When summer ends, heartworm doesn't

Autumn appointment goals: Help clients realize the importance of a yearlong approach to heartworm prevention instead of just during summer. Partial adherence overlooks mosquitos’ continued presence as the weather cools. Photo: Bigstock/chalabala Summer has faded into fall, but warm, humid weather lingers for many regions across the country. So, too, do mosquitos and the threat of mosquito-borne diseases. In the last month alone (September 2024), the spread of rare but potentially deadly diseases such as eastern equine encephalitis and West Nile have been in the news. Headlines urge pet owners to take precautions to keep themselves and their animals safe. To be sure, these diseases require our attention and vigilance. Still, one of the most urgent mosquito-borne risks facing pets is missing from the headlines: heartworms. This is unfortunate because heartworm disease is the biggest threat to pets, and too many pet owners do not take it seriously. Efforts to convince pet owners of the urgency of heartworm prevention are still falling short. That is despite the veterinary community’s longtime advocacy for the value of heartworm prevention and our ongoing work to communicate the risks and severity of heartworms to dog owners. Sadly, we are just not breaking through. To do so, passion and a healthy dose of persistence are needed in the push to educate, raise awareness, and dispel myths so pet owners become vigilant year-round and we reverse concerning trends in heartworm disease. The number of pet owners who leave their veterinarians’ offices without a heartworm preventative in hand appears to be on the rise. In 2009, that who reported data showed 64 percent of dogs left a veterinary clinic with neither a heartworm preventative nor a prescription for one.1 By 2023, this number had increased to 68 percent.1 At the same time, we have also seen a rise in heartworm infections in regions of the United States with traditionally low incidences, including Washington, Oregon, Kansas, North Dakota, Massachusetts, and Connecticut. This trend of increasing incidence and regional spread is the confluence of a perfect storm — including a shift in the way pet owners acquire and care for their pets, a lack of awareness of how easily and efficiently heartworm infections are spread, and a lack of urgency regarding the growing nationwide risk of heartworm infection by pet owners. The evolution of pet ownership and care To understand and contextualize the spread of heartworm disease, it’s important to acknowledge the shift that has occurred in how we acquire our pets. Per the Shelter Animals Count national database,2 shelter pet adoptions increased by an estimated 20 percent between 2016-2023. Many years ago, adopting from a local shelter meant you would probably be re-homing a cat or dog native to your community, or at least to your region. Today, the pet clients find at their neighborhood shelter is more likely to have arrived courtesy of relocation. This is the result of factors like shelter overcrowding, natural disasters, and a desire to meet consumer need in regions with a higher demand for adoptable pets. The American Society for the Prevention of Cruelty to Animals (ASPCA) — the largest transporter of shelter dogs and cats for adoption in the United States — has transported more than 200,000 companion animals since the program started in 2014.3 From an animal welfare perspective, the transfer and relocation of animals to maintain shelter census and reduce euthanasia rates is necessary, and the response from pet owners to rehome these animals is encouraging. However, this rise in pet relocation and adoption has also led to an increase in heartworm incidence among dogs. As dogs are moved from one region to another, they bring with them the heartworm risks of their native environment. This is especially true for dogs relocated from areas with high heartworm prevalence to those with lower rates. Many adopted pets have been exposed to heartworm in their native shelter, but these dogs cannot accurately be tested for heartworm, meaning the infection will not be detected until later, often after the pet has been transferred, adopted, re-homed and examined by a veterinarian — as a new infection cannot be diagnosed for six to seven months. At this point, the damage has been done; mosquitos have a new host to feed on and can quickly spread the infections to other local dogs. It’s a tricky problem to solve. It is important to note, too, mosquitos know their prey well; mosquitos are 10 times more likely to seek out a heartworm-infected animal than one that does not have heartworms. What we once thought was a random process is actually a much more highly refined process than we ever understood, and accounts for the greatly heightened risk our dogs are facing. In addition, research has recently