A CASE A CASE OF WARFARIN RESISTANCE IN RATTUS RATTUS DIARDII (JENTINK)

Y.M. LAM. A.K. LEE. Y.P. TAN and ELANJARAN MOHAN

SUMMARY

Warfarin resistance in R. rattus diardii was confirmed in the laboratory. Five from a sample of 14 R. rattus diardii trapped from a cocoa area in Kuala Bernam Estate. Teluk Anson, Perak, showed a high tolerance to warfarin when compared with warfarin-naive rats of the same species. The mean lethal dose for males and females that succumbed in the 6-day screening test with 0.025% warfarin was 49.8 mg/kg and 30.8 mg/kg respectively. Mean days to death for males was 7.4 days and females 14 days. In the 30-day 'no-choice' test with 0.02.5% warfarin, four out of five rats succumbed, two females on the 14th day after consuming a dose of 107.2 mg/kg and 119.3 mg/kg of warfarin respectively; and two males, one on the 24th day after consuming 205 mg/kg and the other on the 34th day after consuming 241.7 mg/kg of warfarin. One female survived the 30-day test after having consumed a total dose of 347.4 mg/kg of warfarin. The intermittent feeding pattern of the warfarin tolerant/resistant rats is of practical importance in control treatments using warfarin.

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