Heartworms Can Cause Serious Disease that can be Fatal for Pets

Heartworm disease is a serious and possibly deadly disease that affects pet cats and dogs in the United States and elsewhere in the world. Heartworm disease is caused by foot-long worms known as heartworms, that find a place in the heart, lungs and blood vessels of affected pet cats and dogs, and cause lung disease, heart failure as well as serious damage to other organs in the pet’s body.

Common Pets Affected by Heartworms

Dogs are natural hosts for heartworms. Heartworms may live within a dog’s body throughout their life cycles, from birth to adulthood and mating phase, and may leave countless offspring behind. If not identified and treated in time, heartworms cause severe damage to the heart, lungs and arteries of the dog, and have a severe impact on its health.

Heartworm disease in cats is different from that in dogs because the worms don’t survive to adult stage in a cat’s body. So, while dogs have several adult heartworms in them, cats have a very few. But this is not necessarily a good thing because immature heartworms cause as much damage as mature worms, and are more difficult to identify.

Cats with heartworms are usually affected by what is known as heartworm associated respiratory disease (HARD). Also, heartworm disease in dogs can be treated quickly, but in cats, treatment is not so easy. Often, prevention is the only possible cure when it comes to cats and heartworm disease.

Heartworm Disease: Transmission

Heartworms are transmitted by mosquitoes when they bite a heartworm-infected animal. The mosquitoes carry microscopic versions of the heartworm, called microfilaria, which makes its way into the bodies of pet cats and dogs bitten by them.

The microfilarias make their way to the tissues in a pet cat or dog’s heart, where they live for several years and reproduce in thousands. This way the pet cat or dog gets affected by heartworm disease.

Heartworm Disease: Symptoms

Symptoms of heartworm disease vary in intensity depending on the life cycle of the worms and the age of the pet cat or dog infected by them. Since heartworms live in the heart and lungs of pets, they can have a terrible impact on their health, and may even lead to death.

Here are the common symptoms of heartworm disease.

Dogs – Cough, lethargy, difficulty to breath, fainting episodes, drastic weight loss, fever, swelling in the abdomen (known as Ascite) and even death.

Cats – Cats may or may not exhibit any clinical signs of heartworm disease such as asthma, coughing, vomiting and difficulty in breathing. It is actually better if the heartworm disease symptoms in cats become visible, so that some measure of treatment can be given. Otherwise, it is possible that the heartworms may spread in a cat without being identified and lead to a sudden death.

Heartworm Disease: Diagnosis

Let’s have a look at some of the methods used to diagnose heartworm disease in pet cats and dogs.

Blood Tests: Blood Tests are the principle methods of diagnosis of heartworm disease. The different blood tests done are:

– Antibody tests, that determines if a cat’s immune system has been exposed to heartworms.

– Antigen tests, that detect if any adult female heartworms are present in the pet’s body.

– Testing of the blood sample for microfilaria. This is not a reliable test in cats as only 20% of infected cats test positive for it.

– Determining the eosinophil count in cats suspected to have heartworms. Eosinophils are types of white blood cells that are found in greater numbers when a pet has been infected by heartworms.

Other diagnostic tests involve the use of X-ray and Ultrasound technologies.

Heartworm Disease: Treatment

Heartworm Treatment for Cats

Unfortunately, there are no approved drugs available for the treatment of heartworm disease in cats. So basically, cats are treated for heartworm disease in one of the two ways:

– Giving cats the same drugs as those given to dogs for heartworm disease. This treatment isn’t a perfectly reliable one as the drugs may have serious side effects on cats, possibly leading to lung failure and even death.

– Treating the symptoms of heartworm disease and hoping for the cat to outlive the worm. This would require extensive treatment for two to three years as that is how long heartworms live within a cat’s body. Cats may be given supplies of oxygen and corticosteroids (also known as “cortisone”) to offer relief for some of the pain, which is likely to be quite intense. Also, drugs may be given to eliminate fluids from the cat’s lungs.

– A third technique, which is not yet followed in the United States, but done in Japan and in some European countries is the surgical removal of heartworms from the cat’s body. This technique has been found to be quite effective and will hopefully be used by veterinarians in the US as well.

Heartworm Treatment for Dogs

For dogs, treatment of the heartworm disease depends on how long the heartworms have been in the pet dog’s body. While there are better drugs available today that kill the heartworms present in a dog and have less serious side effects, unlike the drugs of the past, these drugs can only be used to treat dogs if the heartworm disease is quite recent.

If the heartworm disease has been diagnosed early enough, treatment consists of a drug (Imiticide) being injected into the dog’s body to kill the adult heartworms present in the heart as well as the adjacent vessels.

WARING: The following video actually shows a dog receiving a heartworm treatment injection.


If the heartworm disease has been diagnosed early enough, treatment consists of a drug (Imiticide) being injected into the dog’s body to kill the adult heartworms present in the heart as well as the adjacent vessels.
Dogs that have had the heartworm disease for years cannot be treated with these drugs as that would risk their lives. Instead, in dogs those have suffered from serious organ damage because of the presence of heartworms for years, the organs – heart, lungs, blood vessels, kidneys, liver – are treated first. Unfortunately, it is very difficult to cure dogs that are at an advanced stage of the heartworm disease.

A month after the treatment that is given to kill adult heartworms, other drugs are used that kill the microfilaria or the baby heartworms still present in its body.

Following the treatment, dog owners are often delighted at how their pet recovers its health, regains lost weight, gets back its appetite and become active again. Dogs that have been treated for heartworm disease successfully can look forward to a healthy and active life ahead.

Heartworm Caval Syndrome

When there are many heartworm, the worms can cause blood flow obstruction, which is classified as stage four heartworm disease. These patients are not good candidates for standard heartworm treatment. Some veterinarians will surgical extract the heartworms to help relieve the obstruction.

WARNING: The following video is very graphic and illustrates how heartworms can be removed surgically. ONLY watch the video if you can handle such material.


Heartworm Disease: Prevention

Treatment of heartworm disease in cats and dogs can get complicated. That is why prevention of the disease is the best thing that can be done. Prevention of heartworm disease is safe and easy.

Heartworm Prevention for Cats

In areas where mosquitoes are common, veterinarians recommend for pet cats to be given preventives for heartworm disease. Cats that are given preventive medicine display no signs of toxicity and even kittens that are just a few weeks old stay safe from heartworm disease if given preventive medication at the earliest.

Heartworm Prevention for Dogs

Dogs can be saved from having heartworm disease if given preventive medication at the earliest opportunity. Even after having been just treated for heartworms, dogs have to begin a comprehensive heartworm prevention program.

Preventive medicine for heartworm disease in dogs is very safe, effective and easy to inject. Preventive medication can be given in the form of a chewable tablet or applied topically. Some of the best oral heartworm preventatives for dogs are Heartgard®, Interceptor® and Program®. Revolution™ (Selamectin), which is a topical treatment from Pfizer, is also very effective as prevention for heartworm disease.