Posted by Administrator on June 16 2004 08:52
Ovine Newsletter 2nd Quarter 2004
Short pasture conditions are favorable for more severe internal parasite infestations because more larvae are normally found on the lower parts of the plants near the soil surface. This makes sheep more prone to problems because they are short grazers.
This free-living stage of the life cycle of these internal parasites can vary from several weeks during cooler months to only a few days in the warmer months. Extreme temperature will affect the development or survival of the infective larvae. In warmer seasons, the development is rapid, but larvae survival is brief. This brings up the one redeeming quality of Minnesota winters.... it kills all the infective larvae that remain on the grass. So it's like we get to start over new every spring with no parasites on the pasture. The only way for parasites to make it through the winter is in the animals, and there are many things we can do to control that.
Clinical signs will vary according to the types of worms present and ages if the affected sheep. Lambs with heavy infection of barberpole worms may be found dead, with pale mucus membranes from massive blood loss. More chronic cases of stomach and internal parasites of sheep will show muscular weakness, pale mucus membranes, and diarrhea. Swelling or edema occurs in the lower body parts. The swelling is most evident under the jaw, resulting in "bottle jaw". Weaker animals lie around, have a depressed appetite and lose weight quickly. Unthrifty and poor bloom are symptoms just before the young sheep start to die. More chronically affected sheep may show a break in the wool, followed by fleece loss.
We can diagnose parasite problems many different ways. If dead sheep are found, a post mortem should be done as soon as possible. Fecal egg counts should be made on fresh feces from suspect animals, but must be interpreted according to history and symptoms. Blood tests can be an aid in diagnosing parasite problems in sheep. Age, nutritional plane, season of the year, and response to treatment should also be used in diagnosing parasite problems.
Treatment and control is based on selecting a wormer that will work to purge the worms from the sheep in conjunction with a pasture rotation system. This will allow the animals that we have just dewormed to go out on worm-free grass and not be reinfected. No matter if you choose a white wormer or an invermectin product, drugs aren't the only solution to the problem. Putting sheep back out on contaminated grass will promote resistance to the drugs and will only prolong the clinical course of the disease. We can help you to design a worming and grazing program that will maximize performance and efficiency in your flock.