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Another Tick-Borne Disease? Borrelia miyamotoi may cause relapsing fever in humans

Written By: Thomas Mather

We've known for years that deer ticks in the northeastern USA are infected with a spirochete that's different from the Lyme disease bacteria. This rare and largely unstudied infection in ticks, Borrelia miyamotoi, is more closely related to relapsing fever-group spirochetes. It was unknown whether this Borrelia caused any human disease. Now comes evidence that it may.

Saliva Extraction used for testing

In a report scheduled for release next month in CDC's Emerging Infectious Disease journal (, lead author Alexander Platonov and colleagues provide some of the first evidence that Borrelia miyamotoi may cause relapsing fever and Lyme disease-like symptoms in people. They report on 46 cases of B. miyamotoi infection all in Russian patients with flu-like illness, some with fevers as high as 39.5oC.

While the infection has not yet been detected in North American or European patients (there is no diagnostic test available yet in these countries), both Ixodes scapularis and Ixodes ricinus ticks can be infected with the agent. About 1 in 100 nymphal deer ticks in Rhode Island, for example, are infected with this agent. (For comparison, about 1 in 5 nymphal ticks carries Lyme disease Borrelia).

In an interview with the NYTimes (, Yale-based study co-author Peter Krause suggested that doctors might want to consider the new infection in patients bitten by ticks who experience recurrent episodes of fever but test negative on Lyme disease tests. The Russian patients infected with B. miyamotoi did not exhibit a bulls-eye rash. The Yale researchers recently received a grant from the National Institutes of Health to develop a rapid diagnostic test for the new agent and to investigate whether it's causing disease in people in the USA.