By ANERI PATTANIJULY 24, 2017
Everybody knows about Lyme disease. But experts say the Northern United States may be in for a bad tick season this summer, raising concerns about Lyme and other scary tick-borne diseases, including the Powassan virus, which causes encephalitis [ Hjärninflammation. Tick-borne encephalitis: TBE, fästingburen encefalit ] and can leave people with permanent neurological damage.
“This spring definitely seems worse than others I remember,” said Dr. Catherine Wiley, chief of general pediatrics at Connecticut Children’s Medical Center. “People are coming in from the yard with numerous ticks on them.”
When we think of ticks, we tend to think of deer, but Richard S. Ostfeld, a senior scientist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y., said it’s really all about mice. He has been studying white-footed mouse population ecology for the past 25 years. Every four or five years, he said, there’s a bumper acorn crop, so more mice survive the following winter, breed and reach what he called “mouse plague levels” in the summer.
These mice will be the main source of infection for the tiny larval ticks that hatch in August and can attach to many mammals and birds, which will try to groom them off. Mice “are just not fastidious groomers,” Dr. Ostfeld said, so their ticks tend to survive. Those larval ticks then morph into the nymph stage and stay dormant through the following winter. And then, in late spring through early summer, the nymphs begin to feed. It’s those nymphs, infected in the larval stage by mice, that transmit the infections to humans.
So what we’re worried about this summer goes back to 2015, which was one of those big acorn years; “2016 was the biggest mouse year we’ve seen in our entire 25 years of monitoring them,” Dr. Ostfeld said.
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