Rat Poisoning

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Rodenticides, commonly referred to as “rat poison” in everyday language, represent a frequent source of intoxication in pets. Their high toxicity is specifically designed to kill rodents quickly or with a delay. Unfortunately, these substances are not selective, so dogs and cats are also at risk if ingested orally. Dogs, with their pronounced eating behavior and tendency to eat unusual things, are particularly often affected. The variety of active ingredients used requires a differentiated approach: In addition to anticoagulants, other poison groups such as cholecalciferol (vitamin D3), bromethalin, and zinc phosphide are increasingly being used – each with very different mechanisms of action and therapy approaches.

The most important facts at a glance

Rodenticide intoxications in dogs and cats represent a common and serious emergency in small animal practice. Anticoagulants, cholecalciferol, bromethalin, and zinc phosphide differ greatly in their mechanism of action, requiring thorough diagnosis and targeted therapy. Early veterinary intervention significantly improves survival chances. Prevention through proper application and safe storage is essential.

Causes, development and progression

Various substances are used to control rats and mice.
Most of these are substances that severely damage blood coagulation by inhibiting the effect of vitamin K in conjunction with various coagulation factors in the liver.
The blockage in the blood coagulation system leads to multiple hemorrhages (Bleeding in the body) after the remaining coagulation factors are consumed. The result is exsanguination of the rodents.
Depending on the amount ingested, the effect can be delayed by 2–5 days due to the remaining coagulation factors and can last for 2–4 weeks.
These substances are called long-acting anticoagulants (LWA).
Since a specific coagulation factor is known to be consumed first (half-life 4–6 h), its decrease can be used very effectively for early diagnosis in cases of suspected rat poison intoxication, even if no other symptoms are present yet.

Rodenticide poisonings typically result from:

  • Uncontrolled access to poison baits, e.g., in basements, gardens, garages, or stables
  • Ingestion of poisoned rodents (secondary poisoning)
  • Incorrect or improper storage of rat poison
  • Accidental administration by uninformed individuals
  • Malicious poisoning by third parties (rare, but relevant under animal welfare law)

Puppies, young animals, and curious dogs are particularly at risk. Cats are less frequently affected as they are less interested in baits, but they can be indirectly endangered through their prey (rats, mice).

Mechanism of action

Products used for rat control inhibit vitamin K synthesis in the liver, causing its levels in the organism to drop.
Some coagulation factors require vitamin K for their synthesis. A deficiency in vitamin K therefore also results in a deficiency of these coagulation factors.
The speed of onset and duration of action of the poisons depend on the amount ingested.
The duration of action can extend over weeks.

The Toxicological Effects Vary Greatly Depending on the Active Ingredient:

Anticoagulants (1st and 2nd Generation)

Substances: Warfarin, Brodifacoum, Difenacoum, Bromadiolone, Chlorophacinone etc.

Mechanism of Action:

  • Inhibition of vitamin K1 epoxide reductase in the liver
  • Impairment of the activation of coagulation factors II, VII, IX, and X
  • Effective coagulation is no longer possible → spontaneous Bleeding

Latency period of 2 to 5 days, as stored coagulation factors are consumed first

Cholecalciferol (vitamin D3)

Mechanism of Action:

  • Increases calcium and phosphate absorption in the intestine
  • Mobilizes calcium from the bone
  • Leads to hypercalcemia, hyperphosphatemia, renal failure, soft tissue calcification

Bromethalin

Mechanism of Action:

  • Inhibits oxidative phosphorylation in mitochondria
  • Energy loss (ATP↓) in the CNS
  • Intracellular edema due to sodium and water retention → cerebral edema, neurological deficits

Zinc Phosphide

Mechanism of Action:

  • In the stomach, under the influence of stomach acid, phosphine gas is produced
  • Cell poison with strong cytotoxic effect on heart, liver, lungs, CNS

Rapid onset of action (within 30–60 minutes)

Symptoms of intoxication

For the substances currently used for rat control, the effect is delayed.
When the first symptoms appear, the ingestion of the poison occurred 3 to 7 days prior.
The symptoms are initially non-specific, such as:

  • Apathy
  • Loss of appetite
  • Drooling
  • Vomiting
  • Diarrhea
  • unsteady gait

Later, more or less pronounced

  • internal and external Bleeding
  • pale mucous membranes with blood spots (petechiae)
  • Anämie
  • nosebleeds
  • blood in urine
  • Bleeding from wounds, prolonged
  • bloody Cough
  • Bleeding in joints, associated with Swelling
  • Abdominal distension due to blood accumulation
  • Paralysis
  • Convulsions

Bleeding can occur in all organs.
Sudden death, without prior clinical signs, is also possible.

