How Do Pets Get Heartworms?

Many parasites can affect our animals. One of the most dangerous is heartworms. While heartworms can affect cats and some other small mammals, dogs are the natural host of this parasite and are also most at risk. Let’s find out more about this potentially deadly parasite infestation and how you can keep your pet safe.

What are heartworms?

Heartworms, or heartworm disease, is a very serious condition where parasitic worms develop and live inside your dog’s body. Although thin, these worms can grow up to a foot long when fully matured. While other worms take up residence in an animal’s digestive system, heartworms live inside the heart, lungs, and associated blood vessels. As they mature and reproduce, their numbers swell. This causes narrowing and blockages of these blood vessels, which can have serious repercussions for your pet’s health. In a heavily infected dog, it is not uncommon for there to be 100 or more worms. Heartworms can live between five and seven years before they die and are processed out of your pet’s body.


Heartworms can cause a variety of unpleasant symptoms and have long-term consequences for your dog’s health. Without treatment, they may even prove fatal.

How do dogs get heartworms?

Unlike other types of parasites, heartworms are not contagious, meaning that they can’t be passed between pets no matter how close they get to one another. Instead, your dog can only get heartworms if they are bitten by an infected mosquito.


Mosquitos travel from animal to animal where they sit on the surface of their body and drink their blood. If a mosquito drinks blood from an animal infected with heartworms, the blood that they consume will contain microfilariae – the earliest stage where heartworms are microscopic. Since heartworms can’t affect mosquitos, these microfilariae are then passed directly into the bloodstream of the next animal that they bite. Once they enter the bloodstream of their next host, they travel to the blood vessels of the heart and lungs, where they become larvae and then mature into adult heartworms. This process takes around 6 months. Until this time, there will be no symptoms and heartworms won’t show up in any blood test. This makes it impossible to know if your pet is infected during this time.

What are the symptoms of heartworms?

If your dog is infected with heartworms, it probably won’t exhibit any symptoms for at least 6 months. As the disease develops, symptoms may start to develop very slowly, and could include:
 

• Shortness of breath or difficulty breathing
   

• Loss of stamina or becoming more lethargic
   

• Dry, nagging cough
   

• Loss of weight
   

• Loss of appetite
   

• Becoming tired after light exercise
   

• Swelling of the abdomen

In cases of severe heartworms, pets may collapse and become unconscious.


If you have any reason to suspect that your pet has heartworms, you should speak to your veterinarian in Port Isabel as soon as you can. The sooner your pet is tested and treated, the better the outcome of their care is likely to be.

Can heartworms be treated?

There are treatments for heartworms, but these are largely unpleasant, expensive, and have a range of side effects. There is also no guarantee that they will be successful, or that your pet won’t have suffered significant damage to their health. Prevention is better than treatment.


There are a wide variety of preventions available for heartworm disease and your pet can be started on one from as early as six weeks old.  Both tablet and top-spot application medications are available to prevent your pet from contracting the disease, however, if your pet has not had any heartworm medication for over 6 months, they will need to undergo a blood test to ensure they do not already have heartworm disease. There are a wide variety of brands available that can help protect your pet from heartworm disease, as well as other parasites. The most convenient and effective form of prevention is a yearly injection administered by your vet in Port Isabel.  This can only be given once your pet is 12 months of age, however, so they will need a different version of preventative (or can start a similar 6-month injection at 6 months of age) until that time.


It is very important to keep on top of your pet’s preventative medication to keep them as happy, healthy, and safe as possible. Even during the winter months when there are significantly fewer mosquitoes, you should still keep up to date with their medication. This way, you are largely reducing their risk of contracting heartworm disease.



If you would like more information about heartworms, or if you are concerned about your pet, please get in touch with our friendly and experienced veterinary team in Port Isabel at Port Isabel Animal Clinic by calling 956-943-6022.