This week, the American Heartworm Society (AHS) published the results of the 2019 AHS Heartworm Incidence Survey and unveiled a new heartworm incidence map. Both are drawn from data submitted by nearly 6,000 US veterinary practices and shelters.

 The society’s conclusion: Despite the challenges of the current pandemic, 2020 is no time for veterinary practitioners to deemphasize the importance of heartworm prevention.

Mississippi and Louisiana lead the country in heartworm infection rates

The five states with the highest incidence of heartworm were Mississippi, Louisiana, South Carolina, Arkansas, and Alabama. In Mississippi, almost 10% of dogs tested for heartworms were heartworm positive in 2019; in Louisiana, just under 8% of dogs tested were positive.

“The most significant finding is that heartworm continues to be diagnosed in all 50 states—including states in the West and Southwest that traditionally were not considered ‘heartworm-endemic,’” AHS president Chris Duke, DVM, told NEWStat. “Unfortunately, the incidence map from 2019 looks a lot like the 2016 map, and the top 5 to 10 states in heartworm incidence tend to be the same states, year after year.”

“These results may not be surprising,” Duke added, “but they’re significant.”

The AHS conducts its Incidence Survey every three years, using data from animals tested over the previous 12 months. The 2019 survey reflects data from more than 5.5 million heartworm tests.

COVID-19 crisis highlights need for heartworm vigilance

Several weeks ago, the AHS released a series of recommendations for veterinarians to follow in cases where pet owners need heartworm preventive prescriptions refilled in the absence of being able to come to the practice for their annual heartworm test and refill.

“Just as veterinarians and MDs are being granted latitude during the COVID-19 crisis to conduct some patient consultations via use of telemedicine, so, too, has it become advisable to bend—temporarily—the preferred practices surrounding heartworm testing,” Duke said. “Pet owners who have been compliant in giving their pet heartworm prevention can typically delay their pet’s heartworm test for a period of six months, with a goal of continuing heartworm prevention in an uninterrupted fashion.”

Duke added a caveat: “It’s important to note that these are temporary delays. Immunizations, wellness exams, and diagnostic testing compromise the cornerstone of good pet healthcare. As an organization, the AHS plans to revisit guidelines on heartworm prevention, diagnosis, and treatment by late summer—if not before—to ensure they remain appropriate.”

Veterinarians seeking guidance on adapting protocols for heartworm prevention, testing, and treatment during the COVID-19 crisis can find the updated AHS recommendations here.

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