Acorns, Mice, Ticks = Lyme Disease

Secrets of the Woods: Acorns, Biodiversity, and Lyme Disease
It has long been suspected that the forest-living mouse carries a spiral-shaped microbe called Borrelia burgdorferi. This "spirocete" causes Lyme disease. As the population of mice increases the incidence of Lyme disease outbreaks increase. Tick larvae that first feed on mice, eventually spread the disease to the human population.
Acorns are an important food source for many forest animals, including these mice. Genetic and climatic factors cause oak forests to vary in the number of acorns that fall to the ground each year. This is called a "mast" crop. Mouse populations will increase or decrease along with the size of the mast crop. Large crops of acorns in the fall lead to a booming mouse population the following summer.
The National Institute for Allergy and Infectious Diseases suggest that a bumper crop of acorns may result in "100 times more mice" than observed in years when the acorn crop is low. More mice increase the number of infected ticks by providing tick larvae with more opportunities to pick up Borrelia during feeding. These larvae then develop into infected nymphs and, ultimately, adult ticks.