and 2007, 34.39% (973/2,829) were from CM cases. The disease accounted for 40.2% (218,787/544,903) mortality in the affected flocks with 89.6% (196,112/218,787) of the affected birds dying within seven days. Major bacteria species involved were Escherichia coli, Salmonella gallinarum, and Proteus species being isolated from 84.58%, 46.15%, and 26.93% of the reported CM cases (n = 973), respectively. Detection of Salmonella typhimurium, Salmonella enteritidis, and Salmonella dublin indicates that poultry has the potential of transmitting zoonotic pathogenic bacteria to humans. The proportion of Salmonella gallinarum reactors in the adult breeding stock was generally low (<0.5%) throughout the study period although its prevalence in CM cases was correlated (r = 0.68, P < 0.011) with seroprevalence of the same pathogen in the adult breeding stock. Given that the disease accounts for a large proportion of the avian diseases in Zambia as shown in the present study (34.39%, n = 2,829), it is imperative that an effective disease control strategy aimed at reducing its occurrence should be developed.