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What is Heartworm Disease in Cats?

Did you know that even indoor cats can become infected with heartworm? Our Corpus Christi veterinarians explain the dangers of heartworm disease, including symptoms, treatment, and prevention.

What is heartworm disease?

This bloodborne parasite (dirofilaria immitis) lives in infected animals' hearts or nearby large blood vessels. Female worms are 6 to 14 inches (15 to 36 cm) long and 18 inches wide (3 mm). Males are about half the size of females.

Though heartworm disease is more commonly found in dogs than cats, cats do get heartworm disease. Usually, cats have fewer adult worms than dogs (typically less than six). The good news is that heartworm in cats is not contagious.

What are the symptoms of heartworm disease in cats?

While heartworm disease is often undiagnosed in cats, even immature worms can do extensive damage by causing heartworm-associated respiratory disease (HARD) and issues in the immune system.

Heartworms can even move to other parts of the body, such as the spinal cord, eye, or brain. Severe complications including blood clots in the lungs and lung inflammation can happen when adult worms die in the cat’s body.

Symptoms of heartworm disease may be subtle or apparent, and there are few, if any, early signs. Symptoms such as these may appear:

  • Asthma-like attacks
  • Difficulty walking
  • Fluid accumulation in the abdomen
  • Fainting or seizures
  • Coughing
  • Periodic vomiting
  • Lack of appetite
  • Weight loss

In some cases, collapse or sudden death is the first sign of heartworms in cats. And, while heartworm medication for dogs may be effective, it cannot be used on cats. As a result, while this condition can be managed in cats, there is no clinical treatment. Prevention is the best form of defense for cats.

What causes heartworm disease?

A mosquito feeds on an infected cat, then picks up immature heartworm larvae which develop for 1o to 30 days inside the mosquito’s gut before entering its mouthparts. The infected mosquito then bites the cat and injects its infected larvae.

These larvae travel through the bloodstream to the pulmonary arteries and the right side of the heart, where they mature into adult heartworms capable of reproducing in 6 to 7 months. A new crop of larvae is born approximately 8 months after the cat has been infected and lives in the cat's blood for approximately one month.

While dogs have been known to have several hundred heartworms in their bodies, few of these larvae are usually found circulating in this area by the time testing occurs. Most do not survive to the adult age, as the cat is not a natural host.

Heartworms are transmitted through mosquitoes - not from one cat to another or from an infected dog to a cat directly. The risk of infection is highest when mosquitoes are present in the environment and actively feeding, and indoor cats are not immune; an infected mosquito may easily get into the house and infect a cat.

Can heartworm in cats be cured?

Because heartworm disease in cats is serious, progressive, and potentially fatal, the earlier your cat is tested and diagnosed, the better. Your veterinarian will take a small sample of blood from your cat, which will then be tested for heartworm proteins.

We process heartworm tests in-house at Everhart Animal Hospital, allowing us to provide same-day results. If a cat tests positive, additional tests, such as x-rays or ultrasounds, may be ordered. While there is no approved drug to treat heartworms, the goal is to stabilize your cat and develop a long-term management plan for the disease.

Treating heartworm infections in cats is risky. Though the heartworms may clear up, the damage caused may be permanent. If worms have been detected in the lungs, your vet may recommend chest x-rays every 12 months or so.

If mild symptoms are noted, small doses of prednisolone may be necessary to reduce inflammation. Severe heartworm disease could mean hospitalization so your cat can receive intravenous fluids, antibiotics, drugs to treat organ issues, and surgery in some cases.

How can I prevent heartworm disease?

Starting at eight weeks of age, we strongly recommend that all cats receive year-round heartworm preventives to be taken orally monthly in mosquito-infested areas. In areas where mosquitoes are seasonal, preventive measures should be implemented for at least six months of the year. Prevention is simple and safe.

Our Wellness Plans includes annual and six-month health checks. We also carry a full line of parasite prevention products to protect your pet from heartworm and other common parasites.

Do you suspect your cat has heartworm? With our in-house laboratory, we can provide same-day testing and results. Book an appointment today.

New Patients Welcome

Everhart Animal Hospital is accepting new patients! Our experienced vets are passionate about the health of Corpus Christi companion animals. Get in touch today to book your pet's first appointment.

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