Ivermectin in horse manure can be dangerous for your dog | © Karen Givens

Eating horse manure can be dangerous to your dog

By isak, February 25, 2012

We know that ivermectin can be very dangerous to certain breeds of dogs. Ivermectin prevents or kills parasites by causing neurological damage to the parasite, resulting in paralysis and death for the parasite. Dogs genetically sensitive to the medication have an anomaly that allows the ivermectin to pass the dog’s blood-brain barrier and into its central nervous system, which can be lethal for the animal.

However, have you ever stopped to consider that the ivermectin you use to treat your horses for parasites could be dangerous to dogs that eat horse manure? We know how dogs love horse manure. So in hindsight, it makes sense that ivermectin in horse manure could pose a danger… and here is one such story:

My American Pit Bull Terrier is at University of Florida Veterinarian School of Medicine right now being treated for Ivermectin poisoning. He had a sudden attack while on our walk. Signs were 1st slobbering/drooling (excessively) then diarrhea. I arrived at an animal clinic within 20 min where he then began vomiting and having seizures. Blood work showed elevation in Liver and Pancreas reading was 1256 He was given fluids and treated for what the Dr suspected was heat stroke after 6 hrs the Dr gave him Vit K injection. I then transferred him to Emergency Hospital for over night care where he was given more fluids and I was informed his temperature had risen significantly and at about 6am he was given charcoal. In the morning the Dr. recommended University of Florida.

So I left immediately for UF. He had been on his side laid out flat for about 20 hours and when i put him in my car I noticed he wagged his tail slightly. During the drive he did raise his head in an effort to be upright! Upon arrival at UF his heart rate was critical. Meds to stabilizes heart/monitored catheter and IV fluids. Next day prognosis Ivermectin poisoning via ingesting Daily Feed Through Wormer in horse manure and or ingesting left over grain/wormer in stalls at night!!!

I had NO IDEA the horse manure could be toxic. I remove feces from pastures everyday and of course the dogs ride in 4wheeler with me and once in a while I would catch them eating the manure. Its been 6 days now his organs show NO damage. He’s been taken off all support. He is eating and drinking and can stand to urinate. He can walk briefly then he starts to have tremors/shaking and wants to sit down. I’m hoping since everything has progressed for the better that eventually his Central Nervous System will recover enough so that he can have a normal life. Going to visit him today and possibly bring him home. I know that I’ll have to provide a lot of physical therapy so if anyone has any ideas I would great appreciate them.

Sorry to be so long winded but I hope through my experience another dog will not suffer and will have a chance to survive. Please tell anyone you know that has horses and uses daily wormers that the manure is toxic!

BTW the UF was absolutely wonderful!!! They let me stay in the Critical Care unit in the cage with my dog anytime I wanted. I was there off and on for 4 days and I never saw anything other than wonderful caring DR.s, students and techs!!! God Bless them all.

Thanks to Cindy in Florida for sharing her story! And thanks to the folks at the University of Florida Critical Care Unit! You rock!


  1. Sharon Strole says:

    New neighbors have two horses a couple of my dogs I’ve seen eating horse poop. My one dog which is half golden retriever has started itching and chewing a lot today. He has some itching allergies usually in winter and has been fine until today, now the itching has come on bad. Do you think the horse poop may have triggered this and I should take him to the vet. Never heard of this before and not sure what to do.

    • isak says:

      Allergies can be triggered by many things. If it is a result of eating the horse poop, it could be that your dog has an allergy to something in the feed the horses are being fed. Often, horses are fed grains and grains are often a source of allergies in dogs.

      Have you checked to be sure your dog has not picked up fleas? That would be another source of itching.

      Another warning about your dogs eating horse manure… horses are generally wormed with ivermectin paste. The quantity used to treat a horse is somewhere in the range of 25-30 times the dosage for a medium to large dog. This is enough to cause ivermectin poisoning and even death to a dog.

      Bottom line is that eating horse poop is not a good thing for dogs, no matter how good they dogs say they taste.

  2. Jill Crazy dog lady AZ says:

    thanks to the UF and the person telling the story
    trying not to let the dogs eat horse manure but it ruins my walk to keep the leashed
    knowing that the neurotoxin could ruin THEIR LIVES….we will avoid that trail forevermore…
    thanks for your story
    it continues to make a difference in 2014

  3. Caitlan says:

    Why us commercial dewormers? My family has been using Diatomaceous Earth forever as a natural parasite control. Wormwood is also a great option. You shouldn’t have to risk any dog’s life.

  4. ann says:

    My dog gotten severly sick in a few weeks took her to Dr. says not much she can do, had enlarged liver,severe dehydrated, lost a lot of weight, diabetic in a short time, A friend read on this and gave her a wormer she seems to slowly come around but still waiting and watching, My other little dogs didn’t seem to have any problems so thanks for this info. Wish I knew more about this and what else to do, vets didn’t seem to even know about this.

  5. Carrie Quatsoe says:

    My dog has just recovered from an incident of moxidectin poisening (Quest horse dewormer) that she acquired from eating the feces of recently wormed horses. As a horse owner, I’m wondering why the package insert from these products do not list the risk of contaminated horse manure? It only states that exposure to the product can cause adverse effects not that it can be transmitted through the horse manure. My vet says that the manure can be toxic for up to 2 weeks post worming. If I had known we would have disposed of the manure more appropriately and have kept the dogs away.

  6. Elizabeth Wiley says:

    Our vet gives prescription worming to all our horses and other boarders where we keep our horses at the same time, so we can watch the dogs. With so many horses, and many on the trails with dogs, it is not always easy to keep dogs out of the manure. Thank you for the warning.

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