Nematode Infections in Sheep 2021 PDF

Nematode and Cestode Infections in Sheep Nematode Infections in Sheep 1.Describe the role of the vet in worm control on sheep farms. 2.Explain the current issues with control of nematode infections in sheep in the UK. 3.Explain how anthelmintic resistance has emerged and how it can be measured. 4....

Nematode and Cestode Infections in Sheep Nematode Infections in Sheep 1.Describe the role of the vet in worm control on sheep farms. 2.Explain the current issues with control of nematode infections in sheep in the UK. 3.Explain how anthelmintic resistance has emerged and how it can be measured. 4.List the 5 anthelmintic groups, describe their modes of action, spectrum of activity and current uses. 5. List and explain the SCOPS principles Vets and advising on parasite control strategies • Devising worm control strategies (Flock Health Plans) • Advising on outbreak parasitic disease occurs • Advising on poor growth in lambs/ thin ewes • Advising when anthelmintic resistance problems occur Current problems with parasite control in sheep U.K • Drug Resistance • The problem: maintain high levels of production in lambs on heavily stocked permanent pasture rely on intensive use of anthelmintic to suppress these parasites. • Lots of sheep on permanent pasture not using pasture rotations • Inappropriate use of anthelmintics • Accumulation of resistant strains not sustainable • Climate change • Mild winters warmer spring summer increased parasite numbers on pasture • increased disease risk • Parasites • Large genomes • Highly polymorphic • Will evolve in response to climate change, management, antihelmintic use Anthelmintic Resistance • Resistance • defined as drug <95% efficacy • Various surveys • • • • ~80% farms have benzimadazole resistant strains ~47% levamisole resistant strains ~30% farms have macrocytic lactone resistant strains Most farms will have some issues with AHR but probably don’t know it. Anthelmintic Resistance • What to do? • Devise sustainable parasite control plans • https://www.scops.org.uk/ • Reducing selection pressure • to slow progression of resistance down • Improve biosecurity • to prevent introduction of resistant strains Common Nematode Infections in Sheep • 20 different species of nematode parasites of sheep commonly found in the UK. • Pathogenicity varies with species, the numbers of nematodes present as well as host factors such as the age of the sheep (maturity), nutritional status and body condition • Nematodirus battus • Telodorsagia circumcincta • Trichostrongylus vitrinus, colubriformis, axei • Bunostomum trigononcephalum • Haemochosis contortus How do they cause disease • Damage lining of guts (reducing absorption) • Remove nutrients • Remove blood (Haemonchus) • Host immune response (host resources and damage) • Clinical signs • • • • • Reduced appetite Poor weight gain/ weight loss Diarrhoea Anaemia Death QUICK REVIEW PARASITOLOGY LIFE CYCLES Basic Life Cycle of nematode parasites of sheep. Telodorsagia, Trichostrongylus, Haemonchus spp. L1 and L2 live in faeces L3 Infective stage, remains in sheath, migrates to pasture If not eaten, consume energy stores and die Winter survive longer Egg to L3 10-12 weeks in early spring or 1-2 weeks in early summer Development L3 to eggs in sheep 16-21Photo days SCOPS 2007 High infectivity pastures summer autumn Species differences • Telodorsagia • Peak early summer • Trichostrongylus • late summer autumn • Haemonchus • not survive well over winter, but very fecund each worm 10,000 eggs per day, warm wet conditions can become infective very quickly • mid spring to late autumn serious outbreaks lambs and ewes Hypobiosis • Teladorsagia, H contortus T axei, interupted development L4 stage inside sheep. Mostly picked up L3 late autumn early winter over winter period. • