How to Tell If Your Dog Has Heartworms: What to Look For

Since heartworms can be a deadly disease for dogs, it's important to know the signs that could mean your dog has been infected. Coughing, lethargy, reduced appetite, and difficulty breathing are all things to look for, and they can show up over time as the worms multiply and cause cardiovascular problems, meaning you should take your dog to the vet as soon as possible.

To learn more about how heartworm disease is diagnosed and treated, we've looked at studies from some of the top veterinary researchers and animal health organizations. Their work has helped us better understand the most reliable ways to test for, treat, and prevent heartworm disease in your dog. This knowledge will help you make sure your furry friend stays safe from this severe, yet avoidable, condition.

Common Symptoms: How to Tell If Your Dog Has Heartworms

Early on in the progression of heartworm disease, dogs may not show any symptoms at all, according to Back Bay Veterinary Clinic. However, as the disease advances, there are several common symptoms that tend to develop. The most frequently reported is a dry, persistent cough that can be exacerbated by exercise and even lead to coughing up blood and fainting, according to HEARTGARD® Plus.

Other common symptoms include decreased energy, exercise intolerance, and a lack of interest in physical activity, which can be attributed to the stress the worms put on the heart and lungs. Weight loss and a loss of appetite are also common symptoms that can develop as the disease progresses. It's important to take note of these more subtle symptoms because, as Pet Wellness Clinics points out, if heartworm disease is left untreated, it can lead to more severe symptoms.

In the later stages of the disease, dogs may experience difficulty breathing, a swollen abdomen or chest due to a buildup of fluid, and even blindness or seizures if the worms migrate to the eyes and brain. In the most severe cases, dogs can develop caval syndrome, a life-threatening condition in which the worms block blood flow to the heart, leading to fainting, shock, and potential cardiovascular collapse. Catching the disease early and seeking treatment from a veterinarian can help prevent the disease from progressing to this point.

Diagnostic Techniques: How Heartworm Is Diagnosed

Diagnosing heartworm disease in dogs involves a series of blood tests and other diagnostic techniques, according to VCA Animal Hospitals. The American Heartworm Society recommends the use of the heartworm antigen test, which detects proteins that are released by the adult female heartworm. This test is very sensitive and can detect the presence of heartworms when there are as few as one to three adult female worms.

However, the Texas A&M Veterinary Medical Diagnostic Laboratory warns that antigen tests can result in false negatives in certain cases, including when the infection is less than five months old or if the worms are all male. As a result, the American Heartworm Society suggests that a positive or "weak positive" antigen test should be followed up with a microfilaria test, which detects the immature larval stage of the heartworm.

Other diagnostic techniques, such as radiographs, electrocardiograms, and echocardiography, can be used to detect changes in the heart and lungs that are caused by heartworm disease, according to Today's Veterinary Practice.

The American Heartworm Society notes that it's important to use a combination of diagnostic techniques because relying on antigen tests alone can result in missed diagnoses. It's important for dogs that are both on and not on preventative medication to be tested regularly in order to catch the disease early and manage it effectively.

Preventative Measures: How to Keep Your Dog Safe From Heartworm

The American Heartworm Society stresses the importance of year-round preventative medication for dogs in all parts of the country. There are a number of different types of preventatives, including monthly chewable tablets, topical "spot-on" treatments, and injectable medications that are given every 6-12 months.

It's important for veterinarians to help dog owners choose the right preventative and to make sure that their patients are getting the right doses. According to the American Kennel Club, missed or late doses can leave dogs vulnerable. In fact, the Advent Veterinary Services notes that even one missed monthly dose can put dogs at risk of infection.

In addition to medication, reducing the risk of heartworm transmission involves reducing dogs' exposure to mosquitoes. The Humane Society of the United States explains that this can include using pet-safe insecticide sprays in the yard and other mosquito-repelling strategies that are recommended by veterinarians.

Potential Health Risks: What Happens If Heartworm Goes Untreated?

If heartworm disease is left untreated, it can lead to serious and potentially fatal health risks, according to the American Heartworm Society. As the disease progresses, the adult worms can cause damage to the heart, lungs, and other organs. The worms can cause heart valves to malfunction and result in pulmonary hypertension, which makes the heart work harder to pump blood to the lungs. This can eventually lead to heart failure.

In later stages of the disease, dogs can develop caval syndrome, where the worms block blood flow to the heart, leading to shock, fainting, and even cardiovascular collapse, according to Pumpkin®. In addition, the American Heartworm Society explains that heartworm disease can also cause liver or kidney failure, which can be life-threatening. Even if the disease is treated, the American Heartworm Society explains that the damage to the heart, lungs, and blood vessels can be permanent, which can impact the dog's overall health and well-being.

To avoid the serious health risks associated with heartworm disease, it's important to detect the disease early and treat it as soon as possible. By learning about the potential health risks, dog owners can make sure they're doing everything they can to protect their pets.

Conclusion: Be Proactive About Your Dog's Health

If left untreated, heartworm disease can be very serious and even life-threatening. As the disease progresses, the adult worms can cause extensive damage to the heart, lungs, and other organs. The worms can affect the heart valves and cause pulmonary hypertension, which is when the heart has to work harder to pump blood to the lungs, eventually leading to heart failure.

In severe cases, dogs can develop caval syndrome, where the worms block blood flow to the heart, which can lead to shock, fainting, and even cardiovascular collapse. If left untreated, heartworm disease can also lead to liver or kidney failure, which can further compromise a dog's health. Even if the disease is treated, the heart, lungs, and blood vessels can be permanently damaged, which can impact a dog's quality of life.

That's why early detection and treatment are so important. If heartworm disease is caught early, it can be treated and the dog can go on to live a long, healthy life. By knowing the risks, dog owners can take steps to protect their pets.