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Ivermectin toxicity?

Species: Dog
Breed: Golden Retriever
Age: 2-5 years
Help! I think that I am accidentally poisoning my boy 4 year old by giving him Iverlectin for horses. A year ago, a friend of mine said that a breeder that he knows gives his dogs this instead of the Heart Guard. Given the fact that this came from a breeder, and the high price of Heart Guard vs the price of the Iverlectin, I switched.We are on a limited budget and can't afford too much. He has been on this for the past year. In the past year he has had a big fight with itchy skin. The vet has given him blood tests that came out negative for any parasites or reasons for his itchyness. He put him on steroids for a short time and this did help some, but did not get the itch to go away. I switched foods from Canadae to Wellness brand Core Low fat, and now he is on Prescription diet z/d ultra allergen-free food. None of this has made a difference. But now all of a sudden he has gone blind. He can still see motion but is walking into things a lot. He also has enlarged pupils and is always thirsty. He was just tested for diabetes and he tested negative. He had a questionable rate for hypothyroid so the vet put him on thyrozine. He now weighs 120 lbs. He hasn't lost weight, his eye site is poor or non existent, his pupils are dialated and he is always panting because he is too warm, and drinks bowls of water per day. Thus having to go pee a lot too. I am stopping the 5 drops from a syringe onto a small amount of canned d/z prescription food per month immediately. But I am afraid to put him on Heart Guard because I want the amount of Iverlectin in his system to clear. Can you tell me how long I should wait for his system to clear? I had him checked for heart worm last year and he tested negative. Sunny was born blind in one eye, so vision has never been his strong suite. But I am worried that my 4 year old Golden is going to die because of something that I did to save money. Please let me know what your feelings are on this. I don't know what to do. I am afraid of huge vet bills that I can't afford and will eventually have to put him down. Please help.


Online vet, Dr. Marie

Dr. Marie replied:

I'm sorry to hear that Sunny is having these problems.

Years ago I did work with some clients who gave ivermectin instead of Heartgard as heartworm prevention. While it can be safe, my main concern is that it is very difficult to properly dose ivermectin. It comes in a bunch of different strengths and often it is very complicated to figure out how much to give. I often have to figure out dosing when I give ivermectin injections to small animals like guinea pigs or mice for parasitic issues and even though I have done the math several times I always have trouble with it! It would be quite easy to be giving too much by a factor of 10 or more.

On top of that, some dogs can be extremely sensitive to ivermectin if they have a defective MRD1 gene. This is much more common in herding breeds of dogs though.

Here are the symptoms of ivermectin toxicity:
  • vomiting

  • ataxia (wobbly walking)

  • lethargy

  • fast heart rate

  • salivation

  • mydriasis (large pupil size)

  • seizures



In cats, blindness can be a side effect of receiving too much Ivermectin, but this is not common in dogs.

Sunny's case has me a little bit puzzled. The increase in his pupil size could be from an ivermectin overdose, but the increase in thirst and urination and actual blindness really should not.

Because I was puzzled by his symptoms I did some research for you and did find something that could cause blindness as well as an increase in thirst and urination. You may want to ask your vet about the possibility of a condition called Sudden Acquired Retinal Degeration (SARD). We don't know why dogs get this, but they can suddenly lose their ability to see and also, most dogs who have this will have an increase in thirst and urination. The symptoms are often similar to cushing's disease (hyperadrenocorticism).

There is no cure for SARD, but dogs can live quite happily with it.

There is also another rare condition called nephrotic syndrome that can cause these symptoms. Dogs with nephrotic syndrome usually have high levels of protein in the urine, so it is a little bit easier to diagnose. There can possibly be a treatment depending on what is causing the protein in the urine.

It sounds unlikely to me that Sunny's recent symptoms are caused by the Ivermectin. I would still stop the ivermectin for now. It's not a bad idea to mention to your vet how much you are giving so they can determine if it really was a toxic dose, just to be safe. Then your vet can advise you on when to start up on Heartgard.

It would be a great thing if your vet could refer you to a veterinary ophthalmologist. You will pay a little bit more for an appointment with this type of vet, but in the long run it will likely get you a diagnosis quicker. That way, if there is anything that can be done for Sunny's vision then the sooner treatment is started, the better!

I hope things improve soon!

Dr. Marie.




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Disclaimer: Although Dr. Marie is a qualified veterinarian, the information found on this site is not meant to replace the advice of your own veterinarian. AskAVetQuestion.com and Dr. Marie do not accept any responsibility for any loss, damage, injury, death, or disease which may arise from reliance on information contained on this site. Do not use information found on this site for diagnosing or treating your pet. Anything you read here is for information only.

Customer reply:

Thank you so much for your advise. Our vet has already asked us to take Sunny to the Vet Opthalmologist. We plan on doing so as soon as I can get some money together. But I do feel relieved that I may not have caused these issues by giving him the Ivermectin. Would either of the eye diseases that you said may be the cause, also be the reason Sunny has gained so much weight? He has not had any treats or anything but his food since the end of May. He is strictly on his dog food. I cannot figure out why he is gaining so much. He has never been a physical type of dog. Even when we first got him at 11 weeks old, he didn't really bounce around like a normal puppy. But I said that he was just right for us.
I also want to thank you for doing the research for Sunny's blindness. He was born with his left eye blind, but that never seemed to stop him. But now with both eyes, he is even afraid to jump into the car.

Thank you again
Diane


Online vet, Dr. Marie

Dr. Marie replied:

Hmmm....I don't think either of those issues would directly cause weight gain. That's got me puzzled as well.

I think a thyroid issue is certainly a possibility but can't really connect hypothyroidism to blindness.

If you do get some answers to what is going on with Sunny I would love to know, so feel free to post back again when you next talk to your vet.

Dr. Marie.



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Dr. MarieDr. Marie is a veterinarian who practices in a busy animal hospital in Ottawa, Ontario. She created Ask A Vet Question as a resource for good, accurate veterinary advice online. Dr. Marie treats dogs, cats, hamsters, guinea pigs, and rats. She has been a vet since 1999.

Is an online vet visit just as good as a trip to your veterinarian? No! But, many times, asking an online veterinarian a question can help save you money. While Dr. Marie can't officially diagnose your pet or prescribe medications, she can often advise you on whether a vet visit is necessary. You can also ask Dr. Marie for a second opinion on your pet's condition.