Warfarin resistance in Rattus losea in Guangdong Province, China

Control of rodent populations is performed worldwide with coumarin derivatives, such as warfarin. After widespread use, their effect has been diminished by the rapid spread of resistant rodents. Warfarin resistance in Rattus loseas in Jiangmen and Zhanjiang City, Guangdong Province, was investigated by lethal feeding tests. Twenty-three of 30 R. loseas trapped in Jiangmen City were assayed as warfarin-resistant individuals, whereas only 1 of 30 rodents in Zhanjiang was resistant. These results emphasize the need for thorough resistance monitoring as a basis for adequate control measures to prevent the use of ineffective rodenticides in Jiangmen City. The resistance mechanism mainly involves VKORC1, the molecular target for coumarin drugs. VKORC1 mRNA expression in wild-caught resistant animals showed no difference compared with that in susceptible individuals. Mutation screening of VKORC1 was carried out and an Arg58Gly mutation was identified as the prevailing type in R. loseas from Jiangmen City, which may constitute the genetic basis of anticoagulation resistance in R. losea in this resistance region.