Sheep keds, Melophagus ovinus, are primarily a pest of sheep, but occasionally are found on goats. The adult is actually a wingless fly resembling a tick in appearance. The adults are grayish-brown, sixlegged, and 1/4 inch long with a broad, leathery, somewhat flattened, unsegmented, saclike abdomen covered with short spiny hairs. Unlike true ticks, keds spend their entire life cycle on the animal; however, they can crawl readily from ewes to lambs. Sheep keds can live up to 6 months, during which time the female produces about 15 young at the rate of approximately one each week. Reproduction is continuous, though slow during the winter, producing several generations a year.
Unlike most insects, the female sheep ked gives birth to living maggots, which are nourished within her body until they are fully grown. The maggots are 1/4 inch long, whitish, oval, and without legs. The skin turns brown within a few hours after birth and forms a hard puparium (case) around the larva. These cases are often called eggs, nits, or keds. Adult keds emerge from the pupal cases in 2 to 5 weeks, depending on temperature. They crawl over the skin and feed by inserting their sharp mouthparts into capillaries and sucking blood, much like a mosquito. This results in considerable irritation, which causes the animal to rub, bite, and scratch at the wool, thus reducing the amount and quality of the fleece. The feeding punctures also cause a condition known as "cockle" in tanned skins. Hide buyers downgrade sheep skins with cockle because it weakens and discolors them. In addition, keds in large numbers can cause anemia, which can weaken the animal and make it more susceptible to other diseases.
Sprays, dips, pour-ons, and dusts are all effective for control of sheep keds. As a general rule, sheep should be treated in the spring after they have been shorn, when the weather is warm and the keds are most exposed. If animals are heavily infested in fall or winter months, however, it is advisable to treat them rather than allow the keds to continue to increase and cause losses. If you spray during fall or winter, select a warm, sunny day. Treat the animals in the morning, and keep them outside until they dry. To reduce the chances of illness, do not let wet animals crowd into a warm building. If all new bucks and ewes are treated before they are turned in with the rest of the sheep, treatment of the flock once a year will control sheep keds.
Application equipment that provides a nozzle pressure of at least 50 psi is adequate for ked and louse control on sheep. To ensure adequate and thorough dosage, do not spray more than 5 or 10 animals at a time. Confine sheep in a relatively small area so they will rub against each other and maximize the effectiveness of the materials being sprayed. Hold the spray nozzle a few inches from the wool, and spray the animals until they are thoroughly wet.