Winter is the time of year we need to be concerned with lice infestation on cattle.  Dr. Aj Tarpoff, an extension veterinarian with Kansas State, indicates in Bovine Veterinarian that cattle lice infestations can affect the health and performance of cows and stocker cattle.  The USDA has estimated that lice cause the loss of $125 million dollars per year as they not only cause decreased cattle performance, but also increase wear and tear on equipment and fences by the cattle’s constant rubbing and scratching. 

There are two types on lice on cattle: biting and sucking lice.  Biting lice feed on skin and secretions outside the animals while sucking lice are blood feeders and pierce the skin.  Both types spend their entire life cycle on the cattle and only survive a few days in the environment off the animals.  Fortunately, lice are species specific so cattle lice do not infect people or other species of animals.  In most cases, every herd has some lice and a few are carried on the coats from year to year although the life cycle of the parasite is about 1 month.  Lice can be found on the coat by parting the hair and looking closely as the adults are about the size of a grain of sand.  A flea comb used for finding fleas on dogs that is available at any pet store is really helpful in finding lice. More than 10 lice per square inch on the coat is enough to have an effect on the cow’s performance. 

Ivermectin products are successful in treating lice as the pour-on products kill both types while the injectable ivermectin products do not kill biting lice.  Topical pyrethroid products are also effective but must be used twice at 14-day intervals unless an insect growth regulator is used in combination with the pyrethroid.