Understanding Heartworms

Prevention and Treatment of Heartworms for Cats and Dogs

Heartworms are a serious but preventable health concern for both dogs and cats. As a new pet owner, it’s essential to understand what heartworms are, how they can impact your pet’s health, and what you can do to protect your pet from them. Heartworms can be life-threatening, but with a good prevention routine and prompt treatment, you can keep your furry family members safe and healthy. Let’s dive into what every pet owner needs to know about heartworms and how to keep them at bay.

What Are Heartworms?

Heartworms are parasitic worms that live in the heart, lungs, and blood vessels of infected animals. They’re transmitted by mosquitoes, which means pets in any region with mosquitoes are at risk. The worms mature over several months and, if untreated, can grow up to a foot in length, causing severe health issues and even death.

While heartworms are most common in dogs, cats can also get heartworms. However, the disease manifests differently in each species:

Dogs: Heartworms can grow, reproduce, and live for years in a dog’s heart and lungs, causing extensive damage.
Cats: While heartworms don’t typically mature in cats, the presence of even a few can cause severe respiratory and cardiovascular problems, known as Heartworm Associated Respiratory Disease (HARD).

How Do Heartworms Harm Pets?

Heartworms cause a range of health issues that can affect an animal’s entire body. For dogs, the disease is particularly severe because adult heartworms can multiply in their heart and lungs.

Heart and Lung Damage: In both dogs and cats, heartworms cause inflammation and restrict blood flow, which damages organs over time.
Reduced Mobility: Pets with heartworms often become lethargic, exercise intolerant, and may struggle with simple movements.
Organ Failure: Severe cases can lead to congestive heart failure, respiratory distress, and, if untreated, death.

Symptoms of Heartworm Disease

Early signs of heartworm disease are often subtle, which can make it difficult to detect without regular vet check-ups. Here’s what to look out for in dogs and cats:

In Dogs:

Coughing and difficulty breathing
Decreased appetite and weight loss
Fatigue and reluctance to exercise
Swollen belly (due to fluid buildup)

In Cats:

Coughing or asthma-like attacks
Vomiting
Loss of appetite and weight loss
Difficulty walking or breathing
Sudden collapse or even sudden death

If you notice any of these symptoms in your pet, it’s important to visit your veterinarian right away for a heartworm test.

Heartworm Prevention

The best way to protect your pet from heartworms is through consistent prevention. Heartworm prevention is much easier, safer, and more affordable than treating an infection. The American Heartworm Association recommends year-round prevention for all pets.

How to Prevent Heartworms in Your Pet

Monthly Heartworm Preventatives: These come in chewable, topical, and injectable forms and protect your pet from heartworms by killing the larvae before they can mature. Be consistent—missing doses can put your pet at risk.
Annual Testing: Even if your pet is on heartworm prevention, annual testing ensures they’re fully protected. A simple blood test can detect any infection early on.
Mosquito Control: Reducing mosquito exposure can lower the risk of heartworm transmission. Use pet-safe insect repellents and keep your yard mosquito-free by removing standing water.

Prevention for Dogs and Cats

Dogs and cats have different options for heartworm prevention:

For Dogs: Monthly chewables, topical treatments, or injectable preventatives (like ProHeart, which provides 6 or 12 months of protection) are common options.
For Cats: While options are fewer for cats, some topical preventatives protect against both fleas and heartworms.

Tip: Be sure to consult your veterinarian before starting any prevention routine to ensure the treatment is safe and appropriate for your pet’s age, weight, and health.

What to Do If Your Pet Has Heartworms

If your pet tests positive for heartworms, don’t panic. While heartworm disease is serious, it can be managed and treated, especially if detected early. The American Heartworm Association provides guidelines to help veterinarians treat heartworm-positive pets safely and effectively.

Treatment for Dogs

Heartworm treatment for dogs involves several steps to reduce the worm load gradually and minimize the risk of complications:

Initial Stabilization: In cases of severe infection, your vet may start with medications to stabilize your dog’s health before treating the worms.
Administering Heartworm Treatment: Heartworm treatment typically involves a series of injections to kill adult worms. This is done carefully to avoid complications from the dying worms.
Strict Rest: During and after treatment, strict rest is crucial. Activity can lead to serious health issues as dead worms break down and are processed by the body.
Follow-Up Testing: After treatment, your dog will need follow-up tests to ensure all heartworms are gone.

