At Georgia Veterinary Associates, our highly experienced team of veterinarians and veterinary support staff have been helping educate our clients and win the fight against heartworms in cats since 2003. The importance of heartworm prevention for cats cannot be overstated. Once a cat has contracted heartworms, it cannot be cured. Therefore, preventive measures are absolutely necessary in order to keep your beloved feline friend healthy and safe.

What Is Dirofilariasis, AKA: Cat Heartworm?

Heartworms are exactly what they sound like, a worm that infects the heart. The worms live in the right side of the heart, and can cause inflammation and damage not only to the heart itself but also commonly to the lungs and kidneys. 

Dirofilaria immitis is a blood-borne parasitic nematode (roundworm), but more commonly referred to as cat heartworm. Heartworms in cats are spread through mosquitos carrying cat heartworm larvae. The severity of heartworms in cats is directly dependent upon the number of worms present a cat's body, the duration of the incubation, and the response of the infected cat.

Although heartworms in felines are less prevalent than in canines, feline heartworms are still a dangerous disease that has been on the rise in America. The risk of heartworm is about equal for both indoor and outdoor cats. If you do not use preventive medication, the risk of contracting cat heartworm disease exponentially increases. This is why preventive cat heartworm medication is so important.

How Do Cats Get Heartworm Disease?

Cats get heartworms from an infected mosquito.

Upwards of 30 species of mosquitoes can act as cat heartworm transmitters. Mosquitoes ingest immature heartworm larvae, called microfilariae, by feeding on either an infected cat or dog. The microfilariae develop further for 10 to 30 days in the mosquito's gut and then enter parts of its mouth.

When an infected mosquito bites a cat, it injects the heartworm larvae into the cat. The larvae then migrate and mature over a period of several months, eventually ending up in the right side of the heart and the pulmonary arteries. Once this occurs, they mature into adult cat heartworms, and can reproduce about six months from the time of invasion. Approximately eight months after the invasion, cat heartworm begins to produce a new crop of microfilariae that will live in the cat's blood for about one month. By the time this occurs, most cats begin showing symptoms of cat heartworm and the disease can become fatal very rapidly.

Unfortunately heartworm disease is very prevalent in our region (Georgia), with many mosquitoes carrying the disease, so even indoor cats are at risk. 

Symptoms Of Cat Heartworm Disease

Cats do not always show symptoms of heartworm disease until severe damage is present. Symptoms can sometimes mimic asthma, with an intermittent cough or changes in breathing. 

One of the most challenging aspects of diagnosing heartworms in cats is that there are no definitive clinical signs that directly indicate the existence of cat heartworm disease. Cats will often not show symptoms of heartworm disease until severe damage is present. Symptoms can sometimes mimic asthma, with an intermittent cough or changes in breathing. However, this doesn't necessarily mean that cat heartworm disease isn't present. Some health signs that might indicate the presence of cat heartworm disease include:

Vomiting and coughing are two of the most common symptoms but there may be other symptoms, including:

  • Difficult or labored breathing
  • Convulsions
  • Blindness
  • Lethargy
  • Anorexia/Weight Loss
  • Blindness
  • Fluid in the lungs
  • Sudden Death

On occasion, an apparently healthy cat may be found dead, or may develop sudden overwhelming respiratory failure. In these cases, cat heartworm disease may be diagnosed on a post-mortem examination.

We can easily prevent cat heartworm long before serious medical issues or life threatening emergencies develop by simply implementing preventive measures.

Diagnosing Heartworm For Cats

Cat heartworm disease can sometimes be diagnosed with the same in-house SNAP test we use in dogs. However since cats typically get infected with fewer worms than dogs, we sometimes have to send out more specialized blood testing to get a diagnosis. 

