Do<strong>rp</strong>e<strong>rn</strong><strong>uus</strong> <strong>•</strong> Do<strong>rp</strong>er news 2012 58
GASTRO INTESTINAL PARASITES In most countries, small ruminants (sheep and goats) contribute immensely to the livelihoods of a large human population, in terms of meat, milk, hides, wool, manure and sales of live animals. There are many constraints to small ruminant production. The most common is gastro intestinal parasites (worms). Worms cause great economic and production losses to the farmer. Productivity and economic losses can be through: <strong>•</strong> Slow growth – animals take longer to reach target weights <strong>•</strong> Mortality - can be high <strong>•</strong> Depressed wool growth <strong>•</strong> Anthelmintic costs (anthelmintic resistance) Sheep tend to be very susceptible to parasites and their damage. This can be due to a combination of several factors, including: 1. The small fecal pellets of sheep disintegrate very easily thus releasing the worm larvae onto pastures. 2. Haemonchus is often the major parasite of sheep and its blood-sucking characteristic makes it very damaging. 3. The ability and tendency of sheep to graze close to the ground where larvae numbers are higher drastically increases their exposure to parasites. 4. Sheep have very little aversion to grazing areas of high fecal contamination. 5. Sheep have a flocking instinct that encourages them to graze close together. 6. The Haemonchus worm is a very prolific egg layer thus worm numbers can build up very rapidly. Even older sheep are unable to develop immunity that controls the parasite life cycle. As animals get older, they can to develop more immunity to parasites, but it takes longer in lambs. When an ewe lambs, her immunity to parasites is temporary compromised. The presence of worm eggs in the faeces is a good indicator that the animal is infected. Sometimes losses occur which are undetected because the signs of parasitism are not obvious. It is therefore advisable to have a program in place to fight gastro intestinal parasites. Important helminthes of small ruminants fall into three major classes, nematodes (roundworms), trematodes JE Venter Provincial Veterinary Laboratory Middelburg, Easte<strong>rn</strong> Cape (flukes) and cestodes (tapeworm). Another parasite that can cause health problems is protozoa (coccidia). Depending on the type of parasite and the severity of infection, the following clinical signs can be observed: <strong>•</strong> Unthrifty sheep. Unthrifty sheep is not eating properly, is losing condition, tends to lag behind when moved and, is clearly weak. <strong>•</strong> Scouring can occur. <strong>•</strong> Rough hair coat. <strong>•</strong> Younger sheep are more susceptible than older sheep. <strong>•</strong> Stress: during the later stages of pregnancy, during lactation, during drought, long periods of wet weather – especially if this coincides with the later stages of pregnancy or lactation. <strong>•</strong> Anaemia – pale mucous membrane <strong>•</strong> Swelling/ Oedema (accumulation of fluid in the tissue) under the jaw (called “bottlejaw”). <strong>•</strong> General weakness Remember that “ill thrift” and scours, the major signs of a worm problem, can also occur with other diseases. So, acting purely on the clinical signs may result in a wrong (and costly) treatment. USEFUL MANAGEMENT TIPS: Most sheep have some worms in their digestive system. This is normal. Indeed, exposure to worms is essential if sheep are to develop and maintain immunity to worms. Worms are only a problem if the numbers increase to the point at which production losses occur or sheep become susceptible to other disease conditions. The overall pu<strong>rp</strong>ose of a worm control program should be to minimize production losses caused by inte<strong>rn</strong>al parasites and to maximize the sheep’s immunity to worms. It is important that everyone with sheep has a worm management plan. An effective plan is simple and will save a lot of money, effort and heartache. It is most important that sheep owners take a long-term and ‘integrated’ approach to worm control. Few components to an effective worm management program: - Testing: It is cheap and easy to do. Without regular testing, you won’t know whether you have a problem, whether your worm management plan is working or whether you have an emerging drench resistance problem on your property. EPG counts 59 Do<strong>rp</strong>e<strong>rn</strong><strong>uus</strong> <strong>•</strong> Do<strong>rp</strong>er news 2012