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OTC_Autumn_p36_Over the Counter28-2#2E9D9D.qxd 19/10/2012 18:31 Page 36 take 3 EXPERTS
TECHNICAL TOPIC – LIVER FLUKE UPDATE Ask the Expert. Lesley Stubbings of SCOPS
Advising on liver fluke control – some practical steps
With a very high risk of liver fluke disease this autumn and winter in grazing animals, many
farmers need help choosing the best control measures and treatments, Lesley Stubbings warns
Some will be at risk for the lack of aftermaths and wettest parts will help.
first time because of the changed grazing patterns all Housing post-treatment is persistent wet weather. For need to be considered.
another management tactic, those who may be used to Don't forget that poaching, particularly for cattle.
the disease, flooding, water- particularly by cattle, pro- Longer term the provision logging and severe poaching vides a habitat for snails in of water troughs as an could bring new areas of areas that may not normally alternative to muddy drink- risk compared with other be considered a risk.
ing places should be consid- years. Dealing with the risk ered. Taking action early can liver fluke egg detection (nitroxynil) weeks post- on individual farms can be have significant impact on tests to establish the pres- housing provides an alterna- complex, involving manage- the level of challenge for ence of adult fluke. The vet tive to TCBZ. Clorsulon can ment actions, diagnosis, Simply keeping stock off the stock later in the year and can also carry out blood also be used for cattle but monitoring and treatments.
wettest fields can signifi- into the next season.
tests which indicate remember that this is a cantly reduce the risk from whether animals have been fluke. When animals have exposed to liver fluke to In all cases, the need to In addition to wet ground been treated, a move to a help with diagnosis. Bulk move the animals to low conditions, higher stocking drier area will reduce the Farmers must be encour- milk tests can also be used risk grazing (or house) post- rates due to larger numbers chances of re-infection. aged to use all the sources for dairy cows and goats treatment is essential. Fail- of sheep remaining on If wet pastures cannot be of information available.
(see www.scops.org.uk for ure to do so will result in farms after a poor season, avoided then fencing off the Even at relatively low levels, more details).
re-infection and the risk of the chronic form of the dis- clinical disease, and the need ease eats into profits.
for further treatments. Investigate deaths. A post- Dosing in the spring to mortem examination will is the only active capable of remove egg laying adult Pre Tupping. usually give a very clear killing the majority of imma- fluke will reduce infection Proven track record.
indication of the presence ture fluke (down to two on the pastures later in the Safe and proven selenium,
of liver fluke. Outbreaks of days old in sheep; two season. In this case an adul- iodine, cobalt and copper
acute liver fluke disease give weeks old in cattle). This ticide such as albendazole little or no warning.
makes it the drug of choice can normally be used, Reliably delivering between
Abattoir feedback on liver when there is a risk of reserving TCBZ for use in 5 and 6 months cover.
rejections is invaluable acute liver fluke disease information. Farmers need (unless there is evidence of to be encouraged to push (NB: Check data sheets very Closantel will kill fluke
carefully. There are significant Clinical signs – in cases of over five weeks of age in variations in activity and with- chronic liver fluke disease sheep. If used as an alterna- drawal periods between prod- these are very important.
tive to TCBZ then two ucts and between use in They include weight loss treatments will be required sheep or cattle.) and ill-thrift, sudden death, at an interval of 10-12 Do not give Copinox® to copper susceptible breeds of sheep.
oedema under the chin weeks (in high risk years like *Resistance to TCBZ has had a (bottle jaw), anaemia, 2012-13 re-treatment may high profile recently and there abdominal pain and respira- be required after just six are now confirmed cases in the tory distress.
weeks and animals should be UK. However, many suspected Performance indicators moved to lower risk (drier) cases are associated with re- such as body condition areas after the first treat- infection and poor treatment more information.
score (BCS), liveweight ment. Nitroxynil also
gains in lambs and young requires two treatments there is a danger of over- cattle, milk yields and scan- with a minimum interval of reaction. This in turn can create ning results are also very seven weeks between them.
problems both in terms of dif er- Animax Ltd
useful and help to underline Housing can be a useful
ing strategies for control, but also Shepherds Grove West the production losses (cost) tool, particularly for cattle.
selecting for resistance to these Stanton, Bury St. Edmunds to the farmer of undiag- Where the risk of acute chemicals. The decision must be Suffolk, IP31 2AR nosed disease.
