Heartworm Awareness Month – How We Can Protect Our Pets

Heartworm disease is a serious illness that can result in heart failure, severe lung disease and often other types of organ damage and death. It is often found in pets – mainly dogs, cats and ferrets. Some wildlife is also affected by this disease, such as foxes, wolves and coyotes.  

April is National Heartworm Awareness Month – serving as the perfect opportunity to emphasize the importance of heartworm disease detection and prevention. The disease severely affects an animal’s quality of life and health, even long after the heartworms are gone.  

While it’s understandable that most pet owners would not deliberately put their animals at risk of becoming infected with harmful diseases, millions of pet parents still fail to recognize the disease growing in their pets.  In fact, more than a million pets have heartworms in the U.S. alone. Cases of the disease have been found in all 50 states.  

For a potentially fatal disease that is easily preventable, there is no reason not to know about it and protect your pet from it. This article will serve as your guide to heartworm disease – what it is, how to recognize it in your pet and the possible treatment and prevention methods you can use. 

What is the Heartworm Disease and What Causes It?

Heartworm disease is caused by worms called Dirofilaria immitis that can grow 10 to 14 inches in length. These worms live within the chambers of the heart along with being present in the blood vessels.  The worms are called “heartworms” because they live in the heart, associated blood vessels, and the lungs of the infected animal. 

In Dogs

The dog is a natural host for heartworm disease. This means that the heartworms that live inside a dog mature, mate and produce offspring. The worms increase in number if left untreated. One dog may have as many as 300 worms when its diagnosis is made. For dogs, heartworm disease causes lasting damage to the lungs, heart and blood vessels, leading to poor quality of life.  

In Cats

Heartworm in cats differs from that in dogs. Most worms inside a cat don’t typically survive till the adult stage.  Unlike dogs, cats usually have just 1 to 3 worms inside them. Sadly, even immature worms can cause significant damage to a cat’s health, causing sudden death.   

In Ferrets

In ferrets, heartworm disease is caused by the same parasite as with dogs and cats. The disease in ferrets is often a mix of symptoms between what we see in dogs and cats.  

Similar to dogs, ferrets are extremely vulnerable to the infection and can harbor a large number of these worms in their body.  However, like cats, a low number of worms can have devastating effects on a ferret’s health, due to the small size of the heart.  

Heartworm is often very difficult to diagnose in ferrets. Unfortunately, there also isn’t an approved treatment for ferrets. The best course of action to take is prevention for both indoor and outdoor ferrets.  

Heartworm Awareness Month

How is Heartworm Transmitted? – The Heartworm Life Cycle

Besides being extremely annoying, mosquitoes are also responsible for heartworm disease. A mosquito is essentially a required part of the heartworm life cycle.  

The adult female heartworms living inside an infected animal produce microscopic baby worms. These tiny worms are called microfilaria and they circulate in the animal’s bloodstream. 

When a mosquito bites an infected animal and takes a blood meal from them, it picks up these worms, which then develop and mature into the “infective stage” over a 10-to-14-day period.  When this infected mosquito bites another animal, the infected larvae then enter the new host animal’s body. 

Once inside the body, it takes the worms roughly 6 months to grow into adult heartworms. These matured heartworms can live up to 5 to 7 years in dogs and 2 to 3 years in cats.  

Owing to the longevity of these worms, each mosquito season can lead to an increase in the number of worms in a pet that is infected.  

Signs of Heartworm Infection

In Dogs

The severity of heartworm disease is gauged by how many worms are living inside the dog (the worm burden), how long the dog has been infected, and how the dog’s body has been responding to the presence of the worms.  

Here is how the symptoms show up in dogs during different stages of heartworm disease: 

Early-Stage Symptoms

  • Persistent cough. The cough associated with heartworm disease is often dry and persistent. In the early stages, this cough could be easily induced by small amounts of exercise. This happens because the worms make their way into the lungs and create a blockage.  
  • Lethargy. This would likely be indicated by your pet losing interest in going for walks or taking part in physical activities. As the condition persists, this could get worse and worse for your pup.  
  • Weight loss. As the disease begins to spread, dogs find it tougher and tougher to even perform the simplest routine tasks like eating or enjoying a snack.  

Mid-Stage Symptoms

  • Difficulty breathing. Your dog may experience breathing problems similar to that of an asthma attack as the condition matures.   
  • Bulging ribs. Fluid builds up around the blood vessels in the lungs due to the parasite’s presence, which makes the dog’s ribs protrude. The ribs can also start to become prominent as a result of weight loss.  

Late-Stage Symptoms

Early-stage symptoms, such as lack of appetite, dry cough, and lethargy, become heightened during the later stages along with some additional complications: 

  • Heart murmur 
  • An enlarged liver 
  • Abnormal sounds in the dog’s lungs  

In Cats

Not all cats show symptoms of heartworm disease despite having it. Some cats can get rid of the worms without having symptoms. On the flip side, some cats die without exhibiting any signs of the disease. 

In case the cats do show symptoms, they are often very non-specific that can easily be confused with other diseases. These symptoms include: 

  • Vomiting 
  • Decreased appetite  
  • Decreased activity  
  • Weight loss  

Typically, cats exhibit symptoms at two points: 

  • When the young heartworms arrive in the cat’s heart and lungs. This causes a respiratory response known as Heartworm Associated Respiratory Disease (HARD). It shows up in the form of increased respiratory rate, trouble breathing, and cough.  
  • When the adult heartworms die. Even a single heartworm dying can release enough toxin in the cat’s body to cause sudden death.  

