‘Super Rats are Immune to Poison’
There is a huge amount of attention in today’s media regarding the rise of the ‘Super Rat‘ and this reinforces public fears that the country will soon to be taken over by ‘Super Rats’. It will not come as a shock to hear that there is a certain amount of hype regarding this, that the reality is very different and the science behind the story is often misinterpreted or ignored.
As commercial pest control experts we will try to explain what is really happening to the rat population and what a ‘Super Rat’ really is.
‘Rat poisons no longer work!’ has been a media favourite for some time now and whilst resistance to some poisons is certainly widespread, there are still a number of widely available rodenticides to which there is no known resistance – (100% kill rate). The problem is that these are licenced for ‘internal use only’, so they cannot be used in most farm situations or in many public infestation scenarios.
Background to Rodenticides and the ‘Rise of Resistance’
The chemical warfarin was the first of the anti-coagulant rodenticides and was widely used as such from around the 1950’s. However in the years that followed at least one genetic mutation developed in rats this rendered the poison ineffective in some populations. Continued use of Warfarin in areas of resistance has allowed these genetically resistant rodent populations to spread. So the problem of resistance is by no means a new phenomenon. Warfarin and other early anticoagulant rodenticides became known as ‘1st Generation Rodenticides’.
New more potent forms of the chemical were discovered, mainly the compounds difenacoum and bromadiolone, termed Second Generation Anticoagulant Rodenticides (SGARs). It is these chemicals that are found in the majority of commercial pest control products available to buy off the shelf; unfortunately it is to these chemicals that a growing population of rats in many areas of the country are growing resistant to. A more detailed explanation of Rodenticide Resistance can be found in this article produced by the Rodenticide Resistance Action Group.
It must be clarified that the fact that a population has resistance does not necessarily mean that all the rats will be resistant; when a treatment is carried out the ‘normal’ rats will still be killed. Unfortunately, continually treating with rodenticides in areas of resistance will speed up the natural selection of the most resistant members, removing susceptible individuals and allowing the survivors to breed without competition.
The Future of Rodenticides
There is one major weapon left in the pest controllers arsenal – single feed anticoagulants. A consultation is in progress at the moment to have Single Feed Anticoagulants licenced for outdoor use (with additional restrictions on when and how they are used). IF the professional pest control industry is allowed to use Brodifacoum and Flocoumafen rodenticides externally in controlled circumstances, this may be the answer to many of the ‘out of control’ populations that are causing so many people so much distress – the Super Rat is not invincible.
There are a number of other control options available to the trained pest control operative and as with most things if you have a problem it is always best to call in the experts. Pest control is a complicated business and a good BPCA approved pest control contractor is always going to do a better job than an amateur.
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