Determination of lethal feeding period of bromadiolone anticoagulant for screening individual rats (Rattus rattus) for development of resistance

The second generation anticoagulant, bromadiolone, is presently being used worldwide for control of rodent pests, however, its intensive use has led to the development of resistant rat populations in many parts of the world. In India, there is no report on the development of resistance against bromadiolone. Present study was conducted to determine lethal feeding period of bromadiolone against house rat, Rattus rattus, one of the most common commensal rodent pest worldwide in order to further use it for screening of rats for development of resistance. A total of eight groups of both the sexes (n=5 per group) were fed on cereal based 0.005% bromadiolone bait for variable periods i.e. 0, 2, 4, 8, 16, 24, 48 and 72 hrs in no-choice feeding tests. Lethal feeding period (LFP50) was found to be 4.69 and 5.63 hrs for male and female rats, respectively. Different LFP50 values for two sexes indicate sex specific variations. None of the rat of either sex survived after 16, 24, 48 and 72 hrs of feeding test while 60% mortality was achieved in both the sexes after 8 hrs of feeding test. Feeding durations equivalent to LFP50 and double the LFP50 can be used for screening populations of R. rattus for bromadiolone resistance.