Crucial Insights: Heartworm Resistance and Its Impact on Veterinary Care

Heartworm disease is a growing threat to canines throughout the United States, with recent data indicating a concerning rise in heartworm resistance. Understanding the current state of heartworm resistance is critical for veterinarians who aim to improve compliance among pet owners and implement effective prevention strategies.

Understanding Heartworm Resistance: A Growing Concern

According to Chris Adolph, DVM, MS, DACVM, presenting at the 2025 WVC Annual Conference, heartworm resistance has evolved significantly over the past four decades. While vaccines and prevention methods remain available, heartworms—caused by the parasite Dirofilaria immitis—can still infect dogs, even those on preventive medications. The American Heartworm Society reported that the majority of heartworm medication failures arise due to non-compliance, stressing that just one missed dose can make a pet susceptible to infection.

Prevalence of Resistance and Geographic Patterns

Adolph shared data highlighting an alarming trend: a 21.7% increase in adult heartworm infections across the U.S. between 2013 and 2016. Prevalence maps from the American Heartworm Society illustrated this escalation, signaling a pressing need for veterinary professionals to recognize and address these changes. Furthermore, the transportation of dogs across state lines has introduced heartworm-infected animals into previously low-risk areas, complicating the battle against resistance.

Strategies for Combatting Resistance

The key to minimizing heartworm resistance lies in improving treatment adherence. It’s vital for veterinarians to engage pet owners in discussions about the necessity of year-round heartworm prevention. Techniques such as injectable preventives, which offer longer-lasting effects than traditional oral medications, can enhance compliance and lessen the chance of developing resistant strains. This proactive approach includes constant education on the importance of regular veterinary check-ups and adherence to treatment protocols.

Future Insights: The Importance of Continued Surveillance

Veterinary professionals must remain vigilant about emerging trends in heartworm resistance and stay informed through ongoing education and research. The utilization of effective surveillance systems will play a crucial role in identifying hotspots of resistance and adjusting preventive measures accordingly. As resistance evolves, the need for adaptable treatment protocols becomes even more pronounced. This not only safeguards the health of dogs but also protects public health, as heartworm disease is transmissible to humans through infected mosquitoes.

Call to Action: Strengthening Prevention Efforts

Veterinary clinic owners and managers must take proactive steps to educate clients about heartworm prevention strategies. By emphasizing the critical need for year-round prevention, fostering adherence to treatment protocols, and staying updated on resistance trends, clinics can effectively protect canine patients from heartworm disease. Together, we can help push heartworm incidence numbers in the right direction.