Further symptoms depend on the active ingredient and the amount ingested:

Anticoagulants

  • Lethargy, pale mucous membranes
  • Hemorrhages (nosebleeds, hematomas, hematochezia, hematuria)
  • Dyspnea (Bleeding in the thoracic area)
  • Hypovolemic shock

Cholecalciferol

  • Polyuria, polydipsia
  • Inappetence, Vomiting, apathy
  • Muscle tremors, arrhythmias
  • Signs of acute renal failure

Bromethalin

  • Ataxia, tremor
  • Hyperreflexia, Convulsions
  • Blindness, Paralysis, coma

Zinc Phosphide

  • Nausea, salivation, Vomiting with putrid odor (phosphine)
  • Dyspnea, circulatory shock
  • Liver insufficiency, bloody Diarrhea
  • Sudden Death

Diagnosis

Diagnostics include:

  • Medical history: Possible exposure to rat poison? Eating rodents?
  • Clinical examination: Indicative symptoms depending on the toxin
  • Laboratory tests:
    • Anticoagulants: PT (Prothrombin time), aPTT
    • Cholecalciferol: Hypercalcemia, hyperphosphatemia, creatinine↑
    • Zinc phosphide: Liver values↑, metabolic acidosis
  • Special examinations:
    • Detection of active ingredients in blood, liver, urine (e.g., via HPLC)
    • CT/MRI for neurological symptomatology (especially bromethalin)

Therapeutic principles

Since various products with different ingredients are used for rat control, it is very helpful for assessing an intoxication if the product name and manufacturer are known.
It is also important whether it is a ready-to-use bait, a mixed bait, or a concentrate.
Products that contain non-anticoagulant active ingredients exert their toxic effect by damaging the nervous system (e.g., bromethalin) or increasing blood calcium levels, leading to renal, liver, or Heart failure (e.g., cholecalciferol). When ingested by rodents, they lead to Death within a few hours and are therefore less often a source of poisoning for wild animals.
They remain dangerous for dogs and cats, with the additional disadvantage that no antidote is available.
In cases of suspected ingestion of rat poison or freshly observed ingestion, decontamination with gastric and intestinal emptying and the administration of activated charcoal are promising.
If clinical symptoms of a coagulation disorder are already present or if corresponding laboratory findings from coagulation diagnostics exist, decontamination is no longer useful.
Therapy consists of high-dose vitamin K1 administration (antidote) until the symptoms subside.
Usually, after initial administration of coagulation factors (plasma transfusion) and intravenous vitamin K1 substitution, continuation of therapy with oral vitamin K1 administration is possible.
In severe cases, the direct administration of coagulation factors (plasma transfusions) may also be necessary.
Therapy must be long-lasting until the symptoms subside.
Mostly, after initial administration of coagulation factors (plasma transfusion) and intravenous vitamin K1 substitution, continuation of therapy with oral vitamin K1 administration is necessary.
Therapy must sometimes be maintained for weeks. A coagulation test is performed 48 hours after discontinuing the vitamin administration. If the values are still pathological, vitamin administration is resumed.
Furthermore, therapy is symptomatic. Vital functions must be secured. In cases of severe Blood loss, blood transfusions are necessary, which also provide coagulation factors. Antibiotic prophylaxis is predominantly indicated.

First Measures

  • Induce Vomiting if no neurological deficits are present (within 1–2 hours after ingestion)
  • Administration of activated charcoal, multiple times for enterohepatic recirculation
  • Stabilization of circulation, fluid therapy

Specific therapies

Anticoagulants:

  • Vitamin K1 (phytomenadione) oral or subcutaneous, for at least 3 weeks
  • Fresh plasma or whole blood transfusion for active Bleeding
  • Monitoring: PT/aPTT every 48 hours

Cholecalciferol:

  • Infusion therapy with 0.9% NaCl
  • Furosemide, prednisolone, possibly calcitonin to lower calcium
  • Gastric protection, monitoring of kidney parameters

Bromethalin:

  • No specific antidote therapy
  • Intensive care: Anticonvulsants (Diazepam, Phenobarbital), Mannitol
  • Intracranial pressure control

Zinc phosphide:

  • Gastric lavage with suction
  • Metoclopramide, antiemetics
  • Oxygen administration, liver and circulatory support

Prognosis & follow-up care

The prognosis is good with timely and consistent therapy.

