When people hear “climate change,” they probably think of severe weather events and rising temperatures. Recent research also suggests climate change could have an impact on Lyme disease.
This illness – which starts as a distinctive bullseye rash and can spread to joints, the heart, and the nervous system if left untreated – is caused in humans by bites from infected blacklegged ticks.
According to research reported this month at the annual meeting of the Society of Integrative and Comparative Biology, “variable winter conditions brought on by climate change” could lead to an increase in blacklegged tick activity, thus making tick bites more likely. In addition to increased activity due to climate change, researchers found that black-legged ticks infected with the Lyme disease-causing Borrelia burgdorferi bacteria actually thrive in below-freezing weather and can be active in the winter.
About 79 percent of infected ticks survived in cold temperatures compared to only 50 percent of uninfected ticks, Laura Ferguson, an ecoimmunologist at Dalhousie University, reported at the recent conference.
“Infection may improve the ability to recover from cold and variable winter conditions may favour the ability of infected ticks to find hosts and continue to spread disease,” said Ferguson and other researchers from Dalhousie University, Halifax, Nova Scotia. They used a sample of 600 ticks over three winters for their study.
Apart from testing the ticks’ ability to withstand cold, researchers subjected infected and uninfected ticks in the lab to one of three conditions: freezing temperatures, temperatures of 37.4 degrees Fahrenheit, or varied temperatures.
Infected ticks in fluctuating temperatures were the most active, waking up four days a week compared to one or two, said Science.org.
“With climate change, there are going to be real consequences, and we need to tease these apart to make [the best] public health decisions,” says Laura Zimmerman, an ecoimmunologist at Millikin University who was not involved with the work, according to the outlet. “We tend to think what when it’s cold, nothing happens…more work like this is needed to find out what it means for disease transmission.”
According to NASA, the Earth's climate is changing. Consequences such as rising temperatures, snow and rainfall pattern changes, as well as more extreme climate events “are already happening,” and many can be linked to rising levels of carbon dioxide and other greenhouse gases in the atmosphere caused by human activities such as burning fossil fuels.
Lyme disease cases have already tripled in the past 20 years, according to Science.org. In 2017, a record number of cases were reported, said the Centers for Disease Control and Prevention, and more than 30,000 cases were confirmed annually from 2016 through 2019.
Those are just the confirmed cases. According to the CDC, an estimate based on insurance records suggests approximately 476,000 Americans are diagnosed and treated for Lyme disease every year. In fact, it is the most common North American illness transferred from animals to people and around 1.6 million people in the U.S. have chronic issues brought on by the infection.
Late last year another study showed that mRNA vaccines, known primarily to the public as the two-shot vaccines available to protect against COVID-19, might be useful against Lyme disease and other tick-borne illnesses.
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