Difenacoum resistance

Greaves, J.H., Shepherd, D.S., Quy, R. (1982). Field trials of second-generation anticoagulants against difenacoum-resistant Norway rat populations. J. Hyg. (Lond.) 89(2) 295-301. 

Neosorexa , and by ICI Plant Protection Division under the trademark Ratak as a 0.005% pelleted bait, and as a wax block. Pure difenacoum is an off-white powder with a solubility of greater than 50 g/1 in acetone, 600 mg/1 in benzene, and less than 10 mg/1 in water. It is more toxic than warfarin, but less palatable (IPCS, 1995c). Difenacoum is still effective against many populations of warfarin-resistant rats (Desideri et al, 1979), but resistance maybe developing in the UK (Greaves et al, 1982). 

Cats may be more resistant to the toxic effects of bro-difacoum and difenacoum than dogs. Cases of abortion and hemorrhage in sheep and goats after misuse of brodifacoum have been reported (Jones, 1996 Watt, 2005). 

Desideri, D., Aldighieri, R., Le Louet, M., Tardieu, A. (1979). Murine resistance to anticoagulants in the port of Marseille. Response to difenacoum. Bull. Soc. Pathol. Exot. Filiales 72(3) 278-83. (In French)... 

As a result of intensive research, derivatives of 4-hydroxycoumarin were found, which proved to be particularly efficient against rodents and resistant to anticoagulant rodenticides. Difenacoum (34) is a chronic rodenticide, which acts as a typical indirect blood anticoagulant similar to warfarin. However, it is effective against rats and mice, which are resistant to warfarin and other anticoagulant rodenticides, and is more toxic than warfarin to susceptible strains of these rodents. The chemical composition of difenacoum is 3-(3-p-biphenyl-1,2,3,4-tetrahydro-naphth-l-yI)-4-hydroxycoumarin. Its acute oral LD50 is 1.8 mg/kg for Norway rats (Hadler et al., 1975a,b). 

Brodifacoum is a member of the second-generation anticoagulant rodenticides known as superwarfarins (27). This compound and others like it (e.g., bromadiolone and difenacoum) were developed to combat rodent resistance to warfarin (27). 

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