Climate Change Could Be Increasing The Footprint Of Lyme Disease

Dr. John Aucott loves to let his dog go off-trail when he hikes. But as the director of the Johns Hopkins Rheumatology Lyme Disease Research Center in Baltimore, he knows better than to do it in June and July — the height of Lyme Disease season, when tiny nymph-stage ticks can move, undetected, from wild host (a mouse or deer) to a dog or human. While dogs can’t directly transmit Lyme disease to their owners, they can harbor ticks capable of doing the job.

People who get Lyme disease suffer from unpleasant symptoms like a rash, facial paralysis and swollen knees. But it isn’t always easy to detect and if left untreated, can progress to complications like memory problems, heart rhythm irregularities and chronic arthritis. A small minority of people with Lyme disease may even suffer symptoms like fatigue and joint pain for months after treatment.

This year, because of the East Coast’s unusually warm winter, ticks seem to be making an earlier appearance, which could make people unknowingly vulnerable to getting Lyme disease. Aucott says he is already finding ticks on his dog.

“I just pulled an engorged tick off [the dog] in February, which would be very unusual if the ground was snow-covered and it was 30 degrees,” he said. “But there’s no snow, and it’s been 60 and 70 degrees for some reason this winter.”

One implication of the warm weather is that it attracts mice, which also harbor the ticks and bacteria that cause Lyme disease: 2017 is expected to be a very risky Lyme disease season, based on the surge of mice in New York measured in 2016, experts Felicia Keesing of Bard College and Rick Ostfeld of the Cary Institute of Ecosystems Studies told NPR this week. Aucott wasn’t surprised to hear this.

Local health departments, state university researchers and local doctors in other high-risk areas are also sounding the alarm in their respective communities about the rise of Lyme disease and tick sightings in their area this year.

“The mice of the previous year are important because they’re the ones infecting the larvae, and [they turn into] the nymphs that are feeding the following spring,” Aucott explained. “So it make intuitive sense — more mice, more infected larvae, more Lyme disease.”

However, just because there are a lot of mice in New York, doesn’t mean there are a lot of mice in other areas where Lyme disease is present.

“It’s really highly unlikely that the same variables in play in New York are in play in Virginia, Nova Scotia or Maryland,” Aucott said. “In other words, predicting one area doesn’t do a good job of predicting what’s going on in an adjacent region.”