Anticoagulant resistance in rodents

Current issues in rodenticide anticoagulant resistance testing are reviewed. Research and management issues for New Zealand agencies include: 1. Assessing and monitoring the spread of resistance. 2. Standardising and improving resistance-testing techniques. 3. Identifying from the range of tests that have been developed for assessing rodenticide resistance which is the best to use. 4. Developing use patterns for anticoagulants, non-anticoagulant poisoning, and trapping to minimise the development of resistant populations of rodents. Resistance to anticoagulants can develop in a population after 5-10 years sustained use of anticoagulant rodenticides. Monitoring the resistance status of rodent populations is a pivotal component of integrated risk management. No data exist on the baseline susceptibility of rodent populations in New Zealand to anticoagulants or their changing patterns of susceptibility in areas of sustained use. Monitoring systems for wild target populations and changes to poisoning methods will assist New Zealand rodent control groups in avoiding the resistance-induced control problems now seen overseas. We recommend the `blood clotting response test' (BCRT) as an integrated component of rodent control to maximise efficacy and safety of rodent population management.