The Rocky Mountain wood tick, Dermacentor andersoni, is a threat to human and animal health in central and western Colorado.

	The human-biting female Rocky Mountain wood tick.   The male Rocky Mountain wood tick.
Photo by JL. Occi from the AFPMB Image Database

Counties in Colorado where the Rocky Mountain wood tick is established (gray) . Adapted from James et al. 2006. Distribution, seasonality, and hosts of the Rocky Mountain wood tick in the United States. Journal of Medical Entomology 43: 17-24

Drag sampling for ticks in Poudre Canyon and Rocky Mountain National Park of Larimer County produced large numbers of adult Rocky Mountain wood ticks, a single nymph, and the occasional winter tick.

Year	Rocky Mountain wood tick (Dermacentor andersoni) Nymphs Females Males	Winter tick (Dermacentor albipictus) Larvae Females Males
Poudre Canyon (18 sites sampled in 2006 and 5 sites in 2007)
2006	0 353 307	0 0 0
2007	1 225 139	>100* 2 0
*Collected on a single 10-sec drag
Rocky Mountain National Park (5 sites sampled in both years)
2006	0 89 75	0 3 1
2007	0 102 78	0 2 2
	Rocky Mountain wood tick (dark legs)	Winter tick (light legs)

Adult Rocky Mountain wood ticks commonly infest humans but there are very few reports of larvae or nymphs biting humans.

The winter tick specializes on large animals such as deer, elk and moose and very rarely infests humans.

From: Eisen, Ibarra-Juarez, Eisen and Piesman. 2008. Indicators for elevated risk of human exposure to host-seeking adults of the Rocky Mountain wood tick (Dermacentor andersoni) in Colorado. Journal of Vector Ecology: 117-128.

Tick paralysis (caused by a toxin in the tick's saliva)
Information on recent tick paralysis cases in Colorado:
http://jama.ama-assn.org/cgi/reprint/296/14/1721.pdf

Colorado tick fever (caused by Colorado tick fever virus)
Case load in Colorado:
http://www.cdphe.state.co.us/dc/zoonosis/tick/Colorado_tick_diseases.pdf

General information:
http://www.cdphe.state.co.us/dc/zoonosis/tick/ctfinfo.html

Rocky Mountain spotted fever (caused by the bacterium Rickettsia rickettsii)
Case load in Colorado:
http://www.cdphe.state.co.us/dc/zoonosis/tick/Colorado_tick_diseases.pdf

General information:
http://www.cdphe.state.co.us/dc/zoonosis/tick/rmsfinfo.html
http://www.cdc.gov/ncidod/diseases/submenus/sub_rmsf.htm

Tularemia (caused by the bacterium Francisella tularensis)
Case load in Colorado:
http://www.cdphe.state.co.us/c/zoonosis/tularemia/Colorado_tularemia.pdf

General information:
http://www.cdphe.state.co.us/dc/zoonosis/tularemia/index.html
http://www.bt.cdc.gov/agent/tularemia/index.asp