Borrelia miyamotoi is an infectious disease transmitted to humans by the bite of a deer tick, Ixodes scapularis, the same tick that also has the potential to infect humans with Lyme disease (B. burgdorferi), babesiosis (B. microti) and anaplasmosis (HGA, Anaplasma phagocytophilum). The organism was first identified in Japan in 1995, and the first documented outbreak of human cases was reported in 2011, from Russia. This pathogen, a spirochete from the Borrelia genus, is distantly related to Borrelia burgdorferi (the causative agent of Lyme disease), and more closely related to the Borreliaspecies associated with relapsing fever.

In nature over the past few years, B. miyamotoi has been found in 1-2% of Ixodes scapularis tick vectors from RI, and in 1-4% of Ixodes scapularis tick vectors in MA. It is presumed that human clinical cases may potentially occur in a similar geographic distribution as Lyme disease and other Ixodes-borne infections.

In 2012, the Imugen laboratory identified the first North American human case of B. miyamotoi infection documented by molecular techniques, and published in the January 17, 2013 issue of the New England Journal of Medicine. This immunosuppressed patient from New Jersey presented with systemic and neurologic symptoms, and numerous thick tightly coiled highly motile spirochetes were seen in a CSF specimen. Definitive identification as B. miyamotoi was established by species specific PCR testing, and confirmed be gene sequencing. Since then, we have confirmed additional cases from NJ and MA.

Clinical manifestations of B. miyamotoi infection include nonspecific flu-like symptoms such as high fever, headache, or muscle and joint aches, but unlike Lyme disease, no characteristic rash has been described. The B. miyamotoi patients thus far have been symptomatic, hospitalized, and have demonstrated laboratory abnormalities such as cytopenias and elevated transaminases. The full spectrum of this infection is under investigation, and the occurrence of milder or even asymptomatic infections is not clear at this time. Reported cases have been successfully treated with several antimicrobial regimens including ceftriaxone, doxycycline, and amoxicillin.

Since this infection is transmitted by Ixodes scapularis, it is at least theoretically possible that co-infections with the other tick-borne pathogens may occur. The appreciation of new tick-borne pathogens has important clinical implications in approaching patients who present with nonspecific symptoms following tick exposure. When tests for the more common tick-transmitted infectious agents are negative, the treating physician may want to expand the diagnostic considerations to include B. miyamotoi infection. Since there is no characteristic rash of other pathognomonic clinical feature, laboratory testing is necessary to make this diagnosis. The Imugen laboratory offers a specific PCR and antibody test for evaluating suspected cases of B. miyamotoi infection. Presently this organism is not culturable.
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