What is Rat Poison Toxicity?
Unfortunately, baits that are utilized to kill mice, rats and other rodents can also be poisonous to horses. Anticoagulant rodenticides, which prevent blood from clotting, are used the most; common anticoagulant rodenticides include brodifacoum, diphacinone and warfarin. As the anticoagulant rodenticides cause blood not to clot, poisoning can lead to excessive bleeding and death. Other rodenticides that are poisonous to horses and other animals include cholecalciferol (Vitamin D analogue), bromethalin, strychnine and 1080.
Multiple types of rodenticide that are used to eradicate mice, rats and other rodents can be toxic in horses when ingested, requiring immediate medical attention.
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Symptoms of Rat Poison Toxicity in Horses
Upon ingestion of an anticoagulant rodenticide, symptoms may be seen within two to five days and will depend on where bleeding takes place within their body. Symptoms can include:
- Pale membranes
- Bleeding from gums or nostrils
- Blood in urine
- Blood in feces
- Difficulty breathing
- Distended abdomen
A less common rodenticide is cholecalciferol, or Vitamin D analogue. Should your horse ingest this poison, his initial symptoms may be hard to notice, to include:
- Lack of interest in eating
As symptoms progress, the following may be seen:
- Blood from mouth
- Minimal urination
- Abnormal heart rate
There are also poisons that work by attacking the nervous system. Examples include bromethalin, strychnine and 1080. After exposure, the following symptoms may be seen:
- Stiff body
- Brain damage
- Disturbance in ability to coordinate chest muscles for breathing
There are a variety of options when it comes to anticoagulant rodenticides. Newer options like brodifacoum are significantly stronger than older products like warfarin, meaning that ingesting much smaller amounts can lead to poisoning in your horse. The products come in different formulations like treated grains, grain-based, blocks, pellets, granules, powders, and bars, and are also available in different colors. As the products are usually flavored to attract rodents, they can be very tempting to your horse.
In addition to anticoagulant rodenticides, there are less common products that are meant to control rats but could lead to poisoning in a horse; the symptoms that the horse experiences will depend on the active ingredient. One such example is cholecalciferol (also known as Vitamin D analogue). Other rodent poisons that can harm your horse include bromethalin, strychnine and 1080.
Causes of Rat Poison Toxicity in Horses
Your horse can experience rat poison toxicity by ingesting the rodenticide that you have put out in order to attract and exterminate rodents. Sometimes, rats and other rodents will move the bait around, putting it in a place your horse has access to. Other times, your horse will break into where you store your rodenticide and find it appealing to ingest.
If your horse ingests an anti-coagulant rodenticide, it can lead to his blood being unable to clot, which can cause excessive bleeding. Should your horse ingest cholecalciferol, it will often lead to increased calcium levels in his blood as well as mineralization of his bodily tissues, which will ultimately cause acute kidney failure. Should your horse ingest bromethalin, strychnine or 1080, the poison will impact his nervous system.
It is not clear what the minimum amount is of each rodenticide that your horse can ingest without experiencing problems.
Diagnosis of Rat Poison Toxicity in Horses
If you think that your horse has ingested any type of rodenticide, you will want to contact your veterinarian right away, even if you have not noticed any symptoms yet. Your veterinarian will ensure that your horse is stable before conducting a physical examination. In most cases of rodenticide poisoning, the owner of the horse observed something that made them believe that ingestion of the poison by their horse was a possibility; for example, they may have observed their horse near the rodenticide or noticed that the rodenticide was moved. It is important to share this information with your veterinarian; should your horse be displaying symptoms this will give your veterinarian a place to start in regards to determining what is going on with your horse. You will want to let your veterinarian know the type of rodenticide that you believe your horse ingested.
When it comes to ingestion of an anticoagulant rodenticide, diagnosis may be based on the horse having had access to the bait along with evidence of exposure, which can include missing or chewed up bait or packaging, or greenish blue feces. The majority of veterinary laboratories will have what is called an anticoagulant screen, which will be able to detect in the horse’s serum, plasma, liver or kidneys most of the anticoagulants that are available to be purchased and the stomach contents of your horse can also be analyzed. Should your horse respond well to vitamin K1, it will also point to anticoagulant rodenticide toxicosis.
When it comes to diagnosing a poison that impacts the nervous system (like bromethalin), diagnosis will be made based on the history of possible exposure to the bait along with your horse having developed neurologic symptoms from 1-7 days after the possible exposure. To confirm the diagnosis, your veterinarian will look to see if there is bromethalin or its major metabolite in your horse’s liver, kidney, brain or fat (though this type of analysis is only available in certain laboratories).
Treatment of Rat Poison Toxicity in Horses
Treatment can be very successful should your horse have ingested an anticoagulant rodenticide, even more so if treatment can be started before the clinical signs manifest themselves.
In the case of poisoning by an anticoagulant rodenticide, Vitamin K1 is utilized as a treatment. Typical recommended dosage is 3-5 mg/kg/day for 3-4 weeks. An extra week of treatment will not cause any problems; conversely, stopping treatment too soon can lead to death. The dose should be given with small portions of fatty foods like milk or cheese, as the fat will help your horse absorb the vitamin K1. It also may be recommended that the daily dose be cut in half and given to your horse at 12 hour intervals. Oral delivery is often preferable due to the risk of bleeding at the site of the injection. Fresh or frozen plasma or whole blood may be necessary in order to replace clotting factors and RBC’s should there be current bleeding. In some cases, oxygen may be administered. It will be important to limit your horse’s activity, particularly during his first week of treatment.
Should your horse have ingested cholecalciferol and developed significant hypercalcemia, the recommended treatment is pamidronate. This is a bisphosphonate that is administered by injection that stops osteoclastic bone resorption. Dosage is typically 1.3-2 mg/kg intravenously in saline over about two hours. Supportive therapies (like furosemide and prednisolone) will also be utilized as calcium and phosphorus levels decrease. A repeat dose may be needed should the hypercalcemia develop again.
If your horse is experiencing toxicity from bromethalin or another rodenticide that impacts the nervous system, treatment will focus on decontamination through intravenous therapy and the use of activated charcoal. Your veterinarian will also work to control seizures and provide supportive care.
Recovery of Rat Poison Toxicity in Horses
Should your horse have experienced poisoning due to an anticoagulant rodenticide and coagulopathy has occurred, your veterinarian will want to continually check the prothrombin time (PT) and activated partial thromboplastin time (APTT) daily until it is normal.
With cholecalciferol poisoning, your horse’s calcium and phosphorus levels should be monitored and treatment should continue until they return to normal. Treatment may be required for days or weeks. Kidney function should be monitored and other symptoms should be treated as necessary.
In bromethalin poisoning, anticonvulsant medication will be used to control seizures and a complete recovery may take days to weeks of treatment.