Newly described tick-borne infection in New England

At least 24 people in the northeast United States have been infected with a newly described, as yet-unnamed, tick-borne illness.

Borrelia miyamotoi is a spirochete related to Borrelia burgdorferi, the microorganism that causes Lyme disease, and is transmitted by the same four tick species that carry B. burgdorferi.

In a case series of 875 patients, B. miyamotoi was present in 1% of healthy people who lived in a Lyme-endemic area, 3% of those with suspected Lyme, and 21% of those with a warm weather viral-like illness in the late spring or summer who attended a Lyme screening clinic.

Eighteen of the cases plus an additional one are described in two reports published in the Jan. 17 issue of the New England Journal of Medicine. These occurred in Connecticut, New York, and Rhode Island; one was in New Jersey. Since these cases were described, five additional patients have been confirmed, according to a spokesperson for Imugen, the Norwood, Mass., laboratory that performed immunoassays on some of the patients. Those were in Massachusetts, New Jersey, Connecticut, and New York.

There is reason to believe that patients can be coinfected with both B. miyamotoi and B. burgdorferi, and that ticks can harbor both simultaneously, says an epidemiologist at Yale School of Public Health, New Haven, Conn., and primary author of one of the papers.

But because the spirochets are genetically similar, the illnesses they cause respond to the same antibiotic regimen.

B. miyamotoi was first identified in Japan in 1995. In 2001, anonther Yale epidemiologist, found it in 2.5% of tick nymphs collected in Maryland. In 2011, together identified were first human cases — a series of 46 patients in Russia.

Reviewed serum samples collected from 1990 to 2010: 584 from healthy subjects who lived in Lyme-endemic areas and participated in a serotyping survey; 277 from the group with suspected Lyme disease; and 14 from those who presented at the Lyme clinic.

Four of the 18 positive subjects had reported the typical erythema migrans skin lesion. Two others had an atypical smaller-sized lesion — less than 5 cm in diameter. The rest had no reported rash.

Three patients were actually negative for B. miyamotoi during their acute illness, but showed seroconversion during their recovery. This indicates that B. miyamotoi probably did not cause the initial illness, suggesting coinfection with B. burgdorferi.

One of these patients was quite ill, according to the report. This patient had no skin lesion and no evidence of human granulocytic anaplasmosis coinfection. He showed a fever of more than 39 degrees C, headache, neck stiffness, fatigue, myalgia, arthralgia, abdominal pain, cough, sore throat, and right inguinal lymphadenopathy. This patient recovered after a 14-day course of doxycycline; all of the other symptomatic patients treated with standard doxycycline or amoxicillin treatment also recovered .

None of the cases in cohort showed any serious neurologic symptoms. However, the single patient reported from New Jersey — an immunocompromised 80-year-old women — did.

Any patient who develops an otherwise unexplained viral-like illness in the spring or summer should be considered at high risk for one — or both — of the Borrelia illnesses. A relapsing fever should be especially concerning. That the emblematic “bull’s-eye” rash may or may not occur.

Clinically, the B. miyamotoi spirochetes are more likely to be seen in blood smears than are their burgdorferi cousins. But B. miyamotoi can be completely distinguished only by serotyping or polymerase chain reaction. These lab tests are not widely available now, but should be by early summer.

Since effective treatment does not depend on positive identification, it’s not clinically necessary to determine B. miyamotoi is certainly more widespread than the current case series suggest.

Because it’s been isolated in Japan, Germany, Russia, and now the United States, and in all of the tick species that carry Lyme, B. miyamotoi can be considered endemic in all northern hemisphere regions that harbor any of the four Lyme disease-causing tick species.

In fact, many presumed cases of Lyme are probably due either to B. miyamotoi alone or to coinfection by both species.

“About 2%,” of ticks analyzed at the Yale lab.“ It appears to be widely distributed, and it’s going to be seen more and more. This disease could actually be occurring as frequently as Lyme.”