Heartworms in Dogs

Every dog parent has, at least, a vague notion of heartworm disease. A single mosquito bite can transmit heartworm larvae into your dog’s bloodstream, potentially leading to severe lung disease, heart failure, and organ damage. At Acton Animal Hospital, we want you to have a clear understanding of how heartworm disease affects your pet, and why testing and prevention matter. Below, we’ll explain how dogs contract heartworm disease, how a full infection is treated, the science behind prevention, and provide detailed answers to common questions to help keep your dog healthy.

 

 

What Causes Heartworm in Dogs?

Heartworm disease in dogs starts with a bite from an infected mosquito. When a mosquito carries microscopic heartworm larvae, it can transmit them directly into a dog’s bloodstream. Over several months, the larvae mature and migrate to the heart and lungs, where they grow into long, thread-like worms. A fully grown heartworm can reach up to 12 inches in length and live for several years within the body.

How Heartworms Are Transmitted

Massachusetts mosquitoes are active for most of the year, particularly during the warmer months. However, due to changes in climate patterns, heartworm in dogs has become a concern even outside traditional mosquito seasons. Any dog, regardless of age, breed, or lifestyle, can be at risk. Heartworm transmission doesn’t depend on whether a dog spends more time indoors or outside—if there’s even one mosquito in the area, the risk exists.

The Role of Climate and Geography

Dogs can become hosts for dozens, sometimes even hundreds, of adult worms if left untreated. The longer the worms remain in the body, the more damage they can cause to the heart, lungs, and associated blood vessels. Early detection of heartworm in dogs is key to limiting the damage and beginning treatment.

How Heartworm in Dogs Progresses Over Time

Heartworm disease develops in stages, and each stage presents different challenges for a dog’s health. Many pet owners remain unaware of the infection until it reaches an advanced stage, which is why consistent screening is so important.

Early Infection

In the early stage, dogs usually don’t show any signs of illness. This phase can last for months. During this time, heartworms are growing inside the dog but haven’t yet reached maturity or begun to cause significant harm.

Mild to Moderate Symptoms

As the worms mature and reproduce, dogs may start showing signs of fatigue, especially after exercise. A persistent cough is often one of the first noticeable symptoms. Dogs might also exhibit a decreased appetite or begin to lose weight. In this phase, the damage to the lungs and heart becomes more pronounced.

Advanced Heartworm Disease

In severe cases, dogs may experience difficulty breathing, fainting episodes, or a swollen belly due to fluid buildup. At this point, the disease can cause long-term or irreversible damage. Treatment becomes more complicated and carries more risks, making early detection and prevention even more important.

Signs to Watch for with Heartworm in Dogs

Heartworm in dogs doesn’t always cause obvious symptoms at first, which is why regular vet checkups are vital. However, if your dog shows any of the following signs, you should schedule an appointment right away:

• Frequent coughing that doesn’t seem to improve
• Lethargy or reluctance to exercise
• Decreased appetite
• Weight loss
• Difficulty breathing
• Pale gums
• Swollen abdomen

Even mild symptoms should not be ignored. Dogs infected with heartworm may seem normal one day and show rapid signs of decline the next. If you notice any changes in your dog’s health or behavior, please contact Acton Animal Hospital at 978-263-7477 to schedule an exam.

Diagnosing Heartworm in Dogs at the Veterinary Office

Veterinarians diagnose heartworm in dogs through a simple blood test that detects the presence of heartworm proteins. This test is typically part of a dog’s annual wellness exam, especially in regions where mosquitoes are common. If a blood test comes back positive, your veterinarian may recommend additional diagnostic tools to confirm diagnosis.  These tests help determine how advanced the heartworm disease is and guide your veterinarian in developing a treatment plan. Accurate staging of the disease allows for the most effective and safest treatment approach possible.

Why Preventing Heartworm in Dogs Matters

Heartworm prevention is far safer, less costly, and easier on your dog than treating an active infection. Preventive medications work by eliminating heartworm larvae before they have a chance to grow and migrate through the body.

Options for Prevention

There are several forms of heartworm preventives, including monthly chewables, topical treatments, and long-acting injections. Your veterinarian can help determine which option fits best with your dog’s lifestyle and health history.

Year-Round Protection in Massachusetts

Some pet owners assume they only need to give heartworm prevention during summer, but that’s no longer the case. Because temperatures fluctuate and mosquito populations can survive in milder months, year-round prevention offers consistent protection against heartworm in dogs. Skipping even one dose of preventive medication can leave a gap in protection and put your dog at risk.

Regular Testing Still Matters

Even if your dog takes heartworm prevention regularly, annual testing remains essential. Preventives are highly effective, but missed doses or vomiting shortly after administration can leave dogs unprotected. Annual testing ensures early detection and gives your vet an opportunity to make any needed adjustments to your dog’s preventive care.

The Treatment Process for Heartworm in Dogs

If a dog tests positive for heartworm, the treatment process must begin promptly and under veterinary supervision. The goal of treatment is to kill the adult worms while minimizing complications. Treatment often includes:

• Antibiotics to combat bacteria associated with heartworm
• Heartworm preventive to stop new infections
• Anti-inflammatory medications
• A series of injections to kill adult worms

Dogs undergoing treatment will need strict exercise restrictions to avoid complications. The dying worms can block blood flow or cause inflammation if the dog’s heart rate becomes elevated. Most dogs require several months of rest and monitoring after treatment begins. Follow-up testing is critical to confirm that the heartworm infection has been successfully cleared.

Supporting Long-Term Health After Heartworm Treatment

Once heartworm in dogs has been treated, follow-up care is just as important as the treatment itself. Dogs recovering from heartworm disease need time to heal and return to full health. A gradual reintroduction to physical activity helps reduce strain on the heart and lungs.

Regular Wellness Exams

Post-treatment care includes routine checkups to monitor the dog’s heart and lung function. These appointments also provide an opportunity to update preventive medications and discuss any lasting effects of the infection.

Ongoing Prevention

After a heartworm infection, lifelong preventive care is essential. Dogs do not build immunity after having heartworm. Without consistent protection, they remain just as vulnerable to another infection. For Acton dog owners, staying proactive with wellness care is one of the most effective ways to protect your pet’s health. To learn more about heartworm disease and what you can do to help protect your pet, check out the American Heartworm Society for additional educational resources.

Why Heartworm Awareness Matters for Acton Pet Owners

Heartworm in dogs is a growing concern across Massachusetts, and the risks continue to increase with shifting weather patterns and longer mosquito seasons. Even healthy dogs are vulnerable if not protected with routine testing and preventive care. With early detection, prompt treatment, and year-round prevention, heartworm in dogs doesn’t need to become a life-altering diagnosis.

Staying informed and working with your veterinarian creates a solid foundation for your dog’s long-term health. If your dog is due for a heartworm test or you have questions about starting prevention, the team at Acton Animal Hospital is glad to discuss heartworm prevention with you. Please call 978-263-7477 to book an appointment and make heartworm prevention a regular part of your dog’s wellness plan.