Anticoagulant rodenticide toxicity

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Anticoagulant Rodenticide Toxicity

Anticoagulant rodenticide toxicity is caused by ingestion of anticoagulant rodenticides or by over supplementing horses with warfarin, often used for managing navicular disease in horses. There are two main categories of anticoagulants which differ in their toxicity:
  • First-Generation Anticoagulants: The chemicals most commonly used are warfarin, chlorophacinone, and diphacinone. These usually require multiple feedings to induce poisoning, with concentrations ranging from 0.025 to 0.005%.
  • Second-Generation Anticoagulants: The most commonly found chemicals are brodifacoum, bromadiolone, and difethialone. This are generally much more toxic, killing the rodent in a single feeding and are much more biologically active.
Upon ingestion, anticoagulants inhibit epoxide reductase which reduces the ability for the horse to regenerate vitamin K. As the remaining vitamin K depletes, it will lead to inhibition of coagulation synthesis. Depending on the amount of poison ingested, there will be a delayed onset of clinical signs of toxicity. Clinical signs are often vague and general.

Symptoms

Excessive bleeding from wounds
Pale mucous membranes
Hematoma formation

Diagnosis

  • History
  • Clinical signs
  • Laboratory testing for rodenticides through submittal of serum, whole blood, or liver samples.

Treatment


TreatmentDetails
Vitamin K1Your veterinarian will need to administer vitamin K1 repeated at specific intervals throughout the next 24 hours. If the horse survives, it will usually require daily oral supplements of vitamin K1 for an additional 7 to 21 days.
PlasmaSome horses with excessive blood loss may require plasma and additional supportive care

Prevention

  • Do not leave rodent traps in areas where horses may obtain access to them
  • If your horse receives warfarin for management of navicular disease, follow the dosage as recommended by your veterinarian. Be careful not to accidentally administer multiple doses.

Prognosis

It depends on the type and amount of poison ingested, how promptly its treated, and health of the horse.

Scientific Research References

Good Overviews

Risk Factors

  • High rodent populations which require depopulation measures
  • Horse receives daily oral supplements of warfarin