Area resistance in rats within the UK refers to the phenomenon where populations of rats in specific geographic regions have developed genetic resistance to commonly used rodenticides, especially anticoagulant rodenticides like warfarin, bromadiolone, and difenacoum.
The Following is why you should contact a specialist to deal with your Rat / Rodent problem. You could quite easily be making your infestation worse. Contact Rattraxs for any further information or advice.
What Is Rodenticide Resistance?
Resistance occurs when rats develop genetic mutations that allow them to survive doses of poison that would normally be lethal. These resistant rats then reproduce, passing on their resistant genes, eventually leading to entire rat populations in certain areas that cannot be effectively controlled with standard rodenticides.
UK Area Resistance – Key Points
Regions with Confirmed Resistance
As of recent data (such as from the UK Rodenticide Resistance Action Group – RRAG), resistance has been confirmed in several areas:
- Southern and Central England: Widespread resistance to bromadiolone and difenacoum.
- Parts of Wales and the Midlands: Mixed resistance to first- and some second-generation anticoagulants.
- South-East and East Anglia: High resistance pressure, including to some second-generation rodenticides.
- Scotland: Generally lower resistance levels but some pockets of concern.
What Causes the Resistance?
- The most well-known mutation is in the VKORC1 gene (vitamin K epoxide reductase complex subunit 1), which affects how anticoagulants work.
- This mutation means the rodent’s blood doesn’t respond to the blood-thinning effect of rodenticides, especially first-generation anticoagulants (e.g., warfarin, coumatetralyl).
Rodenticides and Resistance Levels
| Rodenticide | Generation | Resistance Status in Some UK Areas |
|---|---|---|
| Warfarin | 1st Gen | Widespread resistance |
| Bromadiolone | 2nd Gen | Resistance in southern/central UK |
| Difenacoum | 2nd Gen | Resistance overlaps with bromadiolone |
| Brodifacoum | 2nd Gen | Generally effective (limited resistance) |
| Flocoumafen | 2nd Gen | Also generally effective |
| Cholecalciferol | Non-anticoagulant | Effective, no known resistance |
Why It Matters
- Resistance reduces the effectiveness of pest control efforts.
- Using ineffective rodenticides in resistance areas can worsen the problem and lead to larger infestations.
- Incorrect use may harm non-target species (like pets, birds, or other wildlife) due to prolonged presence of toxic baits.
What You Should Do
Check Local Resistance Maps
Use resources like the RRAG UK Resistance Maps or local pest control guidelines to see which actives are still effective in your area.
Follow CRRU Guidelines
The Campaign for Responsible Rodenticide Use (CRRU) promotes safe and sustainable use of rodenticides to limit environmental impact and resistance spread.
Use Resistance-Breaking Rodenticides
In known resistance areas, switch to brodifacoum, flocoumafen, or cholecalciferol, which are more effective against resistant rats.
Integrated Pest Management (IPM)
Combine baiting with other methods like proofing, trapping, and environmental management.
Summary
- Area resistance in rats is a growing concern across the UK.
- It’s caused by genetic mutations making rats less susceptible to rodenticides.
- Certain actives (like warfarin, bromadiolone, and difenacoum) are no longer effective in some areas.
- Control strategies should be based on local resistance data and follow CRRU guidelines to ensure effectiveness and safety.