They have a broad abdomen which contrasts with their long narrow head. Sucking lice are more common and more irritating than chewing lice. They have piercing mouth parts. When present in large numbers, they can cause anemia. The eggs are attached to the hair and hatch 11 to 20 days later.
Nymphs begin sucking blood immediately.
They complete their life cycle in 2 to 4 weeks. Transmission of lice is by direct contact between horses and through contact with infected brushes, blankets and tack. Successful control requires that equipment is cleaned thoroughly with the same insecticide as used on the horses. The cleaning should be repeated in two weeks. Sterilization of equipment by boiling will also kill the lice, nymphs and eggs as will placing blankets and coolers in the drier at the highest heat setting.