April is National Heartworm Awareness Month! Heartworm disease is likely the most common vector-borne disease in the U.S. Between 1 and12.5% of dogs are heartworm positive nationally. In the Southeastern U.S., prevalence rates can sometimes reach almost 50% of dogs! Heartworm disease is a potentially fatal disease that can affect the heart, lungs and blood vessels of dogs, cats, and even other domesticated and wild animals. It is caused by a parasite called Dirofilaria immitis, which can be found living inside some female mosquitoes. 

How Is Heartworm Diagnosed?

During your dog’s yearly exam, your veterinarian will likely run a blood test to see if your dog is heartworm positive. These tests do not look for heartworms themselves, but check for your dog’s immune system response to an antigen produced by the parasite. Heartworm tests are typicallynot performed on pets until 1 year of age. This is based on the parasite’s lifecycle as well as how the test works. It takes about 6 months of infection to be detected. It is recommended that, even if you are diligent with your heartworm preventative, your pet be tested every year.

heartworm microscopic image

Signs of Heartworm Disease

In early stages of heartworm disease, most dogs do not show any symptoms at all. As the disease progresses, your pet may start to show more signs:

  • Chronic coughing 
  • Lethargy
  • Reluctance to exercise
  • Decreased appetite
  • Weight loss

If the disease progresses, you may notice:

  • Swollen belly from excess fluid in their abdomen
  • A diagnosis of heart disease
  • Sudden onset of labored breathing and pale gums
  • Bloody urine 

How Do You Prevent Heartworm Disease?

Speaking with your veterinarian is the first step in prevention! There are many different options of heartworm preventative on the market, including oral tablets, chewables, topicals, and even injections. Your vet can help you navigate which is best for you and your pet. Don’t forget that even pets considered to be “indoor” pets can get this disease. Mosquitoes can still enter your home and bite your pets. 

What If Your Dog Is Heartworm Positive? How Do You Treat It?

Your veterinarian will first put your dog on a course of antibiotics and a heartworm preventative to lessen the burden of the immature worms.

During this time, further testing will be done that often includes the following:

  • Imaging, like radiographs (x-rays) and an echocardiogram (ultrasound of the heart) to check for any damage to the heart or lungs
  • Blood work, to be sure there aren’t any secondary infections or issues with other organs
  • Urine tests, to be sure that they don’t have any blood in their urine or an infection

After these tests are performed, your dog will most likely receive several injections, spaced out over several weeks to months, with a medication called Immiticide to kill the heartworms.  

During this time, your pet will continue with antibiotics and heartworm prevention. It’s very important that your dog is kept quiet for 1-3 months while the heartworms fade. Any excess activity can cause heart issues, anaphylaxis, lethargy, and respiratory distress. 

Six months after treatment finishes, your veterinarian may want to run another heartworm test to be sure that the parasite has cleared. 

heartworm medication

The best thing that you can do for your pet is put them on a monthly preventative to stop this disease before it starts. It is much safer and less stressful for your pet than the treatment, and much less expensive for you!