Blood clotting response test for detecting resistance to second generation anticoagulant bromadiolone in house rat (Rattus rattus)

Abstract

Blood clotting response (BCR) test is a faster method with fewer ethical constraints than feed-testing and is widely used to monitor resistance. The second-generation anticoagulant, bromadiolone is being used to control rodents all over India for the last several years. To investigate whether its use has resulted in development of resistance in house rat, Rattus rattus, BCR test was standardized. Plasma samples of 15 rats of both the sexes were pooled separately and diluted with phosphate-buffered saline (pH 7.4). Ten different dilutions of plasma i.e. 4, 5, 6, 8, 10, 20, 40, 60, 80, 100% were tested for Prothrombin Time (PT) and International Normalized Ratio (INR) using rabbit brain thromboplastin reagent in coagulation analyzer. Time to clotting was converted into percent clotting activity (PCA) relative to plasma dilutions, to plot a standard curve. The PT of 15.7 and 17.6 sec for 100% plasma corresponded to INR of 0.8 and 0.9 in male and female rats, respectively. PCA of 22.3% corresponded with PT and INR of 70.3 sec and 3.8, respectively in male rats and PCA of 27.6% corresponded with PT and INR of 63.6 sec and 3.5, respectively in female rats. Data for PT and INR and standard curve for PCA vs PT prepared during present study can be further used to determine current status of bromadiolone resistance in R. rattus populations based on discriminating dose of bromadiolone.