Back in July we had the pleasure of meeting Darcy, an adorable 2 year-old Collie. She was fresh off the plane from South Korea where her new owner, an Oregon-based veterinarian, had fallen in love with her sweet personality! During Darcy’s stateside health screening, x-rays showed her heart was bigger than normal, and she tested positive for heartworm. Luckily, her owner understood the importance of assessing her disease. She brought Darcy to Cardiology Northwest for an exam and echocardiogram (ultrasound of the heart) to determine the severity of her heartworm infection and get the all-clear on beginning treatment.

It’s an unfortunate fact that heartworm is becoming more common and widespread. Though it’s a very preventable disease, heartworm can cause lasting damage. Untreated heartworm often leads to death.

But What Is Heartworm?

Heartworm is a parasitic worm that lives in the heart, lungs, and associated blood vessels of affected dogs, cats, and ferrets. Adult worms can grow up to 12 inches, impeding blood flow through the heart and other important arteries. An infected dog may carry as many as 250 adult worms. Since heartworms rarely reach adulthood in cats, they often go undetected while the immature larvae cause irreversible damage.

Heartworm is spread exclusively by mosquitos infected with heartworm larvae, which makes it possible for outdoor and indoor-only pets to contract the disease. There is typically a seven-month incubation period between when your pet is bitten and when they will test positive. Dogs and cats should be tested annually for heartworm disease and prior to being placed on any prevention. Testing is very important as heartworm disease has been reported in all 50 states; contact your primary care veterinarian to inquire about heartworm specific testing.

Symptoms of heartworm

As heartworms grow they begin to impede normal heart and lung function. Signs of heartworm may include coughing, exercise intolerance, and weight loss. Congestive Heart Failure is a concern for severely affected dogs. Some dogs may also experience high blood pressure in the lungs, a rapid heartbeat (tachycardia), and labored breathing.

If your dog begins to exhibit these more severe signs of heartworm disease, your primary care veterinarian may refer you to a veterinary cardiologist for diagnostics to gauge the severity of disease. A cardiologist will have more experience managing symptoms of Congestive Heart Failure and other cardiac issues secondary to the heartworm disease.

Treatment Options

The first goal of treatment is to stabilize your pet if they’re exhibiting symptoms of heartworm disease. Once symptoms are well-managed and your pet is stable, treatment aims to kill all adult and immature worms. Your veterinarian will typically begin treatment following diagnostics such as x-ray, echocardiogram, and lab work, to confirm your pet is a safe candidate. Treatment may vary depending on the severity of heartworm disease, but typically involves antibiotics, steroids, and several injections of a drug called Melarsomine (Immiticide) to kill the adult and mature worms. Following these injections, your pet will need to stay for hospital monitoring, to ensure there are no adverse reactions to the treatment. After each injection, the dying worms will migrate to the lungs where they are absorbed and eventually broken down by the body. A single course of treatment can take up to 60 days or longer from start to finish.

During this time, it’s very important to keep your dog quiet, as physical exertion may cause a large number of dying or dead worms to migrate into the lungs, where they can cause a blockage. For this reason, your dog will need to be watched closely for signs of coughing, wheezing, vomiting and depression. Any abnormal signs should be checked by your veterinarian.

Additionally, 6 months after treatment your veterinarian will recommend follow-up blood tests to ensure all of the adult heartworms were killed. Sometimes a second course of treatment will be recommended.

An ounce of prevention…

Heartworm can be a painful, costly, and time-consuming disease. Luckily, heartworm is easily preventable! A simple monthly oral or topical treatment can prevent heartworm up to 100% of the time. By following your veterinarian’s recommendation for monthly heartworm preventative, your furry family members can stay healthy, happy, and heartworm-free! Have questions about heartworm disease treatment and prevention? Contact our office for more information!

So how is Darcy doing now…?

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