LICE ARE INCREASING IN PREVALENCE ACROSS WESTERN CANADA By Roy Lewis DVM
Page 26 • Fall 2020 • Gelbvieh guide
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have been hearing lots of complaints about scratching cattle and hair loss the last few years in the winter in western Canada. You as purebred or commercial producers may need to change somewhat the way you routinely treat for lice. Timing and type of product used need to be closely looked at. Veterinarians may be changing a bit what they are advising to their clients. We may have got complacent over the years because the ivermectin type pour on products really did a good job. With many years of usage, it is looking like the endectocides are lacking some efficacy and potentially resistance may be developing. With biting lice feeding on the surface and always moving we couldn’t expect a systemic product to totally control them but now we are also identifying large numbers of sucking lice coming back. Lice are the most common and persistent parasite in wintered cattle in Western Canada. There is one species of biting lice (they cause severe irritation and scratching) and three of sucking lice (they cause anaemia and weight loss) on Canadian cattle. In one older two-year study of calves entering southern Alberta feedlots between 5795% of calves were lousy to varying degrees. This indicates very high infestation rates on some of our cow-calf herds. I know this to be true from examinations and autopsies we do, especially on small herds, which often do not treat. We often identify lice when doing C-sections or hooking up calves to IV fluids and once the area is clipped lice are very obvious. These findings are being reported more and more by veterinarians. Herds will have carrier animals, ones that have an abnormally high population of lice. These animals may be immunosuppressed for some reason or have a concurrent disease. Cattle in poor nutritional shape will have lowered immune responses and allow lice to build up quickly. This is also true if cattle become extremely loaded with internal worms. Today’s confinement and larger herds can exacerbate lice transmission. Young calves are especially vulnerable since a lot of their energy is being put into growth. It is extremely important to have the cow’s lice free at the start of the calving season, so the calves don’t become infested. The close proximity to each other and sucking the udder allow for easy transmission of lice between dam and calf. I have seen severe lice build-ups in calves as young as two weeks.
