PSGHS NEWS Premium Sheep and Goat Health Scheme in conjunction with SRUC February 2013 Maedi Visna eats into flock returns 1 Maedi Visna eats into flock returns Nick Marriott Farm and Grounds Manager Brooksby Melton College Brooksby Melton College in Leicestershire has had a flock of sheep since its conception in the mid 1940s. We currently run a flock of 350 North Country mules along commercial lines, buying in replacements annually, selling fat lambs through local markets and deadweight outlets. I took over the management of the farm in 2004, reducing ewe numbers in response to signing up to Countryside Stewardship across the estate. A small group of ewes started to show some odd behaviour followed by collapse and death. After some initial uncertainty as to the cause of the problem VLA Sutton Bonington diagnosed Maeda Visna. A cull of the whole group was the conclusion and for the following few years there was little indication of recurrence of MV. How wrong we were! Last year ewes started to show signs again. Paralysis of a hind leg, wasting, mastitis, high mortality and poor growth were the main symptoms. In summer 2012 we took the opportunity, following a conversation at the NSA Malvern event, to blood test a random selection of ewes. 58% of those tested were positive. Some very useful discussion with SAC outlined the way forward. The next step for our flock is a total cull, ensuring that our sheep don t re enter the UK breeding flock, and purchase of new stock. The problem is where to go for commercial sheep that are MV free, with nearly 4% of the national flock carrying the disease. A difficult task! It looks like a self contained flock, perhaps with a pure breed that can be obtained with a sufficiently high health status, will be the way forward. Hopefully that will keep sheep grazing the pastures around the estate for another 60 years. MV has cost us. Simple calculations, such as higher spending on vets, medicines, feed, replacements and labour, lower performance of the ewes, lower cull value, poor lamb growth rate and higher mortality could easily add up to over 10000 in the flock. STOP PRESS: The whole flock has been culled to slaughter including 90 replacements (a hard decision to take). We have restocked with Lleyn draft ewes and ewe lambs and will lamb around 200 in spring 2013. Our aim will be to sell accredited breeding stock. We chose Lleyn as they were available as MV accredited and we could not risk another MV breakdown by purchasing sheep of unknown health status. As a commercial flock owner more of the maternal breeds need to embrace MV accreditation. MV Reactors at Brooksby SRUC 2013 Ian Pritchard Editor Premium Sheep and Goat Health Schemes, PO Box 5557, Inverness IV2 4YT T: 01467 625385 F: 01463 711103 E: sghs@sac.co.uk W: www.sac.co.uk/sghs SAC Consulting is a division of SRUC. SRUC is a charity registered in Scotland, No. SC003712 2 CLA Questions and Answers 3 Pre Sale Disease Screening of Sheep 4 Schmallenberg Virus Update 4 MV survey 5 Embryo transfers 5 MV testing in Europe 5 Clothing & MV risk 6 MV Testing Protocol 6 Inspections shows and sales 7 Added Animals Extra Testing 7 Commercial Sheep at risk? 7 Are you doing your test correctly? 7 Scrapie Monitoring Scheme (SMS) abide by the rules 8 Poor response to treatment for Liver Fluke? Premium Sheep & Goat Health Schemes
CLA Questions and Answers Here are some answers to common questions that are asked about CLA: After infection how long does it take before an abscess becomes visible? The CLA bacteria often infects sheep through breaks in the skin that may be invisible to the human eye. It is then delivered to the nearest lymph node. Lymph nodes are part of the immune system and there are many of them throughout the body. The glands that swell up when you are ill are lymph nodes. The bacteria form microscopic abscesses in the lymph nodes within 24 hours of infection. Depending on which lymph node is infected lumps caused by abscesses may never be visible as they are inside the sheep. As many as 1 in 4 infected sheep may only have internal abscesses. Are antibody positive sheep infected for life? Yes. The immune system is unable to remove CLA bacteria from the body although infected sheep produce antibodies against them. This is a similar situation to MV where the presence of antibodies indicate that the sheep is infected with the disease rather than immune to it. Are antibody positive sheep infectious? Yes. The CLA bacteria is present in pus within abscesses. When an abscess bursts through the skin or ruptures in the lung then millions of bacteria are released into the environment and can infect other sheep. How can CLA bacteria be killed? Antibiotics are usually ineffective