Five Things You Need to Know About Heartworm Disease and Your Cat

If you think dogs are the only ones who get heartworm disease, I invite you to reconsider. Although dogs are the more natural host for this disease, cats are also susceptible to heartworm infection. It is estimated by the American Heartworm Society that, in any given community, the incidence of heartworm infection in cats is approximately 5% to 15% percent that of dogs who are not on preventive medication.

While the canine and feline versions of heartworm disease share some similarities, there are some striking differences. I discuss these differences below, within the five feline facts pertaining to heartworm disease.

1. The disease targets the lungs
Most dogs with heartworm disease involve many worms and the heart and lungs are the prime targets for damage. In contrast, only one or two worms are typically present in an affected cat1,and the disease takes its primary toll on the lungs. The cat’s immune system goes into overdrive in response to immature heartworms located within the lungs and/or fragments of dying, adult heartworms that flow through blood vessels feeding into the lungs. The result of this immune system activity is a whole lot of inflammation that can wreak havoc within the lungs. The acronym HARD (heartworm associated respiratory distress) is used to describe feline lung disease caused by heartworms1.

2. Common symptoms of heartworm disease
Common symptoms of heartworm disease include:

  • Coughing
  • Rapid breathing
  • Labored breathing
  • Decreased appetite
  • Lethargy
  • Weight loss

In rare cases, more severe symptoms and even sudden death can occur. One of the most surprising symptoms that occurs in cats with heartworm disease, but not in dogs, is intermittent vomiting that is unrelated to eating1.

Not all cats with heartworm disease show symptoms. For those cats who test positive for the disease on routine screening but are free of symptoms, careful monitoring over the course of two to three years (the lifespan of the adult worms) is recommended.

3. Diagnosing heartworm disease
The most reliable screening test for heartworm infection in dogs is called an antigen test. Performed on a blood sample, it detects microscopic particles (antigen) produced by adult, female heartworms. In cats, it’s not unusual to have a male only population, given that often only one to two worms are present. Additionally, many cats develop symptoms and are therefore tested when the worms are immature. For these reasons, cats with active heartworm disease often have negative antigen test results. However, if the antigen test is positive, this is proof of heartworm disease.

Because antigen tests could be negative in cats with heartworm disease, it is very important to pair the antigen test with a blood antibody test in those cats showing symptoms. The presence of antibodies means that the cat’s immune system has been exposed to the heartworm parasite. A negative antibody test is good evidence that a cat has not been infected. On the other hand, a positive antibody test can mean that either there is an active infection, or the cat experienced heartworm infection in the past. Antibody levels can remain elevated long after the heartworms have died.

The American Heartworm Society recommends that initial screening for feline heartworm disease includes both antigen and antibody testing. If results support the possibility or probability of heartworm disease, ultrasound of the heart and X-rays of the chest to evaluate the lungs are recommended to confirm or deny the diagnosis.

4. There is no treatment to get rid of feline heartworms
Unlike the canine version of this disease, feline heartworm infection is not specifically treatable. Melarsomine, the drug of choice to kill adult heartworms in dogs, is toxic for cats. For this reason, feline heartworm disease is considered to be manageable rather than treatable. Corticosteroids such as prednisone or prednisolone are commonly used for their potent anti-inflammatory effects. Treatment often continues until the adult worms have died and are cleared from the lungs (a two to three year process).

5. Prevention of heartworm disease
Disease prevention is the best strategy, particularly in areas where mosquitoes proliferate. The American Heartworm Society recommends orally administered, once a month preventive medication, beginning at eight weeks of age for all cats in heartworm-endemic areas. Talk with your veterinarian about heartworm in your area. Depending on the weather in a particular region, preventive medication may be recommended seasonally or year-round.

An indoor feline lifestyle is not a guarantee against heartworm infection. In fact, one in four cases of heartworm disease occur in cats that live exclusively indoors1.

  • Has my cat been screened for heartworm disease?
  • Should my cat be on heartworm prevention? If so, which months of the year should it be given?
  • What symptoms should I be watching for?


  1. "Summary of the Current Feline Guidelines for the Prevention, Diagnosis, and Management of Heartworm (Dirofilaria Immitis) Infection in Cats." (2014): American Heartworm Society. Web.

