April marks the start of tick season in the Midwest, and this year a new invasive species joins the various other tick species in the St. Louis region: the longhorned tick.
“We've been waiting for this to show up for years now, just watching how quickly it's been spreading across the eastern half of the U.S.,” said Solny Adalsteinsson, a senior scientist at Washington University’s Tyson Research Center.
In the fall, an undergraduate student in Adalsteinsson’s lab discovered the first identified longhorned tick in St. Louis County. With a new grant, researchers in the lab will conduct further research into longhorned ticks this year. Adalsteinsson expects to find more of them — the longhorned tick is parthenogenetic, meaning it doesn’t need a mate in order to reproduce.
“A single female tick can seed an entirely new population. She lays hundreds of thousands of eggs, and if all of those survive, you can just imagine how quickly that population can grow,” she said.

The light brown tick is the size of a sesame seed or smaller. Like other tick species, its bite can deliver disease with symptoms including fatigue, body aches and potentially fatal severe fever.
So far, it’s posed the most threat to livestock. Adalsteinsson hopes that what she and her colleagues discover will further our understanding of the ticks’ impact on humans, wildlife and other domestic species — all of which are at risk of bites and subsequently, disease, from longhorned ticks.
“We already have these really abundant populations of lone star ticks in the region, and folks might be familiar with those because they're one of our most commonly encountered ticks. They are responsible for transmitting Bourbon virus and Heartland virus,” she said. “We think the longhorned tick probably will [also] be able to transmit these viruses.
In addition to her lab’s work, Adalsteinsson hopes Tick Watch STL will help scientists and the public develop a better understanding of the ticks and tick borne diseases in the region. The program encourages residents and visitors to St. Louis County to mail in, or submit via collection boxes, any ticks they find so that they can catalog which tick species were found where and, down the road, detect specific pathogens within the ticks.
Interested citizen scientists can find more information on how and where to submit ticks, and how to apply for a “Tick-Kit” on the county’s website.
For tips on how to avoid tick bites — and what to do if you’ve been bitten — listen to the full St. Louis on the Air conversation with Solny Adalsteinsson on Apple Podcasts, Spotify, YouTube or click the play button below.
“St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is produced by Miya Norfleet, Emily Woodbury, Danny Wicentowski, Elaine Cha and Alex Heuer. Jada Jones is our production assistant. The audio engineer is Aaron Doerr.