Williams's approach is one of several strategies being tested in an attempt to thwart the spread of tick-borne diseases. Some, like the mouse vaccine, interrupt the pathogen's ecological circuitry by targeting the wild animals that pass along and amplify the disease. Others, such as efforts to revive a human Lyme vaccine, aim to protect people from infection directly. A more radical approach could hamper the ability of ticks to bite humans or animals, potentially protecting against dozens of illnesses spreading across the United States, Europe, Africa and Asia.