Snow protects infected ticks

Insects carrying Lyme disease are emerging earlier in spring

By Brian Nearing

This frigid, snowy winter may be keeping many people indoors, but is likely doing little to kill slumbering hordes of ticks that can carry Lyme disease.

And infected ticks that survive winter to emerge each spring, looking for something to bite, are showing up earlier as climate in the Northeast gradually warms.

"If this persists, we will need to move Lyme disease Awareness Month from May to April," said Richard Ostfeld, a research scientist at the Cary Institute of Ecosystem Studies in Millbrook, Dutchess County.

His research on climate change and population of the black-legged tick — which carries Lyme and other dangerous illnesses — was published this week in the peer-reviewed Journal of The Royal Society, which is the national science academy of the United Kingdom. The research built on dozens of scientific studies during the last two decades from North America, Europe and Asia, where ticks are expanding ranges steadily northward and into higher elevations.

"Many people are asking me whether this snowy winter is clobbering the ticks, so we will not have as many coming out this spring," said Ostfeld. His answer? No.

That is because heavy snow is acting as a kind of insulation to protect ticks slumbering near ground level from the worst of the cold, he said.

"As the mice go, so go the ticks," Ostfeld said. When the snows melt, mice are preyed upon by a stage of tick called nymphs, some of which in their larval stage the previous fall had fed on infected mice. Smaller than a poppy seed and difficult to spot, such infected nymphs "are the dangerous ones," said Ostfeld.Called subnivean space, this natural refuge also promotes survival of the white-footed mouse, a tiny mammal that also spends its winter beneath the snow and serves as a carrier for bacteria that causes Lyme disease, as other illnesses like encephalitis, human babesiosis and granulocytic anaplasmosis.

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