Wildebeest-associated malignant catarrhal fever (WA-MCF), a fatal disease of cattle caused by alcelaphine herpesvirus 1 (AlHV-1), is one of the most important seasonal diseases of cattle in wildebeest endemic areas, with annual incidence reaching 10%. Here we report efficacy of over 80% for a vaccine based on the attenuated AlHV-1 C500 strain, in preventing fatal WA-MCF in cattle exposed to natural wildebeest challenge. The study was conducted at Kapiti Plains Ranch Ltd, south-east of Nairobi, Kenya. In 2016, 146 cattle were selected for a randomised placebo-controlled trial. Cattle were stratified according to breed and age and randomly assigned to groups given vaccine or culture medium mixed with Emulsigen®. Cattle received prime and boost inoculations one month apart and few adverse reactions (n = 4) were observed. Indirect ELISA demonstrated that all cattle in the vaccine group developed a serological response to AlHV-1. The study herd was grazed with wildebeest from one month after booster vaccination. Three cattle, two that received vaccine and one control, succumbed to conditions unrelated to WA-MCF before the study ended. Twenty-five cattle succumbed to WA-MCF; four of the remaining 71 cattle in the vaccine group (5.6%) and 21 of the remaining 72 control cattle (29.2%; χ2 = 13.6, df = 1, p < 0.001). All of the WA-MCF affected cattle were confirmed by PCR to be infected with AlHV-1 and in 23 cases exhibited histopathology typical of WA-MCF. Vaccine efficacy was determined to be 80.6% (95% CI 46.5–93.0%). Hence, the AlHV-1 C500 vaccine is a safe and potentially effective novel method for controlling WA-MCF in cattle. The implementation of this vaccine may have significant impacts on marginalised cattle keeping communities.
Cook, E., Russell, G., Grant, D., Mutisya, C., Omoto, L., Dobson E., Lankester, F. and Nene, V. 2019. A randomised vaccine field trial in Kenya demonstrates protection against wildebeest-associated malignant catarrhal fever in cattle. Vaccine 37(40): 5946–5953.