This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Tick-borne diseases are on the rise in the United States. Lyme disease is the most commonly reported, with nearly half a million people diagnosed each year.
Caused by the bacterium Borrelia burgdorferi, it is most often spread by bites from blacklegged ticks. Lyme can be treated with antibiotics, but if untreated, infection can spread to the joints, heart and nervous system, and some people can experience persistent symptoms. For more than 35 years, researchers at the Cary Institute of Ecosystem Studies in Millbrook, New York, have been studying how interactions between acorns, rodents, ticks, predators and climate shape Lyme disease risk in people.
A new paper, published in Proceedings of the National Academy of Sciences, details nine of the research project's most surprising findings to date. Several are outlined below. "On balance, these surprises have enriched our knowledge of this system, helping us to inform management of tick-borne disease risk," said lead author Richard Ostfeld, a Cary Institute disease ecologist who co-directs the research program with Shannon LaDeau.
Ostfeld added that many of the findings would not have been possible without the decades of data the project has collected so far, which helps the team statistically distinguish real trends and drivers from random events and correlations. "Studies of this depth and length are incredibly rare," said LaDeau. "This research has followed an ecological community—including oak trees, mammals and microorganisms—examining how interactions like predation, parasitism and competition shape the system over time.
The evolution of understanding summarized in this paper is something you simply cannot get without such a long-term and system-focused study." When Lyme disease was first recognized in the United States in the 1980s, some researchers assumed white-tailed deer played an important role in spreading the disease because deer killed by hunters in the fall often carry large numbers of adult ticks. Although deer do not infect ticks with the Borrelia pathogen, the logic was that more abundant deer might feed more adult female ticks, which would then be able to lay more eggs and produce more immature ticks. However, after several decades of intensive research, the long-term study on the Cary Institute's campus—a forested ecosystem spanning 2,000 acres (3.1 square miles) in New York's Dutchess County—has not found a statistical relationship between deer abundance and the density of nymphal ticks, the life stage most likely to spread Lyme disease to people.
"We had detected a weak positive relationship between deer and subsequent nymph abundance over short subsets of the data," said Ostfeld, "but the whole data set shows no such thing." While deer abundance wasn't associated with the number of nymphal ticks, mouse abundance was. The long-term study has shown that a strong mouse year boosted the next year's number of nymphs by about 40%. White-footed mice are a high-quality food source for blacklegged tick larvae and also happen to be very good at passing Borrelia burgdorferi bacteria to them.
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