A California man has become the first person in the United States to have a confirmed infection with Borrelia miyamotoi, a corkscrew-shaped spirochete bacterium that causes a rare disease called hard tick relapsing fever. Spread by black-legged ticks, B. miyamotoi has lurked in the region for over two decades, but researchers fear the pathogen may finally be emerging there. B. miyamotoi is a relative of the more well-known Borrelia burgdorferi spirochete, which causes Lyme disease.
Ticks collected in California as early as 2000 were found to carry the new spirochete, but the first cases of disease caused by B. miyamotoi in the US were only confirmed in 2013 in the Northeast and, until now, no confirmed cases have been reported in the western part of the country, despite the bacterium’s prevalence in adult black-legged ticks being similar to that of B. burgdorferi, the Lyme disease spirochete.
A highly magnified scanning electron microscopic (SEM) image depicting several spirochete bacteria, atop a culture of cotton-tail rabbit epithelium cells. (CDC/David Cox)
Symptoms and how to treat
The hard tick relapsing fever is difficult to identify, often marked by fevers that come and go, along with fatigue, chills, and aches and pains. In severe cases, the disease can progress to inflammation of the brain and surrounding tissue. But in many cases, the disease resolves on its own. People infected tend to show low levels of white blood cells and platelets, elevated liver enzymes, and excess protein in their urine. But there are no simple tests to confirm the disease.
The only method to definitively identify a B. miyamotoi infection is to directly probe for fragments of the bacterium’s genetic sequence in a person’s blood or cerebrospinal fluid, which few laboratories do. With so few cases identified, researchers have not been able to run clinical trials.
So far, a two-week course of doxycycline or amoxicillin antibiotics seems to do the trick for most cases, with IV-antibiotic treatments being used in severe cases. A small number of people may experience the Jarisch-Herxheimer reaction, which is marked by fever, chills, nausea, vomiting, headache, rapid heart rate, low blood pressure, hyperventilation, flushing, and pain, and can turn life-threatening for some.
Editor’s warning: in case of symptoms, please consult a licensed healthcare professional, we mentioned potential treatment as general information, not to be used without a doctor.
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