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Clearing the Air: Heartworm in Cats Myths Debunked

Clearing the Air: Heartworm in Cats Myths Debunked


As a veterinarian, there is nothing worse than seeing an animal suffer from a disease that could have been prevented, especially when the treatment or symptoms of the disease are so much worse than the preventive. As an integrative veterinarian who prefers holistic treatments whenever possible, I have to say we need to know when we need the safest Western alternatives. We'll discuss the myths and alternatives in this blog post.


Key Highlights

  • Cats can get heartworm disease, and it is more common than previously thought.
  • Cats are not naturally resistant to heartworms, although they may have fewer adult worms than dogs.
  • Indoor cats are still at risk of heartworm disease since they can be bitten by infected mosquitoes.
  • Heartworm disease in cats can be asymptomatic or show signs similar to feline asthma.
  • A negative heartworm test does not always mean a cat is free from the disease.
  • Heartworms can cause more than just cardiac issues in cats, including lung disease.



heartworms in cats

Heartworm disease is a serious and potentially fatal condition that can affect cats. While it is more commonly associated with dogs, recent studies have shown that the incidence of heartworm disease in cats is far greater than previously thought. Many pet owners are unaware of the risks and misconceptions surrounding heartworm disease in cats, leading to myths and misunderstandings about the condition. In this blog, we will debunk six common myths about heartworm disease in cats and provide accurate information about the real damage caused by even immature worms, to help pet owners better understand and protect their feline companions.


7 Common Myths About Heartworm Disease in Cats Debunked

Heartworm disease in cats is surrounded by various myths and misconceptions. Let's take a closer look at these myths and debunk them with accurate information.


Myth #1: Cats Are Naturally Resistant to Heartworms

One common myth about heartworm disease in cats is that they are naturally resistant to heartworms. While it is true that cats are not the natural host for heartworms, they can still become infected with the parasite Dirofilaria immitis. Although cats have an immune system that is more effective at fighting off heartworms compared to dogs, they are not completely immune. Feline heartworm disease is a real concern, with infection rates reported to be 5-20% of the rate in dogs in the same geographic location.

Cats may have fewer adult worms than dogs, but they can still experience the negative effects of heartworm disease, and the only way to prevent it is by protecting them from mosquito bites.


sad cat in bed


Myth #2: A High-Quality Diet Can Prevent Heartworm Disease

Although a high-quality diet is important for optimal health, it does not protect your cat against heartworm. An exuberant immune response is why cats get sick from heartworm disease in many cases, and they will experience more inflammation in their lungs as they react to the infection.


cat eating


Myth #3: Indoor Cats Don't Get Heartworm Disease

Another common myth is that indoor cats are safe from heartworm disease. While indoor cats have a lower risk compared to outdoor cats, they are still susceptible to the disease. Heartworms are transmitted through the bite of an infected mosquito, and even indoor cats can be bitten by infected mosquitoes that enter the house. Therefore, it is crucial to provide heartworm prevention for both indoor and outdoor cats. Heartworm prevention medications can help protect cats from heartworm infection by killing the larvae before they develop into adult worms.

The only way to prevent your cat from being infected is to keep mosquitos from biting. Although mosquitos can be repelled, it is difficult to ensure they do not bite your cat.

Almost 1/4 of cats diagnosed with heartworm disease were categorized as indoor-only (3).


cat looking in the window


Myth #4: Heartworm Disease Is Asymptomatic in Cats

Some cat owners mistakenly believe that heartworm disease is always asymptomatic in cats. While it is true that some cats may not show any clinical signs, others can experience symptoms related to respiratory disease and distress. Common clinical signs of heartworm disease in cats include coughing, wheezing, and difficulty breathing. These symptoms can be easily mistaken for feline asthma. Additionally, some cats may experience weight loss and a decreased appetite. It is important to monitor your cat's health and seek veterinary care if you notice any of these symptoms, as early detection and treatment can improve the outcome for your cat.


cat is about to cough


Myth #5: A Negative Test Always Means No Heartworm Disease

Another myth about heartworm disease in cats is that a negative test result always means the cat is free from the disease. While heartworm tests are an important tool for diagnosing heartworm disease, they are not always 100% accurate. There are two main types of heartworm tests used in cats: the antigen test and the antibody test. The antigen test detects the presence of adult female heartworms, while the antibody test determines if the cat's immune system has been exposed to heartworms. It is possible for a cat to have a false-negative test result, especially if they have only a small number of worms or if all the worms are male. Therefore, it is important to interpret test results in conjunction with other clinical signs and consult with a veterinarian for an accurate diagnosis.


