A rare form of Lyme disease is making inroads into the United States.
On Thursday, researchers and local health officials in New York detailed a case of Lyme caused by the bacterium Borrelia mayonii—the first ever detected in the state. Though the person was treated with antibiotics and made a full recovery, the discovery is a troubling sign of the pathogen’s spread, which was previously only found in the U.S. Midwest.
“This study provides the first evidence of B. mayonii presence in New York ticks and locally acquired B. mayonii infection in a New York resident,” the authors wrote in their paper, published in the Morbidity and Mortality Weekly Report (MMWR), a journal run by the Centers for Disease Control and Prevention.
A different type of Lyme
Lyme disease is caused by certain Borrelia bacteria, which are transmitted by various species of tick. The primary culprit behind Lyme in the U.S. is B. burgdorferi. In 2016, however, researchers at the Mayo Clinic in Minnesota discovered a new species that could trigger Lyme as well, which they named B. mayonii.
Both Borrelia species are typically spread by the bite of a blacklegged, or deer, tick (Ixodes scapularis) and respond to the same antibiotics, but there are differences in the symptoms they can cause. People with B. mayonii tend to experience rashes along their body, as opposed to the single bullseye-shaped rash at the bite site often seen with B. burgdorferi. They’re also more likely to have additional symptoms like nausea and vomiting and to have a higher concentration of B. mayonii in their blood, which may increase the risk of severe illness.
This new case was detected last summer in a resident from Herkimer County in Central New York. The person first experienced symptoms consistent with a tickborne infection in late June, prompting testing. The commercial lab that performed the testing then notified the New York State Department of Health of the result positive for B. mayonii in early July.
Until now, B. mayonii had only been found in Minnesota and Wisconsin. The person reported spending time outside but no recent travel or transplant history, suggesting that they had likely caught it from the local tick population. So that July, health officials began collecting and testing ticks found in the person’s yard, as well as hiking trails surrounding the property and a nearby forest.
One nymph in the resident’s yard tested positive for B. mayonii, leading to another collection trip later that October. The second time, they found nine adult ticks with B. mayonii, all from the resident’s property. The researchers then checked for B. mayonii in tick samples collected in other New York counties dating back to 2021 and found none, perhaps suggesting that it only recently arrived in the state.
Adding to the resident’s misfortune, they also tested positive for a different tickborne disease at the same time, anaplasmosis. But with standard doxycycline treatment, they made a full recovery.
The future of B. mayonii
Though B. mayonii might cause more severe illness on average, it’s remained a rare cause of Lyme since its discovery. So it’s unlikely to ever supplant the B. burgdorferi version of Lyme, which is the most commonly reported tickborne disease in the U.S.
Still, its sudden appearance in New York, which is several states away from both Wisconsin and Minnesota, is certainly troubling and perplexing. The greater prevalence of the bacterium in adult ticks also suggests there’s an established animal reservoir in the region, such as mice or squirrels, the researchers say, as opposed to a one-off introduction from ticks that bummed a ride from birds in the Midwest.
Unfortunately, B. mayonii is only one of many tickborne diseases that are threatening to become more common in the U.S., thanks to ever-expanding tick populations aided by a warming climate. So it’s important to track the spread of these infections, the researchers say.
“Continued entomological, molecular, and human tickborne disease surveillance are critical for understanding the distribution and public health significance of emerging tickborne pathogens in New York,” they wrote.
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