When dealing with major infestations of rats and mice, the use of rodenticides (more commonly known as rat poison) is often the most effective method for getting things under control. This can be a worry if you have beloved family pets and other animals (or event children) in the area that may try to eat the baits if they come across them.
The good news is that there are laws and regulations in place to ensure that baits are used safely and the risk non-target species. If you purchase baits you are legally and morally obligated to ensure that you are using them correctly. Everything you need to know should be outlined clearly on the product's packaging.
How do rodenticides work?
Almost all rodenticides used in New Zealand are baits containing anti-coagulants. They all have the same mode of action in that they prevent the production of vitamin K which is needed for blood clotting. Rodenticides are also slow to take effect (usually taking 3-5 days). This has two advantages; if a pet or other non-target animal accidentally gets access to, and consumes the bait, there is time to administer the antidote (vitamin K), and it means that by the time the anti-coagulant is taking effect the rodent is likely to have continued feeding on bait and will have taken several times a lethal dose. This is important because if a rodent feels ill soon after feeding on something, it will stop feeding on that food, if this is a bait the rodent is ‘bait shy’, and if it has not consumed a lethal dose, it will recover and no longer will be controlled using that bait.
How to Keep Your Pets Safe when Using Rodenticide Bait
- Make sure you carefully read the instructions on your rodent bait before use. All rodenticides should be used and stored where pets and other non-target animals cannot access them. For many rodenticides it is a legal requirement to only use them in bait stations or locations such as roof voids that non-target animals can't get into.
- Almost all rodenticide poisonings of pets are from the pets that have gained access to the bait directly because of how/where it has been stored and placed.
- Rodenticides are vertebrate toxic agents (VTAs). This means that they are more toxic to rodents and less to other animals, but they are still toxic to some degree and immediate medical attention should be arranged if bait has been consumed.
- Pet owners often have concern about the risk to their pets if the pets catch or eat rodents that have recently consumed bait or died from rodenticide poisoning. The dose of anticoagulant that is harmful to an animal is related to the animal’s body weight. Dogs and cats, being much heavier than rats or mice, would need to consume larger doses of anticoagulant to cause harm. Most anticoagulants used in rodenticides have a lower toxicity to dogs and cats than to rodents. Dogs and cats may catch rodents and they may consume parts, but they rarely consume all the rodent. They are usually too well fed for that. Consequently, there is little likelihood of a pet consuming sufficient recently poisoned rodents to cause harm.
- However, there are two groups of anticoagulants: first generation and second generation. First generation anticoagulants such as coumatetralyl (NO Rats & Mice Bait Blocks) breakdown more quickly in the rodents, and thus pose a lower risk of secondary poisoning. Second generation anticoagulants were developed later to be more effective at controlling rodents. Because they are not broken down so quickly in rodents the lethal dose is reached more easily, and so a single feed of the bait is likely to be lethal to them. For those concerned about pets eating dead or dying rodents we recommend baits containing a first-generation anticoagulant.
- Ensure all old or unused baits are disposed of safely.
Signs to Look for if Your Dog or Cat has Accidentally Eaten Rodenticide
- If you suspect your pet has eaten rat bait or mouse bait, call your vet immediately.
- Rodenticides are required by law to be blue or green in colour to deter birds from feeding on them, and it also means that the colour may show in the mouths of any animal that has eaten the bait. If you see a blue or green colouration on the teeth, gums, tongue, or pallet of a pet, this may be an indication that they have accidentally consumed some bait. A vet should be contacted and if possible, told what bait may have been consumed and how much. The vitamin K1 antidote should be administered as soon as possible.
- The blue/green colour may also show up in the faeces of the animal.
- Symptoms of anticoagulant poisoning usually take 3-5 days to show up in pets. Signs of poisoning include lethargy/tiredness, reluctance to exercise, coughing, difficulty breathing, weakness, and pale or bleeding gums.
Environmental Concerns of Using Rodenticides
- Hunting and scavenging birds, because of their low body weight, are more susceptible to secondary poisoning through consuming rodents, and anticoagulants have been found in such birds in the past.
- Because of their persistence, second generation anticoagulants such as brodifacoum pose a higher risk to the environment.
- Anticoagulants were used as a broadcast method of controlling rodents and, through secondary poisoning, stoats. This is now, generally only done in eradication projects on islands and ecosanctuaries, where the risk to scavenging animals is low or can be controlled.