medwireNews: A new tick-borne infection caused by the spirochete bacteria Borrelia miyamotoi that produces similar symptoms to Lyme disease has been confirmed in a small number of patients in the USA.

"While many symptoms are similar to Lyme disease, patients also may experience other symptoms, such as relapsing fever," said Peter Krause (Yale School of Public Health, New Haven, Connecticut, USA), lead author of the letter published in the New England Journal of Medicine, and colleagues.

B. miyamotoi is related to B. burgdorferi, the causative spirochete bacteria for Lyme disease, and is carried by all the same species of ticks. The first report of human infection was in 46 patients in Russia in 2011.

Krause and team assessed whether infection with B. miyamotoi had reached the USA. They tested three groups of people from areas endemic for Lyme disease for the new infection.

In the first group, 584 people were taking part in a survey about tick-borne infections and were from Block Island, Prudence Island, Rhode Island, and Brimfield in Massachusetts. All the participants were healthy when their blood was sampled. The second group involved 277 people from New England who were being tested for suspected Lyme disease, and the third group consisted of 14 individuals from New York who had symptoms of a viral-like illness and were being evaluated at a Lyme disease clinic.

The team reports that 18 people across the three groups were infected with B. miyamotoi, none of whom were immunocompromised. The seroprevalence was 1.0%, 3.2%, and 21.0% in groups one, two, and three, respectively.

All the patients had a viral-like illness and were successfully treated with doxycycline or amoxicillin.

In the same issue of the journal, Sam Telford (Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, USA) and co-authors report a case of meningoencephalitis in an immunocompromised patient that they believe was caused by B. miyamotoi.

Telford and colleagues suggest: "It is likely that B. miyamotoi is an underrecognized cause of disease, especially in sites where Lyme disease is endemic."

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