cat in the vet's table


Myth #6: Heartworms Primarily Cause Cardiac Issues in Cats

One commonly held myth is that heartworms primarily cause cardiac issues in cats. While heartworm disease does affect the heart, it can also impact the pulmonary arteries and lead to lung disease. The adult heartworms reside in the pulmonary arteries, which are the blood vessels that carry blood from the heart to the lungs. Their presence can cause chronic inflammation, scarring, and narrowing of the pulmonary arteries. This can result in pulmonary hypertension, increased blood pressure in the vessels of the lungs, and additional strain on the heart. Furthermore, heartworms can interfere with heart valves, further worsening the heart's workload and potentially leading to heart failure. It is important to understand that heartworm disease can have a broader impact on a cat's health beyond just the heart.


cat and a human hand holding a heart shape


Myth #7: Cats Can't Die From Heartworm Disease

While cats may have a lower incidence of heartworm infection than dogs, feline heartworm disease can be fatal. Cats can also harbor adult-stage heartworms in their bodies, leading to severe disease and potential death. Even with fewer adult worms compared to dogs, cats can still develop respiratory distress syndrome, heart failure, and other serious clinical signs due to heartworm infection. However, recent studies of cats with heart and breathing diseases have found an incidence of heartworms that is far greater than previously thought, debunking the myth that cats are not affected by heartworm disease. This underscores the importance of preventive measures and regular veterinary care to protect cats from the potentially fatal consequences of heartworm disease.


black and white cat laying in the ground


Understanding Heartworm Disease in Cats

To fully understand heartworm disease in cats, it is essential to grasp the underlying factors, such as the life cycle of heartworms, how the disease is diagnosed, treatment options, and the importance of prevention. Let's explore these aspects in detail.


The Lifecycle of Heartworms in Cats

heartworm cycle in cats

The life cycle of heartworms in cats is complex and requires two host animals to complete it. Mosquitoes act as the intermediate host, ingesting the immature heartworm larvae called microfilariae when they feed on an infected cat or dog. Inside the mosquito, the microfilariae develop further for about 10-14 days. When an infected mosquito bites a cat, the infective larvae enter the cat's bloodstream. They migrate through the cat's tissues and eventually settle in the pulmonary arteries and the right side of the heart, where they mature into adult heartworms capable of reproduction. Understanding the life cycle of the heartworm, including the species of mosquitoes that act as intermediate hosts, is crucial in preventing and treating this potentially deadly disease in cats.


How Heartworm Is Diagnosed in Felines

Diagnosing heartworm disease in cats involves several methods, although none are 100% reliable on their own. Veterinary professionals typically employ a combination of tests for a more accurate diagnosis. The diagnostic sequence usually begins with observing any clinical signs of heartworm disease, such as coughing and rapid breathing. Blood tests, including the heartworm antigen test and the heartworm antibody test, are commonly used to detect the presence of heartworms. The antigen test identifies the presence of adult female heartworms, while the antibody test determines if the cat's immune system has been exposed to heartworms. Other diagnostic methods may include testing for the presence of microfilariae in the blood, measuring eosinophil counts, and performing radiographs or cardiac ultrasound to assess the heart and surrounding vessels. These tests all require a small blood sample from the cat, and they work by detecting the presence of heartworm proteins.

cat blood test


Treatment Options for Heartworm Disease in Cats

Treating heartworm disease in cats can be challenging, as there is no specific drug approved for use in cats. The treatment options available, including surgical removal and managing symptoms, are not without risks and limitations. However, it is crucial to treat heartworm disease in cats, as the parasitic infection can be fatal. Surgical removal of the heartworms is a possible approach, but it is typically reserved for cats with severe signs of heartworm disease and a poor prognosis. However, studies have shown that up to 40% of cats may die during or after this procedure, making it important to seek treatment from a specialist, often at a College of Veterinary Medicine. Another option is treating the symptoms of heartworm disease and providing supportive care, such as oxygen therapy and corticosteroids. This approach aims to manage the cat's clinical signs and improve their quality of life. Treatment can last for several months since heartworms typically live for 2-4 years in cats. It is important to note that the prognosis for cats with heartworm disease is generally poor, and there is no guarantee of a complete cure.


Prevention: The Best Strategy Against Heartworms

The best strategy for protecting cats against heartworm disease is prevention. There are several heartworm preventives available for cats, including topical and oral medications. These preventives work by killing the immature larvae before they develop into adult worms. It is important to administer heartworm preventives consistently, following the recommended dosage and frequency. Heartworm preventives are generally safe for cats, with a wide margin of safety, even for kittens as young as six weeks of age. It is essential to consult with a veterinarian to determine the most suitable preventive option for your cat, considering their age, health status, and lifestyle. Prevention of heartworm disease is the most effective way to keep your feline friend safe from this potentially deadly illness.


cat inside human hand in a heart shape



Heartworm disease in cats is a serious issue surrounded by several misconceptions. Being aware of the myths and facts can help you protect your feline friend better. Remember, indoor cats are not immune to heartworms, and the disease can be symptomatic. Regular testing, prevention, and early intervention are key to managing heartworms in cats effectively. Educate yourself, consult your vet, and take preventive measures to ensure your cat's well-being. Prevention is always better than cure when it comes to heartworm disease in cats. Stay informed and keep your furry companion safe and healthy.


