Don’t Go Breaking My Heart, Or Infecting It With Heartworm For That Matter

If you’re a dog, cat or ferret owner, heartworm should be a concern for you. Heartworm is a serious disease that all starts with one little bug: mosquitos. These tiny blood suckers are how a parasitic worm named Dirofilaria immitis enters your pet’s system. This parasitic worm can cause an array of issues ranging from lung disease to heart disease, and other organ failures. Heartworm in your pet is a very serious problem; make sure you know the basics. And, if you have any questions about your specific case, feel free to reach out to us.

The Basics

Dogs, cats and ferrets can only be infected by mosquitos that have come in contact with already infected animals. Infected animals don’t just include household pets, however. Coyotes, wolves, foxes and even humans sometimes can be carriers. When a mosquito bites into an infected host, the worm travels into the blood sucker and around its beak (a mosquito’s beak is the straw-like part that sucks the blood out). Then, when that carrier mosquito bites another possible host, it inserts its beak, opening a pore for the worm larvae to get into and start the cycle.

After being bitten, it typically takes about six to seven months for the larvae to mature into adults inside their host. The adult worms release their larvae into the host’s bloodstream and that’s when their larvae can transfer to the mosquito carrier and start the process of spreading heartworm all over again. Specifically in dogs, a heartworm can live anywhere between five to seven years, so getting your dog tested and treated is crucial in ensuring those parasitic worms do not live in your dog for that long, if at all.

Keep in mind that heartworm is not contagious; only a carrier mosquito can transfer the worms to another pet. (So, do not be concerned if your loveable little guy is around dogs on heartworm treatment medication! As long as your pet has taken preventative medication, you should be good to go!)


Getting your pet tested for heartworm is very important. There are two types of testing: one test for an antigen (or a toxin released into the body that needs antibodies to fight it) that adult females release into the blood, and the other one is to find out if there are any worm offspring in the blood. In both instances, the testing will only come back positive around six months after infection.

Both of these testing methods require blood work, and depending on your vet and what lab equipment they have access to, it could cost a good amount. The frequency is dependent mostly on you as an owner. Are you giving your pet their preventative medication on time? Have you switched the medication recently? Have you taken them to somewhere where heartworm is more common than their normal surroundings? And, at what age did you start giving your pet the preventative? Your answers to these questions help your pet’s doctor determine a preventative, or if necessary, a treatment regimen.  Together, you can determine the best plan for your pet.


This is an expensive process, a very taxing process on your pet, and does not always work. If your pet tests positive for heartworm, the severity of the infestation will be apparent.  The number of worms in an animal is called the “worm burden”. This worm burden can range anywhere between one to two hundred fifty worms, so knowing the estimated worm burden will help you understand the severity of the heartworm infestation.

Treatment depends on where the worms are and how many there are. There are four stages of heartworm infestations, which are often determined by symptoms:

  • Class One:  No symptoms, or maybe an occasional cough. The worms are in the bloodstream and either their numbers are few or they are still maturing.
  • Class Two:  An occasional cough along with tiredness after only moderate activity. There are not too many worms, or the worms are not fully mature yet. This is when the worms’ presence can start to show up on tests or x-rays.
  • Class Three:  More severe symptoms, including a much more frequent cough, tiredness after only mild activity, and even looking sickly. This is when you know that the worm burden is increasing and they are making their way to the different organs in the animal. This worm burden would be able to be seen on x-rays of the chest.
  • Class Four:  When the worm burden gets this severe, it is called Caval Syndrome. The worms have started to block blood flow to certain parts of the body, particularly the heart. This is the most severe and dangerous to your pet, and surgery is needed immediately. When an animal gets Caval Syndrome, they typically do not survive, even with surgery.

Classes one through three are clearly less life-threatening, but are still concerning. Preventing class four is why getting your pet tested as often as your vet recommends is  important. We do not want to see you go through a loss and we do not want to see your pet suffering with such a high worm burden.

To prevent class four, there are some options. Depending on your vet, there are different medications your animal can take that slowly eradicate the worms. It typically cannot be done very quickly, as quick removal might result in a shock to the system and possibly death.

For most any disease out there, we at Cloud Peak recommend taking preventative measures, rather than dealing with the consequences later down the road. You might think that your infected pet will not get to class four, but the only way to guarantee that is by preventing it from ever happening.

If you have any questions or concerns, feel free to visit our website or call us so we can make sure the furry members of your family are healthy and happy.


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