A cat standing on a table at an animal veterinarian clinic with a veterinarian behind it

What You Need to Know About Cat Heartworm Treatment

Cat heartworm treatment is complex and often ineffective, which is why choosing a heartworm preventive is an important task for cat owners.

Feline heartworm disease is a very real risk for your cat that can cause serious health problems and even be fatal. There is good news and bad news. The bad news is that cat heartworm treatment is complex, time-consuming, and often ineffective. The good news is that heartworm disease is almost entirely preventable with the proper medication.

Here are the facts so you can protect your feline friend from this preventable health risk.

What Is Heartworm Disease in Cats?

Feline heartworm disease is caused by heartworms, which can take up residence in your cat’s organs and blood vessels and grow to about a foot long. To better understand heartworm disease, let’s look at:

  • How it affects cats and dogs differently
  • What causes heartworm disease
  • The signs and symptoms
  • How veterinarians test for and diagnose heartworm disease

Heartworm Disease in Cats vs. Dogs

Heartworm disease is a risk for all pet owners, as the disease can impact dogs, cats, ferrets, and many other animal species both wild and domestic. Dogs can be a natural host for these worms and many can live in their organs, growing to maturity. Cats, on the other hand, are not an inviting host for these worms, which means they are likely to have less worms present in their body – but the worms can cause more serious problems in cats than dogs.

Cats rarely have as many heartworms as dogs, and these worms rarely live long enough to become adult or full-sized. That sounds like it would be a good thing, but the worms that aren’t fully mature still cause heartworm associated respiratory disease (HARD). Plus, dog heartworm treatment does not work for cats, so the consequences of a feline infection are more serious and harder to manage.

A mosquito near water

How It’s Contracted and Transmitted

There is one way for a cat to get heartworms: through a mosquito bite. About 30 different species of mosquitoes can carry heartworms and, if one of those mosquitoes feeds on a heartworm-infected animal and then bites an uninfected cat, they can transmit the disease.

The mosquitoes are actually transmitting heartworm larvae between cats (not the full worms). The larvae then travel through the cat’s bloodstream into the heart, where they live, grow, and reproduce. Cat’s bodies are inhospitable hosts, so the worms rarely reproduce in great numbers, but the adult worms can live in a cat for two or three years.

Cats cannot contract heartworms directly from another infected animal – only through a mosquito. This means even cats that live indoors are at risk (because mosquitos can make their way inside). Heartworm disease has appeared in all 50 states, so even cats in communities that don’t have a prevalent mosquito problem can contract heartworm disease.

Signs and Symptoms of Heartworm Disease

It’s not always easy to tell if a cat has heartworms. Sometimes the signs of heartworm disease and symptoms are very subtle, such as occasional vomiting, loss of appetite (or weight loss), and coughing. More serious signs include fainting, difficulty with movement or walking, seizures, and a build-up of fluid in the abdomen. Sometimes, you won’t know a cat has heartworms until they die from them. This is why prevention of cat heartworms is so important.

Testing and Diagnosis of Feline Heartworm Disease

Regular testing is good practice because the signs and symptoms of heartworm disease in cats can be hard to spot. Using a small blood sample from your cat, a veterinarian can do an antigen test and/or an antibody test, which will show if your cat has been exposed to heartworm larvae. The antigen test will only be effective about five months after your cat has been bitten by an infected mosquito, so even a clear antigen test isn’t a guarantee that your cat doesn’t have heartworms.

Your veterinarian can also do an ultrasound or x-ray to see if there are heartworms in the cat’s body. Diagnosing heartworm disease in cats is a complex and involved process that can be expensive.

Cat Heartworm Treatment and Prevention

If your cat is diagnosed with heartworm disease, it’s important to understand the following:

  • Dog heartworm medication is dangerous for cats
  • Cat heartworm treatment options are limited
  • Prevention is the best way to protect your cat from heartworms

Dog Heartworm Medication Can’t Treat Feline Heartworm Disease

While there is a heartworm medication for dogs who are experiencing the disease, there is no such medication for cats. The drug used for dogs causes such serious side effects in cats that it is not recommended for use in felines, as it is likely to do more damage than good.

Cat Heartworm Treatment Options Are Limited

If a cat is diagnosed with heartworms, there are a few options for how to proceed. Your veterinarian will talk you through these options and help you make the best decision for your pet’s specific case and needs.

