Content Reviewed by an Essentials PetCare Veterinarian

Heartworms in cats are more serious than heartworms in dogs. Why? Treating heartworms may be difficult for dogs, but there is no cure at all for heartworms in cats. This is why prevention and testing are key.

If you have ever thought of skimping on your cat’s heartworm medication for a few months, continue reading to understand the dangers of heartworms in cats – and how to protect your feline friend.

What are Heartworms?

Heartworms are not to be taken lightly. The word may make you squirm – for good reason. These parasitic roundworms take up residence in your pet’s arteries. 

They cluster around the lungs and heart, causing damage to the organs that cannot be remedied.

What Causes Heartworms?

The roundworms that cause heartworm are transmitted through infected mosquitoes. The worms grow from 6-12 inches long inside the blood vessels. You can see why this might cause clogging. 

The subsequent inflammation leads to thickening of the blood vessel walls, which can become scarred. The inflammation and scarring may increase blood pressure to the point of heart failure.

Can Cats Get Heartworm Disease?

It is actually more rare for cats to contract heartworm disease than dogs. Cats are not considered a preferred host for the worms as their bodies typically mount a strong immune response and prevent the worms from maturing into adults. Many cats also spend the majority of their lives indoors.

However, keep in mind that if you do have an outdoor or indoor/outdoor cat, you will need to be especially vigilant about their heartworm medication! And even if your cat does stay inside, we all know that an occasional mosquito (or 10) can drift in… 

How Do Cats Get Heartworms?

Cats and dogs can both get heartworms through infected mosquitoes. Mosquitoes basically act as a carrier between different infected animals. How does this work?

When a mosquito bites an infected animal, they take in the larvae with the blood. After 10-30 days, the larvae have developed enough to travel through the mosquito’s bite to other animals.  This transmission occurs the next time the mosquito feeds on another animal.

Is Heartworm Disease Different in Cats?

Heartworm disease in cats does differ from dogs in several important ways. For one, heartworms usually can’t grow to full maturity in cats due to the cat’s strong response by their immune system. Their immune system will actually produce antibodies that destroy the immature forms called microfilariae. This prevents the microfilariae from ever developing into mature worms.

Sounds like positive news? Unfortunately, it isn’t. In addition to destroying the immature heartworms, this strong immune response also causes severe inflammation in the lungs and airways leading to a chronic medical condition called Heartworm Associated Respiratory Disease (HARD).Also, the small worm size and population mean that it’s much trickier to diagnose heartworm disease in cats. You may not even notice for months or years. And once a cat does contract heartworm disease, they may only have years to live. Remember, there is no cure for cats.

What are the Symptoms of Heartworm Disease in Cats?

In the early stages, it can be hard to discern heartworm symptoms from other common feline ailments, from diabetes to hairballs. Your cat may show any of the following signs:

  • Vomiting – intermittent, may include blood
  • Coughing
  • Gagging
  • Rapid, difficult breathing
  • Loss of appetite
  • Diarrhea
  • Weight loss
  • Lethargy
  • Sudden death

As you can see, this could mimic other illnesses. In general, cats have sensitive digestive symptoms, so they may vomit semi-frequently. This is why keeping your cat on regular heartworm prevention is so important

Will You See Heartworm in a Cat’s Poop?

Since heartworms live in the blood vessels, they will not be passed in your pet’s feces.  This is why relying on seeing them will not do any good as they aren’t found in the feces or on fecal tests like intestinal worms are. 

How Do You Test a Cat for Heartworms?

As we’ve discussed, it is more difficult to detect heartworm disease in cats. You can have your cat’s blood tested for antigens or antibodies that indicate the presence of heartworm. But these test results are not always conclusive.

Most likely, the veterinarian will need another way to confirm. This is usually accomplished through an x-ray or an echocardiogram – basically, an ultrasound of the heart. Your veterinarian will be trying to see the inflammation or enlargement of arteries around the lungs or heart. 

You might be able to spot mature heartworms in an  echocardiogram, but this is another way that diagnosing heartworm disease is tricky in cats. The number of heartworms circulating can be so low that they might not make an appearance during the scan.

Can You Treat Heartworm Disease in Cats?

Unfortunately, the drug used to treat heartworm disease in dogs causes severe side effects for cats, including death. An alternative drug has not been found for cats. Some cat owners agree to surgical removal of the heartworms, but studies have demonstrated a 60% survival chance for that route.

As you can see, there is no solid treatment once your cat has it. Only rarely do cats survive heartworm disease.

How Can You Find Relief for Your Cat with Heartworms?

A cat’s life expectancy with heartworm is 2-4 years. Veterinarians can help you develop a plan to keep your cat comfortable as the symptoms progress. This may include:

  • Corticosteroids for acute attacks of respiratory distress and to reduce regular inflammation
  • Oxygen during crises of the lungs and heart
  • Intravenous fluids to offset dehydration and weight loss
  • Antibiotics to treat secondary infections

How Do You Prevent Heartworms in Cats?

Prevention is the golden ticket if you want to protect your cat from heartworm disease. If you were worried about the cost of heartworm prevention, you can now see that the treatment and consequences are much more worrisome. So, stay up to date on your pet’s heartworm medication and give it monthly year-round! A little goes a long way. 

Essential Tip: Essentials PetCare offers a wide variety of affordable feline testing services and other care packages!