Is Heartworm Contagious From Dog to Dog
January 16th 2026
If you have a dog or cat, you have likely heard the term heartworm disease. Since this term may be unfamiliar—or even scary—we’ve compiled this guide to help you better understand heartworm disease and how it may affect your pet.
There are certainly misunderstandings surrounding heartworms, but the best way to support a healthy, happy pet is to understand this disease as clearly as possible. You don’t have to understand it like a doctor, but having a few simple facts in mind can go a long way in helping you make informed decisions about your pet’s health.
What Is Heartworm Disease?
Heartworm disease is a serious and potentially life-threatening condition that primarily affects dogs, but it can also impact cats and other animals. It is caused by a parasitic worm called Dirofilaria immitis.
Here’s how it works:
- Heartworms are spread through mosquito bites
- An infected mosquito transfers microscopic larvae into your pet
- These larvae mature over several months
- Adult worms settle in the heart, lungs, and surrounding blood vessels
- Fully grown worms can reach 5–12 inches in length
Because heartworms live inside the body and symptoms often develop slowly, the disease can progress significantly before it’s detected.
Are Heartworms Contagious From Dog to Dog?
The short answer: no.
Heartworms are not contagious from dog to dog through direct contact.
Important Facts to Know:
- Dogs cannot spread heartworms by touching, playing, or sharing food and water
- Heartworm disease requires a mosquito to be transmitted
- An infected dog can only contribute to the spread if a mosquito bites them and then bites another pet
Without mosquitoes, heartworm disease cannot spread.
Frequently Asked Questions About Heartworms
1. Can a dog fully recover from heartworms?
Yes. With early diagnosis and proper veterinary care, many dogs recover successfully. However, some long-term damage to the heart or lungs may remain, which is why prevention is so important.
2. Are heartworms contagious in cats?
No. Heartworms are not passed directly between cats. However, cats can become infected through mosquito bites, even if they live indoors.
3. Do I need a prescription for heartworm prevention?
Yes. Heartworm prevention medications require a prescription from your veterinarian. If you suspect your dog or cat may have heartworm disease, please give us a call or visit our website at Bluff Park Animal Clinic. We’re happy to help guide you through symptoms, testing, prevention, and treatment options.
4. Can humans get heartworms from dogs?
Human cases are extremely rare. When they do occur, mosquitoes—not dogs—are responsible. These cases are usually not life-threatening.
Signs and Symptoms of Heartworm Disease in Dogs
Heartworm disease often causes internal damage long before visible symptoms appear. As the disease progresses, you may notice:
Common Symptoms Include:
- Persistent, mild cough
A dry, lingering cough is often one of the earliest noticeable signs.
- Lethargy or fatigue
Dogs may tire easily or lose interest in walks and playtime.
- Weight loss or reduced appetite
Some dogs eat less and gradually lose weight.
- Swollen belly
Fluid buildup in the abdomen can occur as heart failure develops.
- Difficulty breathing
Advanced cases may include rapid or labored breathing in addition to coughing.
Long-Term Effects of Heartworms in Dogs
Even after treatment, heartworm disease can leave lasting damage, including:
• Injury to the heart and lungs
• Damage to pulmonary blood vessels
• Reduced stamina and overall quality of life
Because of this, prevention is far safer and more effective than treatment.
Heartworm Disease Treatment for Dogs
Treating heartworm disease is possible, but it can be:
• Expensive
• Time-consuming
• Risky, especially in advanced cases
What Treatment Typically Involves:
1. Stabilizing your dog medically
2. Administering medications based on disease severity
3. Strict exercise restriction to prevent complications
4. Close veterinary monitoring during recovery
As heartworms die, they can cause inflammation and block blood vessels, which is why calm, limited activity is essential during treatment.
The Best Protection: Prevention
The most effective way to protect your pet is with a monthly heartworm preventive medication prescribed by your veterinarian. Prevention is safe, affordable, and far easier than treating an active infection.
We’re Here to Help
If you’re wondering whether your dog or cat may have heartworm disease—or if you want to ensure you’re doing everything possible to prevent it — we’re here for you.
If you live in Hoover, Vestavia, Homewood, the Birmingham Metro area, or nearby communities, give us a call at Bluff Park Animal Clinic or visit our website to learn more. Our team is happy to help you every step of the way toward keeping your pet healthy and protected.🐾