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But as five scientists are donning white painter's suits and hacking the wrists of their hiking boots, no one is certain that the conditions will be ideal to accomplish their task of the day: catching about 300 ticks, both adults and 150 nymphs.
Minnesota Department of Health (MDH) researchers team up with scientists from Mayo Clinic for this "tick trail", collecting samples to add to surveillance records and testing for pathogens . both help determine the risk that blacklegged ticks pose to people.
Ticks prefer at least 85% moisture, and they tend to go out to feed in slightly warmer conditions. And aside from time, tick collection is never predictable, says Jenna Bjork, epidemiologist at the MDH's Vector-borne Disease Unit.
Fingers crossed-handedly figuring, scientists are collecting the supplies they will need for the day: sesame seed ticks and poppy seed nymphs), fine-tipped tweezers (to tighten the head), flasks (to keep them) and "dragees" – from large pieces of white cloth tied to ankles with a rope. Then they go to the woods.
This is the perfect time for tick-borne diseases. A recent report from the Centers for Disease Control and Prevention, according to which the annual incidence of vector – borne diseases tripled between 2004 and 2016, drew attention to Lyme disease and the disease. other diseases transmitted by ticks.
– control agencies – state health departments and mosquito control districts – noting that about 80% of them "lack essential capabilities of prevention and control control "mosquitoes. The percentage is probably higher for ticks, as few state agencies or vector control agencies do surveillance or tick control work, according to Rebecca Eisen, a research biologist in the United States. the Division of Vector Diseases at the CDC.
This leaves gaping gaps in the data and unanswered questions: What is the level of risk for the average person? Who is most at risk? When? Or? What do you expose yourself when you go for a walk in the woods? In most places, the honest answers are "We do not know."
"The field work gives us the opportunity to really talk about the experience," says Dave Neitzel, supervisor – or Tick Boss, according to the patch on the fanny pack containing his tick supplies – from the unit of MDH vector-borne diseases. "We know what's going on because we've been there."
Each year, approximately 30,000 cases of Lyme disease are reported to the CDC by the public health departments and the District of Columbia, although many are not reported. the actual number at around 300,000 or more. Minnesota reported 1,300 cases in 2016.
The work in Minnesota is unique because few places have the resources that the Minnesota Department of Health appreciates, employing employees twice a week during the tick season to make contrails through the state. My colleagues who are only monitoring human cases for tick-borne and mosquito-borne diseases do not understand the whole ecological side of the disease risk picture, "Neitzel said. This can lead to inaccuracies.
Minnesota is at the forefront of tick habitat in the United States; Neitzel, who has been ticking here since 1989, has observed the slow but steady establishment of blacklegged ticks in much of the state.
The old tradition was to pay attention to ticks and erythema migrans. you were at your cottage in east-central Minnesota from mid-May to July. Now the message from the MDH is simpler: every time you are in the woods where the temperature is above the freezing point, take precautions, but especially from mid-May to mid-July
. The CDC is in the process of developing surveillance guidelines for states, says Eisen.
"State and regional health departments know their regions better than anyone," she says. "As much of the field work" as they can do, the better for everyone, she says.
Fortunately, Minnesota researchers generally value fieldwork. At Camp Ripley, they drag their white canvases about 20 meters (about 65 feet), then stop and look for tiny spots on the canvas. When ticks are ready for a blood meal (they take two or three during their two-year life), they crawl on the ends of the stems to attach more easily to a host, which facilitates their capture. . But for each 100-meter transect, researchers can not find more than five ticks.
"We have to work for them today," says Neitzel. Then he clears up. "Here's a beautiful little nymph, that's what I like to see," he said triumphantly, choosing three nymphs on his clothes. "It's more like Camp Ripley than I know and I love."
The site, which has a large canopy, a layer of shrubs and leaf litter as well as mammals like mice, which are important hosts for ticks. besters, is one of the long-term monitoring sites of MDH. (The intermittent machine gun fire – the National Guard drives to Camp Ripley – does not seem to scare the ticks, although Neitzel was mistakenly taken for the enemy in a training exercise and surrounded of a firearm.)
"Hi, little tick!" said Bobbi Pritt, director of the Clinical Parasitology Laboratory of the Department of Laboratory Medicine and Pathology at Mayo Clinic, grabbing his seventh tick with tweezers and slipping it into a vial. "I have to be very careful because the nymphs, about the size of a poppy seed, can look like small dots," she explains. "But then you look at them and they move – or they have small legs."
The tick will be diced and its DNA extracted.
Borrelia burgdorferi, the main bacterium responsible for Lyme disease, is found in approximately 40% of adult ticks and 20% of nymphs, although researchers have found that rates vary considerably from one place to another. # 39; other. But the CDC report noted that nine new mosquito-borne and tick-borne germs have been discovered or introduced since 2004, two of which were discovered by Pritt's laboratory and were found only in the upper Midwest. These localized pathogens fall into a category of "non-reportable" diseases that CDCs do not follow but that could affect people.
"I would not be surprised if more [localized pathogens] continued to be discovered," says Pritt. perhaps by explaining cases where people are sick but no one knows why.
"These are the cases that particularly interest me," Pritt says. "A lot of my job is trying to understand what's out there."
After returning to her Rochester lab, she tests Camp Ripley's trail ticks for the Powbadan virus in addition to researching bacteria causing Lyme, Ehrlichiosis, babesiosis, anaplasmosis and recurrent fever transmitted by ticks. Powbadan virus, though rare, can be deadly. But Pritt suspects that there are more patients who have a milder form of the disease. Pritt is developing a test for this; she was hoping to use some of the ticks in the job, but none was tested positive for the virus.
Back at Camp Ripley, researchers can wave their flasks like snow globes after six hours to get an idea of the nature of the virus. results: adult females, characteristics of the orange patch on the back, dark brown adult males, nymphs and larvae no larger than the period at the end of this sentence. The official count confirms that they have achieved most of their goals: Mayo researchers captured 12 adult females, 26 adult males, seven nymphs and 128 larvae. The following week, during a dredging of ticks in the northwestern part of the state, the MDH team found enough ticks to confirm the blacklegged tick population in six counties . This brings the total number of counties with established tick populations to 54, up from 45 in 2015 – and nine in the 1990s.
The team has put 4,000 miles on a rental car since May 1 and 1,500 to 2,000 go this season. The summer fieldwork will end soon, but "I have the impression that we are still at the beginning of our quest for knowledge about ticks and tick-borne disease prevention" , says Bjork
.
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