The foot-and-mouth disease epidemic in Dumfries and Galloway, 2001. 2: Serosurveillance, and efficiency and effectiveness of control procedures after the national ban on animal movements

After the foot-and-mouth disease (FMD) epidemic in Dumfries and Galloway in south-west Scotland in 2001, serosurveillance of sheep remaining in the 3 km radius Protection Zones around Infected Premises (IPS), and within a 10 km radius of IPS, revealed no evidence of infection. The epidemic was brought under control by a range of traditional techniques: slaughter of all animals on IPS and of veterinary-assessed Dangerous Contacts (DCS), movement restrictions, biosecurity, tracing of potential sources and spread of virus, and surveillance of At-Risk premises. Novel pre-emptive slaughter of FMD-susceptible animals on premises contiguous to IPS, and small ruminants and pigs on premises within 3 km of IPSs, commenced after the epidemic had peaked. Most of the traditional control procedures were undertaken quickly and with appropriate priority. Animals on IPS were usually slaughtered within one day of confirmation, and veterinary-assessed DCS within two days of confirmation of relevant IPS (a median of two days). The pre-emptive contiguous and 3 km culls took somewhat longer (medians of five and 17 days, respectively). IPS were most commonly identified as a result of reporting by farmers or their veterinarians (72 per cent of IPS); veterinary clinical patrols identified 16 per cent, while veterinary assessment of DCS and tracing each identified 5 per cent. No evidence of infection was found on any pre-emptively contiguously culled premises, and IPS were declared only on three 3 km cull premises. The time from estimated first lesion to end of slaughter on an IP was found, by regression analysis, to be a key component in effective control, manifested by a reduction in the estimated dissemination rate (EDR); there was little evidence that the intensity of contiguous culling affected the EDR. Patrols and serological surveillance of residual animals within 10 km of IPS, supported by more extensive evidence from elsewhere in the UK, suggested that cryptic infection in sheep was not widespread. Ultimately, there was insufficient evidence to support the effectiveness of 3 km pre-emptive culling as a control procedure.