Winter Tick
Causative Agent
  • The winter tick, Dermacentor albipictus, is a skin parasite of wild ungulates that consumes a blood meal from its host to complete its life cycle.
  • While winter ticks have most often been found on moose (Alces alces), other wildlife species have been known to be parasitized by and have disease caused by D. albipictus, including:
    • moose (Alces alces);
    • caribou (Rangifer tarandus);
    • elk (Cervus canadensis).
  • Unlike mites, ticks are visible to the naked eye. Adult winter ticks are large and reddish-brown to grayish-brown in color.
Click on images to enlarge.
Winter Tick Winter Tick Winter Tick
Ticks engorged with blood In early spring, moose may be showing large patches of broken or missing hair where they have tried to rub away ticks. Moose with large patches of broken hair are sometimes referred to as “ghost” moose, as the white base of the hair shaft is all that remains. Heavy infestation of winter tick on a moose.
Winter Tick
Life stages of the winter tick.
Left to right: larva; nymph; adults (with visible legs). 
The last two specimens on the right are adult females engorged with blood.
  • Mostly occurring up to 62ºN latitude in western Canada.
  • Greatest abundance in forested, upland or mountain habitats.
  • All stages of this parasite on large mammal hosts occur between fall and spring.
Hosts, Transmission and Life Cycle
  • D. albipictus requires one host to complete its life cycle.
  • Hosts: highest tick densities are found on moose, but also found on elk, deer and mountain sheep.
  • Individual moose have been found with > 50,000 ticks.
Transmission and Life Cycle:
  • Ticks require blood meals from a host to complete each stage of their life cycle.
  • In the host-seeking stage, larvae climb and congregate on tips of vegetation in September and October. Larvae are very resistant to cold and snow.
  • Once on the host, a blood meal is taken and larvae molt to nymphs and become adults by March-April.
  • Adults that are fully engorged with blood detach in late March through April and lay eggs among leaves or in soil in June. The adults are less resistant to cold and snow at this time.
  • Eggs hatch and larvae seek hosts to repeat the cycle.
Signs and Symptoms
  • Feeding by D. albipictus can result in local inflammation, edema, hemorrhage, irritation, and hair loss from grooming.
  • Heavily infested hosts groom extensively and may suffer from extensive hair loss, loss of body fat stores, loss of blood and even death from exposure and starvation. The incessant need to groom can seriously interfere with feeding.
  • Moose may rub against trees and other objects in attempts to remove ticks.
  • Moose with extensive hair loss look white or grey in appearance and are often called ‘ghost moose’. They are prone to heat loss in winter.
  • Other ungulate species are less affected by winter ticks than moose and, although there can be significant hair loss, it is rare to see other species in as poor condition.
Meat Edible?
  • Meat is edible but the quality may be reduced if the animal is in poor condition.
Human Health Concerns and Risk Reduction
  • D. albipictus may parasitize humans but this appears to be rare.
  • D. albipictus is not known to carry and transmit agents that may cause disease in people.
  • Transfer of D. albipictus to domestic animals may occur. The response of domestic animals to tick infestation is similar to that of wild mammals.
Samples for Diagnosis
  • Remove tick from hide while being careful not to leave mouth parts embedded in the skin.
Further Reading
Return to Manual Home Page Disease List - Body Region Affected Disease List - Causative Agent or Risk Factor Disease Surveillance Form Glossary Contact Information
Return to Manual Home Page Return to Disease List - Body Region Affected Return to Disease List - Causative Agent or Risk Factor Disease Surveillance Form Download Glossary Contact Information