Do Cats Need Heartworm Prevention

icon March 15, 2024

Heartworm disease is a serious condition that can affect cats as well as dogs. While dogs are more commonly associated with heartworm disease, it's important to understand that cats are also at risk. In this article, we'll explore the topic of heartworm disease in cats and whether or not they need heartworm prevention.

What is Heartworm?

Heartworm disease is caused by a parasite called Dirofilaria immitis. The parasite is transmitted through the bite of an infected mosquito and can affect both dogs and cats. The adult worms live in the heart and lungs of the animal, causing damage and potentially leading to life-threatening complications.

The number of adult heartworm parasites in cats is usually very small (on average about 3)
However, female worms can reach a length of >21 cm and male worms >12 cm and can survive for about two years.  
So just two heartworm infections can lead to sudden acute death without warning!
Heartworms can block blood circulation and severely damage the heart, lungs, and liver. 

How Heartworm Infection Occurs in Cats?

  1. A mosquito bites an animal (dog, cat, fox, or even human) that has heartworm larvae in its blood, and the mosquito then has heartworm larvae in its body
  2. After two to three weeks, the larvae develop inside the mosquito and become infective third-stage offspring.
  3. When the mosquito bites a cat or dog, the heartworm larvae will enter the body of the cat.
  4. The heartworm pups penetrate the skin and migrate between the tissues, and when they become young adults, they begin to move into the pulmonary arteries and heart of the cat
  5. The heartworm matures into an adult after approximately four months of infection and is lodged in the pulmonary artery and heart of the cat
  6. Finally, it is a serious threat to the cat's health and can even cause sudden death.  

Can Heartworms be Transmitted From One Animal to Another?

The answer is: NO! Heartworms are not contagious! Heartworm is transmitted by mosquitoes!

Symptoms of Heartworm in Cats

Heartworm disease is a serious condition that can affect cats as well as dogs. Unfortunately, the symptoms of heartworm disease in cats can be difficult to detect, as they are often subtle and may mimic other health issues. Here are some of the symptoms of heartworm disease in cats to look out for:


One of the most common symptoms of heartworm disease in cats is a persistent cough. The cough may be dry or moist and may be more noticeable after your cat has been active.


Cats with heartworm disease may experience nausea and vomiting. They may also lose their appetite and lose weight as a result.


Cats with heartworm disease may seem tired or lethargic. They may not be as active as they once were and may spend more time sleeping.

Breathing Difficulties

As the heartworms begin to mature, they can cause damage to the lungs and respiratory system. This can lead to breathing difficulties, including shortness of breath, wheezing, and panting.


In severe cases of heartworm disease, cats may collapse or faint. This is a sign that the disease has progressed and is causing serious damage to the heart and lungs.

It's important to note that some cats may not show any symptoms of heartworm disease until the disease has advanced. This is why it's crucial to have your cat tested for heartworm disease on a regular basis and to use preventative measures to protect your cat from the disease.

Diagnosis of Heartworm in Cats

X-rays of the cat's lungs and body and a combination of blood tests are used to diagnose heartworm infection in cats. The vet will also need to do special blood tests on the cat to measure the presence of heartworm antibodies produced in the body and the presence of adult worm antigens or proteins.

An echocardiogram is performed to look for the presence of adult heartworms in the cat's heart and associated blood vessels. According to the Tufts University School of Veterinary Medicine, this non-invasive form can also look for other heart problems in pets, such as heart malformations, tumors, dilated hearts, or cardiac hypertrophy.

There are a number of different tests required to confirm whether a cat has heartworm.

Treatment of Heartworm in Cats

Unfortunately, there is no specific treatment for heartworm. If a cat is diagnosed, the main treatment for heartworm disease in cats is to manage the symptoms and prevent further damage to the heart and lungs. This may involve medications to reduce inflammation and improve heart function, as well as oxygen therapy to improve breathing. In some cases, surgical intervention may be necessary to remove the heartworms.

It's important to note that treating heartworm disease in cats can be risky, as the dying worms can cause serious complications, such as blood clots and respiratory failure. For this reason, treatment must be carefully managed by a veterinarian with experience in treating heartworm disease in cats.

Prevention is the best approach to managing heartworm disease in cats. Regular testing and the use of heartworm prevention medications can help reduce the risk of your cat developing the disease. 

Heartworm Medicine for Cats

Currently commercially available are Avermectin, Fenthion, Praziquantel

-Prescription topical protects your cat from heartworm, fleas, and more

-Effective feline parasite control

-It is used for fighting against schistosomiasis, paragonimiasis, cerebral cysticercosis, and ocular cysticercosis.

Puainta® Schistosome/Paragonimiasis Defense-Tablets

How Does Heartworm Prevention Medicine Work?

Heartworm prevention medicine works by killing or repelling immature heartworm larvae (microfilariae) that are transmitted to pets by mosquitoes. When a mosquito bites an infected animal, it picks up the microfilariae, which then mature into infective larvae inside the mosquito. When the mosquito bites another animal, the infective larvae are deposited onto the animal's skin, where they enter the body through the bite wound.

It's important to note that heartworm prevention medications must be given to pets on a regular schedule to be effective. Most heartworm prevention medications are given once a month, and some are available as six-month or 12-month injections. Some medications may also provide protection against other parasites, such as fleas and ticks.

It's also important to have your pet tested for heartworm disease before starting them on prevention medication. If a pet is already infected with heartworms, giving prevention medication can be dangerous, as the dying heartworms can cause a serious reaction. Once a pet has been tested and confirmed to be free of heartworms, they can begin taking the medication and should continue taking it on a regular schedule to maintain protection.

When to Have My Cat Tested for Heartworm?

The American Heartworm Society recommends that all cats be tested for heartworm disease at least once a year, regardless of whether they are currently on heartworm prevention medication or not. However, the frequency of testing may vary depending on your cat's age, lifestyle, and geographic location.

If you have a kitten or a newly adopted cat, they should be tested for heartworm disease as soon as possible before starting prevention medication. This is because a cat may have already been infected with heartworms before being adopted or before starting prevention medication.

When Should I Start Heartworm Prevention for My Cat?

It's important to start heartworm prevention for your cat as soon as possible, as the disease can be deadly and prevention is the best approach to managing it. The American Heartworm Society recommends that kittens should begin heartworm prevention medication as early as 6-8 weeks of age, and no later than 3 months of age. Cats should be tested for heartworm disease prior to starting prevention medication, and it's important to continue giving the medication on a regular schedule to maintain protection. Taking preventative measures to minimize your cat's exposure to mosquitoes can also help reduce the risk of infection.

Home Remedies for Heartworms in Cats

Prevention is key when it comes to heartworm disease in cats. Keeping your cat indoors can help reduce their exposure to mosquitoes, which can lower their risk of contracting heartworm disease. However, even indoor cats can be bitten by mosquitoes that come inside the home. This is why heartworm prevention medication is recommended for all cats, regardless of their lifestyle.

In conclusion, cats do need heartworm prevention. While they are less likely to develop heartworm disease than dogs, they can still be affected by the parasite. If you have a cat, talk to your veterinarian about the best heartworm prevention options for your pet. By taking preventative measures, you can help protect your cat from the potentially life-threatening effects of heartworm disease.

Do Cats Need Heartworm Prevention

Now the answer is: Yes.

Because there is no direct treatment for heartworm, it is vital to prevent heartworm in the first place. You can protect your cat from heartworm by taking your cat to the vet early for an examination and a prescription for monthly heartworm preventative medication, even if your cat is an indoor cat.


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