because the drug can not penetrate the abscess to attack the bacteria. The CLA bacteria can be killed by disinfectants, (if dung and straw etc. are removed first), so it is usually straightforward to clean pens, trailers, troughs, dosing guns, clippers, clothes etc. Nothing can be done about bacteria on pasture however leaving it ungrazed for 2 months will reduce the risk of infection being picked up. Why does the blood test produce false positive and false negative results? Small numbers of uninfected sheep may produce a positive result in in the CLA ELISA test. This may be because the sheep was suffering from another infection at the time of blood sampling. For this reason a second test, the Western Blot, can be used to confirm an unexpected positive result. Alternatively a second blood sample collected a few weeks later and retested can resolve the question. Some infected sheep may, on occasion, produce a negative result in the CLA ELISA. When abscesses form they can develop a thick fibrous capsule around the pus. If the abscess does not leak or rupture then the bacteria within the pus are hidden from the sheep s immune system. This can cause the number of antibodies in the blood to fall to a low level that produces a negative ELISA result. Again, re-sampling the animal can be useful in these circumstances. If a ewe tests positive will her lamb also be infected? Unlike other diseases such as MV this is not necessarily the case. In flocks where CLA has been eradicated this has been achieved without culling the offspring of positive ewes. Does vaccination with the imported vaccine Glanvac work? Yes, to the extent that it will reduce the number of sheep with obvious lumps and will reduce the spread of infection. It will not usually eradicate infection completely and a further complication is that vaccinated sheep will test positive in the ELISA test. How else can the spread of CLA within an infected flock be reduced? Repeated blood sampling of the entire flock with culling and removal of positive animals to a separate infected group is an option. This approach can be supported by checking sheep for swellings and abscesses at each handling and remove any affected animals to the separate group or cull. However regular checking for external abscesses is unlikely to eradicate infection from the flock because of the possibility of internal abscesses. Keep the infected group isolated from other sheep. Always handle this group last when the flock is to be handled e.g. at shearing, dipping etc. All pens, clothing, trailers, troughs and equipment should be cleaned and disinfected after contact with this group. Leave areas grazed by this group free of sheep for a minimum of 2 months. Where possible reduce stocking density +/- time spent housed. Reducing trough feeding will cut back on repeated close head and neck contact between sheep. Screen purchased sheep for CLA to avoid future re-introduction of disease. Finally make sure fences are stock proof and that any visitors have clean and disinfected clothing and equipment. 2
Pre Sale Disease Screening of Sheep More and more cattle breeders now routinely test stock for specific infectious diseases pre sale. This individual animal information is often complemented by herd disease status through membership of cattle health schemes. However it is worth knowing that certain diseases such as BVD/ Border Disease ( the sheep equivalent of BVD) and Johnes Disease can be present within the sheep flock and they could potentially re-infect cattle. The route of entry for many diseases into flocks is via the purchase of infected, but clinically normal, animals. Any flock can incur serious losses following the introduction of Border Disease. A single negative virus test result proves that breeding animals are not persistently infected with Border Disease virus. Eradication can be costly as could the consequences of living with it and suffering on-going losses. Some large commercial Mule flocks have been badly affected following infection with Maedi Visna. In some cases culling of the whole flock has been the end result. Recent surveillance has shown that there has been an increase in MV infection in the national flock over the last decade. There has been increased awareness of CLA within some breeds and a desire to be able to prove, as far as possible, that clean, healthy stock are being offered for sale. In order to prove freedom from a disease whole flock testing is the ideal but can be prohibitively expensive and impractical, particularly for large flocks. Testing small numbers of sheep for sale provides confidence in their health status but is not a 100% guarantee that they are disease free. This is because, for diseases such as MV, it can take several months for antibodies to be produced following infection. In other cases, such as CLA, some sheep can give misleading results on a single test. Testing the ram stud, in addition to the sheep for sale, would provide a bit more security and is a compromise between testing none of the breeding flock and testing the whole flock. Almost all flocks will purchase rams at some point which itself comes with a risk of introducing disease. Close contact with ewes at tupping time means that they can also act as sentinels of disease in the rest of the flock. In 2013 we plan to offer a range of options for pre sale disease screening of sheep. Blood tests results apply to the day of testing and the animals should be isolated from other sheep after testing. An outline of the possibilities is shown below. One or more diseases can be selected, (depending on flock history and buyer demand), and other tests can also be requested e.g. Schmallenberg virus antibody, trace element screening, etc. For CLA, Border Disease and MV can; 1) Test ram stud and all stock for sale Or 2) Test stock for sale. Sell test negative stock. 3
Schmallenberg Virus Update This new disease of cattle, sheep and goats was first identified in Holland and Germany in autumn 2011. It has since spread across much of northern Europe including England, Wales and Ireland. The disease appears in 2 forms. i) Infection of adult dairy cows may result in mild fever, milk drop and diarrhoea. These symptoms are rarely seen in other cattle or sheep or goats. ii) Birth of deformed calves, lambs or kids if infection occurs during the critical first stage of pregnancy. Most affected flocks and herds see only a small number of deformed calves and lambs. However some flocks and herds with a very tight calving or lambing pattern can suffer severe losses when many animals are infected during the critical first months of pregnancy. Schmallenberg virus is spread by midges that become infected through feeding on a recently infected animal. After a period of development in the midge that can last up to a few weeks, the virus is transferred when the midge bites another animal. Most of the spread of Schmallenberg virus is due to infected midges being moved on the wind. Schmallenberg virus does not normally spread directly from animal to animal except when a foetus is infected from its dam. The advice to farmers is 1. Arrange with your vet to submit any deformed lambs or calves to your local disease surveillance centre for comprehensive investigation. The investigation may include testing for Schmallenberg Virus. However the other causes of deformity will also be considered. 2. Pregnant females purchased from farms in infected areas of the country or from overseas should be tested for antibodies to Schmallenberg virus soon after arrival. They may produce a deformed foetus if they have antibodies to the virus. Purchased rams and bulls are unlikely to spread infection in the winter months. 3. Farmers with pregnant cattle or sheep exposed to Schmallenberg virus should discuss their options with their veterinary surgeon. This may include early intervention in any cases where there are difficulties at lambing or calving in order to save the ewe or cow. MV survey A large scale survey, carried out on bloods collected from randomly selected flocks, found evidence of MV infection in almost 3 in 100 flocks and in 8 in 1000 sheep. The survey was funded by EBLEX and the Welsh red meat levy board HCC. A total of 726 flocks were sampled and 11,757 blood samples were tested for MV. This is the first large scale MV survey to be carried out for 15 years and in that period the number of flocks infected with MV has doubled and the number of sheep infected with MV has increased fourfold. Samples were collected from flocks in England, Wales and Scotland and the number of flocks sampled in each region was proportionate to the sheep density in that region. Some regions had evidence of a higher level of infection e.g. in both Leicestershire and Gloucestershire 1 in 7 flocks were found to be infected. High levels of infection were detected within some flocks. The four highest levels were 45%, 70%, 75% and 80% and in these flocks clinical signs of MV and loss of production would be occurring. Signs of disease often do not occur until about half of the flock is infected. As the survey found evidence of MV infection in 3 in 100 flocks and in 8 in 1000 sheep it is essential that biosecurity is at a very high standard to prevent infection from being introduced to accredited flocks from non-accredited sheep. The risk of having a breakdown with MV is 2.3 times higher for flocks that have non-accredited sheep on the same holding compared to holdings that have solely MV accredited sheep. 4
Embryo transfers Embryos derived from MV accredited ewes can only retain their MV accredited status if they are implanted into MV accredited females. All embryos derived from MV accredited ewes immediately lose their MV accredited status if implanted into non- MV accredited recipients. In order for these offspring to regain MV accredited status they would need to pass two qualifying tests at a minimum of 12 and 18 months of age. If non-accredited ewes are used as recipients and they are infected with MV there is a small risk that the lambs will be born already infected. However even if that does not occur there would be a high risk of them becoming infected after birth from nose to nose contact with their dam or from infected colostrum or milk. If non-accredited sheep are to be used as embryo recipients they must have two clear qualifying tests a minimum of six months apart before the embryos are implanted, if the embryos are to retain their MV accredited status. If there is insufficient time for the two qualifying tests to be done then, at the very least, a first qualifying test should be carried out on the group before any embryos are implanted. If they all pass the group would need to be kept isolated from all accredited and nonaccredited sheep until they had their second qualifying test six months later. If all in the group passed this second test the embryo lambs would regain MV accredited status. However this is a risky strategy as it is not uncommon for sheep to pass the first qualifying test but fail at the second which would affect the status of the whole group. A recent large survey showed that 3 in 100 flocks are infected with MV so it is a high risk to implant valuable, MV accredited embryos into non-accredited ewes without having tested them first. We have identified MV infection in groups of sheep that were intended for use as recipients and also in a couple of groups of sheep where embryos had already been implanted. Just because ewes look healthy it does not mean that they are uninfected. You may wish to consider gaining MV accredited status for your commercial flock, or a group from it, for either your own use as embryo recipients or to sell as MV accredited recipients. MV testing in Europe Many European countries, like GB, have voluntary MV accreditation schemes. The rules and testing can sometimes be stricter than what we have here but in many European countries the level of MV is much higher than it is in Britain. Some countries are free of MV and some of them have MV as a notifiable disease e.g. Norway and Ireland. The programmes in other countries usually require all sheep on a holding to be included in the MV accredited flock whereas we allow a separate nonaccredited flock to be kept on the same holding, providing biosecurity rules are followed. This is something that we keep under review because we have calculated that the risk of having a breakdown with MV is 2.3 times higher on holdings where there is a non-accredited flock in addition to the accredited flock. In other countries it is often a requirement to test all adult sheep at the routine test and not just a proportion of the flock and some countries require annual testing to be done. Lab charges for the MV test are usually significantly more expensive e.g. 5-8 euros per sheep. Retests are often required and additional investigation tests can cost in the region of 50 euros each. The ELISA and AGID blood tests that we use here are also used in Europe as the routine screen. Our aim is to provide an effective, cost efficient MV accreditation scheme for British flocks. Clothing and MV/CAE risk Although main spread of MV virus is via nose to nose contact the virus can also spread on clothing and equipment. We advise that a separate set of clothing is worn when working with accredited stock. Ensure any equipment is thoroughly cleansed and disinfected and it is recommended that a separate set of drench guns, taggers, needles, etc are used for accredited stock. The EAE status of recipients should also be considered and EAE accredited ewes should be used to reduce the risk of them aborting valuable embryo lambs due to EAE. Scrapie monitored flocks can only use recipients that are Scrapie monitored. Don t risk the MV accredited status of your flock by using non-accredited ewes as embryo recipients. It is not just your flock that is being put at risk. 5
MV Testing Protocol Last year we changed the primary blood test from AGIDT to ELISA. The change was made to maintain a reliable service and contain costs. The change went well and we can reassure members that there was no increase in numbers of test failures as a result of the change. The new procedure in the lab is : 1) Initial testing for antibodies in pools (of 4 samples) by ELISA 2) If negative that is a clear test. 3) If a pool is positive or inconclusive the individual samples are tested by AGIDT. 4) If a sample is positive in AGIDT then it is tested in triplicate by AGIDT and again by ELISA. As you can see, there is a rigorous testing protocol, before a flock is failed. The decision to fail a flock is never taken lightly. Flock failures are based on positive AGIDT this has always been the case. We recognise that if a flock loses its status considerable distress and cost are incurred. Inspections at shows and sales A proportion of all shows and sales held in the country are inspected each year as are a number of farms. The inspections are conducted by a team of inspectors independent of PSGHS and the inspections are paid from the membership fee. If you have an inspection on your farm you will not be charged for it. Inspections are necessary to maintain members confidence in the integrity of the MV/CAE accreditation scheme by ensuring that non-compliance issues do not impact on members flocks. The most common non-compliance the inspectors find when they visit farmers is inadequate separation between accredited and non-accredited stock. This may be at boundaries, within the farm or at the perimeter. The inspectors also find that many farms do not have a dedicated set of taggers or drench gun for the accredited stock. The MV virus is easily spread on this equipment. It is advised to do so otherwise the equipment should be thoroughly washed and disinfected before and after use. Note washing alone is not sufficient. If when you attend shows and sales, you become aware of situations that may create a risk to the health of your stock, please bring these concerns to the attention of the show secretary or the auctioneers. In addition please telephone the manager of PSGHS on 01467 625385. 6
Added Animals Extra Testing A requirement of MV/CAE accreditation scheme is that added animals i.e. purchased ewes and rams are tested within a year of purchase for flocks on three yearly testing. DO NOT WAIT UNTIL YOUR NEXT ROUTINE TEST. The requirement is there to protect your valued accreditation. We recommend that show stock are tested regularly e.g. at start and end of show season. The scheme requirements and our recommendations are all about managing the risk to your flock. The MV/CAE Scheme is an insurance policy to help to protect your valuable assets. Are you doing MV/CAE test correctly? All too often we have to ask members to call out their vet again to test more sheep as they have tested insufficient numbers or they have not tested rams or added animals. The number to test is a statistical proportion of the flock and is set to minimise the risk of missing infection at an early stage. In other words, testing too few and we may miss evidence of disease. The numbers to test are governed by flock size and a table is sent to you along with the request to test. All rams over 18 months old used in the last or current breeding season must be included. Any sheep over 12 months old that have been bought in since the previous test must be tested over and above the number in the table. If you keep sheep in completely separate groups you must sample from each group rather than just the most convenient one. Commercial Sheep and MV Our experience is that the risk of having a breakdown with MV in an accredited flock where non-accredited sheep are present on the same holding is 2.3 times higher than on a holding with only accredited stock. As well as ensuring that accredited and non-accredited flocks are separate it may be worthwhile for your peace of mind to routinely test some commercial (non-accredited) stock to assess risk. The ideal ewes to test are the thinner culls and 12 of these could be tested for 35 +vat (plus the vet cost of sampling). OR, you may find is preferable to try and accredit your whole flock. If breeding home-bred replacements or replacements for sale this may be worthwhile due to the increasing demand for accredited commercial stock. Scrapie Monitoring Scheme (SMS) abide by the rules Compliance with the rules of the SMS are strictly enforced. 1) It is not permitted to purchase rams into SMS flocks from non-sms flocks although, if they are ARR/ARR an exception is made. Bucks cannot be purchased from non-sms herds. 2) All female replacements must be from other SMS flocks or be of ARR/ARR genotype. 3) Fallen stock i.e. animals dead on the farm and over 18 months of age, should be submitted to the nearest SAC/AHLVA lab for testing. Remember, if you lose your status it will be at least three years before you can get it back. Can you afford the risk? 7
Poor response to treatment for Liver Fluke? Farmers in many parts of the country have been struggling to control liver fluke this winter. The level of infection has been high as a result of consecutive wet summers. In some cases treatment has failed to prevent ongoing deaths and loss of condition. There are many reasons that could explain why treatment appears not to work and it can be difficult to work out what the problem is. Underdosing If the dosing gun is not dispensing the correct amount of medicine or the weight of the animal is underestimated. Incorrect storage/administration if the medicine is out of date, mixed with another product before being given or the dose is not given over the back of the tongue. Wrong product used Not all fluke treatments kill all ages of fluke in the liver. In autumn and early winter products MUST be able to kill immature fluke. Triclabendazole is the best at this, (see later). Products that contain oxyclozanide, (e.g Levafas Diamond, Downland Fluke and Worm), albendazole, (e.g. Albex, Ovispec), or clorsulon, (e.g Ivomec S) only kill adult fluke are more suitable for use in late spring/early summer. Wrong type of fluke targeted Liver fluke is a massive welfare and economic problem particularly in sheep. In comparison rumen fluke is currently of minor importance. Oxyclozanide is the treatment for rumen fluke but will only kill adult liver fluke. Products containing oxyclozanide are NOT suitable for use in the autumn and early winter. Re-infection following treatment Treatments for liver fluke are not long acting and stock can become reinfected with fluke the day after dosing. This has been a problem in 2012 because the level of infection on some pastures is so high. Deaths occurring from 2 or more weeks post treatment can be due to high levels of re-infection. Some sheep have had to be housed because of this. Dosing intervals too long Similar to the previous point. Extra doses should be given when the risk of disease is high. Fluke forecasts are based on the amount of summer rainfall. They are published in the press and can also be found at www.nadis.org.uk. For example, in 2010 and 2011 some flocks that routinely dosed in mid October and late January started to lose sheep in December/early January. On some farms this is likely to be a problem again this year unless an extra dose is given. Severe liver damage This may be a problem in some cases where products containing Triclabendazole have been used, (e.g. Fasinex, Combinex, Tribex, Triclfas, Triclamox). Severe destruction of the liver by large numbers of fluke may reduce the effectiveness of triclabendazole. All these possibilities should be ruled out as far as possible before the final point is considered. Resistance Liver fluke that are resistant to a medicine survive treatment with the correct dose of product. Their offspring will also be resistant. Resistance to triclabendazole has been confirmed on some farms. This is a problem because, if working properly, triclabendazole is the best treatment for sheep in the autumn particularly following a wet summer. This is because it is the only medicine that will kill all ages of fluke in the liver. It is important to know whether triclabendazole is effective on your farm. Carrying out testing in the first half of 2013* to check whether it is working correctly will provide you with useful information for next autumn - particularly if we have another wet summer. Testing should be carried out as follows: Weigh and mark 6 to10 sheep. Collect faeces from each animal and place in INDIVIDUALLY labelled bags or pots. Check that the dosing gun is dispensing the correct amount of medicine. Administer the correct dose of product. Deliver samples to your nearest SAC Veterinary Laboratory or to your vet for posting. 3 weeks later collect faeces from the same animals as above. (If it is not possible to do all of the above then only collecting 6 to10 samples 3 weeks after treatment will provide some information. This testing may also be carried out after treatment with products that contain closantel e.g. Flukiver, Closamectin). The samples will be pooled at the lab and checked for fluke eggs. Adult fluke need to be present in the livers for the testing to be useful. If in doubt speak to your vet about the best time to carry out sampling. Do not carry out this testing if the welfare of the sheep will be put at risk. * Products containing triclabendazole are not recommended for treatment of the whole flock in late spring/early summer. They are best kept for when they are most needed in autumn. Note: The SCOPS 2012 Anthelmintics listing is an up-to-date list of products to kill fluke and worms. It is on the SCOPS website (www.scops.org.uk) 8