Heartworm Symptoms in Cats – What You Need to Know

Where do Heartworms Come From?

The Mosquito

Yes, that’s where it all begins, with the mosquito. Baby heartworms are transmitted through a mosquito bite into the bloodstream of a dog or a cat. A mosquito first bites an infected animal, from coyotes, ferrets, wolves and other creatures may already have infected blood which the mosquito drinks. When a mosquito lands on another animal for a blood meal, the microscopic baby heartworms from the previous meal are transferred into the new bite wound. Once inside of a new host, It takes approximately 6 months before the larvae become adults, and that’s when the real trouble begins.

Dog Vs Cat Heartworm

In dogs, heartworms travel through the blood and wind up directly into the heart muscle. There may be several hundred heartworms inside of a dog, and you can understand the trouble they would cause by restricting blood flow, damaging arteries and usually killing a dog if left untreated. But for cats, it is an entirely different disease.

Since heartworms are genetically made to infect dogs, they don’t do so well in cats. A cat’s body rejects heartworms, and very few, if any, survive until they reach adulthood. If heartworms do survive, only 2 or 3 may take residence in the heart of a cat, unlike the hundreds that would infect a dog. In most instances, even if your cat is infected, you may never know and there may be no lasting problems.

Heartworm Symptoms in Cats

However, some heartworms may actually make it to adulthood and live within a feline’s heart. When this occurs, here are some of the things to look out for that may give you a clue.

  • Coughing — More like a persistent cough than just a couple of coughs here and there from swallowing a hairball.
  • Vomiting — Again, vomiting would have to be persistent and not a very seldom occurrence.
  • Lack of Appetite — Cats are finicky, so most of them, at some point or another, have a lack of appetite. Sometimes even when preparing them favorite homemade food. But if not eating for extended periods of time comes with noticeable weight loss, then that could be a symptom to keep an eye on.
  • Fainting, Seizures, Difficulty Walking — Any of these conditions may be caused by a lack of blood flow from blocked arteries. Under any circumstance, this would warrant a trip to the vet.
  • Death — Unfortunately, one of the symptoms of heartworm in cats is sudden death. There may be no other noticeable symptoms when this happens.

The Cure for Heartworms

Here is where it gets tricky. Unlike dogs, there is no drug that can kill heartworms in cats. Heartworms are not the same as tapeworms or roundworms; click here for more info on the best cat dewormer. The best that can be done with a severe case of heartworms is to operate and actually remove the heartworms by hand. Although an expensive and taxing procedure for both you and your purr buddy, you may not have a choice. But don’t get disheartened at those thoughts, because as they say, cats have 9 lives.

In the vast majority of cases, cats can be stabilized and monitored by you and your vet while the cat’s own body takes care of the problem itself. Drugs can be given to combat any symptoms of discomfort, and since heartworms don’t have a long lifespan in cats, the chances are great that if your cat is infected with heartworms, they will eventually die off without any medical help.


The only real way to keep your cat from getting heartworms is through prevention. Like they say, an ounce of prevention is worth a pound of cure, and in this case, those words ring true. There are heartworm tabs for cats that can be administered once per month, and the formula will kill off any larvae that make it inside of your cat’s body. Although all cats are susceptible, outdoor roaming cats have the most chance of becoming infected.

Heartworms are in all 50 states, with a greater concentration of infections in the warmer parts of the country, with most cases reported during the summer months. Prevention is the key to controlling heartworm for a happy and healthy cat all year long.

Guest Post by Mary Nielsen

Mary Nielsen founded FelineLiving.net and is a passionate cat lover, blogger, and part-time music teacher. She founded her blog to share her ups and downs of being a pet parent to a bunch of adorable kittens and cats. When she is not playing with them or teaching, you can find her experimenting in the kitchen.