CELS Professor Studies Links Between Temperature, Humidity and Lyme Disease in the North
KINGSTON, R.I. – January 11, 2017 — The ticks that transmit Lyme disease to people die of dehydration when exposed to a combination of high temperature and lowered humidity, a new study by scientists at the U.S. Geological Survey and the University of Rhode Island has found. In an earlier related study, the researchers found that southern black-legged ticks, unlike northern ones, usually stay hidden under a layer of leaves, where they are less likely to encounter people.
The research group, whose findings were published Jan. 11 in the journal PLOS ONE, hypothesizes that southern ticks typically shelter under leaves to retain moisture, and that this behavior is a key reason why Lyme disease is very uncommon in the South.
Lyme disease sickens an estimated 300,000 Americans each year, according to the U.S. Centers for Disease Control and Prevention, making it more common in this country than West Nile virus or any other illness transmitted by insects or arachnids. Black-legged ticks pick up the disease-causing bacteria, Borrelia burgdorferi, by biting infected animals, and can then transmit Lyme disease to people in a subsequent bite. The disease causes fever, headache, fatigue, and sometimes a rash. If not treated promptly, Lyme disease can damage the heart, joints and nervous system.
There are big regional differences in Lyme disease prevalence. In 2015 Alabama reported 11 confirmed cases to the CDC from a population of about 5 million people. Vermont, with fewer than 700,000 residents, had 491 confirmed cases. Just 14 states in the Northeast, Mid-Atlantic and northern Midwest typically account for 95 percent of all reported Lyme disease cases.
Seeking an explanation for this phenomenon, USGS Research Ecologist Howard Ginsberg and URI Professor Roger Lebrun have been studying the metabolism, life cycle and behavior of black-legged ticks. In 2014 they collected tick larvae from different parts of the eastern U.S. and found that no matter where they came from, the larvae all live longer in relatively cool temperatures. Longer life spans increase the odds that the ticks will live long enough to first bite an animal carrying Borrelia burgdorferi, and then bite a human.
In a related 2015 study, colleagues on the research team from Michigan State University found that northern ticks often climb plant stems, where a passerby may brush against them, but southern ticks usually stay hidden under a layer of leaves…[Read more]