Internal parasites probably cause more economic loss in our sheep flocks than we realize. We all understand the need for worming, but, sometimes we forget to worm the flock. Since elimination of internal parasites is not feasible, control is the way to reduce losses. Varying management practices make it impossible to recommend one control program for all situations. The optimum control is achieved by considering as much information as possible in developing an integrated control program. Which internal parasites are present is the key. Treatment based strictly on whether or not sheep look "wormy" is not the answer. Fecal egg counts should be taken and the internal parasites identified.

Effective internal parasite control programs should reduce pasture and/or lot contamination, the source of reinfections, as well as removing the worms from the animals. All new individuals should be treated a minimum of one time and held for at least one week and undergo fecal examination prior to introduction into the flock.

Never simply treat new additions and immediately turn them into a pasture or lot where other sheep will be.

Prebreeding treatment of rams also decreases contamination potential. Treatments should also be administered during times of increased stress, such as high stocking rate, intensive grazing, or increased moisture. Lambs going into feedlots should be monitored closely.

What wormers to use should be based on the parasite problem that is present. Wormer resistance can be a problem with some of the parasites. Most wormers are rapidly eliminated from the sheep's system. Reinfestation can occur if sheep are returned to contaminated pastures or lots.

Remember, the effects of parasitism are generally more profound in young lambs than older sheep because adult sheep have more resistance to worms. There is NO EXCUSE for wormy sheep. There are available effective dewormers.

1993