Researchers have discovered a new human disease in the Northeast transmitted by the same common deer tick that can infect people with Lyme disease.
The bacterial illness causes flu-like symptoms, the researchers from Tufts, Yale, and other institutions reported Wednesday, but they also described the case of an 80-year-old woman who became confused and withdrawn, lost weight, and developed hearing difficulty and a wobbly gait. The woman, from New Jersey, recovered after receiving antibiotics.
Researchers estimate that 1 percent of the population in areas where Lyme disease is widespread — such as western Massachusetts and Cape Cod and the Islands — may be infected by the new bacteria, which can be transmitted by the tick when it is as small as a poppy seed. Lyme disease is thought to be 7 to 10 times more prevalent in these areas.
The discovery, disclosed in a paper and letter in the New England Journal of Medicine, marks the fifth human illness spread by deer ticks in the region, highlighting growing concerns about the threat posed by ticks and the burgeoning population of their hosts — deer. The disease is so new it remains unnamed and there is no readily-available test for doctors to screen for it, although some are being developed.
“It was right under our nose the whole time,’’ said Sam Telford, a professor at Tufts Cummings School of Veterinary Medicine who studies tick-borne diseases, and one of the authors on the paper about the elderly woman. He said the bacterium, known as Borrelia miyamotoi, has been known to exist in deer ticks for about decade. But it was not believed to cause human illness until researchers last year linked it to 46 sick people in Russia, some with relapsing fevers.
One scientist said the new disease might be the cause of unexplained symptoms, from fatigue to cognitive decline, in some people who believe they have Lyme but do not test positive for that bacteria.
“The good news is it looks like it is a treatable illness based on the small number of patients reported thus far,’’ said Brian Fallon, professor of psychiatry who runs Columbia University’s Lyme and Tick-Borne Diseases Research Center and is not associated with the studies. “It’s promising to realize that scientists have identified a new organism carried by ticks that might help to explain why some patients who test negative for Lyme nonetheless respond favorably to antibiotic treatment.”
In six cases described in the journal, the patients were treated with a course of antibiotics and fully recovered. None of the infected patients, both treated and untreated, described long-lasting, persistent symptoms.
Researchers from the Yale Schools of Public Health and Medicine who had co-authored the Russian study with Russian scientists set out to see if there was evidence of the infection in people’s blood closer to home. They tested blood samples obtained since 1990 and found positive results in 1 percent of 584 healthy people from Brimfield in Western Massachusetts and Block Island, R.I. In addition, 3 percent of 273 Southern New England residents with Lyme disease or suspected Lyme also had evidence that they had been infected with the new bacteria. The researchers couldn’t determine whether most of those people had the new illness.
Similarly, 21 percent of 14 southern New York patients with an unexplained viral-like sickness showed evidence of infection. Lead author Peter Krause, senior research scientist of the Yale School of Public Health, cautioned that it was difficult to draw many conclusions about prevalence of the disease from these 14 people because the sample size was so small and the group was highly selected.
“The symptoms are similar to Lyme disease … but it is a lot less common than Lyme disease,” said Krause. Still, given that roughly 2,600 people were reported to get Lyme disease in Massachusetts 2011 — and that the federal Centers for Disease Control and Prevention acknowledge underreporting could mean that number is tenfold higher — it stands to reason there could be a significant number of people who are infected with the new bacteria, Krause said, although how many become sick is unknown.