Heartworm Disease in Dogs

Heartworm disease is a serious and potentially life-threatening condition caused by the parasitic worm, Dirofilaria immitis. It affects pets globally, primarily dogs, cats, and ferrets. The disease gets its name as the worms primarily reside in the heart and pulmonary arteries of infected animals. Transmission of heartworm disease occurs primarily through the bite of infected mosquitoes, which makes it a risk for pets everywhere, not just in certain regions or climates.

Important aspects to know about heartworm disease:

Transmission and Global Spread

Heartworm disease is transmitted through the bite of infected mosquitoes. Changes in weather trends missed heartworm preventative doses, and relocation of pets have contributed to the spread of heartworm disease globally. Currently, no state is free from heartworm disease, and hotspots of infection can occur in any region.

Once a pet is infected, it can take years for overt clinical disease to appear, but during this asymptomatic period, the health of your pet is slowly being compromised.

Appearance and Detection

Heartworms are long, stringy worms that reside inside the heart and pulmonary arteries. They cannot be visually detected in pets and cannot be seen in your pet’s stool. The only way to diagnose heartworm disease is through blood testing by a veterinarian.

Symptoms in Pets

The severity of heartworm disease in pets depends on the number of worms present, the health, and activity level of the pet, and how long the pet has been infected. Symptoms may not appear initially or may present as a mild cough. As the disease progresses, symptoms can include fatigue, a persistent cough, trouble breathing, and even fainting. In cats and ferrets, the signs of heartworm disease can show up sooner and may include sudden collapse and death.

Prevention and Treatment

Prevention of heartworm disease is always the best approach. Treatment for heartworm disease can be difficult and expensive, and it carries the risk of complications. In cats and ferrets, there is no approved therapy for heartworm infection. However, prevention is possible in all species. Monthly prescription heartworm preventatives, like Heartgard or Revolution, can be started as early as 6-8 weeks of age and are recommended to be given year-round. Regular testing for heartworm disease is also necessary to ensure the safety of your pet.

Testing for Heartworm

Heartworm disease is diagnosed through a quick and easy blood test that only needs a few drops of blood. It’s recommended to have your pet tested every 12 months, as heartworm preventatives can be harmful if your pet already has heartworm disease. Results are usually available within 24 hours.


Heartworm disease is a serious risk to our pets’ health and well-being. Regular testing and prevention are key to ensuring the health and happiness of our pets. Even if your pet shows no signs of heart disease, it’s crucial to have them tested regularly and to keep them on a heartworm preventative. If you have any concerns about heartworm disease, it’s important to contact your vet right away.

At the end of the day, keeping our pets safe from heartworm disease comes down to awareness, regular testing, and preventative care. If we take these steps, we can provide our pets with the best defence against this dangerous disease.

Schedule a call with Wondervet to discuss any pet healthcare need, such as spaying your dog or cat neutering