ENVIRONMENT YUKON






 

Mammals

Winter tick surveillance

 

Significance

 

Winter ticks (Dermacentor albipictus) are one-host external parasites that can be found on cervids such as elk, mule deer, and moose in Yukon. These parasites can negatively affect host health when present in large numbers, with moose being especially vulnerable because they do not remove larval ticks by grooming. In some regions of Canada, winter ticks can be responsible for severe disease and mortality in moose.

To date, data suggests that winter ticks are not a major disease concern for Yukon cervids. By studying the distribution and occurrence of winter ticks in Yukon, we are monitoring how ticks may affect Yukon’s wild cervid populations, and how tick host and geographical distribution may change over time.

Monitoring wildlife parasites such as winter ticks provides information on the distribution and potential impact of these parasites on wildlife such as moose, which are a key harvest species in Yukon.

Winter ticks do not carry diseases of concern to humans or wildlife, nor do they negatively affect the meat of harvested animals. Winter ticks do not feed on people and are rarely found on domestic animals.

 

Mule deer. Cameron Eckert.

 

Weather may be an important factor in the tick-cervid relationship. Warmer temperatures in the summer and winter may support larger populations of cervids that carry ticks, and allow larval ticks to survive longer in the environment. A changing climate could influence vegetation patterns and winter temperatures, and may influence distribution and presence of wildlife parasites like winter ticks.

 

What is happening?

Winter ticks affect different species in different ways.

  • In early autumn, elk and deer groom off larval ticks, which reduces tick numbers and minimizes negative health impacts.
  • Moose only begin to groom off ticks once adult ticks are present in late winter, which can lead to high numbers of ticks on individual moose. Moose can experience severe disease associated with blood and hair loss from heavy tick burdens.

Since 2012, the Animal Health Unit has examined cervid hides to monitor tick host and geographical distribution over time (Figure 1).

 

Hides examined for winter ticks between 2011 and 2016
Species Number of samples Hides found with winter ticks
Mule deer 39 59% (23)
Moose 6 16% (1)
Elk 48 73% (35)
Caribou 7 0%

 

Figure 1: The known distribution of winter ticks based on hides examined to date (collected between 2011-2016)

 

  • Winter ticks are established on elk in Yukon. Winter ticks likely originated in Yukon from translocation of elk from central Alberta, and/or by range expansion from northern British Columbia and Alberta (Leo et al. 2014).
  • Winter ticks have been found on cervids in 12 out of the 18 game management zones where hides have been examined.
  • The Animal Health Unit uses an index from 0 to 10 to describe the severity of winter tick burdens on the hides that are sampled. While the majority of hides have light burdens (indexed from 1 - 2) some have heavier brudens (indexed from 3 - 8), with one moose hide having 543 ticks, which corresponds to a burden ranging from 4,000 - 8,000 ticks (index of 8).

 

Taking action

 

The Animal Health Unit continues to monitor for winter ticks through assessment of cervid hides. Elk hides are a mandatory harvest submission, while deer, caribou and moose hides are submitted voluntarily.

• So far, all of the hides examined have been from Southern Yukon (see figure 1) which has provided good baseline data on winter ticks in this region. In order to understand what is happening in other parts of Yukon, more hides from other areas are needed for this surveillance. Hunters from all over Yukon are encouraged to contact the Department of Environment to submit cervid hides for examination.

Adult winter tick on an elk.

 

Data quality

The Animal Health Unit uses a standardized hair transect method to evaluate the level or severity of tick burden. The method can be used on hides, unskinned animals or live animals, which increases the number of animals that can be examined. The Animal Health Unit has used the adapted hair transect protocol on hides collected since 2011.

 

References

Leo, S., W. Samuel, M. Pybus, and F. Sperling. 2014. Origin of Dermacentor Albipictus (Acari:Ixodidae) on Elk in the Yukon, Canada. Journal of Wildlife Diseases 50(3):544-551.