Sheep keds are external parasites that commonly affect sheep flocks worldwide. These insects, often mistaken for ticks, are a persistent nuisance for sheep farmers. Their presence can lead to various health issues for sheep and economic losses for agricultural operations. Understanding these parasites is the first step toward effective management.
Understanding Sheep Keds
Sheep keds, scientifically known as Melophagus ovinus, are wingless flies belonging to the family Hippoboscidae. They appear as small, reddish-brown, hairy insects, measuring between 3 to 7 millimeters in length. Despite their tick-like appearance, keds possess six legs, distinguishing them from true ticks which have eight. Their strong claws allow them to firmly attach to the wool fibers of their host.
These obligate parasites are primarily found embedded within the wool of sheep, preferring areas such as the neck, shoulders, and flanks. They feed on the blood of their hosts by piercing the skin with their sharp mouthparts and sucking blood.
Impact on Sheep Health and Production
Sheep keds inflict considerable harm on sheep, leading to visible symptoms and economic setbacks for farmers. The bites themselves are irritating, causing sheep to scratch, rub, and bite at their wool. This behavior can result in damaged, ragged, and thin fleece.
Beyond physical damage to the wool, ked excrement can permanently stain the fleece brown, reducing its market value. Heavy infestations can lead to weight loss, reduced wool production, and even anemia, particularly in lambs and pregnant ewes. The blood feeding also causes nodules on the skin, a condition known as “cockle,” which diminishes hide value. Heavy infestations can also contribute to suffocation in ewes that roll onto their backs to alleviate irritation and become stuck.
Life Cycle and Transmission
The entire life cycle of the sheep ked occurs directly on the sheep. The female ked produces a single, fully developed larva internally. This larva feeds on secretions within the female’s uterus for 7 to 8 days before being deposited onto the sheep’s wool.
Once deposited, the larva immediately forms a dark, hard puparium, which is glued firmly to the wool fibers. After 19 to 36 days, depending on environmental temperature, an adult ked emerges from the pupa. A female ked can live for 4 to 6 months and produce 10 to 20 larvae during her lifetime, one per week. Keds primarily spread between sheep through direct contact, especially in crowded conditions or from ewes to their lambs shortly after birth. Keds do not survive more than a week off the host.
Management and Control
Controlling sheep ked infestations involves strategies for treating existing populations and preventing future outbreaks. Chemical treatments are widely used and include various formulations such as dips, pour-ons, and injectables. Dipping sheep in insecticidal solutions ensures thorough coverage and can destroy all keds present, though a long-acting insecticide is needed to kill keds emerging from pupae. Pour-on products offer a convenient application method and are effective.
Shearing sheep reduces ked populations, removing 75% of both adult keds and pupae with the fleece. Shearing pregnant ewes before lambing also reduces the transfer of keds to newborn lambs. Applying insecticides immediately after shearing is recommended, as the shorter wool allows for better chemical penetration. Following product instructions and consulting a veterinarian for a control plan is advised. Some modern treatments for lice are also effective against keds. Quarantine procedures for new animals entering the flock are important to prevent the introduction of keds.
Are Sheep Keds a Risk to Humans?
Sheep keds are host-specific, primarily parasitizing sheep. While a ked might transfer to a person, they cannot survive or reproduce on humans. These parasites are not known to bite humans or establish infestations on them. Although keds can carry some pathogens, direct transmission to humans is not typically reported.