The detection of rodent resistance to anticoagulants.

The procedures used in the United Kingdom to detect anticoagulant resistance in the Norway rat are described. Preliminary inspections are made of the suspect rat populations to exclude other possible causes of control failure. The inspections are followed by carefully supervised warfarin treatments in which the feeding pattern over 2-3 weeks is compared with that of normal rats. If rats continue to take the bait longer than is usual, laboratory tests are undertaken on trapped animals. It is believed that the methods will be found to be generally applicable to the investigation of anticoagulant resistance in other rodents in many parts of the world.