Effectiveness of systematic foot and mouth disease mass vaccination campaigns in Argentina

The objective of this paper is to evaluate the effectiveness of systematic mass vaccination campaigns against foot and mouth disease in Argentina. The analysis was based on an estimation of the proportion of protected animals and protected farms in vaccinated populations, as reflected by levels of antibodies measured in liquid-phase enzyme-linked immunosorbent assay. The analysis was carried out in 49 animal health districts in Buenos Aires province, using data collected from four cross-sectional studies, in 2004, 2007, 2008 and 2011. Cattle were assigned to one of two categories on the basis of correlation between serological titres and expected percentage protection: non-adequately protected (expected protection <75%) and adequately protected (expected protection >= 75%). The proportions of adequately protected cattle and significantly non-adequately protected farms were estimated and compared among sampled locations. Protection was variable among the districts; cattle aged one to two years showed higher levels of protection than cattle six to 12 months old, and the proportion of protected cattle was higher in the more recent studies. The results of the analysis will allow the national animal health service to investigate in depth those districts where protection was lower than the regional background protection. The authors propose that this methodology could be used to evaluate the effectiveness of vaccination campaigns in other countries or zones where systematic foot and mouth disease mass vaccination campaigns are undertaken.