disease (high levels of fluke) based on a drench check fol- veterinary technology Veterinary tests – farmers is low, delaying treatment lowed by an FECRT under vet- Tel: +44 (0) 1359 252 181
should ask their vet about until six (closantel) or seven 36 OvertheCounter Autumn 2012
THE NATIONAL MAGAZINE FOR ANIMAL HEALTH ADVISERS & COUNTRY STORE RETAILERS OTC_autumn_p37-38 Merial Meet the Parasite_Layout_1 19/10/2012 11:52 Page 37 KEEP FOR REFERENCE
MEET THE PARASITE
Part Series 4 – Meet the liver fluke
several times, ultimately developing into cer- summer disease is likely to be higher when INTRODUCTION: Welcome to the fourth in
cariae. Each individual miracidium entering a there have been high levels of fluke the previ- a series of articles in which we invite you to
snail can result in 600 cercariae leaving it.
‘meet' some of the most common livestock,
ous winter. Although the milder, wetter pet and equine parasites. We hope that
��� Cercariae attach themselves to blades of weather of recent years has resulted in these articles will be a useful reference
grass, where they encyst to form metacer- increased reports of summer fluke disease, resource for you both now and in future.
cariae. These cysts are the infective form of the winter disease remains the most common.
parasite, picked up by grazing animals.
��� Once eaten, the cysts break open to SIGNS AND EFFECTS OF LIVER
release the immature fluke which travel to the liver. They tunnel through the liver tissue, enter The disease can be clinical (ie obvious symp- the small bile ducts where they further toms are noticed) or sub-clinical.
mature, then ultimately move into the largerbile ducts and occasionally the gall bladder, to Acute fasciolosis
Associated with the mass migration of early
complete their development and become the immature fluke stages through the liver, this adult egg-laying fluke stages.
can result in death of affected animals. This ��� The time taken from picking up fluke infec- form of disease tends to be far more common tion to the adult egg-laying stage being reached in sheep than cattle. is approximately eight to 10 weeks in sheepand 10-12 weeks in cattle.
��� Similarly, the time taken from fluke eggs Associated with the presence of adult fluke in being deposited on the pasture to the infective the bile ducts of the liver, affected animals cysts being formed is about 12 weeks. show signs such as weight loss, weakness asso- Merial Animal Health has recently produced ciated with anaemia, jaundice and bottle jaw. Copyright Merial Animal Health a fascinating DVD which shows unique footageof the parasite's life cycle, including miracidia Sub-clinical disease can be more difficult to The liver fluke parasite, Fasciola hepatica, is detect, as there are no visible signs of infection.
✁ responsible for causing the disease fasciolosis hatching from the egg and cercariae swimming However, even low levels of fluke infection can or ‘fluke'. The parasite is not species specific around the snail intermediate host, as well as cause significant reductions in productivity: and can affect both cattle and sheep, as well as live fluke in the liver. Talk to your Merial area In sheep, a 10% reduction in weight gain of other grazing animals, such as horses, deer and business development manager for more ewes, 10% reduction in multiple births, a 5% rabbits. Animals do not develop an effective reduction in the birth weight of lambs and a immunity to liver fluke, such that both adult 30% reduction in the weight gain of lambs.
and young animals are equally at risk from In young cattle weight gain reduced by approximately 1.2kg per week and feed intake According to the latest figures from the by up to 11% compared to treated cattle2.
Food Standards Agency (FSA)1 in 2011, more These factors add days to the time it takes than 22% of cattle and over 6% of sheep sent farmers to finish their cattle, with every extra for slaughter had liver damage associated with day costing them money. liver fluke infection. Indeed the milder, wetter In addition to affecting productivity, fluke infec- weather of recent years has increased the geo- tion can increase the susceptibility of animals to graphical spread, risk period and incidence of other infections, such as clostridial disease.
fasciolosis. Furthermore, the exceptionally highrainfall of 2012 is likely to result in a very high DIAGNOSING LIVER FLUKE
fluke challenge in many parts of the UK this Diagnosis of liver fluke can be difficult. Faeces autumn and winter. It is therefore even more can be examined for the presence of fluke important to be aware of this parasite, the eggs, which indicates the presence of adult signs of disease and the available treatment SEASONAL PASTURE INFECTION
fluke infection. However, eggs are released intermittently so it is possible to have false Generally, infective cysts (metacercariae) are negative sample results. THE LIFE CYCLE OF LIVER FLUKE
found on the pasture at two main times of year: The presence of fluke in the liver and bile Fasciolosis occurs when animals become • August to October: These cysts come from ducts can be identified by alterations in infected by eating infective cysts, called metac- snails that were infected during the summer enzymes detected in blood samples but this ercariae, found on blades of grass on pastures.
