Slow Kill Heartworm Treatment: Is It Right for Your Dog?

Your vet just told you the bad news: your dog has heartworms. These nasty parasites can cause serious health problems if they aren't treated. You might have come across "slow kill heartworm treatment." While it might sound gentler, this approach has its complexities. This article breaks down the "slow kill" heartworm treatment, its pros and cons, and why your vet might consider this option. We'll cover everything you need to know to understand your dog's treatment options and make the best decision for their health.

What is the slow kill heartworm treatment in dogs?

The term "slow kill" might sound a bit nicer than the reality of heartworm treatment. When treating heartworm infections in dogs, we have typically used a medication called an adulticide (melarsomine, trade name Immiticide®) to kill adult heartworms living in your dog's heart and pulmonary blood vessels. This treatment is effective, but it comes with some risks, especially for heavily infected dogs.

With this heartworm treatment protocol, it takes a different route. It uses a specific heartworm prevention medicine, the kind you give your dog monthly. We combine this with an antibiotic called doxycycline to help target adult heartworms.

The idea is that over many months, the heartworm preventatives and the doxycycline will gradually kill off the adult heartworms.

What is the protocol for the slow kill heartworm treatment in dogs?

The original "slow kill" protocols relied solely on regular heartworm preventatives containing ivermectin. This approach was very slow, often taking years to eliminate adult heartworms.

Modern protocols have largely shifted towards a combination of moxidectin (often in Advantage Multi® or Proheart®) and the antibiotic doxycycline. This combination is frequently referred to as "Doximectin" or MOX-DOX. Here's why this newer approach is preferred:

1. Doxycycline targets a type of bacteria that lives within heartworms (Wolbachia), weakening them and contributing to their faster elimination. Studies have shown this combination kills adult heartworms more quickly and effectively than ivermectin alone. Current protocols suggest that doxycycline is to be given for 30 days.
2. Moxidectin, found in medications like Advantage Multi® and Proheart®, accumulates in the bloodstream with regular use. This sustained higher concentration appears to have better adulticidal effects compared to other oral preventatives designed primarily for heartworm prevention. We recommend giving moxidectin monthly, for at least 6 months.

Important considerations:

• Your veterinarian will determine the specific dosages, treatment duration, and how often your dog needs retesting.
• Throughout treatment, strict exercise restriction is still recommended to minimize complications for your dog.
• Regular follow-up testing will monitor your dog's progress and help determine if any remaining heartworms need further attention. We recommend retesting starting at 9 months and repeating every 3 months until the test is negative.

Please note: The American Heartworm Society (AHS) emphasizes that traditional heartworm treatment with melarsomine remains the gold standard when possible. The newer "Doximectin" protocols provide an alternative mainly in specific situations.

Why aren't other oral monthly preventatives recommended?

While monthly oral heartworm preventatives like Simparica Trio® do contain moxidectin, they differ from products like Advantage Multi®.

The concentration of moxidectin in Simparica Trio® is designed for preventative purposes, not for actively killing adult heartworms over a prolonged period. Advantage Multi® contains a higher concentration and accumulates in the bloodstream with repeated dosing, enhancing its effectiveness for the "slow kill" approach.

Why is the slow kill heartworm treatment controversial?

The American Heartworm Society, a leading veterinary organization, recommends the traditional adulticide treatment for most dogs with heartworm disease. Here are some of their concerns with the slow kill heartworm treatment protocol:

• Lower success rates: "Slow kill" may not always clear all the adult heartworms. This leaves your dog at risk of continued damage to their heart and lungs. Recent studies suggest that this protocol can be up to 90% effective.
• Heartworm damage continues: Unlike the faster treatment, "slow kill" means heartworms are causing harm to your dog's body for a much longer period. This damage can sometimes be irreversible.
• Resistance concerns: Prolonged use of heartworm prevention medication, as done in "slow kill," raises concerns about resistant heartworms. These resistant strains could make heartworm prevention less effective for all dogs.

Despite the controversies, there are some specific situations where we might discuss "slow kill" as a potential option for your dog. We'll cover those circumstances in the next section.

When might the slow kill heartworm treatment be beneficial?

While the traditional adulticide treatment is typically preferred, there are certain situations where the "slow kill" method may be considered as an alternative option. These circumstances include:

• Risk of complications: For some dogs, the risks associated with anesthesia for the traditional treatment may outweigh the potential benefits. In these cases, a slower approach may be chosen to minimize potential complications.
• Expense: Due to the high cost of the traditional treatment with melarsomine, some pet owners may opt for slow kill as a more affordable option.
• Severe heartworm disease: In rare cases where a dog has severe heartworm disease and is not a good candidate for adulticide treatment, slow kill may be recommended as a last resort.
• Lack of access to treatment: In areas where traditional adulticide treatment is not readily available, "slow kill" may be the only feasible option for managing heartworm disease in dogs.

Regardless of the circumstances, it's important to carefully consider all options and work closely with your veterinarian to determine the best course of treatment for your dog.

The takeaway: Making the best choice for your dog

Heartworm disease is a serious condition, but with proper treatment, your dog has the potential to live a long and healthy life.

Here are some key takeaways when considering treatment options:

• The traditional treatment remains preferred: The American Heartworm Society recommends the traditional treatment with adulticide medication as the gold standard for most dogs. It's faster, more reliable, and minimizes long-term complications.
• "Slow kill" protocol as a potential alternative: In specific situations, like financial limitations, severe underlying health issues, or limited access to medication, "Doximectin" (a combination of moxidectin and doxycycline) might be considered.

Important considerations for the "slow kill" treatment:

• Success isn't guaranteed: While the "slow kill" has improved, it might not eliminate all adult heartworms. Regular testing is essential to monitor the progress and efficacy of the treatment
• Long-term commitment: The "slow kill" treatment can take many months, requiring consistent medication administration and retesting. We recommend starting testing again at 9 months.
• Exercise restriction is important: Throughout treatment, limiting your dog's activity is essential to prevent complications associated with dying heartworms. Regular walks are perfectly fine, but we recommend avoiding strenuous activity throughout the treatment.

Your veterinarian is your best resource for helping you with your heartworm treatment options. They will assess your dog's individual situation, discuss the pros and cons of each approach, and develop a personalized treatment plan.

Although the gold standard for treating heartworm disease in dogs is the traditional adulticide medication, there are alternative options available. Depending on your dog's specific situation and needs, a "slow kill" protocol with doxycycline and moxidectin may be considered. Newer protocols have good success rates and can be a more affordable option, but careful monitoring is important to ensure the best outcome. Your veterinarian will work with you to determine the most effective and appropriate treatment plan for your dog.