Prevalence of sucking and chewing lice on cattle entering feedlots in southern Alberta

Beef calves from 2 sources entering southern Alberta feedlots in the winter s of 1997-98 and 1998-99, were surveyed for the presence of lice. A random sample of multiple source (MS), that is, auction market-derived, calves ent ering commercial feedlots and single source (SS) calves entering a backgrou nding feedlot were examined for the presence of lice at entry to the feedlo t. A standardized examination, which involved hair-part examination of 8 lo use predilection sites, was conducted on each selected calf to determine pr evalence and intensity of infestation. The long-nosed sucking louse, Linogn athus vituli, was the most commonly encountered species. This species infes ted from 57.8% to 95.6% of the calves selected from both MS and SS calves d uring both winters. Louse index values, indicating intensity of infestation , for L, vituli ranged from 1 to 243 lice per animal. The chewing louse, Bo vicola bovis, was present on MS and SS calves only in the winter of 1998-99 . The louse index values for B. bovis ranged from1 to 230 lice per animal. Mixed infestations of the L. vituli and B. bovis were common. The little bl ue cattle louse, Solenopotes capillatus, was present only on the SS calves in the winter of 1997-98. The short-nosed sucking louse, Haematopinus eurys ternus, was present at very low intensities, 1-2 lice per animal, on 2.6% t o 4.4% of the MS calves during both winters. Comparison of results from the current study with published literature suggests that efforts to determine the economic impact of louse infestations are confounded by the lack of a uniform method to assess louse population levels.