The groundhog tick during all life stages, is the most common tick found on humans and pets in Ontario. The adults usually attack rodents and small to medium-sized animals but attacks on humans do occur. Powassan encephalitis is a disease which may be transmitted by the groundhog tick but reports of this disease are extremely rare.
The adult American dog tick, Dermacentor variabilis (Say), is the second most common species encountered on humans and pets in Ontario. The preferred host of the adult tick is the dog, although it will also feed on horses and other large mammals including humans. In Canada, the American dog tick is found from Saskatchewan to the maritime provinces. These ticks sometimes enter buildings while attached to their hosts but they will not become established indoors. American dog ticks are known to transmit Rocky Mountain spotted fever, tularemia and tick paralysis.
The black-legged tick also known as deer tick has established populations in Long Point on Lake Erie and in Point Pelee National Park. During its immature stages, the black-legged tick feeds especially on white-footed mouse but will also feed on a wide variety of small mammals and birds. Adults feed mostly on white-tailed deer but may also feed on other large mammals. The black-legged tick is the most important vector of Lyme disease and all stages of the tick will readily feed on humans.
The winter tick, Dermacentor albipictus (Packard), is widely distributed in Canada. This species attacks horses, deer, cattle, elk and moose. In Ontario, it is found from Algonquin Park northward following the moose distribution. The winter tick rarely feeds on humans. This species requires only one host to complete its development. The larvae attach themselves to large mammals in the fall. They remain on the hosts until the following spring when they reach the adult stage and are ready to mate. Large infestations of these ticks on individual animals may cause the animals to weaken and die.
The brown dog tick, Rhipicephalus sanguineus (Latreille), has recently become established in eastern Canada. All developmental stages of this tick feed on dogs. In temperate climates, the brown dog tick only occurs in heated buildings where dogs are kept. The feeding activity of these ticks causes blood loss and discomfort. Several canine diseases can be transmitted by these ticks.
The rabbit tick, Haemaphysalis leporispalustris (Packard), is widely distributed in Canada. The preferred host of the tick is rabbit, although it will also attack ground-nesting birds and small mammals. Attacks on livestock or man are rare. The rabbit tick is important in maintaining Rocky Mountain spotted fever and tularemia amongst wild animals.