As autumn quickly approaches and the temperatures begin to decline, producers need to consider what type of lice control to initiate. Cattle lice cost producers millions of dollars each year in decreased weight gains and reduced milk production. Producers should not wait until clinical signs appear before beginning treatment.
The life cycles of the different species of cattle lice are very similar. The life cycle begins with the female attaching her egg to a shaft of hair. The egg will hatch as a small replica of the adult. After several molts, the adult will emerge. The cycle takes around three to four weeks to complete. These newly hatched lice will spend their entire life on the host and are host specific, which means cattle cannot be infected with lice from other animals.
Small numbers of lice may be found on cattle in the summer, but high populations of lice are associated with cold weather. Since cattle tend to be in closer proximity to each other in the winter, lice can spread easily between cattle. A small percentage of cattle tend to harbor larger numbers of lice. These animals are sometimes referred to as “carrier animals,” and they may be a source for maintaining lice in the herd. As with many other diseases, stress also contributes to susceptibility and infestation.
Signs that cattle might be infested with lice are hair loss, unthrifty cattle, and hair on fences or other objects. If producers find these signs, they may want to check a few animals for lice. They can check for lice by parting the hair and observing for the number of lice per square inch. If an animal has one to five lice per square inch, they are considered to have a low infestation. Cattle with six to 10 would be considered moderately infested. Any cattle with more than 10 lice per square inch are heavily infested.
Cattle have two types of lice. One type is the biting or chewing louse. These lice have mouth parts that are adapted to bite and chew the skin. The second type is the sucking louse. These lice have mouth parts that will penetrate the skin and suck blood and other tissue fluids. It is not uncommon for cattle to be infested with more than one species of lice.
The biting or chewing louse is Domalinia bovis, formerly known as Bovicola bovis. This type of lice feeds on hair, skin, skin exudate and debris. Typical clinical signs with this type of louse are hair loss, skin irritation and scabs on the skin. They are found on the shoulders and back.
Four types of sucking lice can be found in the United States. The first is the “short-nose” louse or Haematopinus eurysternus. This is the largest cattle louse. This louse is found on the neck, back, dewlap and base of the tail. The second is the “long-nose” louse or Linognathus vituli. This louse is bluish in color with a long slender head. This louse is found on the dewlap, shoulders, sides of the neck and rump. The third is the “little blue” louse or Solenoptes cappilatus. This louse is blue in color and is the smallest cattle louse. This louse is found on the dewlap, muzzle, eyes and neck. The last is the “tail” louse or Haematopinus quadripertuses. This louse has been found in California, Florida and other Gulf Coast states. This louse is found around the tail.
The sucking lice have the potential to cause severe anemia if the numbers are high. This can result in poor-doing cattle or, in extreme cases, death. They also can spread infectious diseases. The long-nose louse has been found to be a mechanical vector for anaplasmosis.
Prevention of lice infestation should begin in the fall. Producers should not wait for clinical signs to appear before beginning treatment. Several products are available to control lice. Producers should read and follow the label directions. Producers should keep in mind that many of the lice control products require two administrations to control lice. Failure to do this may result in cattle having problems with lice infestations. Some producers have complained that some products do not work. These complaints have not been verified; however, this is a good reason to consult with a veterinarian for advice on what products to use. One last thought on lice prevention: it has been proven that cattle in poor body condition are more prone to lice infestation. Producers need to be sure that their cattle nutritional needs are being met.
If producers would like more information on lice in cattle, they should contact their local veterinarian or local County Extension educator. They may also want to read Oklahoma Cooperative Extension Fact Sheet Beef Ectoparasites VTMD-7000.