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

If your family unit includes mammals like dogs, cats, ferrets, horses, or humans, you should be wary of heartworm disease. Heartworm is a very serious disease that starts with one little, annoying bug: the mosquito. These tiny blood suckers are how a parasitic worm named Dirofilaria immitis enters the mammal’s bloodstream and lays eggs that will hatch into worms. The process of the worms infiltrating a mammal’s body is called dirofilariasis, and it can be extremely long and painful. Heartworm is a very serious, sometimes fatal, disease that requires experienced medical staff to treat. As soon as you think your animal may have a problem, seek medical help immediately. If you have any immediate concerns about your animal contracting heartworm, please give our Cloud Peak Clinic a call. We want all our patients to leave happy and healthy, so give us a call at (307) 347-2781, or stop by our clinic in person. Please do not hesitate if you think there is an issue.

The Basics

You do not need to worry about every single mosquito that comes into your animal’s environment, as the insect can only spread the heartworm disease if they have already fed off an infected host. An infected host could include mammals such as pets, horses, coyotes, wolves, foxes, and even humans. (While it is very uncommon for a human to become infected, it is important to know how your pet’s health can affect your own.) When a mosquito feeds off an infected host, the worm travels into the insect’s bloodsucker and around its beak (a mosquito’s beak is the straw-like part of the head that sucks the blood out). The carrier mosquito then bites into different mammals and possible hosts, spreading the worm to each animal. Once the infected worm larva infiltrates a host, the heartworm life cycle can begin. 

Once bitten, the mosquito passes on a few infected larvae that will use the host’s bloodstreams as highways to the rest of the body. The blood brings the larvae to the lungs, where they will use the pulmonary vessels to mature into adult worms. The maturing process takes between five and seven months, and your animal probably will not show symptoms until then. Once the worms have reached adulthood, they begin to explore the host’s body through their blood vessels and continue to grow in size. Heartworms can grow up to almost 12 inches, effectively blocking blood vessels and organ function. 

Once heartworms have infected the host, there are typically four different stages of heartworm infestations. These different stages are great indicators of what treatment processes will need to occur, where the infectious bite happened, and other important information. These four stages are: 

  • 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. 

If you want more specific symptoms, check out this link!

Keep in mind that heartworms are not contagious; only a carrier mosquito can transfer the worms to another pet. If you are worried about you, your family, or other pets contracting the disease, focus on monitoring mosquito bites. As long as your pet has taken preventative medication, your pet should be okay to play wherever!


When it comes to any disease, not just heartworm, it is crucial that you, a pet owner, take your furry friend to a trusted veterinary clinic to get tested immediately. When it comes to finding a heartworm diagnosis, there are two possible types of testing; one tests for a specific antigen, while the other is to test for larvae in the host’s blood. Keep in mind that in both instances, the testing will only come back positive if the host has been infected for six months or more. 

Both aforementioned testing methods require blood work, which is not always readily accessible to vet clinics. If your animal needs blood work done, keep in mind that it could cost you a pretty penny. The frequency of testing is entirely situational and will change based on your animal’s needs. Questions about your pet that you may have to consider may include: 

  • Are you giving them their preventative on time? 
  • Have you switched their medications recently? 
  • Have you recently taken them to an area where heartworm is more common than their typical surroundings? 
  • At what age did you start giving the preventative medicine to your pet?

All of these questions may seem inconsequential, but they could determine and change your vet’s treatment plan. Together, you and a trusted veterinary team can give your pet the best fighting chance to beat heartworm disease.


Now that you’ve gone through the testing process and have received the unfortunate positive diagnosis, you need to immediately seek medical attention for your animal. Heartworms can live in their host for anywhere from five to seven years, making the treatment process extremely complicated due to the aforementioned four stages. To figure out how long the worms have been in the host and the worm burden (the number of worms in the host’s system), your vet will have to run more tests. Worm burdens can range anywhere between one and two hundred fifty worms, and this count will qualify for one of the four classes. Once the worm burden has been determined, the treatment process can begin. Let’s talk about class-specific treatment options! (If you need a refresher on the classes, you’ll find that information in “The Basics” section of this article.)

Classes one through three are noticeably less life-threatening than class four, which is exactly why we want to prevent any animal from progressing to that point. To prevent any symptoms from getting worse, you will need to collaborate with your vet to determine a specific plan for your animal, as there is no cure-all option. Some ideas your vet might bring to the table include intervention steps like, taking medication to kill off any larvae, plenty of rest, antibiotics, pain relief medication, specialized diets, and so much more. As long as you take these steps, you will see your animal happy and healthy again. 

Class four is a little more difficult and requires more work, time, effort, and money. Depending on your vet and options available, there are a few medications on the market that will slowly kill and eradicate the worms. We emphasize “slowly” because quick removal could put the host’s body into shock, which further complicates the issue. Once the worm burden falls below a certain number, surgery to remove the other worms could be considered. Again, treatment is very individualized, so you need to communicate with your vet to find the best treatment options. 

If you notice any signs of heartworm disease, give our emergency line a call. Dial (307) 347-2781, and we would be more than happy to provide your animal with the medical care they need.

Act Today to Prevent Future Worries

If your pet has heartworms, it could be a very taxing, expensive, and overwhelming process for the whole family, which is why immediate action is crucial. With that being said, please know that there is no guarantee for heartworm disease survival, so it is very important to take the disease very seriously and seek professional care. For most any disease, we at Cloud Peak recommend that you look into preventative measures rather than face negative consequences down the road. You may not think it could happen to you or your pet, but that frame of mind is exactly what the infectious worms are counting on; the only way to prevent class four is to take action now. 

If you have questions, concerns, or anxieties, give us a call at (307) 347-2781 or visit our website. We want every animal in our community to be happy and healthy, so let us know what we can do to help you and your furry family members.



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