Knowing the complex life cycle of the ticks that transmit Lyme disease bacteria can help in understanding the risk of getting the disease and how to prevent it.
The complete life cycle of Ixodes ticks requires 2 years. Tick eggs are laid in the spring, and hatch as larvae in the summer. Larvae feed on mice, birds, and other small animals in the summer and early fall. The larvae may become infected with Lyme disease bacteria when feeding on these animals. Once a tick becomes infected, it stays infected for the rest of its life and can transmit the bacteria to other hosts. After this initial feeding, the larvae usually become inactive until the following spring, when they change into nymphs. Nymphs seek blood meals in order to fuel their growth into adults.
Nymphs feed on small rodents, birds, and other small mammals in late spring and early summer. Nymphs will also feed on humans, and if previously infected with the Lyme disease bacterium, they can transmit the disease to humans. Nymphs molt into adult ticks in the fall. In the fall and early spring, adult ticks feed and mate on large animals, such as deer. Adult female ticks will sometimes also feed on humans. In spring, adult female ticks lay their eggs on the ground, completing the 2-year life cycle.
Domestic animals may become infected with Lyme disease bacteria and some of these (dogs, for instance) may develop arthritis. Domestic animals can carry infected ticks into areas where people live. Studies to determine whether pet owners have an increased risk of Lyme disease have been inconclusive. Veterinary tick control products may be helpful to reduce the presence of ticks on pets.