Serological responses of cattle inoculated with inactivated trivalent foot-and-mouth disease vaccine at the wildlife-livestock interface of the Kruger National Park, South Africa.

Foot-and-mouth disease (FMD) virus is economically one of the world's most important animal pathogens, which can be responsible for losses in livestock trade, as well as frequent and highly disruptive large-scale epidemics. The control of FMD in southern Africa typically includes vaccination of cattle with a trivalent or bivalent vaccine preparation. The objective of this study was to determine the level and duration of the antibody responses conferred by the current FMD vaccination programme in cattle at the western boundary of the Kruger National Park (KNP) in South Africa. Two hundred and eighty-three cattle from four communal dip tanks were longitudinally sampled after vaccination using an inactivated trivalent FMD vaccine (South African Territories (SAT) 1, SAT 2 and SAT 3). Blood samples were collected fortnightly over four months and antibodies were measured using a liquid-phase blocking ELISA. Only 5%, 43%, and 16% of enrolled cattle had evidence of pre-existing antibody responses to the three SAT viruses at the beginning of the study (≥1.6 log10 titre for SAT 1-3 respectively), which was 7-12 months after the last vaccination campaign. However, 14 days after vaccination this proportion increased to between 66% and 93%, with SAT 2 having the highest proportion. Young animals (<1 year old) tended to have higher predicted baseline antibody levels that peaked by 14 days. Positive serological responses were transient and by 56 days post-vaccination antibody levels begun to decline below the threshold of 1.6 log10 titre. Predicted peak antibody levels only consistently reached 2.0 log10 for SAT 2. Serological responses for SAT 2 tended to be longer, but in most cases the duration of antibody levels was short-lived. More research is necessary to determine the reasons for the limited duration of antibody responses, especially among younger cattle, in order to achieve more effective prophylactic vaccination.

Serological evidence of vaccination and perceptions concerning Foot-and-Mouth Disease control in cattle at the wildlife-livestock interface of the Kruger National Park, South Africa.

Communal livestock farming areas adjoining the Greater Kruger National Park Area within South Africa are part of the Foot-and-mouth disease (FMD) Protection Zone with Vaccination due to the proximity to wildlife reservoirs. FMD and its control affect the productivity of resource-poor farmers who often depend on livestock for their livelihoods. A cross-sectional study was performed with the objectives to evaluate the perceptions of farmers concerning FMD control, estimate the proportion of cattle with presumed protective antibody titres against FMD, as well as the proportion of herds with adequate herd immunity at the wildlife-livestock interface within Mpumalanga Province. One hundred and four farmers were interviewed with 73% (76/104) being cattle owners and the remainder hired cattle herders. The majority of respondents (79%, 82/104) reported a high level of satisfaction with the current animal health programmes in general. The educational level of the respondents varied by satisfaction level: the median (interquartile range; IQR) education level was standard 9 (2-12) for non-satisfied respondents, standard 3 (0-6) for little satisfied and standard 7 (2-11) for very satisfied respondents (P=0.036). Animals are not always treated at FMD inspections points, but satisfied respondents were more likely to seek veterinary assistance (P=0.001). The majority of respondents (92%, 96/104) identified the African buffalo (Syncerus caffer) as a risk factor for FMD outbreaks. Liquid-phase blocking ELISA antibody titres ≥1.6log10 were used to indicate positive serology secondary to FMD vaccination. At the time of sampling and relative to this threshold, 23% (95% confidence interval (CI): 12%-34%) of the sampled cattle had positive serology to SAT-1, 41% (95%CI: 33%-48%) to SAT-2 and 29% (95%CI: 19%-39%) to SAT-3. The median (IQR) time between the previous vaccination and sampling was 189 (168-241) days. The sampled cattle had a longer inter-vaccination interval as scheduled by state veterinary services and antibody levels were low at the time of the study. The majority of respondents expressed high satisfaction with the currently applied FMD vaccination programme, which provides an opportunity for progressive adaption of animal health programmes within the study area.