Lyme disease is a bacterial infection that is spread through the bite of one of several types of ticks. Lyme disease is caused by bacteria called Borrelia burgdorferi (B burgdorferi). Blacklegged ticks and other species of ticks can carry these bacteria. The ticks pick up the bacteria when they bite mice or deer that are infected with B burgdorferi. You can get the disease if you are bitten by an infected tick.