Resistance to the Second-generation Anticoagulant Rodenticides

The second-generation anticoagulants, difenacoum, bromadiolone and brodifacoum, have taken over a considerable part of the rodenticidal market during the last six to eight years. This is partly due to the higher efficiency against a larger spectrum of rodent pest species and partly to the increasing problem of physiological resistance to the older anticoagulants. Resistance of practical importance has, however, now been encountered to difenacoum and bromadiolone in Europe, i.e., UK and Scandinavia. Brodifacoum, in spite of the evidence of a somewhat increased tolerance in some commensal rodent populations, still must be considered a highly effective rodenticide against almost all important rodent pest species. Research leading to the synthesis of similar potent anticoagulant molecules or other slow-acting rodenticides should be encouraged in order to cope with the possible development of resistance also to brodifacoum in the future.