This study did not assess flooded paddies due to the difficulty of finding and collecting rodents, ticks, and chiggers underwater. Instead, Kuo trapped rodents in fallow and plowed fields and examined their tick and chigger passengers, testing the arachnids for presence of disease-causing rickettsial bacteria. He found 6 times as many ticks on the rodents living in fallow fields and the proportion of infectious ticks in fallow fields was three times higher, compounding the risk. Chiggers rode rodents at a rate 3 times higher in fallow fields than plowed fields.
"This study is a great example of the kinds of indirect effects that trickle down from human policies," said Bob Parmenter, an ecologist unaffiliated with the study. "It tells a nice story about how changes in international trade barriers can have unforeseen consequences." Parmenter is director of the USDA's Scientific Services Division at Valles Caldera National Preserve near Los Alamos, New Mexico, and an expert on the influence of ecology on deadly Hantavirus outbreaks, like the current episode in Yosemite National Park (California, USA) that has infected nine visitors and killed three.
The consequences of economic pressures on land use are also present in the eastern United States, where the small farms of the eighteen and nineteenth centuries have reverted, to a large degree, to forest. With the return of deer and wildlands has come a rise in ticks, and concurrent rise in Lyme disease. Conversely, opening new land
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Ecological Society of America