Jessica Reeder worries about ticks and the diseases they carry. She had Lyme disease, her brother had Lyme disease, and every fall her children come home from school with notes reminding parents to do a nightly tick check. Even in Philadelphia, where Reeder lives, the bloodsuckers lurk in the woods around the playground. Her family used to go tent camping with friends, but they stopped after a few people in the group contracted Lyme.