Through a recent (2003-2007) survey of ectoparasites on hoofed mammals in western North America, a literature review, and examination of archived museum specimens, we found that the exotic deer-chewing louse, Bovicola tibialis (Piaget), is a long-term, widespread resident in the region. The earliest known collection was from Salt Spring Island, Canada, in 1941. We found these lice on the typical host, that is, introduced European fallow deer (Dama dama L.), and on Asian chital (Axis axis [Erxleben] ), native Columbian black-tailed deer (Odocoileus hemionus columbianus [Richardson] ), and Rocky Mountain mule deer (O. h. hemionus [Rafinesque]) x black-tailed deer hybrids. Chital and the hybrid deer are new host records. All identified hosts were known to be or probably were exposed to fallow deer. Geographic records include southwestern British Columbia, Canada; Marin and Mendocino Counties, California; Deschutes, Lincoln, and Linn Counties, Oregon; Yakima and Kittitas Counties, Washington; Curry County, New Mexico; and circumstantially, at least, Kerr County, Texas. All but the Canadian and Mendocino County records are new. Bovicola tibialis displays a number of noteworthy similarities to another exotic deer-chewing louse already established in the region, that is, Damalinia (Cervicola) sp., which is associated with a severe hair-loss syndrome in black-tailed deer. We discuss longstanding problems with proper identification of B. tibialis, the probability that it occurs even more widely in the United States, and the prospects for it to cause health problems for North American deer. Additional information gathered since our active survey establishes further new distribution and host records for B. tibialis.
