Rat poison in dogs

Overview

The active ingredient

Anticoagulants impair clotting and can cause internal bleeding. Brodifacoum and bromadiolone are second-generation anticoagulants. Warfarin is a first-generation example.

Cholecalciferol, or vitamin D3, poisoning raises blood calcium and phosphorus. Alpha-chloralose affects the central nervous system and can cause rapidly progressing neurological signs.

Persistent cholecalciferol-induced hypercalcaemia can damage kidneys. Alpha-chloralose signs can include both abnormal drowsiness and an exaggerated response to touch.

Packaging usually identifies the active ingredient, as different baits can look very similar.

Causes

Loss of clotting factors

Anticoagulants inhibit a liver enzyme needed to recycle vitamin K into its active form. Vitamin K is needed to produce clotting factors II, VII, IX and X. Existing circulating factors are usually depleted within 24–64 hours of toxic exposure. Factor VII falls quickly because its plasma half-life is around seven hours.

Some long-acting anticoagulants can remain in the liver for weeks. Some anticoagulant secreted into the intestine in bile can be reabsorbed into circulation.

Calcium accumulation

Excess cholecalciferol increases intestinal calcium and phosphorus absorption. Poisoning can also release calcium from bone into blood.

The liver converts cholecalciferol into calcifediol, whose concentration rises markedly in poisoning. More calcium is also reabsorbed into blood from kidney tubules.

Risk factors

Direct exposure occurs when dogs eat rodent bait. Eating a poisoned mouse or rat can cause indirect exposure. Eating bait is the most common route of cholecalciferol exposure specifically. Repeatedly eating exposed rodents can cause chronic cholecalciferol exposure.

In a Canadian study of 349 canine cases, owners reported witnessing bait ingestion in 240, or 69%.

The 349 cases were identified during 1999–2022. The ingredient was known in 157 cases, of which 144 involved second-generation anticoagulants.

Typical symptoms

Anticoagulant bleeding usually becomes apparent three to seven days after ingestion. Cholecalciferol poisoning often produces signs or laboratory changes within 12–48 hours.

• Bleeding can appear as nosebleeds, red urine or bloody vomit.
• Large bruises or pinpoint haemorrhages can develop beneath skin.
• Chest bleeding can impair breathing.
• Cholecalciferol poisoning can increase drinking and urination.
• Exposed dogs may vomit or lose appetite.
• Alpha-chloralose poisoning can cause an unsteady gait and muscle twitching.

Alpha-chloralose exposure can lower body temperature.

Visible cholecalciferol signs, such as inappetence and marked thirst, usually start within 18–36 hours. Anticoagulant bleeding can start as early as around 12–24 hours. Gastrointestinal bleeding can turn faeces black and tarry. Alpha-chloralose can cause drooling or sudden dullness. Anticoagulant poisoning can also cause joint pain if bleeding occurs around a joint.

Complications and consequences

Blood loss and kidney injury

Heavy bleeding can cause severe anaemia, impairing oxygen transport. Blood loss can compromise circulation. Bleeding into lungs can cause coughing up blood.

Persistently raised calcium and phosphorus can deposit minerals in kidney tissue. Kidney mineralisation can cause permanent kidney disease. Heart or lung tissue can also become mineralised.

Anticoagulant bleeding sites and prognosis

In the Canadian study of 349 dogs, 104, or 30%, showed poisoning signs. Of these symptomatic dogs, 91 survived to discharge. Among dogs with confirmed bleeding, 70 of 81, or 86%, survived to discharge.

Another study at two hospitals followed 62 dogs with anticoagulant-induced bleeding. Bleeding around the lungs within the chest occurred in 37%. In this second study, 87% of bleeding dogs survived to discharge.

In the same 62-dog study, 24% had bleeding within lung tissue. Abdominal bleeding occurred in 23%. Skin or subcutaneous bleeding occurred in 21%. Blood can also collect in the pericardial sac without visible external bleeding. Blood products were given to 78% of these dogs.

Prognosis after alpha-chloralose exposure

Surveillance in the Netherlands collected data on 96 dogs reported as exposed to alpha-chloralose. Canine mortality in this surveillance was 1%. Exposures were based on veterinary reports.

Diagnosis at the vet

Identifying exposure

The vet tries to identify the active ingredient as early as possible. Useful information includes the ingredient and estimated amount swallowed. Anticoagulant effects on clotting tests may emerge only two to five days after ingestion. Laboratory testing can look for anticoagulant in stomach contents or blood when needed.

