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, 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other institutions reported Wednesday, but they also described the case of an 80-year-old woman who became confused and withdrawn, lost weight, and developed hearing difficulty and a wobbly gait.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 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, reported 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 concern about the threat posed by ticks and the burgeoning population of their hosts, deer. The disease is so new that it is 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.
Telford, one author of the paper about the elderly woman, said the bacterium, Borrelia miyamotoi, has been known in deer ticks for about a decade. But it was not believed to cause human illness until last year when researchers 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 disease 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, a 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 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 coauthored 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 disease also had evidence that they had been infected with the new bacteria. The researchers could not determine whether most of those people had the new illness.
Similarly, 21 percent of 14 southern New York patients with an unexplained virus-like sickness showed evidence of infection. Lead author Peter Krause, senior research scientist at 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.
Still, given that roughly 2,600 people were reported to get Lyme disease in Massachusetts 2011 and that the US Centers for Disease Control and Prevention acknowledge that 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.
The 80-year-old woman, who previously had been treated for cancer, lives on a farm in New Jersey and suffered four months of mental decline.
At first, doctors thought she might have had a recurrence of cancer, which led them to perform a spinal tap. Cancer was ruled out, but Joseph L. Gugliotta, an infectious disease doctor at Hunterdon Medical Center in Flemington, saw corkscrew bacteria known as spirochetes in her spinal fluid. It looked similar to Lyme bacteria, but he knew the woman, with her compromised immune system, probably would be much sicker if it were Lyme.
He contacted Telford’s group and others, who knew of the recent study in Russia. In the meantime, Gugliotta began treating her with a monthlong course of antibiotics.
“Within a few days we saw an improvement,’’ said Gugliotta. “By one month, she was back.”
Beth Daley can be reached at email@example.com. Follow her on Twitter @Globebethdaley.