There are several types of worms that infect sheep. They reside in the stomach and small intestine of the sheep, and they are blood suckers. Just a few of the different types of worms in sheep include the Barber pole worm (Haemonchus contortus) and the Hairworm (Trichostrongylus). Both the Barber pole worm and the Hairworm are common in the state of Indiana. In large numbers, these types of sheep worms can cause anemia, and they can decrease growth rate, increase susceptibility to other diseases, and lower the value of the wool due to fiber breaks and scouring.

Sheep worms have a complex life cycle. Mature worms residing within sheep shed eggs within the sheep’s feces onto the pasture. The eggs usually hatch within two to three weeks into a larval stage (L3). The L3 larval stage is then consumed by the sheep. The larvae can either develop into the mature larvae (L4) or go into a dormant stage called hypobiosis, within the sheep. The L3 larvae go into hypobiosis to survive adverse climactic conditions, such as winter. This means there are two sources that infect sheep – those that overwinter on pasture and those from animals.

Worm Prevention and How to Worm Sheep

To successfully control worms in sheep, proper timing of treatment is crucial. Thee key to controlling parasites is to prevent pasture infestation, so, strategic worming of the flock with the appropriate dewormers is crucial to winning the war on sheep worms. The four critical treatment times are: two to four weeks before lambing; before turning ewes onto spring grass; Two to four weeks before breeding, and when coming off pasture in the fall.

Dewormers have been proven to be effective in worming sheep. Dewormers approved for use in sheep include: Levamisole, Thiabendazole, Phenothiazine and Ivermectin. Prescription drugs used for sheep include Albendazole and Fenbendazole. Levamisole, Ivermectin, Albendazole, and Fenbendazole are effective against larval, adult, and larval stages in hypobiosis. Thus, they are generally the most effective agents to use. Albendazole should not be used immediately prior or after breeding, as it can prevent uterine implantation of embryos.

Management Strategies

There are many different management strategies to help control worms in sheep.

Strategic deworming, using “safe” pastures for younger animals, pasture rotation, and utilizing more than one species of livestock to assist in control of parasites are some management strategies that can aid in controlling sheep worm and other parasites

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3. How to Worm Goats
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5. Types of Worms that Infect Horses

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