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Queensland worms, flies and lice update - February 2016

Brisbane: Maxine Murphy, Veterinary Parasitologist (maxine@paraboss.com.au)

February/March is the time to frequently check for a build-up in barber’s pole and fly, especially if there’s any green pick about.

How? For worms, a WormTest is the obvious answer, but if you are one of the many who are remote from a testing lab, then looking for signs of anaemia in the straggler group of each mob, especially the young mobs, is your best bet. Why the straggler group? In any one mob, the ‘top’ sheep will carry comparatively few worms, while the straggler group will carry lots of worms. This is the 80/20 rule in action; 80% of the worm burden is carried by the straggler group of about 20% of the mob.

So, with drench at hand, walk, don’t chase with dogs or bikes, the mob over about 100 m. If any fall behind, barber’s pole may be the reason. Lethargic sheep with pale lower inner eyelids, and perhaps bottle jaw, should not be further disturbed, but drenched in the paddock, and then taken home in the back of the ute, not walked. Why? Anaemic sheep have insufficient red blood cells to take oxygen to vital organs and muscles. When sheep are mustered, muscles require increased levels of oxygen to function. If sufficient oxygen is not available then sheep become slow to move, and very anaemic sheep if forced to move, can die.

Very few drenches kill 100% of the infecting worm burden and many worms continue feeding unaffected by the drench. So for our anaemic sheep, if the average worm burden is high, say 6000 epg and the drench was about 90% effective, 600 epg worth of worms would still be ingesting large amounts of blood in already anaemic animals. Another drench required. The chances of survival then, become slim, and the value of effective drenches can be appreciated.

Hot, humid weather, little wind and fleece moist from rain suits the blowfly. Check Seasonal Conditions and Geography to determine your risk of fly this February/March.