Tree disease linked to rise in Lyme ticks

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SANTA CRUZ, Calif., Dec. 20 (UPI) -- Scientists say a tree disease killing large swaths of California's coastal forests may be linked to an increase of human cases of tick-borne Lyme disease.

Changes in the forest cover affect many species of animals, a number of which serve as hosts for the ticks that can bite humans and transmit the disease, which causes painful joint swelling, fatigue and even neurological damage, the Santa Cruz (Calif.) Sentinel reported Monday.

Forests have become infected with Sudden Oak Death disease and the "newly created forest gaps result in hotter, drier patches in the forests, which have different implications for different species," said Andrea Swei, postdoctoral researcher at the University of California, Berkeley.

The question is which animal populations grow and which shrink in response to the breaks in the canopy, she said.

UC Berkeley, UC Santa Barbara and the Cary Institute of Ecosystem Studies in New York have embarked on a multiyear study of animal populations in forests infected with Sudden Oak Death.

Researchers monitored ticks and four of their animal hosts: deer mice, wood rats, lizards and deer.

The researchers found fewer wood rats but more deer mice and western fence lizards in regions affected by Sudden Oak Death.

In 2009 7.6 cases of Lyme disease were reported for every 100,000 people in California's Mendocino County and 6.5 per 100,000 people in Del Norte County, a rate 20 times greater than the state average.