Heartworm disease is a serious and potentially life-threatening condition that affects dogs across the globe. Caused by a parasitic worm called Dirofilaria immitis, heartworm disease can lead to severe health complications and even death if left untreated.
In this blog post, we’ll explore how dogs contract heartworms, the symptoms to watch out for, and the steps you can take to prevent this dangerous condition.
Transmission of Heartworms
Heartworms are transmitted to dogs through the bite of an infected mosquito. When a mosquito bites an infected animal, it ingests microscopic heartworm larvae called microfilariae. These larvae develop into infective larvae within the mosquito and can be transmitted to another animal when the mosquito feeds again.

Once a dog is bitten by an infected mosquito, the larvae enter the bloodstream and migrate to the heart, lungs, and surrounding blood vessels. Over the course of several months, the larvae grow into adult worms that can measure up to 12 inches in length.
Symptoms of Heartworm Disease
In the early stages of heartworm infection, dogs may not show any symptoms. However, as the worms grow and reproduce, they can cause significant damage to the heart, lungs, and blood vessels, leading to more severe symptoms. Common signs of heartworm disease in dogs include:
- Persistent cough
- Fatigue or lethargy
- Difficulty breathing or shortness of breath
- Weight loss or loss of appetite
- Swollen abdomen due to fluid accumulation
- Collapse or fainting
If you notice any of these symptoms in your dog, it’s important to consult with a veterinarian as soon as possible for proper diagnosis and treatment.
Preventing Heartworm Disease
Prevention is the key to protecting your dog from heartworm disease. There are several FDA-approved heartworm preventatives available, including oral medications, topical treatments, and injectable options.
These medications work by killing the heartworm larvae before they can mature into adult worms. It’s essential to administer these preventatives as directed by your veterinarian, typically on a monthly basis.

In addition to administering heartworm preventatives, you can also take steps to reduce your dog’s exposure to mosquitoes by:
- Using mosquito repellents specifically designed for dogs
- Keeping your dog indoors during peak mosquito hours (dawn and dusk)
- Eliminating standing water around your home where mosquitoes can breed
Take Heartworm Seriously
Heartworm disease is a serious and potentially fatal condition for dogs. By understanding how dogs contract heartworms and recognizing the symptoms of the disease, you can take action to protect your beloved pet. Remember, prevention is the best defense against heartworm disease.
Talk to your veterinarian about the most appropriate heartworm preventative for your dog, and ensure that you administer it consistently to keep your furry friend safe and healthy.