Vitamin K deficiency syndromes in warfarin-resistant brown rats ( Rattus norvegicus )

Abstract

Resistance to the anticoagulant rodenticide warfarin and an increased vitamin K requirement appear to be pleiotropic effects of the gene Rw ². A comparison of pup mortality in F₂ (Rw ¹ Rw ² × Rw ¹ Rw ²) and backcross (Rw ¹ Rw ² × Rw ¹ Rw ¹ or reciprocal) matings of wild brown rats in the laboratory revealed significantly greater losses in the F₂ litters at 4-8 weeks of age. Some deaths could be attributed directly to haemorrhage resulting from vitamin K deficiency.

A newborn warfarin-resistant rat from an F₂ litter showed bleeding from the umbilicus and the anus, and died from internal haemorrhage at 18 weeks of age. Another warfarin-resistant male rat dying at the same age had a grossly enlarged skull.