A year after Jenn Beel lost her beloved 8-year-old Welsh corgi, Jack, to cancer, she found herself scanning dog profiles on Petfinder, hoping to find a new friend who might be as smart and sweet as Jack.
She found Louie, a young corgi-golden retriever mix being fostered by K-9 Lifesavers, a rescue group in Stafford, Virginia. He had the cutest face she’d ever seen. “I saw his picture and was in love,” says Beel, senior creative director at the Humane Society of the United States. She immediately emailed the rescue to ask if Louie was still available.
He was, but there was a hitch. Louie had tested positive for heartworm disease, a potentially fatal condition.
Immiticide and ivermectin are the drugs commonly used to kill heartworms, and treatment has a high success rate. But it’s not a quick process: The larvae and worms exist in varying stages, and timing is everything in ensuring that every stage is eradicated. Immiticide injections are effective, but only on adult worms and late-stage larvae, says Dr. Gary Block with Ocean State Veterinary Specialists in Rhode Island. Ivermectin (the ingredient found in most preventatives) targets immature larvae and microfilaria (the early life form of the parasite).
At the Crofton Veterinary Center in Maryland, the treatment regimen typically goes like this, says Dr. Cynthia Harker: “We’ll start them on heartworm prevention to kill microfilaria and prevent spread, [then] we’ll start them on antibiotic” to kill bacteria that live with the heartworm. That’s followed by Immiticide injections over the course of several months to kill adult worms.
The hardest part of the whole process, particularly for young, rambunctious dogs who live to play, is the two- to four-month exercise restriction, which is critical while the worms are dying. No jumping or running or rough-housing allowed. “If they get too excited and have a massive worm die-off, they could get pulmonary emboli or anaphylaxis that could cause sudden death,” explains Harker.
The best defense in warding off heartworm is a good offense—keeping up with blood testing (annual tests are typically recommended) and consistent dosing with heartworm preventative. The preventative is available in chewable treats (or included in some topical flea-prevention medications) given once a month or as injections that last for six to 12 months. Some owners discontinue the preventative during winter months when mosquitoes aren’t active, but Harker cautions against that approach: It can be hard to judge when it’s safe to discontinue the medicine and easy to forget to start giving it again before the weather warms up. Considering that the cost of heartworm treatment can easily run $400 to $800, it’s far less expensive to maintain the preventative, which usually runs less than $10 a month.