Brodifacoum

Why is brodifacoum used for possum and rat control?

Brodifacoum has been used in possum and rat baits in New Zealand since 1992.  Many people know brodifacoum by its marketed brand name Pestoff.

Brodifacoum effectively controls rats and possums by reducing numbers in areas under maintenance control.

It can also be used by landowners to take responsibility for possum and rat control on their land.

Rats and possums rarely associate poisoning symptoms with eating this bait.  This is due to the time lag between eating a lethal dose and the onset of symptoms (usually several days).

How is brodifacoum used?

Brodifacoum is only registered for use in bait stations. Bait stations are placed in bush areas and shelterbelts, approximately 100-150 metres apart.

They hold up to 2 kg of pellets and these are refilled every 2 weeks to 3 months.

Brodifacoum can be purchased from Greater Wellington Regional Council (GWRC) and most farm supply stores.

Important points to remember

• Bait stations must be located out of reach of children, pets and stock
• Warning signs must be erected at all main access points where brodifacoum bait stations are placed
• Brodifacoum baits are dyed blue

 Brodifacoum baits

Risks to humans

Brodifacoum poses a low risk when used correctly. It’s an anti-coagulant chemical, which if taken by humans, domestic animals or pets will reduce the clotting power of blood. Nausea and vomiting may occur soon after ingestion. Typical symptoms include:

• Bleeding gums and excessive bleeding from minor cuts
• Increased tendency to bruising
• Blood in urine and faeces

A lethal dose for humans is estimated to be about 15mg of pure brodifacoum per kg of body weight. This equates to approximately 5 kg of bait for a toddler (five bait stations worth) and about 50-kg of bait for a 70-kg adult.

Contact the National Poisons Centre, in an emergency 0800 764 766.

Risks to dogs

Brodifacoum poses a low risk to dogs. They could suffer brodifacoum poisoning if they

• Eat the bait directly from bait stations (more than 250g)
• Scavenge several possum carcasses containing brodifacoum

Keep dogs under strict control and prevent them from scavenging dead animals. Cats are not attracted to the pellets.

Treatment

If your dog eats poison or a poisoned carcass induce vomiting with washing soda crystals.

If an animal or pet displays the following symptoms take it to the nearest veterinary clinic, where they can administer Vitamin K1, an effective antidote.

• Bleeding gums
• Blood in urine and faeces
• Depression
• Vomiting

Do not rely on the treatment.

Prevention is the only sure way of protecting animals and pets from poisoning.

Risk to livestock

Livestock exposed to brodifacoum should not be sent to slaughter or sold. Research has shown that anticoagulant toxins stay in the body for many months, if not years.

It is an offence under the Meat (Residues) Regulations Act to send animals for slaughter that contain chemical residues above prescribed limits. In the case of poisons any detectable residue is considered a violation.

If you decide to send contaminated livestock to the meatworks, you must contact the MAF veterinarian at the processing plant before freighting the animals.

If dairy cattle become exposed to brodifacoum, immediately notify the dairy supply company. If deaths occur in sheep or cattle, the entire flock or herd should be withheld for nine months.

Please notify the Greater Wellington Regional Council if you suspect livestock has been exposed to poison baits. GWRC may have to notify the Medical Officer of Health.

Risks when harvesting feral game

Under the Meat (Residues) and the Game Regulations MAF has advised that, feral animals intended for sale to a game pack house cannot be hunted in areas where poisons have been laid.

Appropriate declarations have to be supplied to establish that the animals have been obtained from areas free of contaminants.

Therefore, landowners and hunters are advised not to sell feral animals taken

• From an operational area within nine months after the termination of poisoning
• Within 2 km (5 km for feral pigs) of a poisoning operation boundary

The policy applies for feral animals intended for personal consumption.

Environmental effects

Very low levels of brodifacoum are used in possum bait.

Brodifacoum is not soluble in water and binds strongly to soils – making it almost immobile. It will degrade slowly in soils with pH5.5 to pH8 under aerobic or flooded conditions and plants do not absorb it.

Baits are only used in bait stations, so it is unlikely the poison will be found in water.

Brodifacoum can remain in animal livers and may present a danger to other species through both secondary and tertiary poisoning. The half-life of brodifacoum in possum livers is about 36 weeks.