Is Slow Kill the Safest Heartworm Medicine and Treatment for Your Dog?

Updated on July 28, 2019
DrMark1961 profile image

Dr. Mark is a veterinarian. He works mostly with dogs and exotic animals.

If your dog's heartworms are caught early, ivermectin can be the safest treatment.
If your dog's heartworms are caught early, ivermectin can be the safest treatment.

How Can Heartworm Be Treated?

If you allow your dog to develop heartworm, something must be done. If left untreated, the dog will eventually die of congestive heart failure.

Conventional heartworm treatment, however, is expensive, painful and dangerous; this article will let you know about the alternative. It will discuss:

  • the problems with traditional heartworm treatment
  • what the slow kill method is
  • the advantages and disadvantages of using slow kill
  • how you can use this method on your dog
  • the importance of heartworm preventative

With conventional heartworm treatment, the worms die quickly, and if the family does not watch the dog carefully, the worms can cause a fatal embolism. This alternative is not quick. It may not even be the best alternative for your dog since there can be changes to your dog's heart while the treatment is working.

This is a decision you will need to make carefully: If your dog already has advanced heart and lung disease, she may not be able to wait for the slow and safe treatment. Some veterinarians do not recommend this alternative; others think it is safe only in the earliest and mildest cases of infection.

If your veterinarian is open to alternative treatments, you can make this decision together.

Dogs with heartworms will suffer, but slow kill is safest.
Dogs with heartworms will suffer, but slow kill is safest. | Source

What Is Best for My Dog?

Without examining the dog and determining the changes to his heart, it is impossible to recommend which treatment is best.

The slow-kill alternative to the conventional therapy (Immiticide injections) is the use of ivermectin every month. It is given by mouth, so it can be done at home. The American Heartworm Society does not recommend this treatment. (Of course they also recommend that all dogs be on preventative, even when living in areas where there are no mosquitoes.)

The theory behind this alternative is that since the ivermectin will kill all of the developing larva, no new heartworms will develop. The adult worms will take a few years to die, which is why your dog's heart can grow worse. A dog that is already suffering from late-stage congestive heart failure may not make it through the slow-kill method.

Which Treatment Can I Afford?

If you are in tight circumstances and cannot even afford to treat your dog with the conventional method, this alternative costs a lot less.

If you want to treat your dog's heartworm condition using the slow-kill method, I would recommend that you work with a veterinarian willing to use this alternative. Discuss the costs with him, and if you both decide on the injections, there may be some way to make payments.

Slow Kill Details

To kill all of the microfilaria, the dose of ivermectin needs to be higher than regular heartworm preventative (it should be given at 50mcg/kg, instead of 5mcg/kg). So if you buy the 0.08% sheep drench, which contains 800 mcg of ivermectin per milliliter, you need to give your sick dog approximately 0.06 ml per kilogram of body weight. (This is the oral solution that I use for my smaller dogs since it is already diluted.)

The added benefit is that since the ivermectin kills the microfilaria (the immature worms) that would infect your local mosquitoes, it prevents your dog from spreading the disease to other dogs. It is also more affordable than the Merial product and, since generic ivermectin has many manufacturers, it is unlikely to ever become scarce.

Owners of Collies, Shelties, OES, Aussies, and some other mixed-breed dogs might be sensitive to ivermectin. These dogs need to be treated with Immiticide or herbal therapies, which are still unproven at this time. If you are concerned in any way you can test for the mutation on the MDR1 gene that causes sensitivity. Testing is available through the Washington State University College of Veterinary Medicine.

Heartworm free dogs on the beach.
Heartworm free dogs on the beach. | Source

Heartworm Preventative

The only way to guarantee that your dog will not have to endure the Immiticide, nor suffer deterioration to his heart and major blood vessels, is by providing heartworm preventative every month. If you are able to use a simple syringe (without a needle), this is not an expensive option.

There are also some dog owners who choose to go without heartworm preventative. They keep their environments mosquito free, or live in a region with no mosquitoes, and so feel this is the best option of their dogs. If you are not able to guarantee this do not take the risk.

If you want a safe heartworm treatment, then monthly ivermectin is your best bet.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

  • Will black walnut alone get rid of heartworms in dogs all together?

    There are no studies that prove that black walnut will kill off all of the worms, but if they are kept from reproducing for a time all of them will eventually die off. This form of treatment can be a lot more dangerous for a tiny dog that will have symtpoms with just a few worms in the heart.

  • If a dog has heartworm, how does the blood test tell what stage they have?

    The blood test will only tell you if your dog is positive or negative for the antigens in the heartworms body. It will not tell you what stage of heartworm disease your dog has. If your dog is small, and has just a few worms, it can be severe, and your dog may be suffering from congestive heart failure. If your dog is large, and has only a few worms, he may not even have clinical symptoms.

© 2012 Dr Mark


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    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      2 months ago from The Atlantic Rain Forest, Brazil

      Jessica, the slow kill method is more effective and your best option.

    • profile image

      Jessica Mazpule 

      2 months ago

      My 7 year old American bulldog was diagnosed with heartworm. He does not show any signs or symptoms. We took him in to see the vet because of stomach issues so were pretty surprised with the diagnosis. Do you suggest treating with black walnut or the slow kill method?

    • profile image


      2 years ago

      Are there natural supplements that would be helpful to give your dog in addition to treatment?

    • profile image

      Debi Crawford 

      6 years ago

      Its encouraging to see a veterinarian who indorses natural treatments along with caution in the overuse of conventional treatments used by the majority of vets which can be more harmful than the original disorder. Very informative and concise.


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