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Heartworm prevention

Veterinary Viewpoints - Heartworm Disease: Prevention is key

Tuesday, April 2, 2024

Media Contact: Kinsey Reed | Communications Specialist | 405-744-6740 |

As we all anticipate warmer weather and enjoying the outdoors with our pets, it is important to remember to protect your dogs from parasites. One of the parasites that dogs need protection from is Heartworms. 

Heartworms are parasitic worms that infect dogs and live in the pulmonary artery, the vessel that takes blood from the heart to the lungs, and sometimes in the heart itself. They are spread by mosquito bites and can be found in all 50 states. 

Dogs infected with heartworms may not show any symptoms early on. As the disease progresses, they may develop symptoms which can include weight loss, lethargy, coughing, difficulty breathing, and heart failure. Chronic, untreated heartworm disease can be fatal. 

All dogs are at risk of becoming infected with heartworms, but there are a few things that put your pet at increased risk. These include:

  • Not being on heartworm prevention
  • Living in or visiting the southern and southeastern United States
  • Spending more time outside, especially in warmer months when mosquitoes are more active
  • Being near areas where mosquito populations are high (e.g., near bodies of water or stagnant water, which is where mosquitoes reproduce)

While certain environmental factors can increase a dog’s risk of exposure to mosquitoes and contraction of heartworms, it is important to note that avoiding these environmental factors is not enough to prevent heartworm infection. Mosquitoes do come indoors. And, even though Oklahoma has cold winters, we do have enough unseasonably warm days during the winter for mosquitoes to be active and spread heartworms. 

The best thing you can do to protect your dog from heartworms is to keep them on year-round heartworm prevention. All heartworm prevention medications are in the same drug class, macrocyclic lactones. However, these medications come in a variety of formulations to meet your needs and your pet’s lifestyle. They can be monthly oral products, monthly topical products, or injections given either every 6 or 12 months. 

About the author: Dr. David Bailey is a Clinical Assistant Professor in the Small Animal Primary Care Service. 

Veterinary Viewpoints is provided by the faculty of the OSU Veterinary Medical Teaching Hospital. Certified by the American Animal Hospital Association, the hospital is open to the public providing routine and specialized care for all species, as well as emergency care. Call 405-744-7000 for an appointment or see more information at

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