Dog Heartworm Disease


Mosquitos transmit heartworms from pet to pet when they feed. The larval stages develop in the blood stream into adult worms that live in the heart and pulmonary vessels, in the lungs. Heartworm preventative kills off the larval stage before it develops into the adult worm.


Antigen test looks in the blood for the presence of female heartworms. Its takes 6 to 7 months for the microfilariae to develop into an adult and the test will only show a positive result when they are adults. Microfilariae tests looks for microfilariae in the blood, about 30% of positive dogs will show microfilariae. This depends on the severity of infection. Imaging diagnostics like thoracic radiographs will show structural changes caused by heartworms. They cannot determine if the pet is positive or negative as the structural changes are irreversible. This is due to the inflammation of the vessels and dilation of the heart caused by the heartworms.


The recommended treatment is the split dose protocol or also known as the “fast kill” protocol. The Patient starts out on a monthly Heartworm preventative to halt the development of more heartworms. They will continue this for the rest of their life. During the first month, they will be on Doxycycline or Minocycline to weaken the adult heartworms. Then they will be given a dose of Melarsomine to kill off the weak and older heartworm after they finish the Doxycycline or Minocycline.  They will also start on steroids to decrease inflammation. A month later, they will get two doses of Melarsomine 24 hours apart to kill of the remaining heartworms. Throughout this protocol and 6 weeks after the last dose of Melarsomine, they will need to be on strict rest.

The other treatment option is called the “slow kill” protocol, which is not recommended by the American Heartworm Society. The difference in this treatment plan is that you do not give any doses of Melarsomine. The patient is still put on monthly heartworm preventative and given Doxycycline or Minocycline. This weakens the adult heartworms, shortens their life expectancy, and prevents new heartworms from forming. The average heartworm lives 5 to 7 years. The patient needs to be strictly rested until tested negative for heartworms.

There are no “natural” or herbal therapies shown to be safe and effective prevention or treatment for heartworm disease.


The “fast kill” protocol usually takes 4 to 5 months while the “slow kill” protocol could last between 2 to 7 years. The patient needs to be on bed rest during the entire protocol so the “fast kill” protocol will have the patient back to normal activity sooner. Also, the “fast kill” protocol is shorter; there is a less time for irreversible damage to the heart, lungs, and pulmonary vessels to occur. The “slow kill” protocol is initially cheaper but could become more expensive depending on the duration of the treatment and if other issues arise due to the presents of heartworms.

Written by Kelsey McKenna, DVM

Contact Us

We look forward to hearing from you

No form settings found. Please configure it.

Office Hours

Our Regular Schedule


7:00 am-7:00 pm


8:00 am-5:30 pm


8:00 am-5:30 pm


7:00 am-5:30 pm


8:00 am-5:30 pm






Find us on the map


Read What Our Clients Say

  • "Dr. Cox and Dr. McKenna are amazing people! I am so thankful to have such well trained and kind people caring for my fur babies. My sweet old girl, Ruby needed special care and they knew exactly what to do! I can not thank them enough for being so kind when this doggie mommy was freaking out! Love you guys!!"
    Catherine B.

Featured Articles

Read about interesting topics

  • Lost Pets

    Has your pet wriggled their way through the fence or dashed out the front door? When searching for your lost pet, make sure you include these steps in your hunt. ...

    Read More
  • Should You Leave Your Cat Alone for a Long Weekend?

    So you have a trip planned for the weekend, but what should you do with your cat? Learn how to best care for your cat while you're away. ...

    Read More
  • Flea and Tick Season

    Want to protect your pet from fleas and ticks? These tips can help. ...

    Read More
  • Summer Grooming Tips

    Want to keep your pet cool and comfortable this summer? A few changes to your normal grooming routine can help. ...

    Read More
  • What to Do If Your Pet is Stung

    Don't get us wrong, we love the bees! But we don't love when our pets get stung. Follow our tips to treat and prevent bee stings on your furry best friend. ...

    Read More
  • Tips for Traveling With Your Pet

    Do you dread hitting the road with your pet? These tips may make the trip more comfortable and enjoyable for you both. ...

    Read More
  • 6 Questions to Ask At Your Senior Pet's Next Check Up

    Want to keep your senior pet healthy and happy? Ask these six questions at your pet's next check up. ...

    Read More
  • Why the Controversy About Pet Vaccinations?

    As with anything, pet vaccinations can be too much of a good thing. Similar to parents who are learning more about vaccinations for children, veterinarians and pet owners alike are beginning to question some of the standard wisdom when it comes to protecting pets. There are certain fatal diseases against ...

    Read More
  • Pet Clothes: A Fashion Statement or a Necessity?

    There is nothing cuter than a pet in a colorful sweater, but do our furry friends really need to wear clothing? Although clothing is not a necessity for every pet, some animals benefit from a little extra protection during cold or damp days. Others enjoy wearing festive clothing during holidays or other ...

    Read More
  • Introducing a New Pet to Your Current Ones

    Pet Proofing Your Home Introducing your new pet to your current one is only a single part of the equation relating to taking a new pet home. You also have to make sure your new pet is comfortable in your home, which is a foreign environment to the animal. Like humans, animals can experience high levels ...

    Read More

Newsletter Signup

Sign up for more articles