The American dog tick is a member of the hard tick family Ixodidae. Hard ticks are responsible for transmitting nearly all of the major tick-borne diseases in North America. Though generally not believed to be vectors of Lyme disease, American dog ticks are the primary carriers of the Rocky Mountain spotted fever bacterium Rickettsia rickettsii. They are also capable of transmitting tularemia, Colorado tick fever, and anaplasmosis, and may cause paralysis when a neurotoxin they produce is secreted into a host's blood stream.