Cat heartworm treatment might mean simply treating the symptoms in order to keep the cat alive and comfortable, in the hopes the cat (the host) will outlive the worms (the parasite). Because these worms can live for up to three years in cats, cat heartworm treatment is a demanding and long process. The worms can impact a cat’s respiratory function, so your pet may need periodic treatment with fresh oxygen. They will likely need many additional medications to treat other symptoms. Even with treatment of the symptoms, though, cats can still die suddenly from heartworm disease.

Another, less common cat heartworm treatment is surgical removal of the worms. Almost half of cats die during this procedure, so it’s only used when the cat is unlikely to survive the disease without removal.

Cat Heartworm Prevention Is the Best Approach

Because this disease can be fatal and there is no cat heartworm treatment, prevention is crucial to your cat’s health. Luckily, there are plenty of cat heartworm prevention medications available and these can be very effective.

The American Heartworm Society not only encourages cat owners to give their pets a preventive medication every month of every year, but they also encourage testing every 12 months. Early detection of heartworms can improve the prognosis for your cat, so testing with some regularity is another way to protect your feline friend from heartworm disease.

How to Choose a Cat Heartworm Prevention Medication

There are a number of factors to consider when choosing a new medication for your cat. Since there is no cat heartworm treatment medication, the preventive medication will be an extremely important choice. Additionally, you’ll be giving this to your cat consistently, so it’s important that you find a medication that you can afford and that you trust.

Heartworm prevention options, sometimes referred to as “HWPs,” are plentiful. Here are factors to consider when choosing what kind of preventative medication will be best for your cat:

  • Reputation and approvals
  • The regularity and simplicity of administration
  • Cost
  • Other benefits of the medication

Choosing a Trustworthy Heartworm Medication for Your Cat

The heartworm prevention medications that are most safe and high-quality are usually only available with a prescription from your veterinarian. Over-the-counter heartworm prevention medications for cats are rarely as reliable and effective as those that require a prescription. Furthermore, the best products will also be approved and recommended by your veterinarian. Your cat’s doctor should definitely be involved in helping you choose a heartworm prevention medication.

A cat biting a package of medication in the form of pills that a woman is showing it

How Often and in What Way Is the Medication Administered?

Some heartworm preventive medications for cats are available as an oral pill that needs to be swallowed or chewed by your cat. Other preventatives have a topical application. Most prevention products are applied monthly, but this can vary somewhat.

The method and regularity of administration for your cat’s heartworm preventative will be an important factor in your choice. If you know your cat absolutely hates swallowing pills, you might want to try a topical treatment or a chewable pill. Or, if you’re extremely busy and worry about giving your pet their meds each month on time, you might want to look into a treatment that requires less consistent application. You need to find a heartworm prevention method that works for you, your cat, and your lifestyle. Again, your veterinarian can discuss options with you and help you decide.

Cost Will Also Be Relevant for Your Cat’s Heartworm Prevention Meds

Because you have to give this medication to your cat consistently for the rest of their life, it needs to fit into your budget. While we never like to make decisions based on money alone, cost will be an important factor when choosing a good heartworm medication for your cat. Fortunately, you don’t have to sacrifice efficacy – less expensive medications are often just slightly more inconvenient to give to your cat or require more consistent application.

Pro tip: Once you have your prescription, you can purchase your cat’s heartworm medication as a subscription or autoship (never run out!) from popular online pet sites. You can even fill the prescription at large warehouse stores like Costco or Sam’s Club at a discounted price.

Some Heartworm Medications Protect Against Other Pests

Some heartworm medications will also prevent roundworms and hookworms, or even protect your cat against fleas and ticks. This can be beneficial because it reduces the number of treatments you’re having to administer to your cat without sacrificing their safety and comfort. Fleas and ticks can cause a number of health issues for cats, not least of which is trouble with their skin and fur, so prevention is crucial for these bugs as well. The additional protections provided by a heartworm medication might be a selling point for many cat owners.

Cat Heartworm Treatment Is Difficult, so Focus on Prevention

Above all, cat heartworm prevention medication should be affordable for you, easy to administer, and effective in preventing heartworm disease in cats. Choose a medication that will keep your cat safe, because cat heartworm treatment is much more difficult than prevention.