Man’s Rare Tickborne Illness Was Caused by an Unexpected Bacteria

Until now, the bacteria from a lone star tick had not been reported to cause tickborne relapsing fever

Lone start tick on green leaf
Researchers suspect a 75-year-old Alabama man came down with tickborne relapsing fever after being bitten by a lone star tick. James Gathany / CDC

An Alabama man who came down with a rare tickborne illness is the first U.S. case of the disease reportedly caused by Borrelia lonestari, a species of bacteria carried by the lone star tick, reports Ethan Covey for Infectious Disease Special Edition.

New research suggests the bacteria infected the 75-year-old man with tickborne relapsing fever, an uncommon condition that causes nausea, recurring fever, headaches and muscle and joint aches.

Scientists had previously linked tickborne relapsing fever with other species of Borrelia bacteria, but until now, they didn’t know B. lonestari could cause it, the team reported last month in Emerging Infectious Diseases, a journal run by the Centers for Disease Control and Prevention (CDC).

The research began in April 2019, when the man went to see doctors at the University of Alabama’s Kirklin Clinic. He told them that, for the last month or so, he’d been feeling extremely tired and had suffered from relapsing fevers, headache, dizziness, sweating and chills. The man said he had not traveled outside of Alabama in several years, but that he had been bitten by a tick about a month before he first started experiencing symptoms.

After running some initial tests, doctors found spiral-shaped bacteria known as spirochetes in his blood. They gave him antibiotics and, almost immediately, his condition got worse. He developed a fever and became nearly unresponsive. Within 24 hours, however, his health went back to normal, and he was able to successfully finish the ten-day course of antibiotics and recover.

Doctors then sent his blood samples for more tests and discovered B. lonestari. This led to their official diagnosis of tickborne relapsing fever caused by the bacteria. This wasn’t a total shock, as B. lonestari is a close relative of B. miyamotoi, which is known to cause tickborne relapsing fever. What’s more, B. lonestari had previously caused a circular rash—similar to the one caused by Lyme disease—in an elderly patient who’d been bitten by a lone star tick more than 20 years ago. Scientists had also once suspected—but could not prove—that B. lonestari caused another Lyme disease-like ailment called southern tick-associated rash illness (STARI).

Even after solving this patient’s mysterious case, scientists still have a lot of questions. For one, they aren’t totally sure of B. lonestari’s “pathogenic potential” for getting other people sick, they write in the paper. Though scientists regularly detect B. lonestari in ticks, doctors don’t see a lot of patients with infections caused by it. This suggests that other Borrelia species may be responsible for more human illness. This theory is further supported by the fact that the Alabama man was on immunosuppressants for lymphoma—in other words, B. lonestari may not cause illness in most people, but might infect those with weakened immune systems.

“We don’t know whether the patient developed relapsing fever because B. lonestari is always a true pathogen, because he was immunocompromised or both,” says co-author Joshua A. Lieberman, a pathologist at the University of Washington, to Infectious Disease Special Edition.

Complicating matters further is the fact that B. lonestari is hard to identify with typical lab tests—doctors may have missed earlier cases of illness caused by the bacteria entirely. In the future, doctors treating patients who have recently been bitten by ticks may want to conduct additional molecular diagnostic tests to determine which type of bacteria is responsible, researchers say.

Running these tests more regularly may reveal that B. lonestari is, in fact, another bacteria to be concerned about with ticks. In the meantime, following the CDC’s guidelines on preventing tick bites can help avoid such tickborne infections, including Lyme disease (caused by one of B. lonestari’s distant relatives, B. burgdorferi), Heartland virus and red meat allergy.

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