WOODLAND PARK, N.J. — An unusually large abundance of acorns in the northeast two years ago fueled a population boom of white-footed mice last year.
And those tiny mice are breakfast, lunch and dinner to ticks, dozens of which can attach themselves to a single rodent, feed on its blood and acquire the bacteria that cause Lyme disease.
Now some scientists are predicting a surge in the number of Lyme-carrying ticks beginning this month and lasting into early summer.
“The risk to humans is going to be high starting this spring,” said Felicia Keesing, a biologist at Bard College in New York, who has spent years researching tick-borne diseases. “We want to get the word out so people can take precautions. Our dream is that we don’t see this translate to human cases.”
New Jersey health officials said they are monitoring the work of Keesing and other scientists as Lyme disease season gets underway.
Like many northeast states, New Jersey has long had a high rate of the disease, in part because of residential expansion into tick territory. Ticks must be attached to humans for 36 to 48 hours or more before the Lyme bacteria can be transmitted. If detected early, the disease can be treated successfully with antibiotics. If left untreated, it can lead to serious heart and nervous system problems. Other long-term effects include headaches, chronic stomach problems, memory loss, stiffness of joints and speech impairment.
The most common infected tick in New Jersey — black-legged or deer ticks — will feed on just about any animal they can attach themselves to. And although they are often found on deer, which can transport them around a forest, it’s typically the white-footed mouse that infects ticks. The mice host the bacteria that cause Lyme disease, borrelia burgdorferi. Ticks acquire them by feeding on mouse blood and can then transmit them to other animals and humans.
Cases may already be up, with the relatively mild winter allowing ravenous adult ticks to be more active. Joe Zoltowski, director of the New Jersey Division of Plant Industry, found ticks on his clothes in January during his regular treks through New Jersey’s fields and forests.
“It was crazy,” he said. “I’m plucking ticks off me in January. You’re not supposed to see that.”
Ticks have a two-year life cycle, going from larva to nymph to adult.
What concerns Keesing is not the adult ticks, which die off in the spring, but the newly formed nymph ticks that acquired the Lyme disease pathogen when they feasted on mouse blood as larvae last fall. About 30% of nymph ticks are infected in a normal year, Keesing said. That is expected to go up.
Keesing and scientists at the non-profit Cary Institute of Ecosystem Studies in upstate New York say there is a direct link between acorn abundance and a surge in infected ticks.
Oak trees go through a boom-and-bust cycle with acorn production, and 2015 was a boom year in the northeast. With a plentiful food source that can be stored over the winter, the mouse population often swells the following year. “We saw the acorns in 2015 and then we saw a plague of mice in 2016,” Keesing said. “We have 25 years of monitoring that shows the link.”
Although ticks can acquire the bacteria that cause Lyme and other diseases from other animals, the vast majority are infected by mice. Nymph ticks often look to attach themselves to an animal or human beginning in May to feed. But Keesing said rising global temperatures are moving feeding time up by a month. “May has been Lyme disease awareness month, but we may have to change it to April,” she said.
According to the U.S. Centers for Disease Control and Prevention, Lyme disease was present in 260 counties as reported in 2015. The CDC said 95% of confirmed Lyme disease cases in 2015 came from 14 states — Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia and Wisconsin. There was a total of 28,453 confirmed cases in the U.S. in 2015, the CDC said.
Michigan has seen a rise in Lyme disease. According to a recent research paper, there were fewer than 30 human cases of Lyme disease reported in Michigan in any year between 2000 and 2004. By 2009, the number had jumped to 90 reported cases. By 2013, it was 166 cases. Michigan's Lyme disease tends to come from black-legged ticks.
The CDC estimates the number of Lyme disease cases nationwide could be 10 times higher than what's actually reported. Because Lyme disease's early symptoms — fatigue, muscle pain, joint swelling, fever — often mimic the flu or other diseases, infected people — and even their doctors — often don't test for it. Since it requires a special blood test, it is often misdiagnosed.
Other biologists say they, too, will be keeping an eye on the Cary Institute’s work this summer as scientists collect nymph ticks from New York's Hudson Valley and test them for disease.
“There are a lot of factors showing the potential for an increase this year,” said James Occi, a microbiologist at Rutgers New Jersey Medical School who concentrates on tick-borne diseases. “Prophecy can be a tough thing in biology. A lot of people will be looking at this work.”
Contributing: Keith Matheny, Detroit Free Press; Doug MacQueen, The Ithaca (N.Y.) Journal. Follow Scott Fallon on Twitter: @NewsFallon
Preventing tick bites
• Avoid wooded and brushy areas with high grass and leaf litter, especially April through July.
• Cover exposed skin during hikes.
• Repel ticks with DEET.
• Take a shower immediately after outdoor activities.
How to remove ticks
• Use tweezers to grasp tick at its head.
• Pull with gentle, steady pressure.
• Flush it town the toilet.
• Clean spot with soap and water.
Lyme Disease symptoms
• A bull's eye shaped rash at the site of the bite that appears about a week later.
• Severe headaches and neck stiffness.
• Arthritis with severe joint pain and swelling, particularly the knees.
• Irregular heart beat.
• Nerve pain.