Thursday, March 3, 2011

Rats! My Pet Ate Rodenticide!

By Dr. Beth Guerra
Rodenticides are tasty, and not just for rodents. Whether accidental or deliberate, rat bait poisoning in dogs is quite frequent. Even the most well hidden baits can often be ferreted out by curious pets. There are three main types of rodenticides on the market and they have vastly different effects.
Usually ingestion is not witnessed; this can be problematic with anti-coagulant rodenticides as they have delayed onset of action. The most common brands are D-Con, Rodex, and Contrac and they usually come as green pellets or blocks. The active ingredient is Coumadin (brodifacoum or bromadiolone), which directly interferes with vitamin K dependent elements in the clotting pathway. Depending on the type (generation) of this ingredient, symptoms can develop anywhere from 4-7 days after exposure. If ingestion is witnessed, vomiting should be induced by a veterinarian as soon as possible. The pet will be sent home with oral vitamin K, which is the antidote, for several weeks. For cases where ingestion of a toxic dose has occurred several days prior, the affected animal will exhibit hemorrhaging, which can manifest as nosebleeds, gingival bleeding, bloody urine, joint swelling, or respiratory difficulty from bleeding into the lungs or chest cavity. Weakness or collapse can occur from severe anemia. Depending on the location and severity of the bleeding, death can occur. Diagnosis is based on history, physical exam, blood work and clotting times. Treatment is supportive and involves vitamin K, fluid and oxygen support. Transfusions of whole blood or fresh frozen plasma are required in cases of life-threatening hemorrhage. If caught early and treated, prognosis is favorable.
Another other type of rodenticide is bromethalin, which is a neurotoxin and does not affect clotting ability. The most common brands are Assault and Vengence and they can also be green pellets. Symptoms occur within several hours of ingestion and include depression, paralysis, tremors, or seizures. Decontamination with vomiting or gastric lavage should occur if ingestion is witnessed. Supportive care and control of neurological symptoms is key. Death usually occurs from respiratory failure secondary to paralysis. Prognosis is very guarded as only a small amount of bait is needed to cause symptoms.
A third type involves cholecalciferol, or vitamin D. This can lead to elevated levels of calcium in the blood, leading to arrhythmmias, seizures, and kidney failure. Onset of symptoms, including vomiting, diarrhea, and lethargy, is within 18-36 hours. Treatment includes decontamination where applicable, aggressive IV fluid therapy, and monitoring of kidneys and heart. A drug called pamidronate can be used to try and lower calcium levels in the blood.
If you suspect your pet has gotten into any type of rodenticide, contact your vet or Poison Control immediately. If possible, have the packaging on hand because the active ingredient is important in guiding treatment.

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