Quantification of the risk for introduction of virulent Newcastle disease virus into Spain through legal trade of live poultry from European Union countries

Newcastle disease (ND) causes large economic losses in poultry production worldwide. Spain has reported two ND epidemics in poultry farms since 1993, the most recent in 2009. The recent increase in the number of ND epidemics reported in Spain and in other European Union (EU) member countries along with the failure to identify the source of the Spanish epidemics caused concern over the vulnerability that Spain has to the disease. Some of the epidemics recently reported in EU member states were associated with legal introduction of live poultry; the large number of susceptible species annually imported by Spain from the EU suggests that legal imports of poultry may impose a risk for the introduction of virulent ND virus (v-NDV) into the country. This article presents the results of the first quantitative assessment of the risk for v-NDV introduction into an ND-free country via legal trade of live poultry. The geographical variation of the risk and the relative contribution of exporting countries and susceptible poultry species to the risk were also estimated. The model here estimated that if prevailing conditions persist, then it would be expected that ND epidemics caused by legal trade of live poultry will occur, on average, once every 196 years in Spain. These results suggest that the risk for ND epidemics in Spain, and probably the sources of recent epidemics reported in the country, were associated with routes of entry other than legal trade of poultry.