There has been much speculation if mice and rats can become immune to rat poison. In 2010 the Rodenticide Resistance Action Committee investigated the resistance of rodents to anticoagulants.
Rodine Mouse & Rat Killer is a Rentokil anticoagulant rodenticide poison containing Bromadiolone suitable for controlling rats and mice. An individual mouse cannot become ‘immune’ to Rodine in the way that animals can become immune to some diseases as a result of previous exposure.
Some rats and mice are ‘genetically resistant’ to some of the most common rodenticides – this means that they are born with an ability to withstand the effects of the poison if they eat an amount that would kill a normal mouse. They are born with at least one mutated gene that means their physiology is slightly different to normal mice in the way their blood clots. This is not something a mouse can develop – it either has such a gene at birth or it doesn’t.
There are patches of resistant rat and mouse populations around the UK, but Rodine (if used according to the label) should still prove effective in most cases – if not, there are stronger compounds that will work, but these are only permitted to be used by professional users (i.e. pest control professionals). Rentokil has another product for mice (AlphaRapid) that works in a completely different way, and therefore will work just as well against resistant mice as non-resistant mice – this is available for the public to use.