By Stacey Butterfield
There may be dangers on Bourbon Street, but luckily for Internal Medicine Meeting 2025 attendees, Bourbon virus is not one of them.
Speaker Daniel DeSimone, MD, discussed this emerging virus (actually named after Bourbon County, Kansas) and other tickborne infections as part of Wednesday's precourse, “Hospital Medicine: Success in a Complex Environment.”
Of the known diseases caused by ticks globally, the majority are found somewhere in the U.S., reported Dr. DeSimone, an infectious diseases specialist and professor of medicine at Mayo Clinic in Rochester, Minn.
The first challenge in caring for these conditions is recognizing that a tick might be the cause of illness. “Most patients won't even know they got bit or see a tick," he said. “These ticks are very small, like the tip of a ballpoint pen—that's the size we're looking at."
To know when to put them on the differential, it helps to be familiar with your local ticks. Dr. DeSimone reviewed “the big three” disease-spreading ticks, their geographic areas, and their associated diseases.
First up, the black-legged (deer) tick, Ixodes scapularis, who can carry several concerning diseases, including Lyme disease, anaplasmosis, ehrlichiosis, babesiosis, Powassan virus, and relapsing fever.
This species is most prevalent across the upper Midwest and Northeast and varies seasonally. “You're going to see these most commonly in the spring and fall. You'll see them in summer, too, but not too often in the winter,” Dr. DeSimone noted.
Number two on his list was the American dog tick, Dermacentor variabilis, which carries Rocky Mountain spotted fever and tularemia and turns up in the spring and summer along the East Coast. “I think the highest rates are going to be in North Carolina,” said Dr. DeSimone.
The lone star tick, Amblyomma americanum, is named for a distinctive mark on the back of the adult female, rather than the Lone Star state. However, it does range more to the south and midwestern part of the country than the other two ticks, as evidenced by how it carries Southern tick-associated rash illness (STARI), Heartland virus, and Bourbon virus, in addition to ehrlichia and tularemia.
This tick differs from the other two in its behavior, too. “It actually seeks out humans and looks to attach," said Dr. DeSimone. “The other ticks, it's more you're walking in the woods and you brush by.”
This aggressive tick also causes one of the more unusual illnesses Dr. DeSimone discussed. "The lone star tick itself can cause an allergic condition," he said. “It introduces alpha gal into the body, and then your body says, 'Hey, I don't know what this is. Let me make an antibody to it and attack it.'”
After that antibody is produced, when a person consumes anything containing galactose-α1,3-galactose (which includes any kind of red meat), an allergic response occurs. “I'm a meat eater, so it's the worst thing I can think of,” joked Dr. DeSimone. “There's no cure. You just have to avoid red meat.”
STARI is another fairly mysterious condition. "We don't know what this tick is transmitting,” he said. “It's similar to Lyme, but less severe.” As with Lyme, patients may present with a bullseye rash (with this disease, there's always a rash, just not always a bullseye, Dr. DeSimone noted) and should be treated with doxycycline.
Doxycycline is the appropriate treatment for almost all of the common tickborne diseases covered in the talk: Lyme, ehrlichiosis, anaplasmosis, and Rocky Mountain spotted fever. “Seven to 10 days of doxycycline. It sounds like I'm repeating myself,” he said.
Babesiosis is different, requiring seven to 10 days of atovaquone and azithromycin instead. It also stands out for the effects it can cause, including hemolytic anemia and organ failure. For severe cases, red cell exchange transfusion may be required, Dr. DeSimone noted. “You can also get it from a blood transfusion or an organ transplantation, not just the tick,” he said.
Rocky Mountain spotted fever can be pretty scary, too, though. “There's a risk of death without treatment somewhere around 25%. Even with treatment, it remains quite elevated,” said Dr. DeSimone.
The telltale symptom of this tickborne infection is a rash around the wrists and ankles. “There are not too many infections that will cause a rash like that,” he said.
For a final scare (because Bourbon virus is actually not very ominous or prevalent), Dr. DeSimone alerted attendees to Wetland virus, which is found in mice, sheep, pigs, and horses, and recently infected a Chinese patient who had been in Mongolia. On the bright side, this new infection is not expected to spread widely. The effects are frightening, though, resembling Crimean-Congo hemorrhagic fever.
“There's no cure. You can start bleeding in a lot of areas that you don't want to bleed out of,” Dr. DeSimone said. "I don't think that's going to become anything, but you never know." ■