'Global pandemic' possible as Lyme disease creeps north
Umair Irfan, E&E News reporter
Published: Friday, July 28, 2017
The eight-legged bloodsuckers that spread Lyme disease are crawling farther north and infecting more people due to climate change, scientists report.
Rising average temperatures are making more parts of North America hospitable to the Ixodesticks that carry Lyme disease.
The infection's range is expected to move northward into Canada by 250 to 500 kilometers (155 to 310 miles) by 2050, and the season for the disease may start up to two weeks earlier than it does now. Health officials report similar patterns in Europe.
And human-caused climate change is a major contributing factor, scientists say.
"As we are warming the planet, this is becoming an issue of human health," said Dominick DellaSala, chief scientist at the Geos Institute, a nonprofit research group studying climate change.
There are about 440,000 cases of the disease in the United States each year, and it's the most common zoonotic disease — transmitted from animals to people — in North America. The Centers for Disease Control and Prevention notes that 95 percent of Lyme disease cases come from 14 states, mostly along the East Coast and in the Midwest.
The bacterium Borrelia burgdorferi causes Lyme disease, which often presents with a bull's-eye-shaped rash, fever, joint swelling and headaches. However, these bacteria are difficult to detect and notoriously tenacious, sometimes withstanding antibiotics.
In a paper published last month in the journal Earth Systems and Environmental Sciences, DellaSala and his collaborators laid out how climate variables influence the spread of Lyme disease.
The bacteria typically reside in deer and mice, both of which are experiencing population explosions due to changes in their habitat and the loss of predators, DellaSala explained. Warmer winters further increase the survival rate of these animals and expand their range, along with the ticks that bite them and spread Lyme disease to humans.
"I think the biggest surprise is how quickly it's increasing and how little people know this is happening," DellaSala said.
To get ahead of these infections, he noted that tracking climate variables could provide health officials with some lead time.
At the seasonal level, factors like temperature and humidity in early spring and late autumn are important drivers of population increases in ticks.
Over the long term, using downscaled versions of global climate models can illuminate emerging hotspots for Lyme disease infections as temperatures rise. Temperature increases in Canada are likely to double tick populations there, putting more people at risk.
However, there is limited baseline data on which to develop models, and DellaSala said that the disease is underdiagnosed. Some of the regions experiencing increases in infections don't have doctors that are accustomed to diagnosing the illness, and infection reporting can be sporadic.
DellaSala said he wants to raise awareness at the international level to gather more data and mount a concerted response against the disease.
"This has got the potential for a global pandemic," he said. "It needs to be recognized as such."