Back in January, I sat down with Dr. Melissa Nolan, an epidemiologist at the University of South Carolina, in her lab at the Arnold School of Public Health in Columbia. We talked about how well the state could handle an outbreak of an infectious disease like influenza.
Pretty well, it turns out.
“Influenza is one that we’re probably the most prepared for,” Nolan said.
And that would have been the end of the conversation, had she, 34 seconds later, not said this: “What we’re not very well-prepared for, though, are vector-borne diseases.”
Vector-borne diseases are those that come from parasites like fleas, mosquitoes, and ticks. And while the world is increasingly working to contain a pandemic in Covid-19, far less attention is getting paid to itty-bitty insects that can turn a walk in the park into a genuine health problem.
But a walk in the park is where this story of trying to do something about that starts. Specifically, a walk in Sesquicentennial State Park, near Columbia, on a breezy, cool, sunny Leap Day. Nolan and her crew of six US of C graduate students are tromping through these woods, on and off the proverbial beaten path, to find and identify as many species of tick as they can find. They’re part of a grassroots (i.e., not grant-funded) project into October to catalog South Carolina’s tick populations.
For the record, the crew are Kyndall Braumuller, a Ph.D. student who’s also organizing the tick treks for the project, and master’s students Connor Ross, McKenzi Norris, Danielle Johnson, Jose Urive, and Chloe Rodriguez Ramos. They’re spending this particular Saturday afternoon as they will spend another 20 or so – laying broad swaths of white cloth on the ground and plopping hunks of dry ice in the middle of them.
“The CO2 is released [from the dry ice] and they’ll come to it thinking it’s an animal or a blood meal source,” Nolan says.
She calls this method of tick hunting “passive surveillance” because these traps just sit there, stocked with breath-mimicking bait, waiting for some ticks to crawl across the expanse of white. There, they’re collected with tweezers and put into small vials of alcohol – in which they can still crawl around for quite some time, we find. It seems ticks really are some of the hardiest and most adaptable creatures on land.
Unfortunately for the animals they take blood meals from, ticks are also among the most pathogen-ridden creatures on land. Nolan and Braumuller reel off a string of diseases anything with red blood can get from a tick bite: Lyme disease, spotted fevers (once lumped together as Rocky Mountain spotted fever, but that has been reclassified as the spotted fever family), tularemia, Erlichiosis …..
The list is long and the effects of any one of these illnesses can be severe. Some might experience slights aches and rashes; others, symptoms like swollen glands, high fevers, or nerve pain.
What makes all this even less pleasant is that state health officials have no solid data on exactly which species of tick make South Carolina their home, nor the range of the ticks that are known to live here. The cataloguing project by Nolan and her students began field surveys on Feb. 29; it aims to build that database of which ticks are here, where exactly they are, and which diseases they carry.
They accomplish this through the aforementioned passive surveillance and a second, quite active, kind of hunting called “dragging.” It’s exactly what it sounds like – researchers drag one of those same pieces of white cloth behinds them, picking up eager ticks that have heard you approaching.
“[Ticks] can feel your vibrations,” Braumuller says. “That’s when they know they need to climb up on this piece of grass or on this piece of twig.”
They stick their arms and legs out to grab onto you when you pass. Says Nolan, somewhat ominously, “They’re waiting for you.”
Norris and Johnson are just ahead of us, dragging. Scattered around the park, Urive, Ross, and Rodriguez
Ramos monitor passive traps, as does Braumuller. By late afternoon, their haul is only a few ticks – they’ll be more plentiful when red-blooded animals show up in warmer month – but it’s a mix of adults and nymphs (babies almost impossible to see), male and female. Overall, the team finds three species on what is, officially, a training day to learn how to conduct CDC-designed research: black-legged ticks, Lone Star ticks, and brown dog ticks.
One species the team did not find was Haemaphysalis longicornis, also known as the Asian longhorn tick. It’s a particularly nasty invasive parasite first identified in New Jersey a little more than a decade ago and which has since moved closer to South Carolina.
Actually, it might be here, Nolan says. It might just be that no one has found it yet. It’s in several neighboring states, including North Carolina and Tennessee, and Nolan expects someone on this project will find H. longicornis somewhere in South Carolina.
A third of what makes that such a concern for her is that H. longicornis carries all those diseases she and
Braumuller mentioned earlier, plus about six others. The second third is that H. longicornis is also called a cattle tick because it has a particular fondness for bovine. And once it gets into cattle populations, Nolan says, it can decimate them, mainly through transmitting theileriosis – a disease that can cause fatal levels of blood loss.
The third third of why this tick is not welcome in Nolan’s world is that females are capable of parthenogenesis. In other words, she says: “She doesn’t need a man to reproduce.” She can just make as many babies as she needs to without having to worry about the dating scene or natural selection.
Mapping ticks in a formal way could lead to shared research into vector-borne diseases, future grant-funded projects to further study this area of public health, and an education campaign for doctors around the state.
Nolan says rural areas have the least data on vector-borne diseases.
“How can we tell doctors in Florence to look for Lyme if we don’t know there’s Lyme in the ticks in Florence,” she says.
This research is also aiming to build sharable database that allows researchers (and non-researchers) to identify ticks they find.
“One thing I’m interested in developing is an app that has an AI component,” she says. “Right now, people take a picture and send it in and a scientist has to confirm.”
An AI-powered app, she says, would allow on-the-spot identification and enhance researchers’ ability to track populations, species, and densities around the state.
Nolan says she hopes to have the first set of information ready to publish by year’s end.
Scott Morgan is the Upstate multimedia reporter for South Carolina Public Radio. Follow Scott on Twitter @ByScottMorgan.