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Preventative Health Care For Elk: Winter Tick (Dermacentor albipictus)


Robert P Acorn PAg.

About the author: In 1999 Robert Acorn was an agrologist working for the Animal Industry Division of Alberta Agriculture. The article below first appeared as a joint presentation with veterinarian Dr. Carla Lindahl at the 1999 Alberta Elk association Conference in Jasper , Alberta and was then published in The Tracker magazine who have allowed me to include it on this website.

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Introduction

As with many things we do, knowledge is often the key to success. Producers who develop a diverse knowledge and understanding of elk production, requirements for health and related issues, and who work in partnership with their veterinary practitioner and other specialists, will generally be those most successful at elk farming. The following article will help add to the knowledge you now have on keeping elk healthy.

There are about 850 species of ticks world wide, many of which carry and spread serious diseases to man and animals. Ticks belong to the same group of animals as spiders and lice. They have 8 legs as adults and go through several stages of development from egg to adult. The Winter tick (Dermacentor albipictus) is common throughout North America. Moose, elk and deer are normal hosts of the Winter tick, however other livestock can also be affected. It is the Winter tick which commonly affects elk on farms.
 

Life Cycle

The Winter tick is a "one host" parasite, completing its full development from larvae to adult on one cervid host. It has 3 distinct life stages. Eggs on the ground hatch in August and September. The tick larvae ascends to the tops of grasses and bushes in September and October, waiting for the opportunity to attach to an animal it comes in contact with. In Alberta, peak numbers of larvae coincides with the breeding activity of moose and elk. Once on a host, the tick larvae attaches to the skin, take a blood feed and changes into a immature tick or nymph within about 21 days. The nymph remains on the host but does not blood feed again until January or February, at which time it changes to an adult tick. The adult tick remains on the same host without further feeding until March or April, at which time it engorges on blood, then mates and drops off its host. In about June, mature females deposit thousands of eggs on the ground.

The Winter tick is not associated with the spread of diseases like many other ticks because it lives its entire life on one animal. Other types of tick attack different animals each time they require a blood meal, thereby spreading viruses, bacteria and other pathogens. Ticks on elk farms are generally an aesthetic problem; chewing, biting and hair loss results in poor looking elk. Wild moose and elk heavily infested with Winter tick and emaciated and stressed by severe winter conditions, can die from anemia due to severe blood loss from tick feeding. An adult Winter tick is able to expand as it feeds on blood, allowing the tick to grow 200 or more times its normal size.
 

Clinical signs

Ticks feeding on elk cause considerable irritation indicated by chewing, licking and rubbing. The initial signs of a tick problem will show in October and November when tick larvae begin feeding. This is characterized by a disturbed hair coat along the top of the shoulders, lower neck and back. Ticks feed again during the January through April period, once more causing irritation. Rubbing, scratching, and chewing results in hair loss on the lower neck and upper shoulders, and a scruffy, unthrifty appearance.
 

Prevention

As with other parasites, breaking the life cycle is the key to prevention. Winter tick problems can be controlled or minimized through pasture rotation and timely chemical treatment of infected elk.

  • If possible, do not place elk on pastures in September and October (when tick larvae are infecting elk) that had tick infested elk in them the previous April and May (when adult ticks are infecting pasture).
  • When fencing new pasture that has been used by wild game, especially native pasture containing trees and brush, remove your elk from this pasture during September and October.
  • If you notice tell-tale chew and lick marks on the shoulders and backs of your elk in October, treat them as soon as possible, ideally about the first of November. Pour-on or injectable parasite control products will control ticks only if applied when ticks are blood feeding. The next opportunity to control ticks would be the next feeding period, about mid January. Pour-on treatments offer a longer residual period of control than injectable treatments.