 When they find one, they pick it up with tweezers and drop it into a little vial of alcohol. This vial of ticks will go back to the state laboratory to get tested for diseases. Black-legged ticks, also called deer ticks, carry the bacteria that causes Lyme disease. But they also carry a bunch of other bacteria, viruses, and parasites that cause other illnesses. Natalie Quit is with the Vermont Department of Health.