Martok
January 3, 2011
Sheep with parasites
Photo by Sue Weaver
Sheep like to rub against anything they can to scratch the itch caused by external parasites.

Our sheep have bugs! A few of the sheep started scrubbing themselves on things three weeks ago. Uzzi and I were worried that we’d get bugs too, so we booted up the computer read up on lice. This is what we learned: 

Lice are teensy, bloodsucking insects; most mammals and birds can get lice. There are two kinds: sucking lice (sucking lice feed on blood and have mouthparts designed for penetrating skin and sucking blood) and biting lice (biting lice feed on feathers, hair and skin scales and have mouthparts designed for chewing). There are 460 species of sucking lice and 3,000 species of chewing lice throughout the world. Most are highly host-specific—that means they usually feed on a single species.

Lice are teensy but big enough to see with the naked eye. You can tell them apart because chewing lice have big heads that are wider than their middle body parts and sucking lice have middle parts wider than their heads. Lice can’t fly; they spend their entire lives on their hosts and can only be spread by direct contact. Goats and sheep share the goat biting louse (Bovicala caprae). Sheep share the horse biting louse (Bovicala equi) with horses, but we goats don’t get that kind of lice. Mom checked us all, including the horses, for lice but she didn’t find any. (Whew!)

Sheep with parasites
Photo by Sue Weaver
Smoke looks like he’s moth-eaten. He scratched off so much of his fleece because of the external parasites.

So she decided the sheep must have keds. Keds are tiny, hairy, wingless flies. Only sheep can get them. They’re spread by contact with ked-infested sheep and live their lives on host sheep, sucking blood. Keds mostly feed on sheep’s necks, shoulders and belly areas. Ked bites irritate their hosts, so ked-infested sheep rub against everything, trying to sooth the ferocious itch. They ruin their fleeces that way. Mom doesn’t want that to happen, so she checked for keds but she didn’t find any of those, either!

What do they have and how did they get it? It’s mystery, Mom says, because our sheep haven’t been in contact with any new sheep, but because they mostly rub their necks, backs, armpits, and tummies, she thinks somehow the sheep have keds. Yesterday, she and Dad wormed all the sheep with Ivermectin wormer. (It kills most external parasites on sheep and goats.) Now they’ll wait a week and if the itching continues; if it does, they’ll use pour-on wormer they know kills keds.

External parasites are a problem during the winter because we animals stay inside and crowd together for warmth, making it easy for parasites to spread from host to host. Also, our coats are longer and sometimes scruffier this time of year. Chickens, pigs, cattle, horses, turkeys, sheep, goats, and even cats, dogs and humans get lice!

If you want to know more, Cheri Langlois wrote a great article about livestock parasites that you should read. Then to learn what kinds of lice your animals could get, read Michigan State University’s bulletin, “Chewing and Sucking Lice.” It’s a good one! Finally, visit the Maryland Small Ruminant Pages’ external parasites links; if it’s about lice and keds, it’s there.

Will our sheep stop itching since they were wormed with Ivermectin? We don’t know! Stay tuned—I’ll bring you an update next week.

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