Risk analysis on the introduction into free territories of vaccinated animals from restricted zones

Between August 2000 and 14 May 2001 (defined as the 2000-2001 epidemic) bluetongue (BT) was reported in three regions of Italy: Sardinia, Sicily and Calabria. During the 2001-2002 epidemic (between 15 May and 14 April 2002), the disease spread to five additional regions (Puglia, Basilicata, Campania, Latium and Tuscany). In May 2001 the Italian Ministry of Health decided to restrict animal movements and to vaccinate all susceptible domestic ruminant populations in infected and in neighbouring regions. This action was taken to reduce virus circulation with the aim of decreasing direct losses in sheep and goats due to the disease, and indirect losses in cattle populations due to movement restrictions. Furthermore, the Italian authorities implemented an epidemiological surveillance system to monitor the spread of the virus and to provide more effective movement controls. In 2002, the vaccination campaign reached the set goal of vaccinating more than 80% of susceptible domestic ruminants in Abruzzo, Sardinia and Tuscany. The vaccination campaign successfully reduced clinical disease in Sardinia and Tuscany. Before the advent of BT, cattle had always been moved from Sardinia, Sicily and the southern regions for fattening and slaughter in northern Italy. During the tracing of animals that had left infected areas in 2000 it was found that 10 957 cattle had been exported from Sardinia between June and August 2000 and were scattered throughout continental Italy. In addition, most cows selected for culling from the southern regions and the islands were sent to northern Italy for slaughter. However, since August 2000 the animal trade between infected and free areas has come to a complete standstill. Sardinia, in particular, due to the climatic and epidemiological conditions (vectors survive almost throughout the year), was no longer able to export any ruminants to the mainland. Long-term standstill therefore led to heavy economic losses and had even greater social consequences. As farmers are not compensated, it is impossible to enforce these restrictions indefinitely. The Italian authorities and the European Commission thus decided to adopt a policy of risk management allowing some animal movement. This paper presents an analysis that assesses the risk associated with animal movement from restricted areas, according to the level of immunity of susceptible animal populations due to vaccination in the same areas. Results of the analysis indicate that when more than 80% of the susceptible population in the territory of origin is vaccinated, the risk associated with the movement of vaccinated animals to free areas appears acceptable and can be mitigated further by adopting ancillary control measures.