Presenter: Dr. Scott Bowdridge, West Virginia University
Time 1 hour 22 minutes
Host: Dr. Jay Parsons, Colorado State University & Optimal Ag
Many producers have experienced loss in the form of reduced growth and often death as a result of parasitism within their flock. Development of multi-drug resistance in these worms, especially the southeastern US, has left many producers feeling helpless in the face of gastrointestinal nematode parasitism. As a result some have left the sheep business, others have switched to a dry-lot system for lambs and the rest have tried everything else to keep these lambs growing on pasture. The utilization of selective deworming has resulted in at least maintenance of dewormer efficacy, yet with limited drug choices this option remains one of our best tools. Through the incorporation of parasite-resistant breeds many have observed a less frequent need for treatment. However, concerns about the effect on growth and carcass quality, not to mention the effect on wool quality, have limited the use of parasite-resistant hair breeds of sheep. Parasite-resistant sheep have, however, provided much of our understanding of functional host protective immunity, as these sheep generate a very rapid and robust immune response to worms. It is curious why the same response is not seen when commercial-crossbred sheep become infected. Perhaps parasite management should be equally focused on the host as it is on the pathogen.