Ticks are small arachnids in the order Parasitiformes. Along with mites, they constitute the subclass Acarina. Ticks are ectoparasites (external parasites), living on the blood of mammals, birds, and sometimes reptiles and amphibians. Ticks are vectors of a number of diseases, including Lyme disease, Colorado tick fever, Rocky Mountain spotted fever, African tick bite fever, Crimean Congo hemorrhagic fever, tularemia, tick-borne relapsing fever, babesiosis, ehrlichiosis, and tick-borne meningoencephalitis, as well as bovine anaplasmosis and probably the Heartland virus.
Adult ticks have eight legs. Their life cycle is divided into four stages: egg, larva, nymph, and adult. All ticks feed on blood during some or all stages in their lifecycle. Ticks are known to transmit serious diseases to animals and humans even though humans are not the preferred host. They are known to be almost as important as mosquitoes in terms of public health importance.
Several species of ticks attack dogs, but cats are rarely infested. Many of the dog ticks are known as wood ticks and infest dogs when they run through the woods or fields.