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Forget deer — mice and acorns may be the real drivers of Lyme disease risk. A landmark 35-year study from the Cary Institute found that high mouse populations predict a 40% surge in nymphal ticks the following year, and bumper acorn crops can forecast tick spikes two years out. The findings could reshape how public health officials anticipate and prevent Lyme disease outbreaks.
For decades, white-tailed deer were considered the primary culprits behind rising Lyme disease rates — but a sweeping 35-year study from the Cary Institute of Ecosystem Studies is turning that assumption on its head. Published in Proceedings of the National Academy of Sciences, the research reveals that white-footed mice are far stronger predictors of tick population surges than deer. Mice are not only excellent blood hosts for tick larvae but also highly efficient transmitters of Borrelia burgdorferi, the bacterium that causes Lyme disease.
Perhaps the most surprising finding: acorn production. When oak trees have a bumper crop — a phenomenon called "masting" — mouse populations boom the following year, and nymphal tick numbers spike the year after that. This means a heavy acorn harvest today can predict elevated Lyme disease risk two years down the line. Meanwhile, ticks proved far more resilient to extreme temperatures than lab studies suggested, sheltering in soil and leaf litter to survive harsh conditions.
By the Numbers
Why it matters: These findings give public health officials powerful new ecological signals — mouse populations and acorn crops — to anticipate high-risk Lyme disease seasons and deploy prevention strategies more effectively.
