Investigating how Bourbon virus-carrying ticks infect wildlife and humans

On a cold spring morning, Dr. Jacko Boone, a virologist at the University of Washington in St. Louis, and Dr. Solnee Adalsteinson, a wildlife ecologist, waved and dragged a large white flag through the woodland at the western edge of St. Louis County. Boone, an associate professor of infectious disease medicine at the University of Washington School of Medicine in St. Louis, and Adalsteinson, a senior research fellow at the University of Washington’s Tyson Research Center, have identified the solitary star tick, which carries the potentially fatal bourbon virus. looking for.

Earlier this year, the two, along with Dr. David Wang, Robert C. Pacman Professor of Medical Microbiology, published a paper in the journal Ticks and Tickborne Diseases about 1 in 150 people dying alone. showed that Star mites in the St. Louis area carry the virus. Researchers combed forests for tiny but potentially dangerous arachnids, learned more about where the ticks that carry the bourbon virus are, and how the virus infects wildlife and humans. want to better understand

This technique, known as tick flags, looks strange, but it works. After swiping for about 15 minutes in the university’s forested Tyson Research Center, an environmental field station for faculty, staff, and students, Adalsteinson pauses and carefully removes a single black dot from the cloth using forceps. plucked to It’s a solitary star mite, barely visible between delicate metal tips. They took it to Adalsteinson’s laboratory for further study.

“Tick-borne diseases are becoming more common. There are multiple reasons for this,” Boone said. Boone has received more than $4 million in grants from the National Institutes of Health (NIH) since he first began studying the bourbon virus. He is the principal investigator on two of his NIH grants to study viruses, and a collaborator on another two of his grants.

Matt Miller Jaco Boone holds a single star tick collected at the Tyson Research Center at the University of Washington. Lone star ticks can carry the potentially fatal bourbon virus. Boone and his colleagues are studying the virus and how it infects wildlife and people.

Climate change is making winters milder and more mites surviving winter. It’s good that cities are getting greener, but this new green space attracts white-tailed deer and coyotes, and with them come mites. My background is virology, but since I started working on the bourbon virus, I’ve realized that the only way to understand and address the problem of tick-borne viruses is to understand what’s going on. in tick-carrying environments and wildlife. ”

Dr. Jaco Boone, Virologist, Washington University in St. Louis

The virus is named after where it originated, Bourbon County, Kansas. The first case was found there in 2014, when a man died of the disease. Since then, he has recorded only four new cases, including one more death, and statistics show that Bourbon virus is rare but deadly. But a study Boone published last year in the journal mSphere showed a surprisingly high rate of antibodies to the bourbon virus in the St. Louis area, with many people infected and unaware. suggested that it is possible.

To understand how the newly identified virus will affect people in the St. Louis area, Boone worked with Adalsteinson and Sharon L., a wildlife veterinarian and epidemiologist at the St. Louis Zoo. – Cooperating with Dr. Deem (DVM). This trio of researchers represents a commitment to One Health, a framework in which human health is intertwined with animal and environmental health.

The first evidence of the presence of the Bourbon virus in the St. Louis area came in 2017 when a woman was admitted to Barnes Jewish Hospital with fever, rash and body aches, which was attributed to Bourbon virus. found. There is no specific treatment for Bourbon virus infection, and Boone is still working to find an effective treatment that eventually killed her. Boone and his team were able to culture the virus from a St. Louis patient and use it to develop a mouse model of infection to study how the virus behaves in the body. The mouse model has also helped bring about the possibility of drug therapy, but the drug in question has yet to advance to clinical trials. Researchers have also developed a method to test for antibodies to the bourbon virus in the blood.

“We have now tested blood samples from 1,500 people in the St. Louis area,” Boone said, referring to the mSphere study. “Out of 1,500 people randomly selected, 5 have antibodies to the bourbon virus. The fact that five more were easily found suggests that many were probably infected without becoming seriously ill. Boone said.

A person becomes infected with the bourbon virus when bitten by a solitary tick that acquires the virus from an infected animal. Deem’s portion of the project focuses on understanding how local wildlife may be affected by the virus and what role they may play in the epidemiology of the virus. ing.

“Our study reveals key information for understanding the epidemiology of emerging pathogens that can threaten wildlife conservation and human health,” Deem said. “By understanding how pathogens move among wildlife species in the area and how animals act as hosts for ticks and viral pathogens, we can accomplish this.”

Deem leads collaborative initiatives based at the Tyson Research Center that include the Zoo, the University of Washington, and the Center for Endangered Wolves, a nonprofit wolf conservation organization located on Tyson Research Center property. The effort focuses on the migration of local carnivores, such as foxes, coyotes and bobcats, and the diseases they transmit. During the colder months, Deem’s team captures animals and conducts tests, including taking blood samples to test for various infectious diseases. The animals are then marked and possibly tracked before they are released unharmed. Bourbon virus antibodies have been detected in most captive species. The researchers are also collecting ticks directly from captive animals to study whether the bourbon virus is present in these ticks.

Matt Miller Jaco Boone (left) and Solney Adalsteinson look at a star mite under a microscope at the Tyson Research Center.

Meanwhile, Adalsteinson collects ticks from the environment, collects detailed data on habitat characteristics and nearby wildlife communities, and coordinates the collection of blood and ticks from deer collected by hunters. . She sends the collected ticks to Boone’s lab to be tested for the bourbon virus. With Boone’s help, Adalsteinson was able to identify Tyson’s hotspots, geographic areas with high rates of bourbon-positive ticks. She hopes to better understand the causes of infection by identifying the most favorable environments for the growth of tick species and bourbon virus.

“I’m interested in connecting concepts of ecology and conservation to human health,” Adalsteinsson said. “There are many aspects of tick biology and tick-borne diseases that underscore how the way humans interact with and manage their environment impacts their own health.”

Much remains to be done. Boone is working to learn more about the basic biology of viruses, including how they enter cells, as a first step toward drug and vaccine development. In the future, the multidisciplinary One Health team aims to better understand how viruses are spread through wildlife and how and where animals and humans become infected. One goal is to identify so-called reservoir species, ie animal species that harbor the virus and maintain the circulation of the virus. Such information is very important for designing effective intervention strategies. Another goal is to find out how long it takes ticks to transmit the virus to humans, so that we know how often people should check themselves for ticks. increase.

“There’s still a lot we don’t know,” Adalsteinsson said. “We know the tick species that carry the virus, but we do not know which wildlife hosts are involved in its maintenance. We have a lot of basic information, and we are moving forward in finding answers by bringing together complementary expertise.”

Stay safe during tick season

Lone star ticks are most common in the St. Louis area from March to October, but other ticks can be seen year-round. To protect yourself from tick-borne infections, experts recommend:

• Wear long pants, long sleeves, and a tick repellent when outdoors on grass, bushes, or trees.
• After spending time outdoors, check your entire body for ticks. If you find a tick, carefully remove it with tweezers as recommended by the CDC.
• Seek medical attention if a rash or fever develops within a few weeks of removing a tick.