Heartworm in Cats: How To Deal With Them

heartworm in cats

Heartworm in cats is a fatal disease caused by foot-long worms that live in the lungs and heart. Although it is most commonly reported in dogs, it can affect cats too. Even ferrets, foxes, sea lions, coyotes, and wolves can get this disease. In rare instances, even humans can contract heartworms. These worms can cause severe damage to the lungs and other organs of the body. Ultimately, this condition results in death.  

The parasitic worm responsible for the condition is Dirofilaria immitis. These parasites gain entry into the body of the host through a mosquito bite. Dogs are definitive hosts for these worms. The worms mature, mate, and produce offspring while residing within a dog. The intermediate host is the mosquito. This disease is quite common in the United States.  

Heartworm in cats 

The heartworm disease in cats is not the same as the one observed in dogs. A cat becomes an atypical host for heartworms. Most of them cannot survive up to the adult stage in cats. In heartworm instances in cats, just one to three worms have been reported. There is no record of adult worms in cats in most of the cases. This also implies that the condition goes undiagnosed in most cats.  

It is vital to remember that immature worms can cause maximum damage in the form of a condition called Heartworm Associated Respiratory Damage (HARD). Moreover, the medication given to dogs for treating the condition cannot be used in cats. Hence, prevention is the best way to keep heartworms at bay.

How do cats get heartworms? 

The mosquito plays a significant role in the lifecycle of heartworm. Adult females produce baby worms referred to as microfilaria. These circulate in the bloodstream. Whenever a mosquito bites an infected animal, it picks up the baby worms. Then, these develop and mature into the larvae period within ten days. Whenever an infected mosquito bites another cat, dog, or any other susceptible animal, the infected larvae transfer on the skin. These then enter the new host through the wound caused due to a mosquito bite.  

Once the larvae gain entry into a new host, they take around six months to mature into adult worms. Once they have matured, they can live for 2 to 3 years in cats and 5 to 7 years in a dog. Each mosquito season can increase the number of worms in a pet because of the longevity of heartworms.  

What are the signs of heartworm disease in cats? 

The signs in cats can either be very dramatic or may be subtle. Heartworm in cats can result in asthma, periodic vomiting, coughing, and lack of appetite and weight loss. Sometimes, an infected cat may experience seizures and may have difficulty in walking. Also, the condition can result in an accumulation of fluid in the abdomen. Unfortunately, the first sign in some cases is the sudden death of a cat or a collapse.  

How significant is the risk of contracting heartworm in cats?  

You still need to be careful even if heartworms may not be a significant problem in your area. If you travel with your pets frequently, then you need to be alert. Mosquitoes get brown to great distances by the wind. They can carry parasites from an infected animal. This was noted when Hurricane Katrina hit the US. Of the 250,000 pets affected, many of them got infected with heartworms.  

There is always a risk factor that is not possible to predict. The best thing to do is to take precautions. It is better to get your pet tested once in twelve months for heartworm. Preventative medication can also be given to your pets once a year.  

What do I need to know about heartworm testing? 

Heartworm disease is a serious condition. The sooner it gets detected, the better are the chances for your cat to recover. Initially, a few signs show up. So identifying the presence by just looking at the symptoms is not possible. Hence, get a test done by a vet. The results are obtained quickly as the test only involves detecting heartworm proteins in the blood sample. If your cat tests positive, then the vet may prescribe further tests.  

When should my cat be tested? 

It is harder to detect heartworm in cats in comparison to other animals. This is because they are less likely to carry adult heartworms. The method of screening involves the use of an antigen. Also, an antibody test is done to detect larvae. Your vet may also use an ultrasound or X-rays to look for infection. Preventative measures should be taken. As there is no approved treatment available for treating this condition in cats, prevention becomes extremely critical.  

What to do if my cat tests positive? 

Though the condition is not common, there is always a risk of infection. You need to understand that a cat is not an ideal host for heartworm. Some infections resolve on their own in cats. However, there is a possibility of respiratory damage due to infections. The presence of heartworms in the circulatory system can also impact the immune system. The common symptoms noted are wheezing and coughing. 

