Does My Dog Have Heartworm? Signs, Treatment & Prevention

Heartworm in dogs is a terrible, but preventable disease. Learn more about the signs, causes, and treatments of heartworm in dogs to protect your pet.

Brittany Leitner

Updated May 19, 2023 • Published June 25, 2021

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Does My Dog Have Heartworm? Signs, Treatment & Prevention

Heartworm is a serious disease that can cause health complications if left untreated. Heartworms in dogs are caused by parasitic worms that make their way into your pet’s flesh via a mosquito bite. Luckily, there are ways to treat a heartworm infection if it’s detected early enough by your veterinarian.

Here's everything you need to know if you suspect your dog might have heartworms and how you can recognize the signs so you can take action faster. 

What are heartworms?

Heartworm disease is a preventable illness that dogs contract when a mosquito carrying the heartworm larvae bites their skin. The larvae mature into different stages and migrate through the tissues until they've reached the heart and lungs.

The number of female worms that mature into the adult stage will determine the number of worms that will live and reproduce in the body. A low burden of worms can live without causing any signs of heartworm disease until the number of worms begins to affect the dog’s ability to function normally.

Signs your dog has heartworm

As mentioned previously, dogs are less likely to show signs/symptoms of heartworm disease in early larvae development and with a low number of worms, so it’s important to get them on preventative medicine and screened yearly at your veterinarian.

If your dog does show signs of heartworm, they may include:

  • Coughing

  • A reluctance or inability to exercise

  • Fatigue

  • Decreased appetite

  • Weight loss

  • Distended abdomen

As the number of worms increase, they cause damage to the heart and prevent blood from properly pumping into the various organs and tissues. Once a dog is exhibiting signs of the disease, damage to the heart may be permanent and will significantly reduce their life expectancy.

How to prevent and treat heartworms in dogs

It’s important to know that heartworm infection is preventable, so talk to your veterinarian about getting your dog on preventative medication as soon as possible. If your dog tests positive for heartworm disease, a treatment protocol will begin and length of treatment will depend on the severity of the infection. 

When you administer a monthly oral preventative, your dog is dewormed for specific larval stages of the heartworm. It's crucial that your dog receives the medication every month. Since the only way to contract heartworms is by an infected mosquito, every mosquito bite could transmit the larvae to your dog. Giving heartworm prevention on a regular schedule every month will ensure all stages that are susceptible to the ingredients in the medication are killed. In addition, heartworm prevention also deworms for intestinal parasites.

You can decrease the mosquito burden in your backyard by using mosquito repellants, but there are no guarantees that your dog will not be bitten by an infected mosquito.

The truth about heartworm infection

It's important to dispel a few myths about heartworms in dogs.

Some pet parents believe that strictly indoor dogs do not need prevention since they do not go outside—this is false. A mosquito can easily fly inside your home and bite your dog.

Some also think that certain parts of the U.S. don't have mosquitos that carry the heartworm larvae, and therefore, dogs living in those areas don’t need prevention—this is also false. Positive cases have been reported in all 50 states. 

While there are pet parents that have never given heartworm prevention and have never had a dog diagnosed with infection, with the number of dogs traveling the country and an increase in transport of rescue dogs from states with high numbers of infection, the chances of transmission are now significantly higher.

You may be wondering—if mosquitoes carry the larvae and dogs are being transported into your area from the states that have a high risk of infection, then why would that be a concern for you and your dog? Yes, the heartworm larvae is transmitted through an infected mosquito, but the scary part is that when a mosquito bites a dog that is infected with heartworms, they carry that larvae in their mouth and are now able to infect other dogs.

If your dog is not currently taking a monthly preventative, it's not too late to have them tested and get started! Talk to your veterinarian or the Pros at Pawp to discuss the best prevention for your dog.


Reviewed and fact-checked by

Mika, RVT at Pawp

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