months, either from eggs passed in the faeces can be costly and blood sampling is invasive. A The life cycle of the parasite is as follows: of infected grazing animals, or from eggs that really useful source of information on the fluke ��� Adult fluke live in the bile ducts of the host have over-wintered on the pasture. They result status of cattle and sheep going for slaughter is animal's liver and produce eggs, which are in winter disease in cattle and sheep. The risk feedback from the abattoir. passed out with the faeces onto the pasture.
of winter disease can therefore be reduced by Liver damage associated with fluke infection Each adult fluke is capable of laying up to reducing the number of eggs shed by grazing can result in permanent tissue damage, so even 25,000 eggs per day.
after effective treatment has been given, the ��� Eggs hatch to release miracidia, which must • May to July: These cysts come from snails lesions remain. As a result, affected livers will find and enter the mud snail intermediate host that were infected during the autumn and win- (Galba truncatula) within three hours of hatching.
ter months of the previous year. They result in The possibility of fluke infection should be ��� Within the snail host, miracidia multiply summer disease in cattle and sheep. This means considered in animals which fail to thrive or THE NATIONAL MAGAZINE FOR ANIMAL HEALTH ADVISERS & COUNTRY STORE RETAILERS OvertheCounter Autumn 2012 37
OTC_autumn_p37-38 Merial Meet the Parasite_Layout_1 19/10/2012 11:52 Page 38 KEEP FOR REFERENCE
take longer to reach target weight, even in east-ern areas of Britain where this parasite has not traditionally been a problem.
TREATING LIVER FLUKE
Triclabendazole (drench) Triclabendazole (drench) Clearly any treatment regime would benefitfrom trying to prevent livestock from grazing in Closantel (drench) snail habitats, or the reduction or removal of Nitroxynil (injection) – Trodax® Nitroxynil (injection) – Trodax® snail habitats (muddy areas) through drainage.
However, neither of these options is generallypractical on farms. Therefore, the strategic useof flukicides tends to be the accepted way to Wormers at increased dose rates/combination products containing a flukicide:
manage liver fluke.
BEEF CATTLE
Many farmers who know there is fluke present
Albendazole or ricobendazole worm Albendazole oral worm drenches at on the farm are aware of the risks of fluke dis- drenches at increased dose rates increased dose rates ease during the autumn and winter and willroutinely treat their cattle during the housing Combined fluke and worm oral drenches Combined fluke and worm oral containing triclabendazole or closantel drenches containing triclabendazole In terms of the precise timing of this housing Combined fluke and worm injectable Combined flukicide (closantel or tri- dose, some advice in the past has centred containing triclabendazole or closantel clabendazole) and endectocide pour-on around delaying treatment for several weeksafter cattle have been housed, to allow for the Combined flukicide (closantel or clorsu- possibility that fluke infection may need to lon) and endectocide injections, eg develop to the late immature/adult stage. However, new research has shown that the vast majority (97%) of fluke are already lateimmature/adult at housing3. the adult stages of fluke, flukicides with activity Based on this evidence, a treatment at hous- These include either fluke-only products, against late immature and adult stage fluke can ing should eliminate the majority of fluke infec- wormers at increased dose rates (to provide be considered for treatment, thus decreasing tion and allow cattle to maximise their growth activity against liver fluke) or combination prod- the potential selection pressures of resistance rates and gain the greatest benefit from feed ucts containing a flukicide and wormer.
development to the active triclabendazole. As during the housing period. When selecting a fluke treatment some factors previously stated, acute disease, which can lead An ‘at grass' fluke treatment eight to 10 to consider are: to deaths in sheep, is associated with the pres- weeks after turnout wil help to reduce the lev- • Species of animal to be treated as certain ence of early immature stage fluke and the only els of fluke eggs shed onto the pasture in the products can be used in both cattle and sheep.
flukicide with activity against early immature spring and summer, which in turn wil help to • Stage of fluke to be treated noting the impor- fluke is triclabendazole. break the fluke life cycle and reduce the risk of tance of the early immature stage at certain Once triclabendazole is no longer effective winter disease in livestock. times of the year in sheep and the importance against early fluke infection, it becomes much of the late immature/adult stages in cattle.
harder to avoid deaths in sheep exposed to • The flukicide active ingredient and any asso- high levels of infection during the autumn and Acute disease can affect sheep in the autumn ciated resistance issues.
so if animals are grazing infected pastures they Repeated exposure of liver fluke to tri- should be treated with triclabendazole at that clabendazole (TCBZ) in either cattle or sheep time. Once the threat from acute infection has can lead to the development of a resistant pop- ABOUT MERIAL reduced, usually from January/February ulation of fluke, which can infect both species.
Merial is a world-leading, innovation-driven onwards, a flukicide with activity against later The real concern with this is that TCBZ animal health company, providing a compre- stages of fluke can be used as necessary. remains the only flukicide effective against early hensive range of products to enhance the However, when high risk from fluke has been immature fluke, which are responsible for acute health, well-being and performance of a wide forecast, it is possible that pastures will remain fluke disease in sheep. range of animals. Merial employs approximately infective later into the winter months, so the As cattle predominantly suffer from either 5,600 people and operates in more than 150 risk of acute disease can extend into sub-clinical or chronic disease associated with countries worldwide. Its 2011 sales were more Remember that liver fluke is not host spe- €2 billion ($2.8 billion). cific; it is the same parasite that affects both cat- Merial is a Sanofi company. tle and sheep. Therefore, where cattle and 1 FSA 20122 Johnson EG, Agri-practice, 1991.
sheep are grazing the same pastures they 3 MacGillivray et al, 2011 23rd International Conference should both be treated against fluke. For further information contact Merial Animal Health Ltd, CM19 5TG or call the Merial Customer Support Centre on 0800 592699. 38 OvertheCounter Autumn 2012
THE NATIONAL MAGAZINE FOR ANIMAL HEALTH ADVISERS & COUNTRY STORE RETAILERS

OTC_Autumn_p39_Over the Counter28-2#2E9D9D.qxd 22/10/2012 18:53 Page 39 VETERINARY REVIEW – SHEEP Golden opportunity for liver fluke
This month is a golden opportunity to revise parts of the complicated life cycle and medical
treatment of the tenacious trematode liver fluke (Fasciola hepatica), Richard Knight advises
clabendazole, oral closantel week immatures. The time processing by the liver to a warm autumnal spell. This and injectable nitroxynil. taken to maturity in the end work properly, then an appar- may occur through to the Westmorland Veterinary Group The first two, albendazole host can vary between eight ent treatment failure may be and ricobendazole, are effec- and 12 weeks, so this is observed. Also, the infection I hope you're keeping up! With only four different tive against adult flukes and where the first error an pressure on sheep is not Yes, it's involved, but by read- medicines available to treat eggs only, so are useful in creep in. At best a product static, but continuous and ing, re-reading and revising the condition in sheep, the treating sub-acute and that will kill adult flukes is dynamic, meaning that all again and again, more folk devil is in the detail of the life chronic fasciolosis, as well as used eight weeks after the through the fluke maturing will get up to speed and give cycle, on-farm conditions and reducing pasture contamina- infection could have started; process, more infection can better quality advice.
the efficacy of products at worst the flukes will be picked up at different against the stage of fluke we Triclabendazole is effective mature four weeks later and rates. It is safer to assume Richard Knight is a
are expecting them to treat. against immature and adult the product may be less than that an animal has fluke of a director at Westmor-
If timing errors creep in at flukes (Fasinex is the only 90% effective, which means certain stage of progression land Veterinary Group
every stage of the process, product to claim effective- that liver damage will still and every stage behind that in Cumbria, Lancashire
then the recommended ness from two days after too, until a reduction in mean and North Yorkshire.
treatment has a limited emergence of immature At the very worst the ani- chance of success but a high flukes), while closantel and mal could be treated 12 to below 10C causes the life expectation placed on it. nitroxynil are effective weeks after the first risk and cycle to cease, either through Let's look at the medi- against later immature flukes suffers a heavy burden of until next spring when the cines, put most of the trade infection, where liver damage temperature increases, or to names aside and focus on the The datasheet for Flukiver has been occurring active ingredients. They are (closantel) gives us a table unchecked before treatment. oral albendazole, oral showing limited effectiveness If a product such as ricobendazole (which is from three-week immatures ricobendazole or triclabenda- albendazole oxide), oral tri- to good kill rates of eight- zole is used, which requires Heavy duty machine
Cattle and Horse clipper
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Source: http://www.overthecounter.cc/pdf/liver_fluke.pdf