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Introduction

Rodenticides are chemical agents used to control rats, mice, and other rodent pests. Although effective for pest management, accidental ingestion by domestic animals, livestock, and wildlife can result in severe or fatal poisoning.

Rodenticide poisoning is an important topic in veterinary toxicology because many formulations are highly toxic and may affect multiple organ systems. The most significant rodenticide toxicities include anticoagulant rodenticides, cholecalciferol (vitamin D analog) poisoning, and zinc phosphide poisoning.

General Sources of Exposure

  • Accidental ingestion of bait products
  • Consumption of poisoned rodents (secondary poisoning)
  • Improper storage of rodenticides
  • Contaminated feed or environments

Anticoagulant Rodenticides

Overview

Anticoagulant rodenticides interfere with blood clotting by inhibiting vitamin K recycling, leading to spontaneous internal and external bleeding.

Examples include:

  • Warfarin
  • Brodifacoum
  • Bromadiolone
  • Diphacinone
Mechanism of Toxicity
  • Inhibition of vitamin K epoxide reductase
  • Failure to activate clotting factors II, VII, IX, and X
  • Progressive inability of blood to clot
  • Spontaneous hemorrhage develops
Species Affected
  • Dogs (most commonly affected)
  • Cats
  • Livestock
  • Wildlife and birds of prey
Clinical Signs

Signs often appear several days after ingestion because existing clotting factors must first be depleted.

  • Pale mucous membranes
  • Weakness and lethargy
  • Bleeding from nose or gums
  • Blood in urine or feces
  • Respiratory distress due to internal bleeding
  • Collapse in severe cases
Diagnosis
  • History of rodenticide exposure
  • Prolonged clotting times (PT and PTT)
  • Evidence of internal hemorrhage
  • Blood tests showing anemia
Treatment
  • Vitamin K1 therapy
  • Blood transfusion in severe hemorrhage
  • Oxygen and supportive care
  • Activated charcoal if exposure was recent
Prevention and Control
  • Safe storage of rodenticides
  • Use of tamper-resistant bait stations
  • Preventing pet access to treated areas
  • Prompt disposal of poisoned rodents

Cholecalciferol (Vitamin D Analog Rodenticides)

Overview

Cholecalciferol rodenticides contain vitamin D analogs that cause dangerously elevated blood calcium and phosphorus levels, leading to widespread tissue mineralization and organ failure.

Mechanism of Toxicity
  • Increased intestinal calcium absorption
  • Mobilization of calcium from bones
  • Hypercalcemia and hyperphosphatemia
  • Mineralization of kidneys, heart, and blood vessels
Clinical Signs
  • Vomiting and diarrhea
  • Excessive thirst and urination
  • Weakness and depression
  • Loss of appetite
  • Kidney failure in severe cases
Diagnosis
  • History of rodenticide exposure
  • Elevated blood calcium and phosphorus levels
  • Kidney function abnormalities
  • Radiographic evidence of tissue mineralization in chronic cases
Treatment
  • Immediate decontamination if exposure was recent
  • Intravenous fluid therapy
  • Drugs to reduce blood calcium levels
  • Monitoring of kidney function
Prognosis

Prognosis depends on severity of hypercalcemia and extent of kidney damage.

Zinc Phosphide Poisoning

Overview

Zinc phosphide is a rodenticide that releases toxic phosphine gas when it reacts with stomach acid. It is rapidly acting and highly toxic.

Mechanism of Toxicity
  • Zinc phosphide reacts with gastric acid
  • Phosphine gas is released
  • Cellular respiration and energy production are disrupted
  • Multiple organ systems are affected
Species Affected
  • Dogs
  • Cats
  • Livestock
  • Wildlife
Clinical Signs
  • Vomiting (sometimes with garlic or rotten fish odor)
  • Abdominal pain
  • Respiratory distress
  • Muscle tremors and seizures
  • Collapse and sudden death
Diagnosis
  • History of exposure
  • Characteristic odor from vomitus or stomach contents
  • Rapid onset of gastrointestinal and neurological signs
Treatment
  • Careful decontamination in well-ventilated areas
  • Activated charcoal where appropriate
  • Supportive therapy and seizure control
  • Oxygen therapy if respiratory distress occurs
Safety Note

Phosphine gas released from vomitus or stomach contents can also be hazardous to veterinary personnel.

General Diagnosis of Rodenticide Poisoning

  • Detailed exposure history
  • Clinical examination
  • Laboratory testing (blood chemistry and clotting profiles)
  • Toxicological analysis where available

General Prevention and Control

  • Secure storage of rodenticide products
  • Proper placement of bait stations
  • Avoiding use in areas accessible to domestic animals
  • Prompt veterinary attention after suspected ingestion
  • Education of farm and pet owners about poisoning risks

Economic and Clinical Importance

Rodenticide poisoning is a major cause of accidental toxic exposure in both companion animals and livestock.

  • Sudden illness or death
  • High emergency treatment costs
  • Secondary poisoning of wildlife
  • Production losses in livestock systems
  • Public health and environmental concerns

Careful rodent control practices and early recognition of toxic exposure are essential for minimizing losses associated with rodenticide poisoning.