Smith, I.M., Lindquist, E.E., and V. Behan-Pelletier. 1998. Mites (Acari) in Smith, I.M., and G.G. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

MITES (ACARI)

Ian M. Smith, Evert E. Lindquist and Valerie Behan-Pelletier

PARASITIFORMES - IXODIDES - E.E. Lindquist

Ixodides, or Metastigmata, comprises the well known ticks which parasitize and transmit disease pathogens of mammals, birds and a few reptiles such as lizards. The Canadian fauna of Ixodoidea was treated at the species level by Gregson (1956) and reviewed briefly by Wilkinson (1979). A summary of expected species diversity of families represented in the Montane Cordilleran Ecozone is presented in Table 2.

TABLE 2:EXPECTED SPECIES DIVERSITY OF FAMILIES OF IXODIDA KNOWN FROM CANADA IN MONTANE CORDILLERA ECOZONE BASED ON RECORDS OF NAMED AND UNNAMED SPECIES IN CANADIAN NATIONAL COLLECTION OF ACARI

Of the 8 species in 3 genera of the family Argasidae known or expected to occur in Canada, 5 species representing all 3 genera occur in the Montane Cordillera, where they reach the northern limits of their ranges in North America. Argas reflexus (Fabricius) parasitizes wild birds in the Okanagan Valley. Otobius megnini (Dugès), strictly an ear-inhabiting tick, is common on deer and mountain sheep in the southern interior of British Columbia; and Otobius lagophilus Cooley and Kohls is expected to occur on rabbits in the Northern Continental Divide Ecoregion, as it is known from adjacent prairie areas in southern Alberta. Ornithodoros hermsi Wheeler, Herms and Meyer is associated with various birds, rodents and bats in the southern interior of British Columbia, most commonly in the Okanagan Valley area; it occasionally bites humans, and the site of its bite may become a raised weal which itches for several weeks afterward. It has been implicated as a vector of tick-borne relapsing fever in the Okanagan Valley and Kootenay District. Ornithodoros parkeri Cooley, another potential vector of this relapsing fever, is anticipated to occur in nests of burrowing owls and ground squirrels in the Okanagan region.

Of the 32 species in 6 genera of the family Ixodidae known to occur in Canada, 14 species in 3 genera are known to live in the Montane Cordillera Ecozone. Of 10 species of Ixodes known to occur in this region, 5 western species (I. texanus Banks primarily on raccoons and mustelids, I. spinipalpus Hadwen and Nuttall primarily on rodents, I. ochotonae Gregson primarily on pikas, I. marmotae Cooley and Kohls on marmots, I. hearlei Gregson on red squirrels) reach their northern limits there, and 2 common prairie species (I. kingi Bishopp and I. sculptus Neumann on ground squirrels and their mustelid predators) reach the westernmost edge of their ranges in Waterton Lakes National Park. The northeastern edge of the range of Ixodes pacificus Cooley and Kohls, which attacks a wide variety of mammals and even lizards, is not known to quite reach the Montane Cordillera; however, records of this tick as far east as Idaho in the northwestern United States indicate that it may yet be found in the western edge of this Ecozone, perhaps in Manning Provincial Park. Three other species of Ixodes (I. auritulus Neumann on birds, I. angustus Neumann on rodents, I. soricis Gregson on shrews), and the two species each of Dermacentor (D. andersoni Stiles on small and large mammals, D. albipictus (Packard) on large mammals) and Haemaphysalis (H. leporispalustris (Packard) and H. chordeilis (Packard) on various small mammals and birds) extend further north in their more general North American distributions.

As obligate blood feeders, ticks harbor and spread a remarkable variety of disease-causing pathogens of their hosts, including rickettsia, protozoa and viruses. The Rocky Mountain wood tick, D. andersoni, and the rabbit tick, H. leporispalustris, are vectors of the bacterium that causes tularemia and the rickettsia that cause Q fever and Rocky Mountain spotted fever; D. andersoni is additionally a potential vector of the viruses causing Powassan encephalitis and the more benign Colorado tick fever in this region. Ixodes pacificus is a competent vector of the bacterium that causes Lyme disease.

Some ticks cause severe illness to their hosts just from the effects of their feeding. Large tick infestations may directly cause anemia in small hosts such as mice and rabbits. Serious damage may be done to moose or horses by the winter tick, D. albipictus, particularly late during long winters, when thousands of these large ticks may be on individual hosts. Tick salivary components include anticoagulants whose effects may persist well after feeding; other components may act as allergens which lead to exaggerated inflammations, severe itching, and lesions resulting from scratching by hosts. In the Montane Cordillera, D. andersoni can cause a potentially lethal paralytic effect on people, domesticated animals and some wild mammals from its feeding activity alone. Fortunately, recovery from tick paralysis occurs after removal of the ticks.