What Clinicians Should Know About the New Lyme Species

Paul G. Auwaerter, MD


March 01, 2016

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Hello. This is Paul Auwaerter with Medscape Infectious Diseases, from the Division of Infectious Diseases at Johns Hopkins. Tickborne infections continue to surprise us. Lyme disease historically has been the top vector-borne illness in North America, with 20,000-36,000 reported cases annually, although estimates suggest that the actual number of cases occurring in the United States annually might be upwards of 300,000.[1]

Other members of the Borrelia genus cause disease in the United States. Perhaps the oldest, known for many decades, have been the agents of relapsing fever—either louse-borne (which is fairly rare in this country) or, more commonly, tickborne. Tickborne relapsing fever is spread by soft ticks that like to bite at night, especially campers in sleeping bags, and often in elevated climates of 2000-7000 feet above sea level in the western United States.[2]

But two more recent borrelial species deserve some attention for anyone who treats patients who might have acquired a tickborne infection. The first is B miyamotoi.[3] This was first described in Russia a few years ago and was initially thought to cause a relapsing fever-like illness, but in the United States it was first described as causing a meningoencephalitis. B miyamotoi seems to be transmitted by the same deer tick that transmits Lyme disease, and commercial assays for testing for it aren't yet widely available. However, this infection can be severe enough to cause hospitalization with a sepsis-like presentation. More commonly, it is associated with a febrile illness and can be confused with atypical Lyme disease (without a rash), ehrlichiosis, or anaplasmosis.

However, the newest kid on the block was just described by groups at the Mayo Clinic and the Centers for Disease Control and Prevention.[4] The Mayo Clinic has been a reference lab for many tests throughout the United States. They have drawn samples from around the country and found six samples using polymerase chain reaction (PCR) testing for suspected Lyme disease that had atypical melting curves. Upon further genetic analysis, they found that this was a new species, which they have given the candidate name of B mayonii in recognition of where the work was done.

Of interest, the six patients were all from the upper Midwest—Minnesota or Wisconsin. All were ill with fever and rash. One was described as having an erythema migrans rash, others had diffuse maculopapular rashes. There is a suggestion of neurologic syndromes. One patient had arthritis and two others were ill enough to be admitted to the hospital.

Somewhat different from Lyme disease, however, is that some of these patients had very high spirochete loads in their blood. This skews more to what you might find in traditional relapsing fever.

Now, what does this mean? The authors suggest that this is a newly emerging borrelial infection because it hadn't been described in more than 90,000 samples from different regions that they had analyzed earlier, so they think it could just be found in the upper Midwest. Obviously, however, this is very much in the earliest stages.

This situation seems very similar to that in Europe, where B burgdorferi sensu stricto (what we have had here in the United States) accounts only for a small proportion of Lyme borreliosis. B garinii and B afzelii account for far more cases. Several borrelial species account for infections there. We are no longer limited to only one now that B mayonii is a separate entity.

There are no specific diagnostic tests yet. It is uncertain whether a B burgdorferi PCR would pick this up routinely. The Lyme C6 antibody, which is US Food and Drug Administration approved, at least detected the infection in all four patients. Less successful was the traditional two-tier immunoblot testing, although the IgM Western blot was positive in three out of three people tested. The IgG assay was far less successful.

Whether these patients need different treatment is unclear. They were treated the way that we would treat any tickborne infection. That is the right response at the current time.

Stay tuned, because we might uncover more tickborne infections with advanced molecular technologies. Clinicians should pay attention to what they think might be Lyme disease, ehrlichiosis, or anaplasmosis, which may indeed represent some of these alternative infections. Thanks for listening.