In Ferrets

Ferrets are more similar to dogs in their susceptibility to get heartworm infections, but their symptoms are similar to those identified in cats. Heartworm symptoms in ferrets include: 

  • Coughing 
  • Decreased activity 
  • Lethargy  
  • Trouble breathing 


How to Protect Your Pet from Heartworm

Prevention of heartworm infection is easier and a lot less expensive than treatment. Here are three preventative measures you can take to keep your pets safe from heartworm every year. 

  1. Use Preventative Medication

There are various kinds of preventative medicines and products that you can use to prevent your pet from contracting heartworm. These medications can be taken orally or applied topically.  

  1. Repel Mosquitoes in Your Home

Mosquitoes are the biggest culprit when it comes to spreading heartworm disease. So you would want to make sure that you repel them as best as you can by using bug repellents – both indoors and outdoors.  

Note that indoor pets are not immune to heartworm disease as mosquitoes can easily fly inside your home from outside. You should also get rid of any stagnant water laying around the house and your yard.  

Spray insecticide around your yard as well but use one that is pet-friendly. You should also avoid outdoor exercise during seasons when mosquito activity is at its peak.  

  1. Pay Regular Visits to the Vet

It is important to make sure that you are making regular trips to the vet. You would be better off going for routine heartworm tests rather than going after your pet has contracted the disease.  

For this reason, the American Heartworm Society recommends that you “think 12.” This means: 

  • You should get your pet tested every 12 months for heartworm, and; 
  • Give your pet heartworm preventative medication 12 months a year. 

What You Need to Know About Heartworm Testing

The earlier heartworm disease is detected, the better the chances are of your pet surviving. There are not very many early signs of the disease that you can pinpoint. For that reason, a heartworm test administered by your vet is extremely important. 

The test requires a small blood sample from your pet. It works by detecting the proteins of heartworm. The results of a heartworm test are obtained fairly quickly. If your cat, dog, or ferret tests positive, further tests are often carried out.   

What Happens if Your Pet Gets Diagnosed with Heartworms?


Dogs should be tested once per year for heartworm disease. Here are a few testing guidelines to keep in mind: 

  • Pups who are 7 months or under can be started on heartworm prevention without the need for a test. However, they should be tested 6 months after your initial visit, and then 6 months after. After that, they should be tested annually. 
  • Dogs over 7 months of age that haven’t been on heartworm prevention before should be tested before their heartworm prevention begins.  

Even when dogs are on heartworm prevention, they should be tested yearly. While the medications are pretty effective, dogs can still get infected if you miss just one dose of a monthly medication or administer it late.  


In cats, heartworm disease is a lot harder to detect as adult heartworms don’t normally exist in cats. The preferred testing method for cats uses an antigen and an antibody test. The antibody test detects any exposure to heartworms. 

Sometimes, vets may also use an ultrasound or x-ray to look for the infection. Cats should always be tested before being put on prevention medication. They should be retested as advised by your vet.  

Preventative measures are extremely crucial as there is no definite treatment for heartworms in cats. 


The detection of heartworm in ferrets can be difficult.  To detect the presence of heartworm in ferrets, your veterinarian doctor may recommend an x-ray, complete blood count, ultrasound and several kinds of blood tests.  

Heartworm Awareness

Treatments for Heartworm Disease


Most dogs tested positive for heartworm disease can be successfully treated. Here’s what you should expect in terms of care: 

  • Strict rest for 60 days. Giving your dog plenty of rest is the single most important factor in their heartworm treatment. This means 4 weeks of rest after each treatment injection. This is done so that the chances of the heartworm fragments moving into the lungs are reduced. The more severe the symptoms, the lesser the activity of your dog should be.  
  • Use heartworm prevention. Before the first treatment is administered, your dog must be on heartworm prevention for at least 60 days. Prevention comes in the form of pills, administered monthly.  
  • Prescribe antibiotics. A 30-day antibiotic course is often prescribed to the dog before its first treatment. The antibiotic kills bacteria that are vital for the heartworm’s health. This greatly reduces the chances of inflammation down the road that can turn fatal. 


Unfortunately, there is no approved heartworm treatment for cats. Nonetheless, under good veterinary care, many cats can be helped. The goal is to stabilize the cat and create a long-term disease management plan. 

Cats who are heartworm-positive should be monitored. If your cat is not showing any signs of respiratory issues but worms have been found in their lungs, chest x-rays should be carried out every 6 to 12 months. Small doses of prednisolone are given to cats that show mild symptoms.  

For cats with severe heartworm, additional support can be needed, such as intravenous fluids, antibiotics, general nursing care, and other drugs to treat the heart and lungs.  


Similar to cats, there is no approved treatment of heartworm disease. They can, however, follow a path to recovery under good vet care.  

If the symptoms are mild, small doses of prednisolone is administered in order to reduce inflammation.  

If the disease is severe, hospitalization could be needed to provide therapy and nursing care. In rare cases, heartworms can be removed surgically.  

Final Thoughts

Hopefully, this article helped you better understand the importance of knowing about heartworm disease in your pets. If your pet companion is free of heartworm disease, keeping it that way is the best route to take. Heartworm disease may be dangerous, but it is also completely avoidable. 

At Rover’s Recess, we understand how important it is to take care of your pets and their health. Our CPR and Pet First Aid trained staff is always ready and eager to help fulfill your pet care needs. Get in touch @ (219) 916-8548 or info@roversrecess.net 



Submit a Comment

Your email address will not be published. Required fields are marked *

Pin It on Pinterest

Share This