a control flock of swaledales has been used to study and develop scrapie-resistant sheep. an infectious, persistent, and spontaneous disease, animals infected with scrapie must be quarantined and destroyed. the experimental breeding involved selecting a group of swaledale sheep with low suspectability to the disease, injecting them with the agents of the disease, and breeding from the survivors. the research has concluded that the offspring of the infected sheep are more able to survive scrapie.