The prognosis depends on the active ingredient, the dose, the time until therapy, and the general condition:

Active ingredient Prognosis
Anticoagulants Good with early vitamin K1 therapy
Cholecalciferol Guarded to poor
Bromethalin Unfavorable, often fatal
Zinc phosphide Very poor with late diagnosis

Aftercare:

  • Monitoring of blood count, coagulation, electrolytes
  • Long-term support of liver and kidney
  • Owner education to prevent further exposure

prophylaxis

The methods of controlling rats and mice lead to a painful, slow, and agonizing Death for the rodents. The methods are inhumane.
We largely have prophylaxis in our own hands.

  • Rat poison only in bait stations, inaccessible to children and pets
  • hygienic measures for rodent control
  • safe waste disposal
  • promote natural enemies of rats and mice
  • Live traps
  • Snap traps that kill the animals instantly

In addition to endangering our children and pets, the usual methods of rodent control endanger wild animals such as birds, polecats, wild cats, and foxes.
According to a study in Australia, poisoned mice and rats are the cause of 50% of owl deaths.

Research outlook

Toxicological research focuses, among other things, on:

  • Development of specific antidotes for bromethalin and zinc phosphide
  • Molecular markers for early detection of subclinical intoxications
  • Non-toxic rodenticides to prevent secondary intoxications
  • Rapid tests for veterinary practices to differentiate between toxins
  • Assessment of ecotoxicology in wild animals due to rodenticide residues

Frequently asked questions (FAQs)

  1. How quickly do symptoms appear after ingestion?
    Depending on the active ingredient, between minutes (zinc phosphide) and several days (anticoagulants).
  2. How can I tell if my pet has eaten rat poison?
    Noticeable symptoms such as Bleeding, weakness, Vomiting, Seizures are warning signs.
  3. What should be done if poisoning is suspected?
    Seek immediate veterinary emergency care, bring packaging (if known).
  4. Can activated charcoal help?
    Yes, if given early, it can reduce poison absorption.
  5. How long does vitamin K1 treatment last?
    Usually 3 to 4 weeks, depending on the active ingredient.
  6. Are there home remedies for rat poison?
    No – self-treatment can be life-threatening.
  7. Are cats also at risk?
    Yes, especially by eating poisoned rodents.
  8. How can I protect my pet?
    No freely accessible baits, control over hunting behavior, secure storage.
  9. Are all rat poisons equally dangerous?
    No, there are significant differences in toxicity, effects, and treatment options.
  10. Can a single ingestion be fatal?
    Yes, for certain poisons, even a small amount can be fatal.

Literature

  • https://gizbonn.de/giftzentrale-bonn/archiv/gerinnungshemmendes-rattengift
  • Gwaltney-Brant, S. M. (2012): Rodenticides. In: Peterson, M.E., Talcott, P.A. (eds.): Small Animal Toxicology, 3rd ed. Elsevier, pp. 612–635.
  • Khan, S.A., McLean, M.K. (2012): Toxicology of newer anticoagulant rodenticides in animals. J Vet Emerg Crit Care, 22(1), 2–9.
  • Murphy, L.A., Talcott, P.A. (2019): Vitamin D3 rodenticide toxicosis in dogs and cats. Vet Clin North Am Small Anim Pract, 49(6), 1123–1136.
  • Cortinovis, C., Caloni, F. (2015): Toxicological risk assessment of rodenticides to non-target pets. Toxins, 7(10), 3952–3972.
  • Vandenbroucke, V. et al. (2008): Distribution of anticoagulant rodenticide residues in raptors in Belgium. Environ Int, 34(6), 861–866.
  • Löwe G, Löwe O. Poisonings in Dogs and Cats – A Veterinary Guide. 2nd Edition. Kreuztal: Kynos-Verlag. 2021; 208 p.