This summer’s drought failed to reduce the deer tick population – as some experts had hoped – and Lyme disease cases have soared this fall, turning 2016 into a possible record-setting year for the disease.
Through Dec. 5, Lyme disease cases were 12 percent higher this year when compared to all of 2015, according to statistics from the Maine Center for Disease Control and Prevention.
“If any summer drought would have knocked the tick population back, this would have been the summer,” said Charles Lubelczyk, a field biologist with Maine Medical Center Research Institute’s “tick lab.” Rainfall was far below normal this summer, and Maine experienced many hot, dry days, which can be harmful to tick populations, experts said.
But the deer ticks survived, perhaps by migrating into the deep woods and hiding under leaves. Lyme disease is transmitted to humans via the deer tick.
“Under leaf litter, the ticks were as happy as could be,” Lubelczyk said.
The Lyme disease cases seem to match the theory of a dry summer causing ticks to be inactive or retreating into the woods, followed by a fall of the ticks returning and finding human hosts.
Lyme disease was trending below five-year averages through July, when 469 cases had been recorded, according to the Maine CDC. The five-year average was 583 cases through July, which had suggested that this year could be a mild year for Lyme disease. But instead, Lyme cases came roaring back in the fall, with 1,336 cases counted through Dec. 5.
Maine saw record numbers of Lyme disease in 2014, with 1,399 cases. The number of cases in 2015 dipped to 1,176 after the harsh 2014-15 winter.
Paula Jackson Jones of Nobleboro, who said she has been in remission for chronic Lyme disease since 2014, said she never believed the ticks would die from the drought.
“It gave people a false sense of security, and then this fall all hell broke lose with the ticks,” Jones said.
Jones said with such a high number of Lyme cases, Mainers need to be vigilant about protecting themselves from Lyme disease, by wearing protective clothing, using repellents and being aware of tick habitat.
Lyme disease symptoms include fatigue, dizziness, swelling, joint and nerve pain, persistent headaches and flu-like symptoms.
Meanwhile, anaplasmosis, another tick-borne disease, is also seeing record numbers this year, with 358 cases so far, compared to 186 through Dec. 5, 2015.
James Dill, pest management specialist at the University of Maine’s Cooperative Extension, said he believes what happened is that the deer ticks went deep into the woods where it’s more moist, to survive the dry, hot summer. Maine had the driest summer in at least 15 years, according to the National Weather Service, and most of the state was undergoing moderate to severe drought conditions by the end of summer.
Ticks do not like arid conditions, which is one reason Lyme disease is not a problem in a low-humidity state like Arizona or Nevada, but has exploded along the muggy East Coast.
Dill said while in the deep woods, the ticks were less likely to come into contact with humans, but instead would have attached to forest animals like rodents, rabbits and foxes.
When the wet weather came back in the fall, the ticks returned to their normal habitat, which is closer to humans, like on the edges of forests, backyards or near trails.
“We had reports this fall of people’s dogs coming in from backyards covered with 50 to 100 ticks,” Dill said.
Dill said another factor is that when the fall population of ticks surged, people were more likely to notice that a tick had attached to them and get tested for Lyme disease. In most cases, a tick needs to be attached to a host for 36 to 48 hours before Lyme disease can be transmitted, according to the U.S. Centers for Disease Control and Prevention.
By the fall, the ticks are adults and easier to spot, while in the summer they are in the nymph stage and difficult to notice. Many people end up with undetected Lyme disease because they didn’t notice they had a tick on them.
Lubelczyk said another factor is that coastal Maine retained more humidity than the interior, helping to keep tick populations thriving along the coast. Even in the interior, though, tick populations were better than expected this fall, he said.
The tick’s range continues to expand as well, as Lubelczyk said more reports of deer ticks Down East are coming in.
The only condition that might substantially reduce the tick population is extremely cold weather – 0 degrees Fahrenheit or less – that lasts 10 days in a row or longer without significant snow on the ground, Lubelczyk said. Snow acts as an insulator, allowing ticks to survive the winter.
CLARIFICATION: This story was updated at 1:48 p.m. on Dec. 12, 2016 to clarify the amount of time a tick needs to be attached to a host for Lyme disease to be transmitted.