Canine Heartworms: How Do Dogs Get Heartworms and How to Prevent and Treat Them

Share This Post

Heartworms are a potentially life-threatening parasitic infection that can affect dogs and other animals. So, how do dogs get heartworms?

Heartworms are transmitted through the bite of infected mosquitoes and can cause severe damage to a dog’s heart, lungs, and other organs if left untreated.

In this article, we will explore the process of how dogs get heartworms, the signs and symptoms of heartworm disease, the importance of prevention, and the available treatment options for infected dogs.

how do dogs get heartworms new braunfels tx

How Dogs Get Heartworms

The heartworm life cycle begins when an infected animal, such as a dog or a wild animal like a coyote, has adult heartworms that produce microscopic offspring called microfilariae. These microfilariae circulate in the host’s bloodstream.

When a mosquito feeds on the blood of an infected host, it ingests the microfilariae. Inside the mosquito, the microfilariae mature into infective larvae over a period of 10 to 14 days. When the infected mosquito bites a healthy dog, it injects the infective larvae into the dog’s bloodstream.

Over the next several months, the larvae travel through the dog’s bloodstream, eventually reaching the heart and lungs where they mature into adult heartworms. Adult heartworms can grow up to a foot long and live for five to seven years.

Signs and Symptoms of Heartworm Disease

Early stages of heartworm disease may present with no noticeable symptoms. However, as the disease progresses and the worms multiply, signs may become more apparent. Some common symptoms of heartworm disease include:


Persistent coughing can be a sign of heartworm infection, especially if it worsens with exercise.


Infected dogs may tire easily or become lethargic, even after light physical activity.

Weight Loss

Dogs with heartworms may experience weight loss and a decreased appetite.

Rapid or Labored Breathing

Heartworms can cause damage to the lungs, leading to difficulty breathing.

Swollen Abdomen

Fluid buildup in the abdomen can occur due to heartworms affecting the dog’s circulatory system, resulting in a swollen or distended appearance.


In advanced cases, dogs may suffer from severe heartworm-related complications that can lead to collapse and even death.

Preventing Heartworm Disease

Monthly preventatives

The most effective way to protect your dog from heartworms is by administering monthly heartworm preventatives. These medications are available in various forms, including oral tablets, chewables, and topical applications. Consult your veterinarian to determine the best preventative option for your dog.

Annual testing

Even if your dog is on a heartworm preventative, it’s essential to have them tested for heartworms annually. Early detection is crucial in preventing severe complications and increasing the likelihood of successful treatment.

Mosquito control

Since heartworms are transmitted through mosquito bites, reducing your dog’s exposure to mosquitoes can help lower their risk of infection. Use pet-safe insect repellents, keep your dog indoors during peak mosquito hours, and eliminate standing water around your home where mosquitoes can breed.

You can also help protect your dog from heartworms by taking steps to minimize mosquito exposure in your home and yard. Remove standing water sources, such as birdbaths or puddles, where mosquitoes can breed. Regularly clean and maintain gutters to prevent water buildup, and keep your lawn trimmed and free of debris. Installing screens on windows and doors can help keep mosquitoes out of your home, and using pet-friendly mosquito repellents can provide additional protection for your dog during outdoor activities.

By implementing these measures along with regular heartworm prevention, you’ll create a safer environment for your beloved pet.

Heartworm Disease Treatment

If your dog tests positive for heartworms, your veterinarian will recommend a treatment plan based on the severity of the infection.

Before beginning heartworm treatment, your veterinarian may need to address any complications, such as severe inflammation or organ damage, to ensure the dog is stable enough for treatment.

The primary method for treating heartworm disease involves the administration of a drug called melarsomine dihydrochloride, an adulticide that kills adult heartworms. This medication is typically given through a series of injections over a period of time. It’s essential to follow your veterinarian’s instructions carefully to ensure the safe and effective treatment of your dog’s heartworm infection.

After the adulticide treatment, your dog will need to be closely monitored and kept on restricted activity to minimize the risk of complications. As the adult heartworms die, they can break apart and potentially cause blockages in the dog’s circulatory system. Limiting your dog’s physical activity during this time reduces the risk of severe complications.

Depending on the severity of the infection, your dog may require additional treatments, such as medications to address inflammation or antibiotics to treat secondary infections. Your veterinarian will guide you through the appropriate treatment plan for your dog.

Once your dog has completed their heartworm treatment, your veterinarian will perform follow-up tests to ensure that all heartworms have been eliminated. It’s crucial to continue with annual heartworm testing and monthly preventatives to protect your dog from future infections.

The Importance of Heartworm Prevention for Dogs

Preventing heartworm disease is far more straightforward and cost-effective than treating it. By administering monthly heartworm preventatives and conducting annual heartworm tests, you can significantly reduce your dog’s risk of infection and the associated health complications. Additionally, heartworm prevention can protect your dog from other parasites, such as hookworms and roundworms, which are often included in broad-spectrum preventatives.

Educating Yourself and Others

Awareness is key in preventing the spread of heartworm disease. As a pet owner, educating yourself on the risks, signs, and prevention methods can help keep your dog healthy and safe. Additionally, sharing your knowledge with other dog owners can contribute to reducing the overall incidence of heartworm infections.


Understanding how dogs get heartworms is essential for pet owners to protect their furry companions from this potentially life-threatening disease. By implementing preventative measures, such as administering monthly heartworm medications, conducting annual testing, and controlling mosquito exposure, you can significantly reduce your dog’s risk of infection. If your dog is diagnosed with heartworm disease, prompt treatment and proper post-treatment care are critical to ensuring a successful recovery. By staying vigilant and informed about heartworm prevention and treatment, you can help your dog live a healthy, happy life free from the threat of heartworms.

For pets in the New Braunfels, TX area, Comal Pet Hospital is here to help! Give us a call at (830) 625-8074 or make an appointment online.

Subscribe To Our Newsletter
Enjoy Helpful Pet Tips & Promotions
Newsletter Sign Up
More To Explore

Canine Hip Dysplasia

We know how much you love your four-legged family members, and that’s why we’re tackling a topic today that many dog owners unfortunately have to


How Long Do Dog Vaccines Last?

In this informative blog post, we’ll discuss a crucial aspect of your dog’s well-being: vaccinations. We’ll answer the burning question on every pet owner’s mind

Get the best care for your best friend.

Walk-in or request an appointment online
Newsletter Sign Up
Newsletter Sign Up