THE BIOLOGICAL EVALUATION OF BRODIFACOUM AND DIFENACOUM

Biological evaluation of second generation anticoagulants, brodifacoum and difenacoum, was carried out in 1980-1981. The samples of these anticoagulants were synthesized by Institute of Microbiology and Epidemiology Academy of Military Medical Sciences. Determinations of acute ( single dose ) and chronic( 5 consecutive daily doses ) oral toxicities were performed on Rattus norvegicus, R. flavipectus, Mus musculus, R, losea, Apodemus chevrieri, Cricetus triion, Microtus brandti, Meriones unguicula-tus, Citellus dauricus and Ochotona curzonise, etc.Meriones unguiculatus and Citellus dauricus are very sensitive to brodifacoum. The values of LD_(50) are as low as 0.003mg/kg and 0.093mg/kg respectively. Cricetus triton and Microtus brandti are very resistant to difenacoum. The values of LD_(50) are as high as 112.4mg/kg and 29.96mg/kg respectively. In 4-days choice feeding tests, 15/15 of Mus musculus, 9/10 of R. flavipectus and 9/10 of R. norvegicus were killed with 0.005% brodifacoum baits, andl0/10, 7/15 and 17/20 of mortality were induced respectively with 0.005% difenacoum. In 2-days no-choice feeding tests, 10/10 of Mus musculus and 10/10 of R.norvegicus were killed both with0.005% brodifacoum and 0.005% difenacoum,and cnly 8/10 of R. flavipectus were killed with 0.005% difenacoum. In 11 field trials against warfarin-sensitive commensal rodents were conducted. In equivalent tests the performation of brodifacoum and difenacoum is similar to that of warfarin. In field trials single application of bait containing 0.005% brodifacoum against R.losea, Meriones unguiculatus and Citellus dauricus result in 86.7%, 82.9% and 84.1% of reduction of these rodent populations respectively. If brodifacoum baits are properly applied,significant increase in yields of agricultures is possible. It is concluded that economically, warfarin is preferred to brodifacoum because there are no evidence of resistance to warfarin in China.