|scientific name Dermacentor albipictus |
common name Moose tick; winter tick
Forested areas of North America (Samuel 2004; Yunker et al. 1986; Bishopp and Trembley 1945). Commonly found feeding on moose, elk and deer (Samuel 2004).
Winter ticks are most commonly encountered in fall and winter. Larvae hatch and begin questing (host seeking) from August to October. Winter ticks feed and stay on their hosts until March/April, when adult females detach and drop to the ground. Females die soon after laying eggs in June. Males may remain on their hosts until May (Samuel 2004).
Adult winter ticks are various shades of brown with grey patterning on their scutum (shield) (Cooley 1938). The rectangular basis capitulum (base of mouthparts) is wider than long, and the palpi are short and stout (Cooley 1938). The hypostome (piercing mouthpart) has three rows of dentition (teeth) on either side of the median. Spurs are present on all four pairs of coxae (base of legs) (Cooley 1938). The first pair of coxae (coxae I) have two spurs each. Coxae II and III also have two spurs each, although their internal spurs are always much shorter. Coxae IV only have one well-developed spur each. An adult winter tick has eleven festoons (marginal divisions) on the end of its body (Cooley 1938; Yunker et al. 1986).
Adult winter ticks are distinguishable by rounded spiracular plates that consist of moderate numbers of large goblet cells (Cooley 1938; Yunker et al. 1986). Dorsal prolongations on the spiracular plates may or may not be present (Leo et al. 2010) (See images).
It is difficult to identify larval and nymphal winter ticks based on morphology due to their small size.
The winter tick produces one generation per year. Females oviposit in June, and eggs hatch late summer or early fall (August – September). Six-legged larval ticks will scale vegetation (September – October) up to about 2 meters high while questing for host animals (McPherson et al. 2000). Once on a host, the larvae immediately initiate feeding before molting to the eight-legged nymphal stage (Samuel 2004). Nymphs remain on the host for most of fall and winter (October – March), feeding continuously and becoming engorged. The nymphs then undergo their final molt to become sexually mature adults (January-May). Adult winter ticks continue feeding and begin to mate on the host. In late winter or early spring (March – April), mated females will engorge and then detach from the host. Females expire after laying their eggs (Samuel 2004).
The reproductive success of a female tick is dependent on a variety of factors including host health, host avoidance and grooming behaviour, predation and weather conditions (Welch et al. 1991; Samuel and Welch 1991; Drew and Samuel 1987).
The winter tick is not of conservation interest. However, it is an important veterinarian pest in North America (Samuel 2004).
Winter ticks specialise in feeding on the blood of ungulate hosts (Cooley 1938; Bishopp and Wood 1913). They are found primarily on
• Moose (Alces alces)
• Elk (Cervus canadensis)
• Mule deer (Odocoileus hemionus)
• White-tailed deer (Odocoileus virginianus)
Winter ticks may also parasitise
• Horses (Equus ferus sp.)
• Cattle (Bos sp.)
• Rocky Mountain sheep (Ovis canadensis)
The winter tick has a range that spans most of North America (Banks 1908; Bishopp & Wood 1913). It has not been recorded from Nunavut, Newfoundland and Labrador, Prince Edward Island, Alaska and Delaware, although Zarnke et al. (1990) suggest that populations in these areas may establish where conditions are suitable.
Heavy infestations of winter ticks on a host individual can result in severe anaemia, extensive epithelial damage, allergic reactions, and death (Anderson, 2002; Glines and Samuel, 1989; McLaughlin and Addison, 1986; Samuel 2004). The winter tick also carries a variety of pathogens (Baldridge et al. 2009) and is known to transmit anaplasmosis among cattle in the United States (Aubry and Geale 2011).
pourquoi on donne pas un vaccin comme les chats les chiens pour eliminer ce tiques
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