It’s a beautiful Montana day, so you decide to take your dogs, Daisy and Sally, for a hike, which they love. Unfortunately, after days of heavy rain, the weather has warmed up, and mosquitos are out in full-force. When you get home, you pick up the mail, which includes a reminder that both your dogs are due for their annual heartworm test. You try to remember if the heartworm test is the one that requires you to bring a poop sample.

You call Livingston Veterinary Hospital, schedule an appointment for the next day, and ask about the sample. “No,” says the customer care specialist. “All you need is for your dogs to be on their best behavior. We look forward to seeing you tomorrow.” 

Off to the clinic you go the next day to see Dr. Clausen, who has been caring for your dogs since they were puppies. Their physical exams go well, and then a small blood sample is taken from each dog to test for heartworms. The testing reminds you of a heartworm medication incident several months ago, when one of the dogs ate all the heartworm prevention chews in the house. You were never sure which dog was the culprit, and hope that the few months it took to replace the chews is not a problem.

Unfortunately, it is. Dr. Clausen tells you that Daisy has tested heartworm positive, and confirms that during the lapse in medication, Daisy could have been bitten by a heartworm-infected mosquito. Now you know which dog ate the heartworm chews seven months ago.

Dr. Clausen reassures you that all is not lost. “That’s what I am here for,” he says. “We can start treating Daisy today.”

Daisy did well on her treatment, and never missed a heartworm preventive again.

Protecting pets from heartworm disease

Few medical conditions can actually be prevented, but heartworm disease in pets is one. In humans, childhood vaccines help protect children from many infectious diseases, so much so that some infections have been eradicated. Vaccines help inform the immune system about a potential enemy (i.e., the infectious disease), and the immune system creates a specialized plan to combat the infection. 

The same strategy is used for dogs and cats for viral and bacterial illnesses, but there is not yet a vaccine against parasites, such as heartworms. However, medications, including heartworm preventives, are available that prevent worm infestations. 

What is a heartworm?

Heartworms are transmitted as larvae by infected mosquitoes when they bite your pet. The larvae slowly move through the pet’s bloodstream, maturing into worms as long as 12 inches, and causing damage as they move through to the dog’s  heart, where they can cause cardiovascular and breathing problems, and blood-clotting issues. Dogs can also develop general malaise, lethargy, and exercise intolerance, and death may occur.

Cats can be infected, too, but generally with fewer heartworms that go to the lungs, although they can cause sudden death.

Heartworm disease prevention

Treatment for heartworm disease is painful and expensive, so prevention is the best course of action. Oral and topical heartworm prevention medications that must be administered monthly year-round are available at a reasonable cost, and an injection that can prevent heartworm disease for six or 12 months has recently been introduced.

With oral heartworm medications, precise timing is essential. The medication kills baby heartworms (i.e., the larvae) that entered the body during the past one to two months, but may not kill older worms. However, after six to seven months, the heartworms will have matured into adults, which can be detected on a heartworm test. 

At Livingston Veterinary Hospital, we want to be allies in your pet’s health, and we are always happy to discuss our recommendations for heartworm disease—year-round preventives and annual testing—and other preventable health conditions. Set up an appointment, so that together we can develop a protection plan for your pets.