Discussion about heartworm prevention is part of virtually every wellness exam, yet prevention compliance is seemingly still inconsistent. Survey data reported by Banfield Pet Hospital in 20231 provides some insight as to why: the gap isn't about access to preventives, it's centered around beliefs. Too many dog and cat owners mistakenly believe that heartworm does not apply to their pet, is not a concern in their geographic location, or that risk is just a seasonal thing. However, the reality is much different and the scope of the problem is reinforced by some sobering facts.
The American Heartworm Society (AHS) estimates that more than a million pets in the U.S. currently carry heartworm, and the incidence of infection continues to trend upward. The geographic distribution is shifting, too. The AHS's most recent (2025) nationwide incidence survey2 found that there is no state in the U.S. that is heartworm-free, and that case density is climbing in areas that, historically, had low rates of infection (parts of the interior West and upper Midwest among them).
Source: American Heartworm Society 2025 Incidence Survey
Wildlife reservoirs moving into populated areas, pet relocation through adoption programs, severe weather events, and a longer transmission season are all cited as contributing drivers. The bottom line is that heartworm is not a static or regional risk — it's a moving target, and this information needs to be conveyed to pet owners. While veterinary practices may be talking about heartworm testing and prevention, there is clearly a gap in how dog and cat owners are receiving and acting on the information, and this is evidenced by the incidence map that is updated by the AHS every two years. We also have other data to support this — a client survey conducted by Banfield Pet Hospital1 (coupled with their own medical record analysis) found that:
- 21% of pet owners don't believe that mosquitoes in their state carry the parasite
- ~40% of owners don't believe their pet is at risk of heartworm at all
- 41% believe heartworm risk is seasonal and, accordingly, 51% skip year-round dosing, with 18% giving preventive only in spring and summer
- ~30% report their pet is NOT currently on any preventive
- 32% of dog owners are neutral or unconcerned about heartworm because it’s treatable
- Only 22% of cat owners know that there's no approved treatment for feline heartworm infection
Of note, Banfield's own 2023 case data showed that diagnosis rates were essentially flat across all four seasons — direct clinical evidence that the "warm weather only" belief (that's driving seasonal dosing vs. year-round prophylaxis) is erroneous.
Like any recommendation, we are more likely to be effective in gaining adherence if we reframe our talking points to create an understanding of “why” rather than lecturing or reciting guidelines. Here are a few suggested ways to reframe heartworm discussion points that can help to address client misconceptions:
- To counter the notion that "my pet isn't at risk":
Instead of saying "heartworm is everywhere," ground your discussion to what’s happening locally, and explain the biological mechanism in terms that are more relatable than population-level statistics: "It only takes one mosquito bite to transmit this, and we're seeing cases move into areas that, historically, didn't have much heartworm activity — including some near here. I'd rather we stay ahead of it and here's how."
- To address those who believe that heartworm is just a seasonal problem or that, geographically, your location isn’t at risk:
This is a good opportunity to bring in your own hospital's data (if you track it), or refer to the national data and incidence map that shows consistent detection in all 50 of the United States. Regarding seasonality, refer to the Banfield data that found similar infection rates across all four seasons, and bring attention to the documented shift in vector behavior — explain that "in a lot of regions, mosquitoes are adapting to survive indoors during the winter.”
- To counter complacency of dog owners — those who shrug off prevention based on a belief that “heartworm is treatable”:
This is where clinical detail can help in securing adherence to recommendations. The Banfield research data found that dogs treated for heartworm infection carried elevated long-term risk for right- and left-sided heart failure and cardiomyopathy — lasting cardiac sequela, not just short-term treatment risk. Pairing that with the practical burden of treatment (months of strict activity restriction, cost, monitoring, etc.) can be more effective in grabbing someone's attention than citing mortality statistics alone.
- Regarding cats specifically:
Given how low awareness is about feline heartworm disease, this is probably the single highest-leverage conversation we can have with cat owners. When talking about heartworm prevention, there needs to be compelling messaging to shift a cat owner's thinking from "optional" to "essential." The conversation can include the fact that, in some cases, cats may experience sudden death in association with heartworm infection (without premonitory signs). Emphasizing that there is no approved adulticide treatment for cats, management is symptomatic, and that long-term monitoring or hospitalization is often needed for severe cases can prompt owners to more seriously consider preventive measures. It’s also really important to convey that indoor-only status does not confer protection; a meaningful share of feline heartworm cases occur in indoor cats.
Additionally, here are a few technical points regarding the importance of annual heartworm testing that are worth repeating, as well as some practice pearls:
- Annual testing is recommended even for pets consistently on prevention — no method is entirely foolproof against missed or delayed doses, and catching infection early can be significant as to outcome.
- Discordant results (antigen-positive / microfilaria-negative) can occur in dogs on a prevention program and shouldn't be dismissed as a lab error.
- Antigen-antibody complex formation can mask a true positive — heat pre-treatment of a sample can unmask bound antigen when results seem inconsistent with clinical suspicion.
- Avoid over-interpreting faint color changes on antigen tests as an indicator of "light" burden — that is speculative and not well supported.
- Repeat testing on a fresh sample is warranted any time results are unexpected, whether positive or negative.
- Cats need the antigen/antibody combination, not a dog-style antigen-only screen, given how few adult worms cats typically harbor.
Veterinary practices should be positioning annual heartworm testing and year-round prevention as an important component of preventive wellness care — on par with vaccination protocols — and not as an "upsell" or a discretionary recommendation. Consider integrating something similar to Banfield's messaging around "chasing zero" heartworm infections: prevention is safer, easier, and meaningfully cheaper than treatment, and it's one of the few serious pet diseases that's nearly 100% preventable when protocols are followed.
Let's crowdsource some ideas and solutions! We'd like to hear from our Members on this topic. Does your practice track heartworm testing and preventive adherence / compliance? Have you seen improvements with any specific type of initiative or effort? If so, what worked (e.g. messaging or communication and who in the practice is delivering that)? Have you had success in transforming a reluctant owner into one who commits to heartworm prophylaxis? Login to share what’s worked in your practice.
References:
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New pet owner survey suggests common myths fueling significant gaps in prevention of deadly parasite for U.S. dogs and cats. PR Newswire. April 2024.
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The American Heartworm Society - 2025 Heartworm Incidence Survey (released in April 2026).
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