Are Heartworms Contagious? The Truth Behind This Pet Health Threat

You may think that since you live in Montana, you don’t have to worry about heartworms, but the disease is increasingly problematic for pets across the country and can lead to life-threatening consequences for your four-legged friend.

"Are heartworms contagious?"

“Can indoor pets really get heartworms?”

"Can humans get heartworms from dogs?"

“Do dogs still need heartworm prevention during the winter?"

These are just a few of the common misconceptions pet owners have, especially when trying to understand the risks and realities of heartworm disease. 

We believe informed pet owners make empowered decisions. That’s why in this post, we'll break down the facts, debunk the myths, and help you protect your beloved pet.

Misconception: Heartworms only affect pets in warm climates.

Fact: While heartworms are transmitted through mosquito bites and are more prevalent in warm, humid climates, they have been reported in all 50 states, including Montana.

According to the Companion Animal Parasite Council (CAPC), heartworm disease is spreading to areas once considered low-risk. This means every pet, regardless of where they live, can get heartworm disease.

Misconception: My pet lives indoors, so they won't get heartworm disease

Fact: Unfortunately, mosquitoes can easily sneak indoors through windows, doors, or vents. Even indoor pets that lounge on a screened porch or patio are not immune. One mosquito bite is all it takes to transmit heartworm larvae, leading to a dangerous heartworm infection in your pet.

Misconception: My pet only needs heartworm preventive measures in the summer

Fact: Mosquitoes thrive in warm weather, but “mosquito season” can fluctuate from year to year, and hibernating mosquitoes can emerge in the winter during warm snaps to infect your pet. Providing year-round heartworm prevention is the safest way to protect your pet from these parasites.

Misconception: Only dogs get heartworms

Fact: Dogs are the pet most commonly affected by heartworms, but cats are also at risk. The disease appears differently in each species:

Heartworm disease in dogs

Dogs are a natural host for heartworms, which means they can mature quickly and reach up to 12 inches long, causing serious damage to the heart and blood vessels. A dog may develop inflammation, respiratory issues, and eventually heart failure if left untreated. Heartworm disease in dogs can be severe but is often preventable.

Heartworm disease in cats

Cats are an atypical host for heartworms, and their immune system reacts strongly when the parasites reach the lungs’ blood vessels. This causes severe inflammation that results in a condition called heartworm-associated respiratory disease (HARD), which is often misdiagnosed as asthma. Even one adult worm can be life-threatening for a cat.

Misconception: My pet is healthy and not affected by heartworms

Fact: Heartworms are silent attackers. Most pets don’t show symptoms in the early stages of infection. In some tragic cases, the first sign of heartworm disease is sudden death. Early detection through regular heartworm testing is crucial:

• Dogs: Starting at 7 months old, dogs should have annual in-house screening that checks for antigens first, and if adult antigens are detected, additional microfilariae testing is performed.

• Cats: Require a combination of antigen and antibody tests, as heartworms are harder to detect in felines.

Other diagnostic tools may include chest X-rays or an ultrasound to confirm the presence of adult heartworms.

Misconception: Administering heartworm prevention to my pet is too difficult

Fact: Heartworm prevention medications come in different forms to make administration easy and convenient. Options include:

• Chewables — If your pet is food-motivated, you can give them their medication as a tasty monthly treat. 

• Spot-on treatments — If your pet tends to be picky, you can administer their medication as a monthly spot-on treatment.

• Injectable — Our veterinary team can administer heartworm treatment every six or 12 months to protect against the parasites.

Misconception: Heartworm prevention for my pet is too expensive

Fact: Providing heartworm prevention is much less expensive than treating your pet for heartworms. Treatment is extensive, takes several months, and is far more risky. 

• Dogs: Treatment for heartworm disease in dogs includes multiple veterinary visits, medications, strict activity restriction, and close monitoring for various complications that may arise.

• Cats: No approved treatment exists. Heartworm prevention is the only safe route.

Investing in monthly heartworm medication is not only affordable but life-saving.

Misconception: Heartworms are contagious

Fact: No, heartworms are not contagious between dogs and humans. Heartworm disease is not spread through contact or shared environments. It can only be transmitted through mosquito bites.

While rare cases of humans getting heartworms from dogs have been recorded, these are extremely uncommon and typically not life-threatening. The concern lies more in protecting our furry family members than in worrying about human transmission.

Frequently asked questions

1. Can a dog fully recover from heartworms?

Yes, with proper care, many dogs recover fully.

2. Are heartworms contagious to other dogs?

No, not directly. An infected dog can’t spread it without mosquitoes.

3. Are heartworms contagious in cats?

No, heartworms aren’t passed between cats.

4. Do I need a prescription for my pet’s heartworm prevention?

Yes, a prescription is required. Download our Emergency Vet Card in case you ever suspect your dog needs treatment immediately.

5. Can humans get heartworms from dogs?

While it’s extremely rare, mosquitoes, not dogs, are responsible for the human cases.

Protect your pet from heartworms year-round

Heartworms are contagious, but only through mosquitoes. They can’t be spread from pet to pet, and although many pet owners ask, can humans get heartworms from dogs? — The answer is no. The real risk lies in leaving your dog or cat unprotected.

Heartworm disease is preventable, and the key is protecting your pet with the right heartworm prevention. Contact our team at Billings Animal Family Hospital to discuss the best plan for your beloved pet.