What are Signs of Heartworm in Cats?

A cat? Really? Heartworms in a cat? That's right: those same gross, noodle-like worms that invade the lungs and hearts of dogs, also infect cats. The babies from these troublesome creatures can be transmitted to your cat through a mosquito bite. And if your cat isn't on heartworm prevention, these worms can cause serious health problems or even death.

Here's what you need to know about signs of heartworm in cats.

Learn the facts

There are common misconceptions about heartworm disease in cats. Knowing basic facts can go a long way toward caring for your cat:

  • Myth #1: Heartworms are a dog thing. False! Unfortunately, mosquitoes bite cats, too. And when they do, they can pass heartworms on to the cat. In fact, in some parts of the country, heartworm infection rates for cats mimic that of dogs.
  • Myth #2: Heartworms don't infect indoor cats. False! While it's true that outdoor cats are at greater risk, mosquitoes often find their way indoors and may bite any cats they encounter.
  • Myth #3: Heartworms only affect the heart. False! The disease can affect a cat's heart, causing a murmur or irregular rhythm, but symptoms also affect the lungs, usually causing respiratory problems such as trouble breathing or coughing, often mimicking feline asthma.
  • Myth #4: Heartworm testing in cats is very easy and there are many effective treatments options if they test positive. False! While dogs get screened for heartworms annually, cats generally do not. Dogs that test positive can be put on a treatment protocol. The same is not true for cats. That's why prevention is so important for cats.
  • Myth #5: All heartworm preventives for cats are oral tablets. False! Luckily, there are topical options that are convenient, easy to apply and require no pilling.

Be alert to symptoms

Heartworms start affecting a cat's health more quickly than is the case for dogs. The main signs of heartworm in cats are usually breathing problems, which are often confused by cat owners with asthma or airway disease. And unlike dogs, cats can become extremely sick from just one or two worms. Also, the illness in cats is usually not a long, drawn out process. Sometimes the disease will appear to go away quickly or a cat may die suddenly -- another common symptom of the disease.

Infected cats tend to show symptoms such as:

  • coughing
  • wheezing
  • increased breathing rates and/or more difficulty breathing
  • intermittent vomiting
  • poor appetite
  • sudden collapse
  • expanding belly (from fluid build-up).

And while rare, neurological signs, such as seizures or difficulty walking, can also show up.

cat with vet

Remember, cats do not normally pant with their mouths open, like dogs, so it is easy to overlook signs of trouble. Take note of your cat's chest movements. Does the cat's chest expand more outward or faster? If so, make a vet appointment immediately.

Prevent, prevent, prevent

According to the American Heartworm Society, infection in cats is harder to detect than in dogs and there is no approved treatment. Veterinary testing for heartworms in cats varies with the details of the case, but can include any combination of physical exam, blood work, x-rays and ultrasound. Luckily, as harsh and unforgiving as this disease is, it's one of the easiest ones to prevent.

Our pets deserve to live their happiest and healthiest life. Protecting your cat involves annual trips to the veterinarian for checkups as well as regular use of prescribed heartworm prevention.


Related Articles:

Heartworms in cats

Mosquito diseases in dogs

Intestinal Worms in Cats

Bayer Products

  • Advantage Multi® for Cats (imidacloprid + moxidectin) packaging

    Advantage Multi® for Cats (imidacloprid + moxidectin)

    An all-in-one monthly topical that prevents heartworm disease, kills adult fleas and treats roundworms and hookworms.

    Advantage Multi® for Cats (imidacloprid + moxidectin)

    Indicated for:


    CAUTION: Federal (U.S.A) law restricts Advantage Multi® for Cats (imidacloprid + moxidectin) to use by or on the order of a licensed veterinarian.

Advantage Multi® for Cats (imidacloprid + moxidectin)
CAUTION: Federal (U.S.A.) law restricts Advantage Multi® for Cats (imidacloprid + moxidectin) to use by or on the order of a licensed veterinarian. WARNINGS: Do not use on sick or debilitated cats. Do not use on underweight cats. (see ADVERSE REACTIONS). Do not use on cats less than 9 weeks of age or less than 2 lbs body weight. PRECAUTIONS: Avoid oral ingestion. HUMAN WARNINGS: Children should not come in contact with the application site for 30 minutes after application.