A young Asian girl nuzzles noses with a tabby kittenA young Asian girl nuzzles noses with a tabby kittenA young Asian girl nuzzles noses with a tabby kitten
Barks & Mewsings

The Trupanion blog

Heartworm Awareness Month: A Prevention Guide for Pet Owners

By: Brianna Gunter

A cat and dog in harnesses side by side in a field

Heartworm (Dirofilaria immitis) is a serious but preventable parasite in dogs and cats alike, yet thousands continue to be infected every year. While heartworms in pets can be gross to think about, it’s a subject all pet owners need to be well versed in. Seeing as April is National Heartworm Awareness Month in the United States, now’s the perfect time to brush up on your heartworm prevention knowledge and make sure you’re doing what you can to protect your pet.

What is heartworm disease?

Heartworm disease, also known as heartworm infection or dilofilariasis, is a potentially fatal illness in pets caused by a parasitic worm infestation. Heartworms are long and skinny, often reaching around a foot long. After entering the body, they typically migrate to the heart, lungs, and blood vessels. Left untreated, heartworm disease can lead to organ failure and ultimately death.

For cats, symptoms may develop 3-6 months after infection, while those in dogs may set in between 5 and 7 months. However, it’s worth noting that many pets with heartworm are asymptomatic. Signs depend on the number of worms present, and the infection may only be noticed in screening tests.

“The risk of death from heartworm disease is higher in cats that are older,” says Trupanion veterinarian Dr. Sarah Nold. “The longer a dog has a heartworm infection, the greater their risk of illness and death.”

While dogs and cats are most synonymous with heartworm disease, other mammals like ferrets, foxes, and coyotes can also be affected. On rare occasions, humans have been diagnosed with heartworm infection.

How do pets get heartworms?

Both dogs and cats get heartworms exclusively via mosquitos. After biting an infected animal, a mosquito can then transmit microfilariae (small larva) into the bloodstream of its next host.

As for people with pets (particularly cats) who don’t venture outdoors, Nold says prevention steps are still necessary.

“Even if your cat is indoor only, if an infective mosquito can enter your home your cat can still become infected with heartworms,” she explains. This applies to dogs that are mostly indoors as well.

It’s worth noting that although pests like mosquitos have stronger populations in some areas over others, all pet owners should nevertheless take steps to prevent heartworm infection regardless of their location. According to the American Heartworm Society (AHS), “heartworm is considered at least regionally endemic in all 48 of the contiguous states, as well as Hawaii, Puerto Rico, the Virgin Islands and Guam.”

Quick facts from the American Heartworm Society

  • More than 1 million U.S. pets currently have heartworms.
  • A 2019 AHS survey of 6,000 veterinary practices found heartworm diagnosed in all 50 states.
  • Adult heartworms can live 5-7 years in dogs and 2-4 years in cats.
  • Dogs are more likely to get heartworm disease than cats.
  • Infected dogs may have 30+ worms, while cats usually have 6 or fewer.
  • 25% of heartworm-infected cats are indoor cats.
  • By the time heartworm infections in pets are discovered, it may be too late to prevent severe organ damage or death.

Heartworm prevention for dogs and cats

Heartworm disease can be prevented in both cats and dogs with the use of monthly medications. It’s important to talk with your veterinarian about which one may be the best choice for your particular pet.

“There are oral, topical and injectable (dogs only) products available,” Nold says. “How often your pet takes heartworm prevention depends on the product used, many are given monthly but some can be given every 6 or 12 months (dogs only). Your veterinarian will help you determine which product is best for your pet.”

Signs of heartworm infection

A cute brown and tan puppy is held during a vet exam.

Wondering what are the signs of heartworm infection in pets? They can be subtle, especially in earlier stages. Signs of heartworm may also be different between cats and dogs.

“Many cats with heartworm infections are asymptomatic and eventually clear the infection on their own,” Nold says. “If cats have symptoms of heartworm disease, they are usually more severe than in dogs. Dogs with a small number of heartworms may have no symptoms.”

According to Nold, the most common signs and symptoms of heartworm include:

  • Difficulty breathing
  • Coughing
  • Vomiting (more common in cats)
  • Neurological signs / changes in behavior
  • Exercise intolerance / severe lack of energy (more common in dogs)
  • Weight loss (more common in dogs)

Advanced stages may also result in sudden death. If you suspect heartworm disease in your pet, seek veterinary care immediately.

Heartworm treatment

Your pet’s heartworm treatment options depend on whether they’re a cat or dog, and how advanced the infection is. Heartworm treatment for dogs will typically include medication to kill adult worms. Your veterinarian may also advise restricting your dog’s levels of exercise during treatment.

In rare cases, surgery may be necessary to remove large infestations or heartworms that are posing an immediate threat.

As for cats, there are currently no treatments that are considered safe for feline heartworm disease. According to Nold, heartworm treatment for cats is not currently recommended, as it is associated with significant side effects and risk.

“Often the best choice for cats is to allow time for them to ‘self-cure,’” she explains. “In cases where treatment is necessary, surgical removal of heartworms has been used, but this comes with risk as well.”

Does pet insurance cover heartworm?

Because heartworm disease is considered a highly preventable illness, Trupanion pet medical insurance policies do not cover it. Instead, it is strongly recommended that all pet owners practice routine heartworm prevention and understand the how serious parasite infestations can be.

Learn more about your pet’s health and important parasite prevention tips in our Pet Care guide!

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Welcome to the Trupanion blog. A place to celebrate pets, pet health and medical insurance for cats and dogs.

This blog is designed to be a community where pet owners can learn and share. The views expressed in each post are the opinion of the author and not necessarily endorsed by Trupanion. Always consult your veterinarian for professional advice.

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