Heartworms in Dogs: What You Need to Know

By: Chewy EditorialUpdated:

Heartworms in Dogs
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Heartworms in Dogs: What You Need to Know

Heartworm disease in dogs is a potentially deadly condition, but caught early, diagnosed by your vet and treated with appropriate heartworm medicine, your pet can fully recover. Here’s what you need to know about heartworm, how to spot, and tips for how to prevent your pet from becoming affected.

What Are Heartworms?

Heartworms, Dirofilaria immitis, are worms that live in the heart, lungs and blood vessels of infected dogs. The adult worms look like long, white threads, and they can grow up to a foot long. Are you wondering if heartworms are in fact actual worms that are living in your dog's body? Well, yes. As gross as that may sound, these parasites develop from larvae into adult worms. According to the U.S. Food and Drug Administration (FDA), they can live for five to seven years in your dog's body, and grow four to six inches long in males and ten to twelve inches in females. Take a second to digest that information!

How Do Dogs Get Heartworms?

Mosquitoes play a big role in spreading the disease. “A mosquito bites an infected dog and ingests the blood that has the microfilariae—or baby worms—circulating around in it,” Dr. Zaffarano explains.

Those little babies grow into infective larva, at which point, they then go into the mosquito’s mouth parts.

“When [the mosquito] bites another dog or animal, the infective larvae are deposited on the surface of the animal’s skin and enter the new host through the bite wound,” Dr. Zaffarano says.

Heartworms in Dogs
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Treatment of Heartworms in Dogs

Heartworm treatment in dogs is a long and complicated procedure that’s expensive and quite difficult on the dog, Dr. Zaffarno says. It’s centered on eliminating all life stages of the heartworm—microfilariae, larval stages, juveniles and adults—with minimal complications. Your dog’s veterinarian will determine the best course of action for the heartworm-infected patient, of course, but here is a look at what the American Heartworm Society recommends for heartworm treatment.

According to Dr. Zaffarno, a three-dose protocol, including the preventives, is 99.9-percent effective.

Shop all heartworm prescription options for your dog for fast delivery to your door.

Heartworm Prevention in Dogs

How do you prevent heartworms from infecting your dog in the first place?

It starts with keeping your four-legged friend on a safe, FDA-approved heartworm medicine for dogs that contains ivermectin, milbemycin oxime, moxidectin or selamectin, Dr. Zaffarano says. Your veterinarian can prescribe these products for you, and they are highly effective in killing heartworms in their active, pre-adult stage, she says.

The best way to treat this disease is to avoid it in the first place by using heartworm medicine for dogs year-round, no matter where you live, Dr. Kornreich says.

Did You Know...?

Most heartworm preventatives are monthly chewable tablets prescribed according to your dog’s age, size, and weight. Brands your veterinarian might prescribe include:

Shop all heartworm prescription options for your dog.

“Make sure you work very closely with your veterinarian to make sure your pet is tested and put on preventatives appropriately,” he says. “You definitely want to prevent this disease. You don’t want to have to treat it. It’s definitely preventable.”



By: Chewy EditorialUpdated: