Are you winning the war on worms?

Transcription

1 HCC Winning the war on worms A5:13605 Practical sheep breeding Are you winning the war on worms? 8/7/10 15:21 Page 1

2 Hybu Cig Cymru / Meat Promotion Wales Tŷ Rheidol, Parc Merlin, Glanyrafon Industrial Estate Llanbadarn Fawr, SY23 3FF Tel: Fax: info@hccmpw.org.uk July 2010 Design Hybu Cig Cymru 2010 The information provided in this booklet includes the new SCOPS* updates and has been reproduced with permission. HCC acknowledges the technical input from Mr Eurion Thomas and Dr Julie Finch (Innovis Ltd) in the production of this booklet. This project has received funding through the Rural Development Plan for Wales which is funded by the Welsh Assembly Government and the European Union. No part of this publication may be reproduced or transmitted in any form by any means without the prior written consent of the company. Whilst all reasonable care has been taken in its preparation, no warranty is given as to its accuracy, no liability accepted for any loss or damage caused by reliance upon any statement in or omission from this publication. *Sustainable Control of Parasites in Sheep (SCOPS) is a group representing the interests of the sheep industry and recognises that, left unchecked, anthelmintic resistance is one of the biggest challenges the industry faces in the next few years. SCOPS is an industry wide group, chaired by the NSA and includes representatives from the animal health companies and distributors, Defra, the Welsh Assembly Government, VLA, Sheep Veterinary Society, RUMA, SNFU, SAC, AMTRA, universities and sheep advisers.

3 Contents Introduction 5 Why Bother? The patterns of parasite infections keep changing 6 Stay out of the red 7 Understanding the enemy 8 What is wormer resistance? 9 How has wormer resistance developed? 10 How much does resistance cost? 11 Weapons in our armoury against worms 12 Introducing the fourth wormer group 13 Guidelines for responsible and sustainable worm control 14 Know your enemy test for wormer resistance 15 Only use wormers when necessary 16 Dosing lambs 17 How/where can you get a Faecal Egg Count done? 18 Choose the right wormer for the job 19 Administer wormers effectively 20 Avoid bringing in resistant worms use quarantine treatment 21 Avoid selecting for wormer resistance 22 Reduce your dependence on wormers 23 Management techniques to reduce wormer usage 24 Work out a control strategy with your vet or advisor 25 Waging war against worms on organic farms 26 New approaches in practice 27 Future approaches 28 Summary 29 Further information 30 Are you winning the war on worms? 3

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5 Introduction The incidence of wormer resistance in sheep flocks in Wales and the UK is widespread but many farmers do not realise that they have resistant worms on their farms. In most cases the levels of resistance found are relatively low which means that most farms could still maintain effective worm control by following the latest advice and recommendations. Wormers continue to be an important part of worm control and the introduction of the first new wormer group in more than 25 years offers an opportunity for us all to review our current worm control practices and in doing so, prolong the effectiveness of the existing chemicals and delay the development of the resistance to this fourth wormer group. This booklet aims to provide the latest information to enable you to develop effective and sustainable worm control practices that will help you to reduce production losses and delay the development of wormer resistance on your farm. As always, specific advice should be sought from veterinary surgeons and sheep advisors. July 2010 Are you winning the war on worms? 5

6 Why bother? The patterns of parasite infections keep changing The original guidelines for worm control were drawn up nearly 30 years ago. Over the same period of time there have been significant changes in the size and structure of the sheep industry, the pattern of parasite infections and the type of products available. The continued, repeated and blanket use of a limited number of chemical groups has also lead to the development of wormer resistance. Changes to the climate have also brought warmer, wetter weather patterns and increased the grazing season. This has also changed the pattern of worm populations. For example, Nematodirus is now not only seen in the spring but can also be seen in the autumn. Haemonchus, the Barber s Pole Worm, a tropical blood sucking parasite is now found throughout the UK despite not normally surviving well in colder northern climates. All of these affect the way that we treat worm infections. Climate change also presents us with production challenges the need to maintain production from as low a carbon emissions base as possible. Effective worm control plays an important part in optimising the outputs from our sheep, by reducing the impact of worms on growth rates, feed requirements and time to finishing as well as by reducing our use of chemical treatments. Guidelines for the Sustainable Control of Parasites in Sheep (SCOPS) were first developed in 2004 and these continue to be revised and updated as more information becomes available. Wormer Resistance the unseen threat Wormer resistance has been detected on more than 80% of the farms that have been tested in Wales and across the UK. Resistance to the benzimidazole (BZ) group is widespread and the incidence of levamisole (LV) resistance is increasing. Reports now indicate that resistance to the macrocyclic lactone (ML) group is also now occurring. 6 Are you winning the war on worms?

7 Stay out of the red! Resistance is not all or nothing. There is a period between being able to detect resistance and the point at which that wormer group actually fails to kill enough worms to give adequate control. This is illustrated in the graph below. While the % of resistant worms stays in the amber zone, the level of kill is sufficient to provide reasonable control, although all the time performance is being lost. Acting at an early stage to slow the progress toward the red zone, where control is not achieved, will not only slow the progress of resistance but also improve animal performance. Sheep performance Resistance Undetected Optimum Performance Resistance Undetected Acceptable Performance Resistance Obvious Poor Performance As the proportion of resistant worms increases, sheep performance decreases % Resistant worms The levels of resistance found on 10 Welsh farms tested in 2007 showed that in several cases the percentage of resistant worms present were sufficient that performance is already being affected. Optimum performance is still likely to be seen on the farms where >95% of worms are killed (green) and is likely to be acceptable where the percentage of worms killed is still above 80% (orange). But already the effectiveness of some wormer groups has fallen below 80% and animal performance is likely to be poor as a result. Farm no. 1 - BZ 2 - LM 3 - ML 1 99% 100% 100% 2 82% 67% 99% 3 69% 98% 99% 4 81% 100% 97% 5 85% 84% 99% 6 90% 98% 100% 7 77% 96% 100% 8 77% 100% 100% 9 65% 100% 97% 10 35% 71% 100% Results from Faecal Egg Count Reduction Tests on a sample of 10 farms in Wales. Are you winning the war on worms? 7

8 Understanding the enemy Most worms have a similar life cycle: Larvae eaten with grass Larvae develop into adult worms adults lay eggs in faeces In general, eggs passed out of infected sheep take 2-12 weeks to develop into infective larvae on the pasture. L3 larvae migrate on to grass eggs develop into larvae worm eggs in dung Once ingested, infective larvae mature into adult worms. Within days they begin to shed eggs and the cycle begins again. Diagram courtesy of FECPAK International Some exceptions: Nematodirus needs a cold spell followed by a warm spell to trigger hatching and so Nematodirus eggs can remain on the pasture for up to a year. In some circumstances larval development may be halted or arrested at a specific stage, this enables worms to overwinter within the sheep as inhibited stages. Worming only affects those worms which are within the sheep at the time of worming. The eggs and larvae on the pasture are not exposed to the wormer and are not affected. In general, the population outside the sheep is usually much bigger in comparison to the exposed population. 8 Are you winning the war on worms?

9 What is Wormer Resistance? A worm is considered to be resistant if it can survive exposure to the standard recommended dose of that particular chemical group of wormer*. Wormer resistance is inheritable - the worm s ability to survive is passed on to its offspring. *wormer refers to all anthelmintics including drenches and injectables Frequent, indiscriminate use of wormers at sub-lethal levels (underdosing of sheep). Wormer resistance naturally exists in worm populations but usually at very low levels. In a normal worm population, a few wormer resistant parasites shouldn t pose a problem. susceptible resistant Worms which are resistant to that particular product continue to survive and the numbers of resistant worms in the general population increases dramatically. Hence the numbers of resistant worms in the general population has increased and the balance of the worm populations in the UK is no longer normal. Wormers only ever claim to be around 95% effective and so we rely on the larger normal worm population to dilute the number of surviving resistant worms. Are you winning the war on worms? 9

10 How has wormer resistance developed? Under Dosing eg: Guessing weights, Incorrect drenching technique Dosing sheep with a full stomach Drug Overuse eg: Repeated use regardless of need Inadvertent over-use of combination products e.g using a combined flukicide & wormer The use of injectable products to treat sheep scab that also control worms. Incorrect use of drugs eg: Mixing / administering different drugs together Using them past their use-by date Drenching sheep & moving them to clean pasture on clean pasture there are fewer susceptible worms to dilute the resistant worms Stock Movement failure to quarantine and treat incoming stock on arrival can introduce wormer resistant worms Mis-diagnosis worming sheep in poor condition regardless of whether worms are the cause of the problem 10 Are you winning the war on worms?

11 How much does resistance cost? The EU-funded PARASOL (PARAsite SOLutions) project (2006-9) tested the practical application of various new approaches to worm control across Europe. This project assessed the impact of faecal egg counting (FEC) on 10 UK farms. Regular FEC helped those farmers to determine the timing and need for treatments, allowed treatments to be targeted on the groups of sheep that needed treatment and to check the effectiveness of those treatments. On some farms this resulted in the identification of anthelmintic resistance that would otherwise have gone undetected until problems were experienced much later in the livestock. After finding we had extensive white wormers resistance we took advice and changed our wormer group this year. Our lambs have looked far better than ever and we have saved 1500 on creep feed alone as we didn t have any lambs left in the autumn to feed!! EU PARASOL Project Farmer Studies have also shown 1 that when lambs grazing on pasture with a history of BZ resistance were treated with a wormer from the BZ group, they had: Higher FEC than lambs treated with an effective wormer group Lower weight gain 33.5% lower than lambs treated with an effective wormer group A 2.8kg lower deadweight than lambs treated with an effective wormer group p per kg lw Welsh SQQ lamb prices - live weight Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Poorer growth rates will delay finishing. Given recent market trends, this will result in lambs being sold when the market price is falling. Based on average prices in 2009, resistance could be costing you around 9.60 per lamb without you knowing it! 1 The production costs of anthelminitic resistance in sheep managed on a monthly drench program. Sutherland, A.I., Bailey, J and Shaw, R.S. AgResearch Ltd, The Hopkirk Research Institute and Novartis Animal Health, Australasia Are you winning the war on worms? 11

12 Weapons in our armoury against worms Wormer resistance is specific to a particular group of wormer and not to the individual product. When resistance appears to one wormer in a given group, then other products in the same group will also be affected. Broad-spectrum wormers kill more than one type of parasite. These wormers are divided into groups based on their structure and mode of action. Group Type Compounds 1 BZ White 2LV Yellow 3ML Clear includes the injectables 4AD Orange Benzimidazole Levamisole Macrocyclic lactones Derivatives Albendazole Fenbendazole Mebendazole Ricobendazole Oxfendazole Levamisole Ivermectin Doramectin Moxidectin Monepantel Wormers available for use against gastrointestinal nematodes As well as the broad spectrum wormers, some narrow spectrum treatments are available. These are only effective against Haemonchus (the Barber s Pole Worm) and liver fluke. A full list of wormers can be found in the Farming Connect factsheet available from HCC called Know your anthelmintic groups. 12 Are you winning the war on worms?

13 Introducing the fourth wormer group Monepantel is the first wormer available from the newly discovered Amino- Acetronitrile Derivative group (AD). It is orange in colour. As a new wormer group, it is currently unaffected by resistance to the other groups and so even worms which are resistant to the three other groups (multiple resistance) will be susceptible to the Group 4 Orange wormer. Monepantel is currently only available through your veterinary surgeon and correct use is essential to avoid the development of wormer resistance to this new group and to prolong the efficacy of the other wormer groups. For more information about the use of this new Group 4 (AD) wormer, contact your vet or sheep advisor. Are you winning the war on worms? 13

14 Guidelines for responsible and sustainable worm control With careful management and good practice we can all manage the resistance threat. The SCOPS guidelines highlight 8 key areas which can help to slow the development of wormer resistance in UK sheep flocks. These best practice guidelines also apply to organic enterprises (see page 26). 1. Know your enemy - test for wormer resistance on your farm 2. Only use wormers when necessary avoid wasting time and money on unnecessary treatments 3. Choose the right wormer for the job 4. Administer wormers effectively good drenching practice is key to making sure that the maximum number of worms are killed when the right drench is used. 5. Avoid bringing in resistant worms use quarantine treatments to protect your flock 6. Preserve susceptible worms on the farm and reduce the selection for wormer resistance 7. Reduce your dependence on wormers 8. Work out a control strategy with your veterinarian or advisor 14

15 Know your enemy Test for wormer resistance on your farm It is not advised to use wormers without knowing which ones are effective on your flock. Wormer resistance is said to exist if the wormer has reduced the egg count by 95% or less. There are a number of ways in which you can test how effective the wormer has been against the worm populations present. Your veterinarian or sheep advisor will advise you on the right test for your farm. Post-treatment Faecal Egg Counts (Drench test) In this simple test, faecal samples are taken from sheep before treatment and then again a defined number of days after treatment. The exact number of days varies according to the product. Worm counts in the samples are compared to check if the wormer has worked. This should be discussed with your vet or sheep advisor. Faecal egg count reduction test (FECRT) The FECRT is a more detailed way to identify which wormers are effective against the worms present on the farm at that time. These should be undertaken with support from a veterinarian or sheep advisor. Since worms have to be present to do the test, it is normally done on sheep that have not been dosed for at least 10 weeks. Larval development tests A range of laboratory tests are available and can be done in extreme cases where product failure or resistance is suspected. Larvae are cultured in a laboratory with different doses of wormer. Any larvae which are susceptible to that particular wormer are killed whereas larvae which are resistant survive and develop further. Larvae Eggs Are you winning the war on worms? 15

16 Only use wormers when necessary Adult sheep are normally immune to worm infections This is an acquired immunity and depends on the sheep having sufficient exposure to worms during its life. A fit, healthy adult sheep will carry a small worm population, but this is necessary to maintain their immunity. Despite this, many farmers in Wales continue to dose ewes more than three times per year, regardless of the fact that in most cases it is unnecessary and may reduce their natural immunity temporarily. Dosing Ewes pre-tupping Very few adult ewes will have significant worm burdens at tupping time so treatment on a group basis is discouraged. Poor body condition and age of the ewes (i.e immature ewes are more likely to be affected than older ewes) are possible indicators of infection. If you suspect that ewes may have worms then test groups of ewes to check that worms are the cause before treatment. The treatment of all ewes pre-tupping, regardless of need, can actually increase the risk of wormer resistance developing. Dosing ewes at turn-out Adult ewes generally have high levels of immunity but this immunity relaxes around lambing time. This relaxation of immunity usually begins 2 4 weeks before lambing and lasts for 6 8 weeks. Evidence shows that not all ewes need to be treated at lambing time and so farmers can use FEC to target treatments to particular groups of sheep and to when they are actually needed. The timing of treatments will vary from farm to farm and year to year. The timing of worming and the choice of wormer are both important so advice should always be sought before treating ewes. Always leave a proportion (10%) of ewes in the best condition untreated unless you have haemonchus. Speak to your vet for further advice. 16 Are you winning the war on worms?

17 Dosing lambs Lambs will normally become immune to worms by the time they are 5-6 months old but this does depend on them having sufficient exposure to the worms during this period. The Wales Worm Watch survey indicated that more than 56% of farmers dose lambs three times per year or more. Lambs are often treated frequently to ensure that they achieve high growth rates without any of the negative effects that might be caused by worms. However, targeting treatment of lambs only when needed reduces the number of treatments given without any negative impact on production. FECs can be used to monitor worm burdens. If sheep have high FECs it is likely that treatment is needed. However, low FECs need careful interpretation so always seek advice from a vet or sheep advisor. Lambs which have been kept on clean grazing, or kept indoors for long periods of their early life, may not have been exposed to worms and so may succumb to infection regardless of their age. This can also be an issue for hill lambs when they are moved down to heavily infected lowland farms, or for pedigree rams that have had little exposure to grazing when put to work on a commercial farm. Before treating lambs ask yourself: Is treatment only needed for Nematodirus? If so use BZ wormers rather than MLs but check with your vet if you have known resistance to BZ. Is treatment actually needed? Use FEC monitoring to help predict the need for treatment. Use FEC monitoring to extend the time between treatments to four or five weeks, or longer if possible. Are you winning the war on worms? 17

18 How / where can you get a Faecal Egg Count done? From your veterinarian some vet practices offer an in-house FEC service or will send your samples to the Veterinary Laboratories Agency (VLA) for counting. Ask your vet about FEC services that they can provide. Details of commercial services and on farm kit for monitoring FEC can be obtained from HCC. Support may also be available through Farming Connect to eligible farm businesses to help to develop parasite management plans. Contact HCC for further information. FECs can be done on farm or in the laboratory and are interpreted with advice from a vet or sheep advisor 18 Are you winning the war on worms?

19 Choose the right wormer for the job Unnecessary exposure of worms to a wormer will increase the proportion of worms that are resistant, so it is vital that the wormer used is the right one for the worms present on your farm and that it is actually effective against those worms. Purchasing decisions based on cost or special offers available will only compound your problems in the longer term. Beware of using combination products. If liver fluke is the target, use a flukicide on its own. Avoid products which contain a flukicide plus a broad-spectrum wormer. Consider the guidelines for the use of the new Group 4 AD wormer for quarantine treatment and if you already know that you have multiple resistance. Rotating Wormers The standard advice used to be to rotate between the three wormer groups on an annual basis. However, with increasing levels of resistance to all 3 groups, and the introduction of a 4th group (AD) in 2010, this is no longer best practice. This is because there are times when the reason for the choice of wormer is more important than the need to rotate between the wormer groups. For example, quarantine treatment of incoming sheep with a ML (clear) and AD (orange) wormer should always be done regardless of the current wormer in your rotation. Advice should always be sought from your vet or sheep advisor on the most appropriate wormer for use at that time. Are you winning the war on worms? 19

20 Administer wormers effectively Good drenching practice will help to make sure that the maximum numbers of worms are killed when the right drench is used. Dose by weight and not by eye Competitions that are run at various meetings and events still show that judging weight by eye nearly always underestimates an animal s weight. Always weigh two or three of the biggest sheep and use the dose recommended for them for the whole group. If the weight range means that the lightest sheep will receive more than a double dose of wormer, divide the sheep into two groups based on size and then work out the dose for each group based on the heaviest in each. Check your dosing gun Check dosing guns regularly to ensure that they are delivering the right dose. Deliver two or more doses of wormer into a graduated measure such as a 20ml syringe and adjust the gun to deliver the right dose. Don t use water to check the gun - it is less viscous than the wormer and so won t give you an accurate measure. Clean and check the dosing gun for kinks or damage after use. Dosing technique Dosing guns are specially designed to deliver the wormer into the correct part of the mouth (i.e. over the tongue and not into the cheek). Correct placement determines whether the treatment is delivered to the rumen (large stomach) or bypasses it to the true stomach (abomasums). If any wormer by-passes the rumen then the worms may not be exposed to the levels of wormer that are needed to kill them. Store unused wormer properly To maintain the product s effectiveness, store it away from direct sunlight at 4-25 o C. Always check the use by date and once opened, use it within the time specified. There is also some evidence that the effectiveness of some white and clear wormers can be improved by withholding food for hours before dosing. However, always maintain access to water and never withhold food from heavily pregnant ewes. 20 Are you winning the war on worms?

21 Avoid bringing in resistant worms - use quarantine treatments Bringing sheep onto a farm, often from many sources, and usually without effective quarantine treatments is a major contributor to the development of wormer resistance and to the spread of many other diseases including fluke and scab. Quarantine strategies should be applied to all sheep purchased from other flocks (including rams) and to your own sheep which have been grazing on other farms (or common grazing). This is particularly important to control the spread of Haemonchus (the Barber s Pole worm) which affects adult sheep. 1. Assume that all incoming sheep have resistant worms 2. Hold sheep off pasture when you get home and for hours after treatment After 24 hours, about 90% of the eggs will have been passed from the sheep and by 48 hours, 99% will have gone. Ensure that the incoming sheep have feed and water while they are held off pasture. Dispose of the faeces incinerate them or apply them to ground that isn t grazed don t apply them to pastures that will be grazed by sheep or goats. 3. Treat all the sheep during this time Give monepantel AND moxidectin or another wormer from the ML group. Using an injectable formulation will also deal with any threat from sheep scab. Give the treatments one after the other never mixed together and always give the full dose of each wormer. Beware of using monepantel (4-AD) alone because inevitably the over-use of this wormer will lead to the development of resistance against it. 4. Quarantine the sheep on dirty pasture for at least 3 weeks Grazing dirty pasture will help to ensure that any resistant worms which do survive quarantine treatment are outnumbered by the normal populations on the farm. Keeping new sheep separate from your main flock for at least 3 weeks will also ensure that you can see any other unwelcome diseases that the sheep may have brought in. Are you winning the war on worms? 21

22 Avoid selecting for wormer resistance The traditional dose and move strategy encourages wormer resistance because any resistant worms which survive the worming treatment will only produce resistant eggs to contaminate the fresh pasture. The cleaner the pasture, the faster the numbers of resistant worms will increase and over several years this can produce a highly resistant worm population. It is a fine balance between drenching ewes to reduce pasture contamination and exposing all worms inside the ewes to wormer treatments. How, can I reduce the worms on my pastures without encouraging wormer resistance? Provided you know that the wormer group to be used really is effective, and you are not dealing with Haemonchus (Barber s Pole worm) leave % of the flock untreated. Choose the sheep to be left untreated at random fit, mature sheep in good condition may have lower FECs than average anyway and are likely to have good natural immunity. Use FEC to monitor worm eggs at or soon after lambing Drench only when it is needed Do not drench ewes two or even three times regardless of need Monitor ewes pre-tupping and do not blanket drench in the autumn 22 Are you winning the war on worms?

23 Reduce your dependence on wormers Drenches are an important part of worm control but there a number of management decisions that can help to reduce the need for worming: Use grazing management Avoid any unnecessary exposure to worms by using field plans, grazing records and basic risk assessment for pastures Identify the safest and the dirtiest pastures know where the greatest risks are Identify the most vulnerable and least vulnerable class of stock to graze particular fields Identify animals you want to develop immunity Mixed grazing Pasture contamination can be reduced by grazing cattle and sheep (but not goats) together Consider Alternative Forages and Feed Additives Considerable research is being done to look at different feeds which might help to reduce worm burdens in sheep. Alternative forages, such as chicory, lucerne and clovers have been investigated to study their effects on internal parasites in growing lambs. Research by organisations such as the Institute of Biological, Environmental and Rural Sciences (IBERS) at Aberystwyth University has shown that chicory and white clover can reduce the internal parasite burdens in grazing lambs. The research also investigated the effects of dietary forage on worm hatching and development. Findings revealed that alternative forages reduced the number of worms which developed, survived and migrated when compared to ryegrass pastures. There have also been some reports that a number of substances such as diatomaceous earth, wormwood, garlic and radionics can affect parasite infections. The effects of these substances still needs to be scientifically evaluated. Chicory (Cichorium intybus) 56 days after sowing Are you winning the war on worms? 23

24 Management techniques to reduce wormer usage Group lambs by age at turnout This has benefits when it comes to the need for treatment and the use of FECs to work out when treatment is needed. Lambs can then be weaned at the same time and share the same withdrawal times after treatment. Weaning From late June onwards, lambs (which require a much smaller area) can be moved to less contaminated areas after weaning. Examples of this are aftermath or pasture grazed by cattle since turnout. Ewes can be left on the heavily contaminated grazing. Good Nutrition Good nutrition helps to ensure that an animal is less susceptible to disease and should always be part of the overall management plan. Monitor rainfall and temperature Since temperature and moisture affect the levels of infective larvae on the pasture management strategies should take into account the weather conditions that year. Online disease forecasts can be a very useful source of information on the incidence of parasite infections across the UK. Use rams that are bred for resistance to worms Ewes sired by worm-resistant rams will cause less contamination of pastures with worm eggs at all times of the year, including lambing time. This will give substantial benefits to their lambs. Until recently, the flocks selecting for Low FEC tended to be terminal sire breeds but some breeders of hill-breed and maternal rams are now beginning to include FEC in their breeding programmes. 24 Are you winning the war on worms?

