Effect of coumatetralyl baits to warfarin-resistant and susceptible colonies on roof rats, Rattus rattus

Abstract

The authors discussed the effect of bait formulation containing coumatetralyl of 0.025% and 0.0375% on warfarin-resistant and susceptible roof rats, Rattus rattus, and wild roof rats caught in Shinjuku Ward, Tokyo, Japan.

When 0.025% and 0.0375% toxic baits of coumatetralyl were given respectively to the warfarin-resistant roof rat, there was a significant difference (P<0.05) in mortality and bait intake between the two test groups. With an increase in coumatetralyl concentration, the effect was substantial even to the warfarin-resistant group. It was evident that coumatetralyl exceed efficacy than warfarin at the same concentration.

When 0.025% and 0.0375% toxic baits of coumatetralyl were given to the warfarin-susceptible group, there was no significant difference in mortality and bait intake. It was not essential to increase the coumatetralyl concentration in case of the warfarin-susceptible roof rat and coumatetralyl was effective at the low concentration. When 0.025% toxic bait of coumatetralyl was given to the wild rats caught in Shinjuku Ward, Tokyo, the results were similar to that of the 0.025% test group of warfarin-resistant rat in lethal feeding period and bait intake. It was proved that those rats exhibited high resistance to warfarin.