found that the transfer of heartworms from mosquitoes to dogs is an extremely efficient process. Therefore, the combination of mosquitos’ ability to seek and feed on heartworm-infected dogs, plus their high-efficiency transmission of heartworms, creates a potent recipe for disease transmission. Saving animals’ lives is why we practice medicine, so we should never begrudge these honorable efforts to offer homing opportunities for shelter animals. My point is that because of this movement, it is paramount that we as practitioners be aware of and provide education and counsel to new pet owners who may not be familiar with heartworms. Most importantly, we need to ensure the entire clinic staff emphasizes how critical heartworm prevention is for the health of all pets in the practice. In the same way we face challenges to ensure compliance in our veterinary clinics, shelter staff are limited in how much they can educate adoptive pet owners who have so much to learn. It is critical we reinforce just how common and severe the threat posed by mosquitos and heartworm disease can be. A persistent lack of awareness Ask the average dog owner: What is your biggest fear for your pet. Cancer? Joint issues? Running away? I doubt you will hear them say mosquitos — but they should. Mosquitos are the deadliest animal in the world, and despite the factors explored above, the rising incidence of heartworm indicates pet owners are not sufficiently motivated to take action. This may be partly because they may not fully understand the risks that mosquitos pose and the severity of a heartworm infection. One of the most commonly held misconceptions among pet owners is the belief heartworms are not a problem in their region. This is a stubborn and persistent myth. Incidence mapping shows that heartworm disease has been detected in all 50 states, with a higher incidence of heartworm transmission along the humid and wet Atlantic and Gulf coasts. A thimble of standing water is enough to create a mosquito breeding ground. Many pet owners are surprised to hear this. As we consider ways to inspire our clients to protect their pets from heartworm, this talking point can be an opportunity to start a discussion. Is there a bird bath on their property? Backyard playgrounds or play equipment? Flowerpots? Trashcans? Landscape décor? Even cars, gutters, downspouts, and garden hoses can be enough to foster a small breeding ground. Helping dog owners realize everyday landscaping items in their yard or in a neighbor’s yard can foster an inviting environment for mosquitos can be eye-opening and help underscore the value of heartworm prevention. Another common misconception is heartworms are only a risk during the summer months, when rainfall is more plentiful and dogs are spending more time outside. A 2024 survey conducted by Banfield Pet Hospital found nearly 51 percent of pet owners are skipping year-round heartworm prevention, with only 18 percent using heartworm prevention for their pets during the spring and summer.4 The fact that concrete-and-brick structures create zones of warmer temperatures (heat-sink effect) should be enough to inspire dog owners to adopt a yearlong approach to prevention. Yet, this level of partial adherence is a problem because it overlooks mosquitos’ behavior as the weather cools. Like humans and most animals in the winter months, many species of mosquitos overwinter as adults, seeking warmth as the weather turns colder. If they cannot find that warmth outside, mosquitos huddle close to buildings and homes, where they can easily enter through open doors, damaged screens, or poorly sealed windows. Of course, all this counsel and education is something veterinarians can easily dispense to dog owners, and it doesn’t cost a dime. However, it appears dog owners are missing opportunities to get basic heartworm education and information provided at these visits, so our message must be pointed. Our ability to get clients into the exam room has its limits, but when we do see a dog — regardless of what the visit is for — heartworm education and creating an opportunity to dispel incessant myths should be a priority. Underscoring urgency and elevating pet owner awareness A proactive approach to heartworm prevention is critical because the disease is a silent one. Heartworm disease can begin to manifest well before any recognizable clinical signs appear, causing irreversible lung damage long before it is diagnosed via a standard antigen test. This is a common misconception among pet owners. A reported, 32 percent of dog owners said they felt neutral or unconcerned about their dogs getting heartworms because the disease is treatable.3 Treatable? Yes, but its effects are irreversible. By the time many dogs are diagnosed, the disease can result in diminished lung capacity or permanent lung damage. If our clients claim to love