Difethialone (LM-2219): a new anticoagulant rodenticide for use against warfarin-resistant and -susceptible strains of Rattus norvegicus and Mus musculus.

Data on the efficacy of difethialone, a new anticoagulant rodenticide derived from 4-hydroxybenzothiopyranone against rats and mice, are reported. After one day of feeding with 25 mg/kg of bait, 100 and 85%, respectively, male and female warfarin-susceptible Rattus norvegicus were killed. With the resistant strain, mortality was 90 and 94% for males and females, respectively. 100 and 96% of warfarin-sensitive males and females, respectively, were killed after 3 days of feeding with the same bait. Those of the resistant strain were respectively, 100 and 93%. In Mus musculus, after one day of feeding, mortality was 97, 94, 95 and 93% for males and females of susceptible and resistant strains, respectively, and 100, 97, 100 and 91% after 3 days of feeding. No significant difference in bait intake was observed between 25 mg/kg difethialone bait and a control bait. Compared to other anticoagulant rodenticides, these results show that difethialone is a promising rodenticide.