Lyme disease is caused by a bacterium carried by the deer tick. When an infected deer tick attaches to a person (host) long enough to take a full blood meal, the bacteria could be transferred to the host’s blood and cause illness. This disease is one of three diseases caused by the bite of an infected deer tick (Ixodes scapularis). The tick carries a type of bacterium called Borrelia burgdorferi which is responsible for lyme disease. The two other less common diseases carried by deer ticks are human babesiosis and human granulocytic ehrlichiosis. The deer tick is capable of co-carrying these disease agents. Another common tick in Connecticut, the dog tick, (Dermacentor variabilis) is not capable of carrying the lyme disease bacterium.