Heartworm In Cats

Understanding the danger of heartworm in cats is vital for every cat owner. Although heartworm disease is more commonly associated with dogs, cats are still susceptible to this potentially deadly parasitic infection. Mosquito bites transmit heartworms, which can cause significant harm to a cat’s cardiovascular system, resulting in respiratory distress and other severe health complications.

Recognizing the symptoms, comprehending preventive measures, and promptly seeking veterinary care are crucial for ensuring a cat’s well-being. This guide will explore the essential aspects of heartworm in cats, offering valuable knowledge to assist cat owners in navigating the challenges presented by this parasitic menace.

What is Heartworm In Cats?

Heartworm disease in felines is caused by a parasite known as Dirofilaria immitis, which is transmitted through mosquito bites. Cats exhibit a relatively higher resistance to adult heartworm infection compared to dogs, with the infection rate in cats being reported as 5-20% of that in dogs within the same geographical area.

The symptoms of heartworm disease in cats can vary from subtle to dramatic, encompassing coughing, asthma-like attacks, periodic vomiting, loss of appetite, and weight loss. In certain instances, the initial indication may be sudden collapse or even sudden death.

Heartworm disease is a severe and progressive ailment, and early detection significantly improves the cat’s chances of recovery. Currently, there is no approved medication for treating heartworms in cats, thus preventive medication is recommended for all cats, regardless of whether they reside indoors or outdoors.

How Common is Heartworm in Cats?

The occurrence of heartworm in cats varies across different regions, with infection rates ranging from 0.9% to 4.6% in the United States. Cats exhibit a relatively higher resistance to adult heartworm infection compared to dogs, with the infection rate in cats being reported as 5-20% of the rate observed in dogs within the same geographical area.

In the United States, the overall seroprevalence of heartworm infection in cats is 0.4%, with the highest prevalence observed in southern states. The infection occurs when a mosquito bites a cat, allowing the entry of heartworm larvae that the mosquito has acquired from another animal, typically an infected dog. The symptoms of heartworm disease in cats can vary, ranging from respiratory issues to sudden death.

What You Need To Know About Heartworm In Cats

What You Need To Know About Heartworm In Cats

Heartworm disease is a serious medical condition that can be fatal, and it is caused by parasitic worms that live in the heart and lungs of infected animals. Although dogs are the main hosts for these worms, cats can also become infected with heartworm disease, although it is less common. It is important to have a good understanding of this disease and its symptoms in order to protect your beloved feline friend.


Heartworm infection is caused by the transmission of heartworm larvae from an infected mosquito to a cat through a bite. These larvae then travel through the cat’s tissues, eventually settling in the heart and lungs and developing into adult worms. Female adult heartworms can reach lengths of up to 12 inches and can produce numerous microfilariae, which are young heartworm larvae. These microfilariae circulate in the cat’s bloodstream and can be transmitted to other mosquitoes, perpetuating the cycle of infection.

Heartworm in Cats Symptoms

Heartworm disease in felines can pose a grave and potentially fatal threat if not addressed promptly. The indications of heartworm disease in cats may differ based on the extent of the infection, yet a few prevalent symptoms include:

Signs of Heartworms in Cats

  1. Coughing: Coughing is a prevalent indication of heartworm disease in cats. The cough can either be dry or productive, and it tends to intensify during exercise or moments of excitement.
  2. Lethargy: Heartworm disease in cats can cause a decrease in their usual activity level, resulting in lethargy and sluggishness. They may appear tired and less energetic than usual.
  3. Weight loss: Cats suffering from heartworm disease may experience weight loss despite maintaining a normal eating pattern. The underlying reason for this occurrence is the utilization of the cat’s nutrients by the heartworms.
  4. Decreased appetite: Cats suffering from heartworm disease may experience a loss of appetite, resulting in a decrease in their food intake and subsequent weight loss.
    A reduced appetite is a common symptom in cats affected by heartworm disease, leading to a decline in their food consumption and eventual weight loss.
  5. Difficulty breathing: Cats suffering from heartworm disease may experience breathing difficulties, particularly during physical activity, due to the obstruction of blood flow to the lungs caused by the presence of heartworms.
  6. Vomiting: Cats suffering from heartworm disease may experience occasional vomiting, which may be accompanied by blood in the vomit.
  7. Diarrhea: Cats suffering from heartworm disease may experience diarrhea as well.


Timely identification is crucial for effective therapy and averting severe complications. In feline cases, veterinarians commonly employ two diagnostic techniques to detect heartworm disease:

  1. Blood test: This method involves detecting the existence of heartworm antigen, a protein generated by adult female heartworms, through a blood sample analysis.
  2. Microscopic examination: By scrutinizing a blood sample under a microscope, veterinarians can ascertain the presence of microfilariae, aiding in the diagnosis of heartworm disease in cats.

