Lyme disease is roughly 10 times more prevalent nationwide than the number of cases reported by doctors would suggest, according to a report by the U.S. Centers for Disease Control and Prevention presented at a Boston medical conference.
The center’s report, based on the results of three ongoing studies that approached the issue from different angles, suggests that Lyme disease is a bigger problem than previously realized in states such as Maine, where tiny deer ticks that carry the disease thrive.
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The report was unveiled Sunday night at the 2013 International Conference on Lyme Borreliosis and Other Tick-Borne Diseases, which runs through Wednesday at Harvard Medical School’s Joseph B. Martin Conference Center.
According to the report, an estimated 300,000 Americans are diagnosed with Lyme disease each year, compared with the roughly 30,000 cases reported to the Centers for Disease Control.
The report did not provide estimates for individual states, but data from the Maine Center for Disease Control and Prevention show that reported cases of Lyme disease have increased significantly in the state over the past decade, from 175 in 2003 to 1,111 in 2012.
Another troubling phenomenon is the recent explosion in Maine’s deer tick population, according to researchers at Maine Medical Center, caused by factors such as farmland reverting to woods, and the lack of long periods of cold, dry weather without snow cover, which kills the ticks.
Dr. William Breen, who treats Lyme disease patients at Eastern Maine Medical Center in Bangor, said the increase in ticks has caused more cases of the disease. “We had a really, really busy spring this year pulling ticks off of people,” he said.
Breen said Lyme disease is on the rise in Maine but is still not as common as in Connecticut and Massachusetts.
“I don’t think that it’s overwhelming (in Maine), but it’s becoming more and more prevalent,” he said.
If federal estimates of underreporting are accurate, the actual number of diagnosed cases in Maine could have exceeded 11,000 — although state medical experts believe the number is lower.
Maine State Epidemiologist Dr. Stephen Sears said it is widely known that cases of Lyme disease are underreported in the state, but he said the ratio of actual diagnoses to reported cases in Maine is probably more like 2 to 1.
Still, Sears said closer examination of the new federal report and its methodologies could prompt officials to adjust that ratio. “We know that the disease is underreported,” he said. “This suggests that it’s more so than we thought.”
The federal agency’s preliminary estimate of diagnosed Lyme disease cases in the United States per year is based on findings from three ongoing studies that use different methods. All three aim to define the approximate number of people diagnosed with Lyme disease each year, the Centers for Disease Control said.
The first project analyzed health-insurance claims for roughly 22 million people over a six-year period, the federal agency said. The second is based on a survey of clinical laboratories, and the third looked at self-reported Lyme disease cases from a survey of the general public.
The new estimate of underreported Lyme disease cases supports research published in the 1990s that suggested the true number of cases at that time was three to 12 times the number of reported cases, it said.
“We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater,” Dr. Paul Mead, chief of epidemiology and surveillance for the Atlanta-based center’s Lyme disease program, said in a written statement. “This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States and clearly highlights the urgent need for prevention.”
Lyme disease is caused by a corkscrew-like bacteria and is transmitted to people by deer ticks. It is the most common tick-borne disease in the United States and North America, although it was not understood and named until the mid-1970s.
Ticks, which survive by feeding on the blood of other animals, pick up the bacteria by biting rodents and then transfer it to people. Lyme disease in humans usually begins with a large, circular rash that looks like a bullseye centered on the tick bite, followed by flu-like symptoms such as fever, headaches and sore muscles.
If not treated with antibiotics, Lyme disease can cause more acute symptoms such as arthritis, fatigue, dizziness, intermittent paralysis, shooting pains, short-term memory loss and other neurological disorders.
Centers for Disease Control officials said the new report emphasizes the importance of Lyme disease prevention efforts in states such as Maine, where deer ticks are prevalent.
“We know people can prevent tick bites through steps like using repellents and tick checks,” said Dr. Lyle Petersen, director of the center’s Division of Vector-Borne Diseases. “Although these measures are effective, they aren’t fail-proof and people don’t always use them.”
Efforts are under way by the centers and other researchers to identify novel methods to kill ticks and prevent illness in people, he said.
One favored method is a community-based approach to preventing the disease, Petersen said. It involves homeowners killing ticks in their own yards, eliminating rodents that carry the Lyme disease bacteria, and using methods such as urban planning to limit the interaction between rodents, ticks and humans.
“We need to move to a broader approach to tick reduction, involving entire communities, to combat this public health problem,” he said.
The report’s data are preliminary and will be finalized when the three ongoing studies are complete, the Centers for Disease Control said.
J. Craig Anderson can be contacted at 791-6390 or at: canderson@pressherald.com
Twitter: @jcraiganderson
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