Lyme disease in dogs is showing up in places it didn’t used to. And that could mean humans are at increased risk for catching a disease that’s already on the rise in dogs.

That’s according to a new study by the Companion Animal Parasite Council (CAPC), an independent, nonprofit organization dedicated to increasing awareness of the threat parasites present to pets and family members.

The CAPC developed the study to investigate regional trends in antibody prevalence to Borrelia burgdorferi, the tick-borne bacterium that causes Lyme disease.

The study analyzed the results of more than 16 million serologic test results for B. burgdorferi done on domestic dogs across the United States between January 2012 and December 2016, aggregated by county and month.

The analysis revealed evidence that Lyme disease is getting worse in some regions where it’s already endemic, such as Maine, West Virginia, Virginia, and the northern parts of Minnesota and Wisconsin. More problematic, the figures show that it could potentially be spreading to other, nonendemic areas, such as Illinois, Iowa, North Dakota, Ohio, Michigan, and Tennessee.

Further, given that Lyme disease is a vector-borne zoonotic disease spread by the bite of slow-feeding, hard-shelled deer ticks, this analysis could potentially reveal areas of increased human risk.

Corresponding author Christopher McMahan, PhD, associate professor of mathematics and statistical sciences at Clemson University in Clemson, South Carolina, told NEWStat, “Our analysis shows that there are several areas, especially in the Northeast, where risk [of Lyme disease] is increasing . . . at least for canines.”

What about the widespread belief that Lyme disease is less of a concern in winter months? With the start of the new year and colder weather, has the risk of contracting the disease in areas of the US where it’s been less common risen, particularly in colder areas where there might understandably be less of a concern?

“As for risk during winter months, generally, it’s less of a risk for humans in the winter because the predominate active stage for adult [deer ticks] is in the winter. They’re more easily found and removed by people compared to [deer ticks in the nymph stage, which are more active in the summer months].” Nymphs generally present a higher risk to humans in the summer months because, being smaller, they’re harder to spot.

But that doesn’t mean pet owners can let down their guard.

McMahan says the CAPC recommends playing it safe: “For dogs, we would advocate for year-round prevention because even in winter months, adult ticks are present, can transmit [disease], and could be easily missed on a dog.” That goes for cats, too.

And as the CAPC points out, by protecting their pets, clients reduce the risk of zoonotic transmission, which protects their families, too.

The CAPC’s website now provides 30-day forecasts for Lyme and other tick-borne diseases to help veterinarians, physicians, pet owners, and travelers assess the risk of exposure across the US and Canada.

Photo credit: © iStock/jwilkinson