Aided by global warming, ticks spread to new areas of U.S., bringing diseases that threaten humans and animals

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It's the peak time of year for ticks, and they are spreading to new areas of the U.S. as the planet warms, bringing with them infectious diseases that can hurt or kill humans like Rocky Mountain spotted fever and Lyme disease, Nina Pullano reports for InsideClimate News. Warming helps ticks and other pests spread since warmer winters don't kill them off.

"While the total number of tick-related illnesses is difficult to gauge, since so many go unreported, the trend is clear," Pullano reports. "The number of cases of reported tick-borne diseases has been on the rise in the U.S., doubling from 2004 to 2016, and reached a record high in 2017, the latest annual data reported by the U.S. Centers for Disease Control and Prevention."

Ticks can threaten livestock, too. One species called the Asian longhorned tick has spread to at least 11 states since 2013, aided by the fact that it can clone itself. It carries a parasite that has likely killed cattle in three Virginia counties. "In a study published last week about the infections, researchers warned that the tick could put the Virginia cattle industry at risk. Once an animal becomes infected, there is no treatment or cure," Pullano reports.

University of Rhode Island researchers are gathering data about the spread of ticks through TickSpotters, which invites people all over the country to photograph or mail in tick samples they've found for analysis. Thomas Mather, who runs the project, "said there's been a clear increase in submissions over the past few years: From the site's inception in 2014 until 2017, he saw fewer than 8,000 entries. Last year alone, he saw nearly 15,000," Pullano reports.