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Ectoparasites - Melophagus

Melophagus ovinus: Sheep ked.

General Description: Wingless, hairy fly, 4 to 6 mm. long with a short, broad head, brown thorax, and large, greyish-brown abdomen. Legs are strong with claws at end.

Life Cycle: Larvae hatch from eggs while they are in the adult female which attaches larvae to wool with an adhesive materiel. Larvae remain in place and soon moult to the pupal stage, which is brown in colour and 3 to 4 mm. long. Pupae last 19 to 23 days in summer and 36 days in winter. This is important since pupae are resistant to insecticides during dipping. Adults emerge, mate within 3 to 4 days, and deposit larvae 10 to 12 days later. Keds live 4 to 5 months and may produce 10 to 15 larvae in this time. Heaviest infestations occur in winter and spring. Adult females can survive only 7 to 10 days off sheep.

Location: Skin of various body parts. Most commonly the neck, shoulders, and belly.

Geographical Distribution: Worldwide.

Significance: The piercing mouth parts of keds cause open wounds susceptible to further bacterial and parasitic infection. Itching makes the sheep bite and rub, which damages fleece.

Effect on Host: Parasite worry and decreased appetites result in less growth of sheep and possibly weight loss. Intense itching from irritation causes sheep to rub, bite, and scratch themselves, tearing the fleece. Wool is also stained by ked faeces. Anaemia may occur. Adults live on the skin and suck blood by puncturing the skin. This is always done in fresh skin, causing widespread irritation. Iron-deficiency anaemia may result from continual blood-feeding. Infestations are generally worse in cold months.

Diagnostic Information: Adults and pupae may be seen on sheep, usually close to the skin.

Control: Dips and sprays are effective. Pupae are resistant, and treatment should be repeated at 24 to 28 day intervals. Ivermectin has provided very effective control when used during routine parasite control programs. Shearing reduces ked populations.


 
Melophagus– adults   Sheep "ked" seen in parted wool

           

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