ワルファリン毒餌に対する数地区のクマネズミ Rattus rattus の LFP (lethal feeding period) の比較検討

抄録

Using six populations of roof rats, Rattus rattus, captured in various parts of Japan, the lethal feeding period (LFP) of warfarin was studied by feeding 0.025% bait. On recognizing Amami, Ogasawara and Ikebukuro-B populations as susceptible, the standard susceptible LFP-line was established by combining the data of the three populations. The Tako population with the resistance ratio 1.5 was suspected to include some resistant gene. The Shinjuku population, which was confirmed as a mixed population of RR, RS and SS in the previous study (Tanikawa, 1992), was reconfirmed as highly resistant, because of its high resistance ratio (28.5) and also based on other aspects. The Ikebukuro-A population was concluded to be intermediately resistant. As the death of rats due to bait-feeding occurred usually within 5 days of the last feeding, the observation period after bait-feeding could be only 10 days at the longest. Proposed here is a tentative plan for susceptibility surveillance of field-captured roof rats, using the LFP-line established herewith. That is : 1) to feed the rats with 0.025% warfarin bait for 12 days in separate cages, 2) to feed them with unpoisoned bait for 10 days afterward, in case mortality on the 12th day is not less than 50%, and categorize them as a pure susceptible population with only SS gene, if mortality at the end of the test is more than 80%, 3) to feed them with warfarin bait till the 28th day, in case mortality on the 12th day is less than 50%, and categorize the survived individuals, if any, as those with RR gene, 4) to classify them as a population with a resistant gene to some extent, if the mortality is between the above two categories.