Treatment for Cats with Heartworm Disease

Heartworm treatment in cats is complex because there are no approved drugs that safely kill adult heartworms in cats, unlike in dogs. Only around 25% of heartworms reach adulthood in cats. This is partly why heartworm disease in cats presents differently than in dogs and requires a different, more cautious approach to care.

However, veterinarians have strategies to manage symptoms and support a cat’s overall health. Here are some key elements of heartworm treatment for cats:

Supportive Care

For cats with lung disease due to heartworms, supportive care is essential. Prednisone is often prescribed to help reduce inflammation in the lungs. Cats experiencing respiratory distress may receive oxygen therapy, intravenous fluids, and bronchodilators to support breathing and overall comfort.

Surgery

In severe cases where a cat shows intense signs of heartworm disease, surgical removal of heartworms might be considered. However, this approach carries significant risks and is typically reserved for cases with a poor prognosis, as surgery can be fatal for cats with severe heartworm disease.

Antibiotics

Doxycycline may be used to target certain bacteria associated with heartworms, which can contribute to inflammation and worsen symptoms. While it doesn’t kill heartworms directly, it helps reduce inflammation and can improve the cat’s condition.

Limited Therapeutic Options

Treating heartworm disease in cats is challenging because many therapies used in dogs, such as melarsomine, are toxic to cats. The American Heartworm Society does not currently recommend adulticide treatment (drugs that kill adult worms) for cats due to the associated risks. Instead, veterinarians focus on managing symptoms and monitoring the disease over time.

Monitoring and Potential for Spontaneous Cure

For cats not displaying significant symptoms, veterinarians may recommend a conservative approach, closely monitoring the cat’s condition in hopes of a spontaneous cure. A spontaneous cure occurs when a cat’s immune system naturally clears the heartworm infection without intervention. In some cases, ivermectin might be prescribed to reduce worm loads over an extended period (two years or more), but it carries risks, including potential allergic reactions and inflammatory responses.
All heartworm-positive cats, regardless of their symptoms, should undergo regular testing every six to twelve months. This typically includes serologic testing, echocardiograms, and chest radiographs to monitor their heartworm status. Ideally, both antibody and antigen tests are performed to provide a comprehensive view of the infection and its effects on the cat’s body.

Long-Term Prognosis

Veterinarians will cautiously consider a cat “recovered” from heartworm disease only once blood tests return negative and all clinical and radiological signs of the disease have resolved. While heartworm disease in cats is serious, it often presents with a lower worm burden than in dogs, usually only one to four worms, and less than 20% of these worms will produce microfilaria (the infective form of heartworms). In addition, cats have a higher rate of aberrant heartworm migration, meaning that worms may travel to other areas of the body, such as blood vessels, body cavities, or even the central nervous system.
The median survival time for cats diagnosed with heartworm disease is about four years.

Additional Tips for Heartworm Care and Prevention

Here are some practical tips to keep your pet safe and healthy:

Stick to Your Prevention Schedule: Set a reminder on your phone or calendar to give preventatives on the same day each month.
Monitor Your Pet’s Health Regularly: Watch for any changes in appetite, energy level, or breathing, and talk to your vet if you notice anything unusual.
Limit Outdoor Exposure in High-Mosquito Areas: If you live in a mosquito-prone area, try to limit your pet’s outdoor time during peak mosquito hours, like dusk and dawn.
Educate Fellow Pet Owners: Heartworm prevention can seem overwhelming to new pet owners, so share what you’ve learned to help others keep their pets safe too.

Key Takeaways

Heartworms Are Serious But Preventable: Heartworms can cause life-threatening issues in both cats and dogs, but regular prevention keeps them safe.
Monthly Preventatives Are Essential: Heartworm prevention is safer, easier, and more affordable than treatment.
Symptoms Can Be Subtle: Early signs of heartworm disease might be hard to notice, so schedule annual tests even if your pet seems healthy.
Treatment Varies by Species: Dogs undergo specific treatments to kill adult worms, while cats rely on symptom management due to limited treatment options.
Rest and Patience Are Crucial During Treatment: If your dog is being treated for heartworms, strict rest is essential to avoid complications.
Consult Your Vet for the Best Prevention Plan: Tailor your prevention routine to your pet’s age, weight, and lifestyle with your vet’s guidance.
Mosquito Control Helps Too: Keep your pet’s environment as mosquito-free as possible to further reduce risk.

Heartworms may sound intimidating, but with consistent care and prevention, you can keep your pets safe and give them long, happy lives. If you ever have questions about heartworm prevention or treatment, don’t hesitate to reach out to your veterinarian.