In cats, the heartworms can even migrate to the spinal cord, eye, and brain. Severe complications such as lung inflammation and blood clots in the lungs are also noted upon the death of an adult worm in the body of a cat.   

What to expect if the cat tests positive? 

Here are the common procedures that the vets follow for treating heartworms in cats.  


Although an infected dog may carry around 30 or more worms, an infected cat has lesser than five worms in their body. However, having just one or two worms can affect a cat severely. The diagnosis is pretty complicated. It may require an X-ray, a physical exam, and a blood test. In some cases, an ultrasound may also be performed. 


Unfortunately, there isn’t any drug approved for heartworm in cats. Further, the drug prescribed for dogs is not safe for cats. Nonetheless, cats with this condition can be helped by providing good veterinary care. A long term management plan would be needed to stabilize your cat’s condition.  

Monitor your cat 

Cats tested positive for heartworms can demonstrate respiratory distress. If worms are detected in the lungs, then it would be necessary to get X-rays done once every six months. If the heartworm symptoms are mild, then small doses of prednisolone can be given for lowering inflammation.  

Providing care

If the condition is severe in your cat, then you may have to opt for additional support. Your vet may ask you to hospitalize your cat for providing therapy such as intravenous fluids, drugs for treating symptoms, and for administering antibiotics. General nursing care is also essential. In extreme cases, surgical removal of heartworms may become necessary.  

Preventative measures 

A cat that has developed heartworm may be susceptible to the infection. Both indoor and outdoor cats are at risk. Hence, it is vital to take preventative measures as described by your vet. Heartworm prevention for cats is not as easy as the symptoms don’t show up. Still, appropriate measures can lower the risk.  

Heartworm guide in cats


  • An infected cat may carry less than five worms

  • Diagnosis is pretty difficult in cats

  • X-ray, blood test and a physical examination may be done

  • Ultrasound may also be done


  • No drug available for heartworm treatment in cats

  • Good veterinary care can help

  • A long term management plan is essential for stabilizing the cat’s condition


  • Respiratory distress observed in cats

  • X-rays to be done once in six months

  • Medications are given for lowering inflammation

Providing care

  • Additional support may be required if the condition is severe

  • Hospitalization is essential in extreme cases

  • Therapy such as intravenous fluids and antibiotics may be administered

  • Surgical removal of heartworms in some cases

How do heartworm preventives work?  

Heartworm preventives are usually available in the form of a pill or a spot-on medication. Even injections are given to cats for preventing the condition. Heartworm preventive medications work by eliminating the larvae of the parasite in cats. This includes the larvae deposited by an infect mosquito. 

Is there any vaccination available for heartworm in cats? 

No. There isn’t any medication available commercially for treating heartworm in cats. Currently, the condition can be managed with preventive medications. Vets prescribe these based on the symptoms noted. However, the options are pretty much limited for cats. You need to get in touch with a vet and discuss all the options available. Just giving regular medications for preventing parasites, in general, may help.  

Home remedies for heartworms in cats 

In cats, heartworm prevention is easier than treating it. The first line of defense would be to ensure that your pet cat is getting optimal nutrition, play, and exercise. Also, minimizing stress and adhering to the correct vaccination schedule can help to prevent the condition. 

Dr. Michelle Tilghman believes that strengthening the resistance in animals by giving whole foods can keep their immune system strong. The next thing to do is eliminate mosquito breeding environments in your home and around. 

The FDA recommends adhering to following preventative measures for heartworm in cats and other animals.  

  • Tablets and oral pills
  • Spot on treatment 

You can also consider allopathic medicines. There are also other holistic products available for preventing heartworm in cats. You can also use essential oils. Herb blends can be beneficial in preventing mosquito bites. You can also use home remedies for increasing the immunity of your pet cat. If your cat has a cough, then you can use over the counter cat heartworm cough medications. It is best to use the medicines prescribed by your vet.  

Is heartworm in cats contagious? 

You may be having a lot of questions in mind. Heartworm in cats cannot transmit from one cat to another. Only a carrier such as a mosquito carrying the larvae from an infected animal can transmit the condition. 

Is heartworm in cats fatal?  

Heartworm can prove to be fatal if the condition has severely progressed without demonstrating any symptoms. It is best to take precautionary measures to avoid the condition altogether.