their pets as much as they say — and Pew Research says they do, with 97 percent of pet owners saying pets are as much a part of the family as any human5 — then it is time we start prioritizing their health in a way that reflects that. Heartworm education and advocacy have been a clinical area of interest and passion of mine for decades. Still, I recognize this is just one of the multitude of health issues, conversations, and questions veterinarians are tasked with addressing during a visit and may not feel like a priority among the array of challenges and demands facing our industry today. All of this, coupled with research that indicates many pet owners may still disregard the point-of-care education and counsel they do receive and leave clinics without a preventative in hand, can make continuing to promote the benefits of heartworm prevention seem Sisyphean. I ask us — urge us — to not give up, to continue to explore how we can communicate the urgency of this issue to clients. Regardless of how rote these conversations might feel, we must find a way to relay our passion for prevention. Unless we can authentically demonstrate our commitment to addressing this issue, how can we expect dog owners to do the same? With so many educational tools at our disposal — case studies, research, clinical photography — we are well-equipped to show the risk dog owners take when they let preventative care lapse. In addition to changing the way we educate dog owners about heartworm, let’s also consider how we can ask more pointed questions about heartworm adherence. Instead of: “Would you like a heartworm preventative?” Try: “I’m writing you a prescription for a heartworm preventative” or “What heartworm preventative are you currently using?” Depending on the pet owner's response, it can be easier to interpret where our clients are in their understanding of heartworm. This may reveal some bias or misconception we can work to address in real time instead of letting them walk out the door without a preventative in hand. These efforts also need to extend beyond the exam room. To prevent clients from walking out the door without the proper prevention, a warm handoff to a technician or other member of the team is key to adherence. The goal is not to strong-arm or pressure pet owners but to demonstrate to our clients, through both education and routine, that we as veterinary professionals really care about their pets and heartworm prevention is a priority. As you consider all these things, try to keep the message as simple as possible. As a great friend and colleague of mine once told me: The five primary rules of pet ownership are: Keep them off the road Feed them right Keep them vaccinated Spay or neuter them Keep them on year-round heartworm prevention Doug Carithers, DVM, EVP graduated from the Iowa State University College of Veterinary Medicine in 1984, and in 2000 received a certificate degree in the Executive Veterinary Program at the University of Illinois. He practiced veterinary medicine and surgery in Iowa for nearly a decade before joining Boehringer Ingelheim, where he has contributed to the field of parasitology for more than 30 years. He has developed, conducted, and been directly involved in over 125 clinical and field studies, including large-scale field trials involving nearly 20,000 companion animals. In addition, as a committee and board member for the American Heartworm Society, he regularly conducted the American Heartworm Society heartworm incidence surveys and created the national Heartworm Incidence Maps. For his contributions to the field of parasitology, he received the Association of Veterinary Parasitologists (AAVP), Distinguished Service Award in 2024. References Data on file at IDEXX Laboratories, Inc. Westbrook, Maine USA. Shelter Animals Count. (2024) National Animal Welfare Statistics Dashboard. https://www.shelteranimalscount.org/explore-the-data/data-dashboards/national-animal-welfare-statistics-dashboard/ ASPCA. (2024) Annual Report 2022: https://www.aspca.org/about-us/annual-report Banfield Pet Hospital. (2024, April 2). New pet owner survey suggests common myths fueling significant gap in prevention of deadly parasite for U.S. dogs and cats. https://www.banfield.com/about-banfield/newsroom/press-releases/2024/survey-shows-common-myths-fueling-gap-in-dog-parasite-prevention Brown A. About half of U.S. pet owners say their pets are as much a part of their family as a human member. Pew Research Center. July 7, 2023. https://www.pewresearch.org/short-reads/2023/07/07/about-half-us-of-pet-owners-say-their-pets-are-as-much-a-part-of-their-family-as-a-human-member/

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When summer ends, heartworm doesn't

Persistence and passion needed to dispel stubborn heartworm myths and boost compliance

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