Resolution of a classical swine fever outbreak in the United States-Mexico border region

On 11 August 1999, an outbreak of classical swine fever (CSF) occurred in the municipality of San Carlos in the State of Tamaulipas, located on the United States-Mexico border. Sixty-eight dead and two sick pigs from a village were reported to the animal health authorities; tissue samples of sick pigs were confirmed as positive for CSF virus by indirect fluorescent antibody test. The population at risk consisted of 521 pigs, with crude mortality and attack rates of 13.05% and 0.38% respectively. However, on 24 August 1999, two more pigs were detected with clinical signs and their tissue samples confirmed as positive by indirect fluorescent antibody test and neutralizing peroxidase-linked assay, with a secondary attack rate of 0.38%. The outbreak was eradicated by implementing a slaughter policy, movement control, quarantine and surveillance, among other measures. After 6 months of quarantine, the disease was eradicated without resorting to vaccination. The possible sources of introduction of the CSF are also discussed.