Clotting tests and internal bleeding

Prothrombin time, or PT, measures clotting and usually prolongs before another clotting time, aPTT. Once bleeding begins, both are usually prolonged. If exposure is uncertain and vitamin K1 has not started, the vet may repeat PT 48 hours after ingestion. Red cell proportion is also measured to assess possible bleeding. Imaging can look for chest or abdominal bleeding if the dog's condition allows.

Blood compatibility can be checked before possible transfusion in a bleeding dog. Platelet numbers can be normal despite anticoagulant bleeding. Other causes of prolonged clotting include liver disease and obstructed bile flow.

Cholecalciferol and alpha-chloralose tests

After cholecalciferol exposure, calcium, phosphorus and kidney values are measured. Calcium and phosphorus may be monitored until 72–96 hours after exposure even without symptoms. For suspected alpha-chloralose poisoning, rapid-onset neurological signs are assessed alongside exposure details. Detection in urine or tissue can confirm poisoning.

The vet may measure ionised, or free, calcium after cholecalciferol exposure. Initial results are compared with later values to detect slowly developing hypercalcaemia.

Treatment

Soon after ingestion

The vet may consider induced vomiting soon after exposure if the dog can protect its airway. For an asymptomatic dog swallowing anticoagulant, this may be considered at the clinic within four hours. Activated charcoal can bind certain poisons in the intestine and reduce absorption. High aspiration risk can prevent its use.

Anticoagulant antidote and transfusion

The vet prescribes vitamin K1 as the antidote to anticoagulant poisoning. Clotting factors start forming within six to 12 hours of treatment. Clotting times usually improve within 12–24 hours. Plasma can supply working clotting factors to a bleeding dog. Severe blood loss may require a red cell-containing blood product.

Vitamin K1 treatment is often prolonged after anticoagulant poisoning. In the Canadian follow-up, home treatment lasted longer on average after second-generation than first-generation anticoagulant exposure. Clotting time is usually rechecked two to three days after vitamin K1 ends. If PT remains prolonged, the vet may continue treatment and retest after the course.

Dogs with breathing difficulty may need oxygen. Bleeding patients typically need one to three days in hospital. Restrict activity until clotting recovers.

Cholecalciferol and alpha-chloralose treatment

Cholecalciferol treatment aims to reduce excessive blood calcium. A bisphosphonate may reduce calcium release from bone. Effects can persist and require laboratory follow-up for weeks. Alpha-chloralose treatment supports vital functions and manages symptoms.

Calcium usually falls within one to three days of bisphosphonate treatment. If phosphorus rises, the vet may prescribe aluminium hydroxide to control it. Alpha-chloralose has no specific antidote.

After cholecalciferol poisoning, blood calcium may be monitored for two weeks after medication stops.

Prevention

Some countries restrict consumer rodenticides to indoor mouse control. In some countries, rodenticides require approval by a national regulator. Position bait boxes so dogs cannot reach bait. Search for and dispose of dead rodents during control to prevent dogs eating them.

In some countries, rat poison use is restricted to pest control professionals. Collecting fallen apples reduces rodents' food supply outdoors. Keep food-waste composters inaccessible to rodents. Place traps out of dogs' reach.

Important for dog owners

Information for the emergency call

Move your dog away from the possible poison source. Bring packaging if immediately available. Report what it says and how much bait may be missing. Have your dog's weight and current condition ready for the call. Estimate when ingestion may have occurred. Give medicines only after the vet explains what is needed. Without packaging, report where bait was bought and its target rodent if known. Do not induce vomiting yourself because vomit could enter the airway. Immediately report zinc phosphide on the label, as vomit can release gas toxic to people too.

Check whether a substance is poisonous.

Frequently asked questions

Can eating a dead mouse poison my dog?

Yes, if the mouse ate rodenticide before dying. Indirect exposure can occur with anticoagulant baits. Contact a vet immediately if a swallowed mouse might have been exposed.

Can I monitor a dog without symptoms at home?

Call a vet immediately after possible rodenticide ingestion. Anticoagulant bleeding may become apparent only after three to seven days. Exposure details guide whether immediate treatment or later clotting tests are needed.

Does vitamin K1 work for every rodenticide?

Vitamin K1 is the antidote to anticoagulants that inhibit clotting. Cholecalciferol treatment aims to reduce excessive calcium and phosphorus. Alpha-chloralose symptoms require supportive care, and severe neurological signs may need hospital monitoring.

Why repeat clotting tests after treatment?

After treatment, PT shows whether normal clotting can be maintained once the antidote stops. Sampling is usually two to three days after stopping. If clotting remains prolonged, the vet may continue treatment and repeat testing.

What if the label says zinc phosphide?

Tell the emergency clinic immediately because zinc phosphide can form phosphine gas in the stomach. Gas released from vomit can also endanger people. Follow the clinic's transport and ventilation instructions because your dog may vomit en route.