Heartworms

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Read Time: 6 minutes

What Are Heartworms?

Heartworms are a type of parasitic worm that resembles a thread in appearance. They can infect a variety of animals, although they are most commonly found in dogs. They can grow up to a foot long and live in the heart, lungs, and veins of affected animals. Despite their name, heartworms can cause organ damage in not just the heart, but also the lungs and veins.

Can Cats Get Heartworm?

While heartworm most commonly affects dogs, cats can get heartworm, too. They’re considered atypical hosts and when cats do get heartworm, there are usually fewer worms at once, but there is still a risk to the cats’ health if they get heartworms.

Unlike in dogs, there is no treatment that can kill adult heartworms in cats. Heartworm prevention is therefore essential for the life and health of cats.

How Do Cats Get Heartworm?

Cats get heartworm through mosquito bites. Baby worms are transmitted to the mosquitoes when they bite infected cats or other animals. Heartworms can only live in the mosquitoes for part of their lives and must move to a larger host in order to grow to adults. The mosquito would then bite the cat, which allows the worms to transfer to the cat’s body, where they would, if the cat didn’t get heartworm prevention, grow to adult size and have young of their own.

How Can My Cat Be Tested for Heartworm?

A veterinarian can test your cat for heartworm even when it is still in its early stages. Often times, we can identify heartworm before your cat even shows symptoms.

The test involves taking a small blood sample, which the veterinarian will then test for heartworm proteins. Further testing may be ordered if the vet detects any signs of heartworm. Testing should be done once a year. If your cat is less than six months old, the first test should be after six months of heartworm prevention and then on an annual basis after that.

How Is Heartworm in Cats Treated?

Heartworm in cats is treated by preventing baby heartworms from growing into adults. There isn’t a treatment for heartworms once they have become adults, so it’s important that cats receive the monthly heartworm prevention medicine.

How Does Heartworm Prevention Medicine Work?

Heartworm prevention medicine kills any heartworm larvae that have infected your cat’s body within the last 30 days. A monthly dose of heartworm preventative simply prevents the existing heartworms from reaching adulthood. Heartworm prevention only works on larval heartworms, however, and won’t kill any existing adult heartworms.

How Are Adult Heartworms Treated?

Because cats are atypical hosts for heartworms, if they are allowed to grow to adulthood, there’s no treatment that can kill them. Once a cat has adult heartworms, the only thing vets can do is treat the symptoms, which are usually respiratory in nature and often resemble asthma.

When Should I Start Heartworm Prevention for My Cat?

You should start heartworm prevention in your cat as early as 6-8 weeks old. Because your kitten is still growing, the dosage will need to increase as it gets older. Kittens don’t need to have a test first because it can take up to six months for a pet to test positive for heartworms after the initial infection.

What Heartworm Medication Is Best for Cats?

Does My Indoor Cat Need Heartworm Prevention?

Even if your cat is primarily an indoor cat, it should still be on heartworm prevention. No home is completely insulated from the outside. An indoor cat may still spend some time outside, even unintentionally, and mosquitoes can get inside the house.

Do I Need a Prescription for Heartworm Prevention?

Heartworm prevention is usually a prescription issued by your vet. This is so that the vet can first conduct a heartworm test in your pet.

What Are Signs and Symptoms of Heartworm in Cats?

The signs of heartworm in cats vary from subtle to very serious and can include:

• Coughing
• Asthma attacks
• Weight loss
• Loss of appetite
• Vomiting
• Difficulty walking
• Fainting
• Seizures
• Abdominal fluid accumulation

Some will show symptoms right away, while others show no symptoms at all until they collapse and die.

How Dangerous Is Heartworm in Cats?

Heartworm in cats is dangerous because, if not prevented in its early stages, it can be fatal. It can also cause respiratory symptoms that are similar to asthma. Once heartworms have grown to adulthood, there is no treatment that can cure cats.

Does Heartworm Cause Heart Disease in Cats?

Heartworm doesn’t usually cause heart disease or heart failure in cats. Instead, it primarily affects the cat’s respiratory system, causing symptoms such as coughing and difficulty breathing.

Can Heartworm Be Fatal?

Heartworm in cats can be fatal if it is left untreated. Because cats are an atypical host for heartworms and the symptoms are usually respiratory, heartworm can often be misdiagnosed as asthma or other respiratory conditions. There is no treatment for heartworm in cats once the worms have reached the adult stage.

What Other Conditions Are Caused by Heartworm?

Heartworm in cats primarily causes respiratory issues that resemble asthma. Heartworms can cause damage to the cat’s lungs and airways at every stage from larvae to adult. Heartworm can also cause lethargy, weight loss, and loss of appetite. In the worst cases, heartworm can cause death.

How Can I Prevent Heartworm in My Cat?

Especially because heartworm in cats is easily misdiagnosed and there is no treatment for it, it’s vital to prevent heartworm in the first place. You can protect your cat from heartworm by taking your cat to a vet as early as possible for testing and for a prescription for a monthly heartworm preventative medication, even if your cat is exclusively an indoor cat.