The comparative rodenticidal efficiency of five anti-coagulants

1. Results are presented of palatability tests and chronic toxicity tests with five anti-coagulant rodenticides at a variety of concentrations against wild Rattus norvegicus, R. rattus and Mus musculus. These results are compared with similar data for warfarin. Estimates are also given of the acute oral toxicity of two of the five, fumarin and diphacinone, to white rats.2. The toxicity of the compounds vis-à-vis warfarin is examined from the standpoint of the risks to domestic animals involved in their use as rodenticides.3. Coumachlor, 2-isovaleryl-1, 3-indandione and 2-naphthyl-1, 3-indandione are considered to be less effective than warfarin against R. norvegicus. Their effectiveness against R. rattus remains to be demonstrated.4. Fumarin appears to be about as good as warfarin against R. norvegicus and R. rattus at similar concentrations. It appears to be slightly less effective against M. musculus.5. Diphacinone at 0·0025% is regarded as a good alternative to 0·005% warfarin against R. norvegicus. At 0·0125% it is probably more effective against R. rattus than is 0·025% warfarin. The two poisons are about equally effective at this strength against M. musculus, but diphacinone is probably slightly more dangerous for domestic animals.6. The results of a small number of field trials with fumarin and diphacinone are briefly summarized.So many of our colleagues and others have helped at some stage or other of our investigations that it would be tedious to mention them all by name. We must, however, single out for our special thanks Mrs M. Rowe and Miss E. Taylor who carried out a large number of the laboratory tests, Mr A. Taylor on whose chemical experience and facilities we have freely drawn and Mr C. H. B. Worrall, Miss B. Jones, Mr S. R. Surtees and Mr J. H. Cuthbert (Department of Agriculture for Scotland) who carried out the field trials.