Developing a Frame Work for Evaluating Vaccination Strategies Against Foot and Mouth Disease Required for the Establishment of ‘Disease Free Zones’ in Kenya

Abstract

Foot and mouth disease is the most economically devastating disease that affects cloven-hoofed animals. In most parts of Kenya, the disease has become endemic because the available control measures (prophylactic or reactive vaccination) are not being applied at an intensity that would curtail the maintenance of the disease. The effectiveness of the control interventions is complicated by factors that reduce vaccination coverage and efficacy; these factors include spatial and host heterogeneities, low rates of uptake of the vaccines and the multiple serotypes of the virus. The conditions necessary for the establishment of disease free zones, given these limitations, are explored using a mathematical model that combines the mass-action transmission principles with spatial correlation structure describing the contact patterns between clusters of cattle and potential reservoirs. Cattle clusters are nested within those of potential reservoirs. The relative contact probabilities between clusters vary depending on the distances between them. The outputs indicate that with a trivalent vaccine, very high vaccination coverage would have to be realized on a regular basis if disease free zones were to be established. This may require a review of the existing cost sharing policy as it is the main cause of the low uptake of prophylactic vaccination.