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Decreasing the prevalence of heartworm infection in pets

A CVT greeting a dog and their owner

Heartworm is considered at least regionally endemic in the 48 contiguous United States as well as Hawaii and Puerto Rico, according to the American Heartworm Society (AHS)1. As we constantly strive to deliver on our purpose –  A Better World for Pets – Banfield made a concerted effort to lower the prevalence of heartworm infection among our patients in 2023. Preventing heartworm infection is generally safer, easier and less expensive than treating an existing infection, and the AHS recommends year-round administration of preventive medication as well as annual testing for the parasite. After we incorporated year-round heartworm prevention administration into our quality assessment in 2023, our data revealed that prevalence of heartworm infection dropped by more than 10% across our hospitals. Given that heartworm prevalence is trending upward in the general pet population2, however, there is much more to be done. Banfield will continue to promote reduction of heartworm infection in pets throughout our network in 2024, and we invite other practices to join us.

What this means for veterinary teams
Heartworm is a life-threatening parasite that is present in every state in the United States. With focused effort to encourage prevention, veterinary teams can reduce the prevalence of heartworm infection among the pets they see. We hope our learnings and tips will help practices across the nation to implement their own heartworm reduction initiatives.

Fewer heartworm infections
Our data shows that heartworm infection among Banfield patients decreased by more than 10% in 2023. Put another way, this means that 1,000+ pets were protected from heartworm infection during the year. Preventing heartworm infection not only saves lives but also avoids the short- and long-term negative health impacts of this parasite. Even after successful treatment of heartworm infection, dogs are more likely to have long-term cardiac damage compared to those that were never infected at all3.

The decrease in heartworm prevalence is a gratifying outcome of Banfield’s intentional effort to promote adherence to the AHS heartworm guidelines, which call for annual parasite testing and year-round administration of preventive medication. Similar to our work in anesthesia safety4,5 and antimicrobial stewardship6-8, the result demonstrates that dedicated efforts to improve the quality of veterinary care can improve patient outcomes in veterinary medicine9.

Keys to success
We believe several elements can contribute to success in controlling heartworm infection among pets.

  • Be aware of heartworm incidence in your region and across the nation – and how it is changing over time. The AHS provides detailed heartworm incidence maps that are updated every 3 years. The latest survey map reflects heartworm testing done during 2022 and shows that rates continued to trend upward in both heartworm “hot spots” and places where it was once rare2.
  • Monitor heartworm prevalence at your hospital. The AHS incidence maps are created using data from heartworm antigen tests collected from veterinary practices and shelters across the country on a voluntary basis. Tallying test results at your own practice can help you set your baseline and see how well your initiative is working.
  • Act locally. Cases are rising even in areas where heartworm incidence was historically low. If heartworm is not currently endemic in your region, try to keep it that way.
  • Involve the whole team. While a veterinarian must prescribe heartworm prevention, veterinary technicians and assistants can discuss the medications with clients and emphasize the need for year-round administration. Receptionists and office managers can point out when refills are due and help clients obtain them.
  • Keep it top of mind. Make heartworm prevention a regular topic of discussion internally and externally. The AHS has a wealth of information and educational tools available on heartworm management aimed at both hospital teams and pet owners.
  • Engage your pharma reps. The companies who manufacture and/or distribute heartworm prevention medications are a great resource for information and communication materials.

Continuing the campaign
Reducing heartworm infection is a continuing focus for Banfield in 2024, and we encourage others in the veterinary profession to join us. Heartworm is 100% preventable, and prevention is less expensive and has better outcomes than treatment. But heartworm disease is present in all 50 states, and its incidence is increasing in the general population. Furthermore, its geographic distribution seems to be changing, as it spreads to regions where it was once considered rare. An influx of heartworm-positive pets between areas and an increasing frequency of weather conditions conducive to mosquito proliferation, driven in part by climate change, are probable contributors to its spread2. We all have a part to play in “chasing zero” heartworm infections for pets.


1. Miller M. AHS Board Speaks Out. https://www.heartwormsociety.org/veterinary-resources/veterinary-education/ahs-board-speaks-out

2. American Heartworm Society. New American Heartworm Society Heartworm Incidence Map Reveals Upward Trend in Heartworm Cases. https://www.heartwormsociety.org/in-the-news/825-new-american-heartworm-society-heartworm-incidence-map-reveals-upward-trend-in-heartworm-cases

3. Mwacalimba K et al. (2024) Prevention and long-term outcomes of naturally occurring canine heartworm infection in primary care settings. Frontiers in Veterinary Science doi: 10.3389/fvets.2023.1334497

4. Morrison JA, Spofford N, Yang M et al (2022) Development and implementation of veterinary anesthesia medical quality standards for primary care. Veterinary Anaesthesia and Analgesia 49, 233-242.

5. Banfield Pet Hospital. Anesthesia Medical Quality Standards. https://www.banfieldexchange.com/Anesthesiaresources

6. Banfield Pet Hospital. Use of Antimicrobial Agents in Veterinary Dentistry. https://www.banfieldexchange.com/News/Antimicrobial-agents

7. Banfield Pet Hospital. Making Better Use of Antimicrobials When Treating Pets’ Urinary Tract Infections. https://www.banfieldexchange.com/News/Urinary-tract

8. Banfield Pet Hospital. Veterinary Emerging Topics Report 2024. Sustainability in veterinary medicine. https://www.banfieldexchange.com/VET-Report

9. Banfield Pet Hospital. Veterinary Emerging Topics Report 2022. Domains of quality: Implementing safety and quality improvements in veterinary medicine. https://www.banfieldexchange.com/VET-Report