By Jack Kelly
Each year, an estimated 500,000 Americans are diagnosed with Lyme disease — a bacterial infection that can cause rash, fever, extreme tiredness, and joint stiffness, among other symptoms.
Karen Fuenzalida, a veterinarian and PhD student in the Comparative Biomedical Sciences Graduate Program, is among the scientists at the UW School of Veterinary Medicine (SVM), College of Agricultural and Life Sciences, in the Midwest Center of Excellence for Vector-Borne Disease that is working to curb that number.
Fuenzalida studies the ectoparasite that spreads the bacteria that cause Lyme Disease: the blacklegged tick. She is being mentored by Lyric Bartholomay (PhD’04; Director, Comparative Biomedical Sciences Graduate Program; Dept. of Pathobiological Sciences) and Susan Paskewitz (Dept. of Entomology).
A native of Curicó, Chile, Karen always had an academic interest in parasites. She frequently encountered them while working in veterinary clinical practice, and she studied mites while earning a master’s degree at the University of Concepción. She was awarded with a prestigious, four-year Fulbright Scholarship to pursue a PhD degree in the CBMS program.
Through her research, Fuenzalida is investigating ecological aspects of the blacklegged ticks with the goal of improving tick control and ultimately reducing Lyme disease risk. This includes examining key host species and their role in the life and movement of ticks.
One prong of her research involves “dragging” outdoor areas to collect ticks. This is done using a large piece of fabric that ticks will attach to as it is pulled over the ground. These ticks are ‘ambush predators,’ waiting to grab on to a host in backyards and woodland areas in Wisconsin and elsewhere.
Once the ticks have been collected — particularly when they are nymphs (juvenile ticks) — Fuenzalida performs blood meal analyses. “These tests are important because they help us identify all of the hosts that are sustaining these ticks in a given environment,” Fuenzalida says, which is important for discovering new ways to intervene and prevent Lyme disease.
While many animals provide the blood ticks need to survive, not all of them are “competent” hosts for the pathogen that causes Lyme disease, Fuenzalida says. The tests help researchers determine if the ticks are biting animals that often carry large amounts of the bacteria that causes the disease.
Mice, Fuenzalida explains, are very competent “reservoirs” for the bacteria that cause Lyme disease. This means they can acquire the bacteria from the tick, allow it to proliferate in their bodies, and maintain the infection long enough to infect another tick that comes to feed on it. If many ticks are feeding on mice, they are then more likely to spread the bacteria to other hosts, including humans, leading to more disease the next year.
Nymphs in particular pose a threat to humans: “The nymphs are very tiny,” Fuenzalida says. “They are much more difficult to spot than fully grown ticks.”
A second part of Fuenzalida’s work focuses on reducing the tick population by actually removing the parasites from their hosts.
She is analyzing the effectiveness of devices that attract rodents in woodland areas and then kill ticks with specialty pesticides known as acaricides. The “bait boxes,” as the researchers refer to them, are often deployed in urban forests for research purposes but are designed to be used in residential years as tick control. They include a bait to entice small, tick-carrying rodents to climb into them. Once inside, the animals enjoy a snack while being painted with an acaricide to kill the ticks. The acaricides are not harmful to the animals.
Using motion-activated cameras, she studies the behavior of the rodents interacting with the bait boxes. Fuenzalida and her colleagues are working to refine the design of the boxes to encourage even more animals to interact with them, especially chipmunks and other rodents. They’re also testing whether deploying an external bait outside the box can draw additional small animals into the boxes.
In the long-term, Fuenzalida says, the goal is to deploy these boxes en masse in tick hotspots to help control the spread of Lyme disease and other tick-borne illnesses.
“It’s critical to understand what animals the ticks are feeding on and where those hosts are located,” Fuenzalida says. “Understanding the ecology of this tick is important because of its role in spreading pathogens and viruses that can make people really sick.”