BOSTON -- Like syphilis, Lyme disease can lie dormant in the body for years without creating symptoms and then cause progressive nervous systemproblems such as memory loss, researchers said Wednesday.
Findings from a study of 27 people with the disease indicate the corkscrew-shaped bacterium which causes it 'can survive latently for years in the nervous system,' said Dr. Allen Steere, director of the Lyme Disease Clinic at the New England Medical Center in Boston.
In a manner that is 'like what occurs in syphilis, we found Lyme infection can have long periods of latency and then cause slowly progressive disease' leading to chronic problems including memory loss, fatigue, sleep disorders, numbness and spinal pain, Steere said.
Steeree and his colleagues also found that in some people, antibiotic treatment is ineffective against the disease and neurological impairment may be irreversible. Their report appeared in The New England Journal of Medicine.
Although similar symptoms have been seen in others with Lyme disease, this is the first time researchers have discovered such a long latency period between initial infections and the development of neurological problems, Steere said.
Steere stressed that only a fraction of people infected with Lyme disease are likely to develop the kinds of symptoms seen in those in the study, although he said researchers do not have any precise estimates of how many. But he said 'in very few people who have memory loss or tingling in the arms and legs' is Lyme disease the probable cause.
One man in the study 'had initial symptoms after infection, but then did not develop chronic symptoms until 14 years later,' he said. At the time the man entered the study, Steere said 'he had experienced symptoms for 13 years, so presumably he had 27 years of infection.'
The study raises questions about how the Lyme disease bacterium is able to remain quietly in the nervous system for long periods and what triggers symptoms when they do appear, he said. The findings also may cause doctors to reevaluate standard antibiotic treatment for the disease, he said.
Lyme disease is spread by one of several types of tiny deer ticks, which attach themselves to the skin and inject the infection-causing bacterium into the bloodstream. Within about a week, the infection typically causes flu-like symptoms and a distinctive red rash shaped like a bull's eye.
Since 1980, more than 14,000 cases of Lyme disease have been reported in 43 states, with most cases occurring in the Northeast and Mid- Atlantic coastal states and Minnesota, California, Wisconsin and Oregon.
The 14 men and 13 women in the new study, who ranged in age from 25 to 72, developed neurological abnormalities an average of 26 months after the initial infection. However the range of time spanned from one month to 14 years, Steere said.
He said 24 of them developed a mild form of encephalopathy, a brain disease characterized by memory loss. 'They forgot names, missed appointments, or misplaced objects. To compensate, they often made daily lists,' the researchers said. Ten patients also had symptoms of depression and five had 'subtle symptoms of a language disturbance, with difficulty finding words.'
Disorders of the central and peripheral nervous systems developed in 17 people that included tingling and numbness of the arms and legs and pain in the spine, he said.
In addition, one man developed stiffness in the arms and legs and there was evidence the disease had damaged the coating of nerves. Similar symptoms are seen among people with multiple sclerosis. Although Steere said he doubts a bacterium causes that disease, 'our understanding of Lyme disease eventually may give us more information about multiple schlerosis.'
In most people, prompt antibiotic treatment can kill Lyme infection and prevent delayed symptoms that often include arthritis-like joint pain. Steere said only seven of those in the study had received antibiotics at the time of their initial infection.
All of those in the study were treated with intravenous antibiotics for two weeks. Six months after the treatment, 17 people were better although 'recovery was seldom complete,' the scientists said. Of the remaining 10 patients, six improved improved but later relapsed and four did not improve at all.
Of those who showed no improvement, Steere said it is possible they suffered irreversible brain damage or that their symptoms were not caused by live bacteria susceptible to antibiotics. He said it may also be that they needed longer drug therapy or treatment with different types of drugs.