By Elizabeth Foy Larsen
“It’s like a butterfly,” says David Neitzel, as he helps me adjust the focus on the microscope in his windowside cubicle at the Minnesota Department of Health in St. Paul.
Neitzel (B.S. ’84, M.S. ’90) is an epidemiologist and the state’s go-to bug guy. He supervises the health department’s Vectorborne Disease Unit, and he sees nuance and beauty in insects that most people would prefer to simply swat and kill. Today, he’s talking about the scales on the wings of Aedes triseriatus, better known as the eastern tree hole mosquito, a noted carrier of La Crosse encephalitis.
Any resemblance between this delicate gray arthropod and nature’s showiest pollinator is lost on me. But Neitzel’s genuine affection for these creatures keeps me looking. The tree hole mosquito, he explains, is similar in appearance to the Japanese rock pool mosquito, except that its body is more silvery and it doesn’t have bands of white on its legs. The way Neitzel tells it, these markers are as distinct as the plumage on a bird or leaves on a tree.
For more than three decades, Neitzel has been on the front lines of identifying, monitoring, and preventing vectorborne diseases in Minnesota. As illnesses linked to “vectors,” such as ticks and mosquitos, appear in and spread across the state, Neitzel is on the scene, gathering information and telling the public how to avoid falling prey. When the tick-triggered red meat allergy known as “alphagal”—normally found farther south and linked to the lone star tick—surfaced in Minnesota recently, Neitzel explained that lone star ticks are still rare in the state, but moving north.
He’s scouted local car tire dealers to discover Asian tiger mosquitoes, which were accidentally imported into the United States through shipments of tires from South Korea and are possible carriers of the Zika virus. In 2002, he was part of a team that identified West Nile virus for the first time in Minnesota, an event that became an immersion experience in talking to the press. And, in 2016, he and a team identified Borrelia mayonii, a novel species of bacteria that causes an especially virulent form of Lyme disease in the upper Midwest. “One of the constants in our field is that the world’s a small place and people are moving around all the time and will assist the movement of other animals and pathogens,” he says.
Neitzel’s accomplishments are impressive, but he wears them lightly. “He’s an easygoing, lighthearted guy,” says Daniel Ziemann, one of Neitzel’s student workers, who recently received his master’s from the University of Minnesota’s School of Public Health. “He has good stories about being out in the field for years and years” and revels in sharing them.
As a child growing up in what was then known as Lebanon Township—now called Apple Valley—Neitzel displayed an interest in natural science from an early age. “My mom likes to tell me that she knew I’d be a biologist from birth,” he says. “They actually have a home movie of me crawling in our front yard in a diaper. I picked up a snake and it was biting me but I was too busy looking at it to care.”
Neitzel spent his childhood largely outdoors, forging a strong connection to nature. “I spent a lot of time watching the change of seasons and how that affects all sorts of different things,” he says. When he started at the U in 1980, Neitzel explored that interest more deeply, majoring in wildlife management. Unfortunately, at the time Neitzel earned his degree, he says the primary employers for graduates with his experience were the Minnesota Department of Natural Resources and the U.S. Fish and Wildlife Service, both of which had hiring freezes.
Not having a ready-made path turned out to be an opportunity, however, as the lack of employment options made Neitzel wonder about other biology-related fields where he could have an impact. He remembered a class he took at the U on wildlife diseases. “Learning about diseases and how they affect wildlife and how disease agents can jump from wildlife to people was always very interesting to me,” he says.
In 1987, Neitzel enrolled in the U’s Environmental Health graduate program, which offered a focus in public health biology. While at school, he started an internship at the Metropolitan Mosquito Control District in St. Paul, one of the largest mosquito control agencies in the world. He created and launched the district’s vectorborne disease surveillance and control program, which still operates today.
It would be easy to assume that his extensive knowledge of disease-carrying bugs puts Neitzel on guard every time he leaves the house. “Just the opposite,” he says, with complete sincerity. “I think knowledge is power when it comes to vectorborne diseases. I know exactly when and where I’m at risk when I’m in the field.”
In fact, Neitzel looks forward to the 10 percent of his job that’s spent outdoors monitoring ticks and mosquitos (the rest of the year he and his team are analyzing and reporting data). Each spring, just as the final snow melts, Neitzel heads out into the woods to perform tick surveys. Dressed in a pair of white coveralls with duct tape wrapped around his ankles, he drags a white canvas cloth behind him. And then he counts: blacklegged ticks (better known as deer ticks), wood ticks, and any other species that might cling to the drag cloth. Neitzel’s research has shown that, contrary to popular belief, blacklegged ticks, which carry myriad diseases including Lyme disease, prefer the humid conditions of the forest floor to open, grassy patches.
Neitzel and his team bring the ticks back to the Department of Health, where they identify them and test for six different disease agents. By this means and others, they track the appearance and spread of vectorborne diseases in order to assess risk levels for people across Minnesota. (Neitzel calls Camp Ripley, a National Guard training site in Little Falls, a “tick wonderland.”) Over the course of his career, he’s seen enormous shifts, including the rise of Lyme disease and West Nile virus.
At the department’s monitoring station in Itasca State Park, for example, Neitzel says that as recently as the mid-1990s, there were very few blacklegged ticks. Today, his team consistently finds them. Neitzel says this change could be due to a variety of factors, including a string of warmer winters, an increase in the population of whitetail deer (which ticks like to feed and breed on), and a change in logging practices that has resulted in younger forests with more brush.
Neitzel recounts this development with the kind of detail and enthusiasm you’d associate with a statisticsobsessed baseball fan. But, his students say, he’s a natural storyteller. Which, it turns out, is a good thing, considering the public’s growing awareness of the dangers of vectorborne diseases. “Whenever my wife and I go to various social occasions she actually gets a little irritated with me because people will ask her, what do you do? She’ll say, ‘I’m an accountant,’” he says. “And then they’ll ask me what I do and then it stimulates a conversation.”
Those unconventional ice breakers are just another way Neitzel leans into the same bugs most of us are eager to avoid. “I think people understand that the more they know, the better they can protect themselves.” Elizabeth Foy Larsen is Minnesota Alumni’s senior editor.
Photos by Mark Luinenburg
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