Preventing Heartworm in Cats

Prevention proves to be significantly more efficient and economically viable compared to treatment. Veterinarians strongly advise the implementation of year-round heartworm prevention for all cats, irrespective of their indoor or outdoor lifestyle. A range of heartworm prevention methods are accessible, such as monthly oral medications, topical spot-on treatments, and injectable formulations.

Treatment of Heartworm in Cats

Regrettably, there is no remedy for heartworm disease in felines. Nevertheless, there are treatment alternatives accessible to control the infection and decrease the possibility of complications. The treatment usually comprises a blend of drugs to eliminate adult heartworms, prevent microfilariae growth, and manage any additional complications, such as lung impairment.

Heartworm In Cats

How Do Cats Get Heartworms?

Cats acquire heartworms when they are bitten by a mosquito that carries the infection. The mosquito injects heartworm larvae into the cat’s skin during the bite. These larvae then migrate through the cat’s bloodstream to the heart and lungs, where they develop into adult worms. Female adult heartworms can reach a length of up to 12 inches and produce numerous microfilariae, which are young heartworm larvae. These microfilariae circulate in the cat’s bloodstream and can be transmitted to other mosquitoes, thus perpetuating the cycle of infection.

Here is a more detailed breakdown of the steps involved:

  1. An animal, usually a dog or fox, is bitten by an infected mosquito, which then consumes immature heartworm larvae known as microfilariae.
  2. Inside the mosquito’s body, the microfilariae develop and transform into infective larvae.
  3. The infected mosquito then bites another animal, which can include a cat, and injects the infective larvae into the animal’s skin.
  4. The infective larvae travel through the animal’s tissues, eventually reaching the heart and lungs.
  5. Once in the heart and lungs, the infective larvae mature into adult worms.
  6. Adult female heartworms produce numerous microfilariae that circulate within the animal’s bloodstream.
  7. When an infected animal is bitten by another mosquito, the mosquito picks up the microfilariae, and the cycle begins again.

It is worth noting that cats are less prone to heartworm infection compared to dogs due to their more efficient immune system, which can eliminate some of the infective larvae. However, cats can still contract heartworm disease, and if left untreated, it can pose a serious health risk.

The following are several factors that may heighten the likelihood of a cat contracting heartworms:

  • Residing in an area where heartworms are prevalent.
  • Engaging in outdoor activities, particularly in regions abundant with mosquitoes
  • Not being administered heartworm prevention medication
  • If you have concerns regarding your cat’s susceptibility to heartworms, it is advisable to consult with your veterinarian.They can provide suitable recommendations for heartworm prevention medication and conduct necessary heartworm testing for your cat.

Tips Prevention for Heartworm in Cats

Below are a few recommendations to prevent heartworm in cats:

Ensure year-round usage of heartworm prevention medication. Heartworms remain active throughout the year, hence safeguarding your cat from infection is crucial, irrespective of whether they venture outdoors or not. Various forms of heartworm prevention medication are accessible, such as oral tablets, topical solutions, and injectable forms. Consult your veterinarian to determine the most suitable type of heartworm prevention medication for your cat.

It is crucial to have your cat undergo an annual heartworm test, regardless of whether they are taking heartworm prevention medication. This is because the medication is not foolproof, and early detection of any heartworm infections is vital for prompt treatment. Therefore, make sure to schedule your cat’s annual heartworm test to ensure their continued health and well-being.

It is advisable to refrain from utilizing over-the-counter heartworm prevention medication. Such medication may lack effectiveness and could potentially pose harm to your feline companion. It is imperative to solely administer heartworm prevention medication that has been prescribed by your veterinarian.

Ensure that all windows and doors have screens to prevent mosquitoes from entering your home.

  • Removing stagnant water from your yard
  • Utilizing mosquito repellent
  • Setting up mosquito netting around your patio or porch.

It is highly recommended to keep your cat inside your home to avoid them from getting heartworms. But if you still prefer to let your cat go outside, ensure that they are taking heartworm prevention medication.

Heartworm in Cats Treatment

The lack of an approved drug therapy specifically for cats makes the treatment for heartworm infection in cats challenging. It is important to note that the drug melarsomine, which is used for treating dogs, is not safe for cats and can have significant side effects.

In terms of management approaches, cats with heartworm disease can be managed conservatively by restricting their activity and providing corticosteroid treatment to alleviate symptoms such as vomiting and respiratory issues. However, it is worth mentioning that surgical removal of heartworms is recommended for cats with severe signs of the disease, although this procedure does come with its own risks.

Prevention plays a crucial role in protecting cats from heartworm infection, especially in areas where it is prevalent. Monthly heartworm preventives in the form of tablets or top-spot applications are highly recommended to safeguard cats from this potentially fatal disease.

To summarize, the treatment options for heartworm disease in cats are limited, and it is essential to prioritize prevention through regular use of heartworm preventives in order to ensure the well-being of cats and prevent the onset of this potentially life-threatening condition.

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