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Wednesday, March 22, 2017

Everything You Need to Know about Heartworm Disease and Prevention

Heartworm disease is a serious condition that affects the lungs and right side of the heart of dogs, cats and other animals. As a pet owner, you have undoubtedly been warned about the seriousness of this disease and the necessity to ensure your beloved pet is heartworm free. From taking your pet to your vet on a regular basis and keeping an eye out for any of the heartworm symptoms listed below, you are being a responsible pet owner and doing everything in your power to keep your pet healthy and happy.

Because dogs and cats of any breed are susceptible to heartworm disease, it is important for all pet owners to familiarize themselves with the characteristics of the disease as well as what can be done to prevent it.

Everything You Need To Know About Heartworm Disease

Most pet owners would agree that protecting their pets from preventable health risks is an easy-to-keep priority. And while exercise, eating right and drinking plenty of water can help to keep pets healthy and active for many years, preventing deadly heartworm disease should also be among your top priorities. Understanding how heartworm disease is transmitted, how it affects pets’ health and how you can prevent your pets from contracting heartworm will help you to keep it top of mind.

How Heartworm Is Transmitted

Heartworm is a parasite that can enter into a dog’s or cat’s bloodstream by way of a mosquito bite. Some mosquitoes can carry heartworm larva on their needle-like mouth parts from biting animals that are already infected with the disease. When an infected mosquito bites your pet, the heartworm larva enters her bloodstream. Infected pets are not contagious, so remember that heartworm is not spread from pet to pet.

How Heartworm Affects Pets

The heartworm larva begins to mature in an infected pet’s bloodstream before taking up residence – and growing to maturity – inside the pet’s heart. As the heartworms multiply and grow, they obstruct blood flow, damage the heart and adversely affect breathing and circulation to vital organs. Although infected pets may not immediately show any symptoms of heartworm disease, eventually they will cough, become lethargic, lose their appetite and breathe heavily. Advanced stages of heartworm disease can lead to death. However, there are a number of things you can do to prevent heartworm disease from affecting your pets.

How You Can Prevent Heartworm

Preventing heartworm disease from affecting your beloved pets is a fairly easy task. Giving your pets a monthly chewable tablet of a preventive medicine is by far the most effective form of heartworm prevention. As well, keeping pets out of mosquito-infested areas and waterways (where mosquitoes breed) in warm weather can reduce the risk of heartworm by preventing the likelihood of mosquito bites.

Additionally, you can drain standing water from areas where your pets spend time and empty outdoor water dishes regularly. These simple tasks will keep mosquitoes from breeding and living in your pets’ happy places and also reduce the risk of bites from mosquitoes that are infected with heartworm.


Symptoms of heartworm can quickly progress and lead to life-threatening conditions for your dog, so early detection is key to treating this disease. Your veterinarian may prescribe medication to treat the infection and lessen the severity of symptoms. In addition, it is important to limit your dog’s exercise, as physical activity can worsen the damage that heartworm causes to the lung and heart.

Unfortunately, there is no approved medication to treat heartworm in cats, so prevention is critical. If your cat does test positive, a veterinarian may recommend hospitalization to manage symptoms and stabilize your cat. Continued administration of preventative medications is essential to ensure that your cat does not develop new infections that worsen the severity of the disease.

With temperatures warming up for the summer, mosquitos will become increasingly abundant leading to more transmission of this disease. If you do not use heartworm preventatives for your cat or dog already, now is a great time to start. It may just save their life!

Unfortunately, outdoor cats are more at risk, as they are more exposed to mosquitoes. Also, cats living in the south, southeast, midwest, and northeast United States. That said, heartworm disease has been reported in all 50 states—so it’s out there!

The best way to keep your cat safe is by keeping them indoors and using heartworm preventative for cats. However, please know that mosquitos are adept at coming inside, and I’ve even found them in my house in the middle of Minnesotan winters! Heartworm medications like Advantage Multi, Heartgard, and Revolution (listed in alphabetical order) can be safely used year-round in cats to help protect your cat.

For more great information specifically regarding heartworm in cats, check out the American Heartworm Society.

Watch the video: Heartworm Disease - Plain and Simple (October 2021).

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