The forecast map, created by Michael Yabsley, a parasitologist at the University of Georgia, and Christopher McMahan, an assistant professor of mathematical sciences at Clemson University, shows the predicted Lyme disease prevalence–the percentage of dogs who are likely to test positive–by county in each of the 48 contiguous states. It draws on monthly test data from veterinarians, providing the most timely picture of Lyme disease cases available.

"Our research into modeling disease in space and time shows us how dynamic canine Lyme disease is on an annual basis. It's our hope that these maps can be used to optimize patient care by veterinarians and public health officials or physicians," McMahan said.

Ticks that carry the disease–causing bacterium, Borrelia burgdorferi, were once thought to be limited to northern parts of the United States, but recent research shows they are now in half of the counties across the country, including Southern states.

Yabsley and McMahan combined factors associated with Lyme disease–forestation, surface water area, temperature, population density and median household income–with nearly 12 million Lyme disease test results collected between 2011 and 2015 in dogs, by county, in the contiguous United States, provided by the veterinary diagnostic company IDEXX Laboratories Inc.

Ticks feed throughout the year, Prior said. As mice and other animals that ticks feed on move into new habitats, the ticks, and Lyme disease, move with them. The research also has implications for Lyme disease in people.

"Dogs really are the canary in the coal mine for human infection. Our research team has evidence that the relationship between canine disease and human disease is strong," Yabsley said. "Because dogs are being tested for exposure during annual exams, these data are available on a national scale, something that is difficult to get when studying the ticks and environment directly."

McMahan and Yabsley are expanding this analysis and plan to release additional data on the relationship between human and canine disease later this year.

"Integrating data on a national level allows for a more advanced view of the variables impacting Lyme disease prevalence, and expands our understanding of the true prevalence of disease across the U.S.," said Chris Carpenter, chief executive director of Companion Animal Parasite Council (CAPC). "The scientists observed an apparent convergence of Lyme disease infection of dogs from the Northeastern and Mid–Central United States in the Great Lakes region, encompassing Indiana, Ohio, Illinois, Kentucky and Michigan, all of which is supported by recent studies and CDC reports of expansion of the ticks that carry the pathogen into this region."

"The research conducted by doctors Yabsley, McMahan and their interdisciplinary team has been instrumental in helping CAPC fulfill our mission to protect pets against vector–borne diseases, such as Lyme disease, and in helping us create the 2017 Lyme disease forecast," Carpenter said. "We are pleased to have funded this research effort and we look forward to expanding this research in support of human health as well."

Other research collaborators were epidemiologist Jenna Gettings, recipient of the Boehringer Ingelheim–CAPC Infectious Disease Postdoctoral Fellowship, mathematicians Robert Lund, Stella Watson and Yan Liu from Clemson, and immunologist Shila Nordone from North Carolina State University.

The study was published in the journal PLOS ONE.