British farms becoming breeding grounds for ‘super' rodents
Farming Monthly National|September 2020
British farms becoming breeding grounds for ‘super' rodents
Recent research published by the University of Reading Vertebrate Pests Unit (VPU) suggests that resistance is spreading as a result of two rodenticide actives. Bromadiolone and difenacoum are the active ingredients in a number of common and widely available rodenticide baits. However, a growing number of rodents are showing signs of resistance. It is also now believed that the use of these rodenticide baits by farmers is compounding the problem and increasing the population of resistant rodents throughout Britain.
A nticoagulant rodenticides have long been considered the most effective way to control rodent infestations. However, since the use of the first anticoagulants such as warfarin in the 1950s there have been increasing reports of resistance. “Following the first-generation anticoagulants (FGARs) second generation (SGARs) alternatives were produced in the 1970s that addressed the growing resistance problem. These included bromadiolone and difenacoum. In the 1980s and 1990s resistance was once again identified and furthermore potent SGARs were made available including brodifacoum, flocoumafen and difethialone. However, until 2016 these were limited to indoor use, meaning many farmers were using baits with actives that rodents had developed a resistance to,” says Clare Jones VPU research officer at the University of Reading.

It is now widely understood that in addition to the FGARs, rodents are also showing resistance to two of the five SGARs available in Britain. Bromadiolone and difenacoum have both been identified as actives that rodents have shown a resistance to. These resistant rodents have been selected over decades of exposure to the first two SGARs and some are now able to consume both with little, or no, life-threatening effects.

Ms Jones explains: “Anticoagulants work by interrupting the vitamin K cycle in the liver. Vitamin K is essential for the clotting process in the blood of mammals and without it blood cannot coagulate, causing spontaneous haemorrhaging and death. Resistant animals have a mutation in their genetic code which allows the vitamin K cycle to continue uninterrupted making them tolerant of the anticoagulant. The University of Reading has reported multiple mutations from test samples. There are nine mutations in rats and two in mice. Against the most resistant rats, those with the L120Q mutation, bromadiolone and difenacoum are completely ineffective.”


You can read up to 3 premium stories before you subscribe to Magzter GOLD

Log in, if you are already a subscriber


Get unlimited access to thousands of curated premium stories, newspapers and 5,000+ magazines


September 2020