Don’t let up yet: keep fighting off cattle lice until spring

 Lice infestations can run through March, so continue to be on the lookout for signs of a lice problem in your herd.

Cattle lice infections can affect the health and performance of our cows and stocker cattle during the winter months. The lice season generally ranges from December through March.  The USDA has estimated that livestock producers lose up to $125 million per year due to effects of lice infestations.

Not only can they be the cause of direct animal performance losses, but they also increase wear and tear on our facilities and fences. The direct losses to cattle come in forms of decreased average daily gains (documented 0.25 pounds per day reduction in growing calves), skin infections and potentially blood loss and anemia. Lice are very species specific, so cattle lice cannot affect people, horses or any other species.

In general, every herd has some level of lice infestation. Lice are carried from season to season by a small percentage of the herd that act as hosts. Adults lay eggs on the hair of infected animals. The overall lifecycle for an egg to mature into an adult and lay eggs is roughly 28 days.  Most females lay one egg per day.

Clinical signs of lice-infected cattle generally begin with constant rubbing and scratching within the herd. Fences, posts, water troughs, trees and any other stationary object could be subject to damage from this rubbing. As the infection and irritation continues, large hairless patches will become evident on animals.

There are several options when it comes to treatment of lice in our cowherds.  One option is the avermectin endectocides. These products come in pour-on formulations and injectable formulations.  It is important to note that the injectable formulations do not work on biting lice since they do not blood feed.

The other options are topical treatments that are non-systemic. These products are typically pyrethroid products similar to what is commonly used to control horn flies during the summer months. These products are very effective against the adult lice, but do not affect the larvae or eggs. Retreatment is often indicated 14 days after initial treatment. When treating cattle, it is important to treat the entire group. Missing one animal could allow it to serve as the host for reinfesting the entire herd. The same thought should be given to new additions to the herd from an outside source. Basic biosecurity such as treating and segregating new additions for 30 days is not only good to reduce risk of lice, it is also a great tool in decreasing introduction of other diseases.

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Jerry Little, County Extension Agent for Agriculture/Natural Resources