beagle sitting in grass
My parents have always been dog owners, from before I was born until today. Since my childhood they have had four dogs of various breeds. Each one has lived a long and full life, some even making it to the ripe old age of 18. My mom would buy special treats for each dog, as well as new toys and beds (sometimes dotting each room with a bed). My stepdad wasn’t far behind, although it would be hard to get him to admit it. He would snuggle with the dogs while watching TV in the evening and sneak them snacks. One of his favorite things to do was take the dogs for car rides, which they loved.

But even the best pet owners make mistakes, and this is the story of what can happen when you stop giving your dog his heartworm prevention medicine.

A Long History With Animals

“My first dog as an adult was a Poodle named Rocky. I got him in 1976, and although he was kind of a grumpy dog, I spoiled him and did everything I could to help him live a long, healthy life. He lived to be 18 years old. I don’t even remember heartworm prevention being prescribed back then,” says my mom, Deb Love. “Maxi, our Maltese, whom we got in 1991, was the first dog I ever gave heartworm prevention medicine to after my vet recommended it.”

My stepdad grew up around animals on a farm, where their pets were allowed to roam free and there was never any talk of long or expensive treatments if a pet became ill, let alone worrying about heartworm prevention.

In 1998, while I was in high school, we still had Maxi, but we also welcomed a Beagle puppy into our home. I named him Bailey. Both dogs lived without any major health problems, until my mom and stepdad stopped giving Maxi and Bailey their heartworm preventive in 2008.

A Changing View of Heartworm Protection

Heartworm disease is transmitted through the bite of an infected mosquito. Initially veterinarians tended to prescribe heartworm prevention medicine based on where you lived. If you were in the South, where mosquitoes can be found all year, you were told to give the preventive all year long. But for those who lived elsewhere (like my parents, who live in Nebraska), generally you gave it to your dog from around May through about December, because it was believed to be too cold for mosquitoes to live in the winter. Today, since cases have been reported in all 50 states and because mosquitoes can live inside (even in winter), it’s recommended that no matter where you live, you give your dogs and cats heartworm prevention medicine year-round. In addition, you should try to keep your pets away from mosquitoes when possible. 

“I don’t really know what made us decide to stop,” says my mom, looking back. “We didn’t think they were susceptible. All of our other dogs were fine when we didn’t give it to them, so why continue doing it?”

Signs There Was Something Wrong

family in front of Christmas tree with Beagle and Maltese
In early 2009, my parents started to think something was wrong with Bailey. He wasn’t eating like he usually did, and he seemed lethargic. So my mom took him to the family vet. That was in March.

The vet conducted blood tests and suspected that Bailey had some sort of autoimmune disease. He still wasn’t himself in June, so my mom took him back to the vet. That’s when they conducted a heartworm test and the vet came back with a diagnosis of heartworm disease. Before treatment, the vet did X-rays and an echocardiogram to evaluate the severity of the disease and see if there was any damage to his heart, a process called “staging.” Bailey then received the heartworm treatment, and the vet kept him for two days for observation.

The Road to Recovery

When Bailey came home he was prescribed steroids, which my parents gave him daily. We were also advised to restrict his activity, which meant my parents had to keep him on a leash and deter him from running. The reason? As the worms die, they can break apart and the pieces can leave the heart and enter the circulatory system, where they can act as clots. Exercise makes this more likely.

“I felt terrible and very guilty that I hadn’t done what I could to prevent this,” my mom says. “It was hard on him because he couldn’t run or play, and it was a lot of work for us because we had to keep a very close eye on him instead of letting him run in our fenced-in yard. Plus, it cost a lot of money for his treatment.”

Bailey was better by mid-July, and a few months later the vet tested him again for adult worms and microfilaria (the immature worms). He was clean — and he continued to live a healthy life for many more years. We were lucky. As of now, there are no medical treatments for heartworm disease in cats, but in rare cases veterinarians may surgically remove the adult heartworms. However, unlike with dogs, it’s the immature worms that are usually more problematic in cats.

A Lesson Learned

The treatment cost my parents 10 times what the preventive medicine would have cost, not to mention a lot of guilt for putting the dog through the treatment and, of course, the additional time they spent caring for him. After that, all of my parents’ pets were given heartworm preventive as prescribed by the vet.

“I would never skip it again after what happened with Bailey,” my mom says. “Thankfully he made it through it, and we got to enjoy him and our other dogs after that. It’s a hard lesson to learn, but a good one.”    

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