A new survey shows the highest density of pet heartworm cases in Alabama, Arkansas, Louisiana, Mississippi and Texas.
According to the American Heartworm Society, three of those states — Arkansas, Louisiana and Mississippi — are in the lower Mississippi Delta, a region favorable to mosquito proliferation and with large wildlife populations and untreated domestic pets.
The organization’s 2023 survey was based on 2022 testing data.
Among other findings:
- States with historically low rates, including Connecticut, Kansas, Massachusetts, North Dakota, Oregon and Washington, had unexpected increases and developed new hot-spot areas.
- Urban locations, such as Bismarck, North Dakota; Boise, Idaho; Seattle; and Tucson, Arizona, saw significantly higher rates.
Education is critical to stopping heartworm, said the organization’s president, Jennifer Rizzo, DVM.
“While the past three years have been tumultuous for the veterinary profession and our clients, the good news is that heartworm disease continues to be almost 100% preventable with faithful year-round heartworm prevention,” Dr. Rizzo said.
“Whether it’s educating new pet owners about heartworm prevention or reminding long-time owners of its importance, it’s clear that the AHS and the veterinary profession must continue to work together to raise awareness of this devastating disease.”
The American Heartworm Society tracks incidence data every three years to help veterinary professionals, shelter personnel and pet owners understand trends.
National estimates of heartworm-positive dogs were slightly under 900,000 in 2001, 1 million in 2010 and 1.2 million in 2016. The 2019 estimate dropped slightly to 1.1 million infected dogs, likely triggered by drier-than-normal conditions and lower mosquito populations in the Western United States in 2017 and 2018.
In areas where heartworm incidence decreased, veterinarians cited improved compliance with year-round preventives, on-time doses and more pet owners providing preventives.
Where the incidence rate rose, some veterinarians pointed to heartworm-positive pets moving from endemic areas. They also cited poor prevention compliance and warmer weather.
“Urban sprawl has led to the formation of heat islands as buildings and parking lots retain heat during the day,” said board member Tom Nelson, DVM. “Temperatures in these microenvironments can be much higher and more conducive to the persistence of mosquito viability.”
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