Unfortunately, there is also no one benchmark standard used across the veterinary industry for diagnosing heartworm for cats. Rather, our veterinarians employ a battery of lab tests in order to determine a cat heartworm diagnosis. These tests include:

  • A urinalysis, or the testing of a cat's urine.
  • A heartworm antibody test determines whether or not a cat's immune system has been exposed to heartworms. This is a very sensitive test, and is usually employed first.
  • A heartworm antigen test determines the presence of adult female heartworms. This is more specific than an antibody test, but not as accurate in all cases.
  • Radiographs, or X-Rays, that allow us to view the size and shape of a cat's heart. This is helpful because many cats with cat heartworm develop enlarged pulmonary arteries, or have obstructions in the arteries leading to the lungs.
  • Ultrasounds allow us to view the internal structures of the heart and surrounding vessels, in order to assess the condition and function of the heart. However, in some cats with low levels of cat heartworms, this test does not always yield accurate results.
  • A white blood cell count can be measured in cats suspected of having contracted heartworms. Eosinophils are a type of white blood cell which occur in higher numbers when heartworm for cats is present, but can also indicate the presence of other parasites besides cat heartworm.

Can Heartworms Be Treated In Cats? Is There Heartworm Medicine For Cats?

Unfortunately, there is currently no viable heartworm medicine for cats that can fight off an active infestation. Therefore, if your cat is diagnosed with heartworm, we cannot cure it. However, while we cannot defeat existing heartworm disease with medication, this isn't necessarily an indication that they will die soon. While sudden death is possible, it isn't common. If your cat is diagnosed with heartworm they may still live a long life under the supervised medical care and treatment of your veterinarian. This may include anti-inflammatory treatments and medications to aid in breathing, similar to those used to treat asthma.

This is why heartworm prevention is so important; we can prevent the disease, but we cannot treat it if cats become infected.

What Are The Long Term Effects Of Heartworm In Cats? 

Heartworms can cause serious health problems by damaging the heart, lungs, and kidneys, and by affecting blood pressure. They can also increase the risk of blood clots, which may lead to dangerous emergencies if left untreated.

How Can I Prevent Heartworm In My Cat?

The good news for cat owners and their feline friends is that reliable heartworm prevention for cats does already exist. Veterinarians strongly recommend that all cats receive monthly heartworm preventive medications in areas where mosquitoes are active all year round. Here in GA , and because of our mosquito population, we highly recommend all cat owners adhere to this annual preventive medicine protocol.

Heartworm can be effectively prevented with a monthly parasite medication such as Revolution Plus. This is a topical treatment that is applied every 30 days, and it prevents fleas and intestinal parasites as well as heartworms.

How Often Should My Cat Be Tested For Heartworm? 

Heartworm testing for cats is part of recommended routine annual screening. In cats who go outdoors it is often combined with their annual FIV/FeLV screening test, or it can be sent out with regular annual wellness bloodwork.  

What Should I do If I Suspect Heartworm Disease In My Cat? 

If you’re concerned your cat has heartworms, the first thing to do is schedule an appointment with your vet for blood testing. 

Are Certain Breeds More Susceptible to Heartworm Disease? 

All breeds of cats have the same risk of developing heartworm disease if they are bitten by an infected mosquito.

Can Heartworm Disease Be Transmitted To Humans? 

Heartworm disease cannot be transmitted directly from cats to humans. Heartworms must complete part of their life cycle in the mosquito to be infective. Even if humans are bitten by an infected mosquito, humans do not get heartworm disease - at worst they may develop a local rash at the site of the bite. 

What's The Difference Between Heartworm in Cats and Heartworm in Dogs? 

The biggest difference between heartworm disease in cats and dogs is that dogs are the “definitive host” of heartworms and cats are not. This means that dogs immune systems have evolved to be more tolerant of heartworm infection, whereas cats can develop significant systemic inflammation from infection with even 1 or 2 heartworms. This also means that heartworms cannot complete their normal reproductive cycle in cats, so cats cannot spread the infection. 

What Should I Do If My Cat Misses A Dose Of Prevention? 

If you realize your cat has missed a dose of prevention, go ahead and give the missed dose right away, then give the next dose as scheduled. Let your veterinarian know at your next wellness visit so heartworm testing can be done – it’s important to know that cats take about 6 months after exposure to heartworms before they will test positive. 

Have A Veterinarian Check Your Cat For Heartworm At Your Next Appointment

We recommend scheduling an appointment to discuss heartworm prevention for cats with us before your cat contracts heartworm. If you witness any symptoms that might be indicative of cat heartworm disease, please contact us immediately to schedule an appointment. Our veterinary team will provide you and your feline friend with an effective cat heartworm prevention protocol.