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) wasreported 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 restrictanimal movements and to vaccinate all susceptible domestic ruminant populations in infected andin neighbouring regions. This action was taken to reduce virus circulation with the aim ofdecreasing direct losses in sheep and goats due to the disease, and indirect losses in cattlepopulations due to movement restrictions. Furthermore, the Italian authorities implemented anepidemiological surveillance system to monitor the spread of the virus and to provide moreeffective movement controls. In 2002, the vaccination campaign reached the set goal of vaccinatingmore than 80% of susceptible domestic ruminants in Abruzzo, Sardinia and Tuscany. Thevaccination campaign successfully reduced clinical disease in Sardinia and Tuscany. Before theadvent of BT, cattle had always been moved from Sardinia, Sicily and the southern regions forfattening and slaughter in northern Italy. During the tracing of animals that had left infected areasin 2000 it was found that 10 957 cattle had been exported from Sardinia between June and August2000 and were scattered throughout continental Italy. In addition, most cows selected for cullingfrom the southern regions and the islands were sent to northern Italy for slaughter. However, sinceAugust 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 almostthroughout the year), was no longer able to export any ruminants to the mainland. Long-termstandstill therefore led to heavy economic losses and had even greater social consequences. Asfarmers are not compensated, it is impossible to enforce these restrictions indefinitely. The Italianauthorities and the European Commission thus decided to adopt a policy of risk managementallowing some animal movement. This paper presents an analysis that assesses the risk associatedwith animal movement from restricted areas, according to the level of immunity of susceptibleanimal populations due to vaccination in the same areas. Results of the analysis indicate that whenmore than 80% of the susceptible population in the territory of origin is vaccinated, the riskassociated with the movement of vaccinated animals to free areas appears acceptable and can bemitigated further by adopting ancillary control measures.[...]