Emergency vaccination use in a modelled foot and mouth disease outbreak in Minnesota

Epidemiological modelling is an important approach used by the Veterinary Services of the United States Department of Agriculture Animal and Plant Health Inspection Service to evaluate the potential effectiveness of different strategies for handling foot and mouth disease (FMD). Identifying the potential spread of FMD by modelling an outbreak, and then considering the impacts of FMD vaccination, is important in helping to inform decision-makers about the potential outcomes of vaccination programmes. The objective of this study was to evaluate emergency vaccination control strategies used in a simulated FMD outbreak in Minnesota. The North American Animal Disease Spread Model (NAADSM, Version 3.2.18) was used to simulate the outbreak. Large-scale (1,500 herds per day) emergency vaccination reduced the size of the modelled outbreak in both swine and dairy production types, but the effect was larger when the outbreak began in a dairy herd. Large-scale vaccination also overcame limitations caused by delays in vaccine delivery. Thus, even if vaccination did not begin until 21 days into the outbreak, large-scale vaccination still reduced the size and duration of the outbreak. The quantity of vaccine used was markedly larger when large-scale vaccination was used, compared with small-scale (50 herds per day) vaccine administration. In addition, the number of animals and herds vaccinated in an outbreak originating in a herd of swine was substantially lower than in an outbreak beginning in a herd of dairy cattle.