25 Work out a control strategy with your veterinarian or advisor The factors which affect worm infection patterns are now so numerous that controlling worms is a complex process. The need to combine an expert knowledge of parasites with a practical and detailed understanding of the individual farm and its sheep flock is greater now than ever before. Veterinarians, sheep advisors and farmers must work together to achieve this. The weather and production pressures on the farm vary from year to year so this must be an ongoing dialogue. FECs provide valuable information about the worm status of a flock of sheep and can be used to help decide if worming is necessary, or if it can be safely delayed or left out completely. Are you winning the war on worms? 25

26 Waging war against worms on organic farms These best practice guidelines also apply to organic sheep enterprises. Careful flock and grazing management strategies form an integral part of worm control on organic farms. Diligent husbandry and attention to detail together with the lower stocking rates and rotational grazing in the mixed farming systems found on organic farms play a key role in worm control. Managing pastures so that sheep, and particularly lambs, are only put into fields that have very low or no worm infestation can help to reduce the need for worming. Regular faecal egg counts will help to monitor when worm populations are becoming dangerously high. Faecal egg counting can also be used to assist the selection of ewe lamb replacements on their ability to resist worm infection. Organic farmers who buy in breeding stock are always advised to check the health status of incoming stock and to quarantine them before mixing with the resident flock. If worming is necessary then certain treatments can be used, provided that approval is given by your vet and permission obtained from your organic certification body before use. When wormers are used the recommendations for the use of wormers described here apply equally to both organic and conventional farmers. 26 Are you winning the war on worms?

27 New approaches in practice Results from the PARASOL project showed that regular faecal egg counting could be incorporated into routine sheep management practices. The graph below shows the impact of regular faecal egg counting on the number of wormer treatments that needed to be given on 8 farms. No. treatments/100 ewes/year Number of treatments needed per 1000 ewes Farm no. 2 years BEFORE start of project 2 years AFTER start of project The average annual reduction in the no. of treatments per farm was 3,825 (ranging from 481 to 10,810) This equates to a 35% reduction in dosing across all farms These effects were seen without a decrease in animal performance The financial impact of this can be considerable (see below). Farm code No Ewes Financial saving from reduction in purchases of anthelmintics Total annual saving Annual saving per adult ewe Percentage reduction in cost % % % % % % % % AVERAGE OVER 8 FARMS % The annual change was calculated by comparing the average figure for the 2 years before start of project with the average figure over the 2 years after the start of the project. Are you winning the war on worms? 27

28 Future approaches Research is being undertaken worldwide to try to provide alternatives to wormers for the future with careful management of our use of wormers in the meantime we may be able to extend their life until some of the research yields answers which can be converted into practical recommendations. Vaccines Despite considerable research there are, as yet, no commercially available vaccines for the control of sheep nematodes. The development of vaccines against the major parasite species have proved to be particularly problematic. Understanding how sheep develop their naturally acquired immunity to gastrointestinal worms is key to this but the mechanisms involved are proving to be particularly complicated. Only when these mechanisms are understood will attempts to artificially stimulate them using a vaccine enjoy any degree of success. Work at the Moredun Research Institute and elsewhere is looking at directing immune responses towards potentially susceptible targets e.g. those on or produced by parasites such as Haemonchus. Genetic Markers Research is taking place in the UK and abroad to identify genetic markers which will help to tell us which animals are naturally susceptible or resistant to parasite infections. The use of these markers alongside a prudent breeding and culling policy will help to breed animals with an inherited ability to resist parasite infections. Some progress has been made recently by Glasgow University Veterinary School who have identified a genetic marker for increased resistance to T. circumcincta in Scottish Blackface sheep. This is currently being validated on commercial farms. Biological and other control mechanisms Researchers are also investigating the effects of plants and their extracts that have been found to have properties that help expel parasites from the body. 28 Are you winning the war on worms?

29 Summary To wage an effective war on worms Know your enemy Choose the right weapons Use them properly and responsibly Remember that worms are only one of many causes of scouring in sheep. Always ensure that the cause of scouring is correctly identified before automatically reaching for the drenching gun. So check it out: Do you know whether all the wormer groups do still work on your farm? Do you perform a FEC to check whether your sheep need treating? Do you know which wormer you need to use? Do you weigh animals before worming? Does your dosing gun deliver the right dose to the right place? Do you check and follow the manufacturer's instructions? Do you store products correctly and use them within their use-by date? Do you mix your wormers with other products? Do you plan your grazing each year and are your animals re-infected by highly infective pastures? Have you quarantine-treated all your incoming sheep? Are you winning the war on worms? 29

30 Further Information For further information about any of the content of this booklet or on the work undertaken by HCC please contact HCC on tel: or visit Advice can also be sought from your vet or sheep advisor. Further information about the Sustainable Control of Parasites in Sheep (SCOPS) can be found at 30 Are you winning the war on worms?