What happens when a dog is heartworm positive? A Complete Guide

What happens if my dog tests positive for heartworms?

No one wants to hear that their dog has heartworm, but the good news is that most infected dogs can be successfully treated. The goal is to first stabilize your dog if he is showing signs of disease, then kill all adult and immature worms while keeping the side effects of treatment to a minimum.

Heres what you should expect if your dog tests positive:

Confirm the diagnosis. Once a dog tests positive on an antigen test, the diagnosis should be confirmed with an additional—and different—test. Because the treatment regimen for heartworm is both expensive and complex, your veterinarian will want to be absolutely sure that treatment is necessary.

Restrict exercise. This requirement might be difficult to adhere to, especially if your dog is accustomed to being active. But your dog’s normal physical activities must be restricted as soon as the diagnosis is confirmed, because physical exertion increases the rate at which the heartworms cause damage in the heart and lungs. The more severe the symptoms, the less activity your dog should have.

Stabilize your dogs disease. Before actual heartworm treatment can begin, your dog’s condition may need to be stabilized with appropriate therapy. In severe cases of heartworm disease, or when a dog has another serious condition, the process can take several months.

Administer treatment. Once your veterinarian has determined your dog is stable and ready for heartworm treatment, he or she will recommend a treatment protocol involving several steps. The American Heartworm Society has guidelines for developing this plan of attack. Dogs with no signs or mild signs of heartworm disease, such as cough or exercise intolerance, have a high success rate with treatment. More severe disease can also be successfully treated, but the possibility of complications is greater. The severity of heartworm disease does not always correlate with the severity of symptoms, and dogs with many worms may have few or no symptoms early in the course of the disease.

Test (and prevent) for success. Approximately 6 months after treatment is completed, your veterinarian will perform a heartworm test to confirm that all heartworms have been eliminated. To avoid the possibility of your dog contracting heartworm disease again, you will want to administer heartworm prevention year-round for the rest of his life.

Treatment Options for Heartworm Disease in Dogs

Once a diagnosis has been obtained, heartworm disease is often categorized into four classes based on severity of infection and risk of treatment.

Class 1 Heartworm: Dogs with a positive heartworm test but often show no signs or relatively mild signs like cough.

Class 2 Heartworm: Dogs with a positive test and often have moderate signs like exercise intolerance.

Class 3 Heartworm: Dogs with a positive test and often are sick and debilitated.

Class 4 Heartworm: Often referred to as caval syndrome; these dogs are in a life-threatening situation as worms are blocking blood from exiting the heart (typically requires immediate surgery by a specialist to survive).

Additional testing is often recommended and performed to help determine the dog’s heartworm class. Speak with the shelter staff to determine what testing has been performed and the results. If there has been no formal testing outside a general heartworm test at the shelter, make sure a heartworm test is done at the first visit to your veterinarian.

The good news is that your dog can be cured of heartworm disease. Treatment often includes the following:

Steroids to decrease inflammation created by the worm itself.

Antibiotics, such as doxycycline, to kill Wolbachia, a symbiote organism that lives within the heartworm. Without the symbiote, the host heartworm becomes easier to kill and secondary inflammation is minimized.

Heartworm preventive to prevent younger worms from developing into adults and to rid the bloodstream of any circulating microfilariae

An injection containing the arsenic-based compound melarsomine, a medication designed to kill adult heartworms. This is referred to as the “fast kill” method and is the recommended treatment by the American Heartworm Society (AHS). The “slow kill” method (a combination of doxycycline and a monthly preventive), while not recommended by the AHS, may be an alternative when “fast kill” is not an option. However, because the length of time to a heartworm-disease-free state is longer, continued damage to the heart and organs will occur. It’s important to discuss all options with your veterinarian to determine the best one for your dog.

What causes heartworm disease?

Heartworm disease or dirofilariasis is a serious and potentially fatal disease. It is caused by a blood-borne parasite known as Dirofilaria immitis.

Adult heartworms are found in the heart, pulmonary artery, and adjacent large blood vessels of infected dogs. Rarely, worms may be found in other parts of the circulatory system. Female worms are 6 – 14″ long (15 – 36cm) and 1/8″ wide (3 mm). Males are about half the size of females. One dog may have as many as 300 worms present when diagnosed.

Adult heartworms may live up to five years. During this time, females produce millions of offspring called microfilaria. These microfilariae live mainly in the small vessels of the bloodstream.

Since transmission requires the mosquito as an intermediate host, the disease is not spread directly from dog to dog. Spread of the disease therefore coincides with mosquito season, which can last year-round in many parts of the United States. The number of dogs infected and the length of the mosquito season are directly correlated with the incidence of heartworm disease in any given area.

All About Heartworms, Treatment, and Recovery

My vet cant remember the last time she had a heartworm-positive case. Until now. My 8-year-old Dalmatian, Jolie, tested positive for heartworms at her annual checkup. We retested the blood in hopes that it was a false positive. But there was no need to send the sample back to the lab. Through a microscope, my vet could see microfilaria swimming in her blood sample. Obviously, I was shocked and upset because I take excellent care of our dog — how could this have happened?Â

Heartworm in dogs (dirofilariasis) is a serious and potentially fatal disease caused by a parasitic Dirofilaria worm that grows up to 14 inches long. These worms grow to live in a poor infected dog’s heart, lungs, and pulmonary artery. Mosquitos infect dogs with heartworms through their bites, so warmer areas are more prevalent with this pest.

Heartworms can live up to five years and can produce millions of offspring. This disease causes long-term damage to a dog’s internal organs, so it’s crucial to use heartworm prevention medications. If you’re wondering how you can tell if a dog’s got heartworms, here are some of the signs:

Does your pup have a pot belly? Have you noticed something moving in their poop? Yep — it’s time to talk about puppy parasites.

So, where did I go wrong? When I lived in New Orleans’ subtropical climate, it was a given that the dogs received heartworm preventative year-round. But, despite now living in the Chicago area, I learned that you to give your dog heartworm preventative through the winter, not just the warmer months.

I didn’t notice any significant changes in my dog’s behavior. But, before administering preventative medication, vets will perform a simple blood test. If your dog tests positive, as my dog did, additional testing will be required to determine the severity of the infection. In some cases, your vet may need to perform an ultrasound to determine your dog’s ability to tolerate treatment.Â

If your dog is showing any unusual behavior or listlessness, head to your vet to follow up. The American Heartworm Society recommends a dog be tested annually. Doing so will ensure the infection can be detected quickly, minimizing damage caused by the disease.

By the time most dogs show signs of heartworm, they are typically already in advanced stages. Due to the life cycles of the worms, it takes anywhere from five to seven months for young heartworm to become detectable by a blood test.

Dr. Ashley Saunders, a veterinary cardiologist and professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences explains, “The recovery rate with treatment depends on how bad the disease is at the time it is treated and which treatment protocol is used,” She continues, “Dogs can recover following treatment, but those with severe damage may have long-term clinical signs or develop them at a later date.”Â

There are three stages of heartworms — adults, young adults, and microfilariae larvae — each requiring a unique treatment. Your vet will prescribe the best course of action. In addition, antibiotics and steroids will likely be necessary. Depending on the severity of the disease, the outlook may be grim. Some pets may even require a life-long regimen due to these horrible worms, and, in other cases, dogs may only have mere months to live.