Frequently Asked Questions


What is the Heartworm Incidence in My Geographic Location?

You can look at the map to see the reported incidence of heartworm disease.

New American Heartworm Society Heartworm Incidence Map


Is Heartworm Disease Increasing?

Unfortunately, mosquito-borne (and tickborne) diseases are spreading due to our environment becoming more hospitable to mosquitos, rehoming of pets from infected areas, and travel to affected areas. This is a good time to remind people traveling this summer to check the heartworm incidence at their destination to see if preventive measures are necessary.

Although the highest incidence of heartworm disease was in the South, it is increasing in the Pacific Northwest where it is warming and there is increasing rainfall (3).


Why Do Some Cats Show No Symptoms of Heartworm Disease?

Some cats infected with heartworms may not show any symptoms because their immune response can keep the infection in check. However, even asymptomatic cats can experience an inflammatory reaction caused by the presence of heartworms.


Can Indoor Cats Really Get Heartworm Disease?

Yes, indoor cats can get heartworm disease. Although the risk is lower compared to outdoor cats, they can still be bitten by infected mosquitoes that enter the house, leading to heartworm infection.


How Effective Are Heartworm Preventatives?

Heartworm preventatives are highly effective when administered correctly and consistently. The American Heartworm Society recommends year-round heartworm prevention for cats to ensure maximum protection against heartworm infection. Discuss alternatives with your trusted veterinarian to identify your risk factors and safe preventive options. You can do more research here regarding heartworm disease: American Heartworm Society


What Should I Do If My Cat Tests Positive for Heartworms?

If your cat tests positive for heartworms, it is crucial to consult with a veterinarian. They will guide you on the available treatment options and provide appropriate care for your cat's specific condition. Prompt veterinary attention is essential, especially for cats with severe heartworm disease.


Are Certain Breeds of Cats More Susceptible to Heartworms?

There is no specific breed predisposition to heartworm disease in cats. However, certain genetic factors and individual susceptibility may play a role in determining the severity of the infection in affected cats.


How Long Can a Cat Live with Heartworm Disease?

The life expectancy of a cat with heartworm disease can vary depending on various factors, including the severity of the infection and the cat's overall health. Heartworm disease can significantly impact a cat's quality of life and, if left untreated, may lead to heart failure.


Can Heartworm Disease Be Completely Cured in Cats?

Currently, there is no curative treatment available for heartworm disease in cats. Complete eradication of heartworms is challenging, and the condition often becomes a chronic health issue that requires ongoing management and monitoring.


What Are the Signs That My Cat Might Have Heartworm Disease?

Clinical signs of heartworm disease in cats can include coughing, wheezing, difficulty breathing, weight loss, and decreased appetite. Sudden death can also occur in some cases. If you notice any of these signs, it is crucial to seek veterinary attention.


How Often Should My Cat Be Tested for Heartworms?

Veterinary guidelines recommend annual heartworm testing for cats as part of their preventive healthcare. Regular testing allows for early detection and prompt intervention if heartworm infection is present.


Is There a Specific Season When Heartworm Prevention Is Most Critical?

While heartworm prevention is important year-round, the risk of infection may be higher during peak mosquito season when mosquito activity is at its peak. However, it is essential to provide continuous heartworm prevention to ensure maximum protection.


Can Heartworm Disease Affect My Cat’s Lifespan?

Heartworm disease can have long-term effects on a cat's health and may result in a reduction in lifespan. Chronic health issues, such as heart and lung damage, can significantly impact a cat's overall well-being and longevity.




(2) Montoya-Alonso JA, Garcia-Rodrigues SN, Carreton, E, et al: Seroprevalence of Feline Heartworm in Spain: Completing the Epidemiological Puzzle of a Neglected Disease in the Cat. Front Vet Sci 2022 Vol 9 (1) pp. 900371.(2)


Hi! I'm Dr, Dody, DVM.

Passionate about animal welfare, I dedicated my life to helping animals from a young age. After years of traditional medicine, I discovered a lack of dietary options for optimal health. Combining my experience in both traditional and holistic care, I created Holistic Vet Blend® to empower consumers in choosing healthy ingredients and provide essential nutrients. As a seasoned veterinarian and thought leader, I advocate for a personalized approach to improve pets' lives. We support you in curating your pet's bowl, monitoring their progress, and offering the latest recommendations as their needs change.

Together, let's redefine pet care with love and attention.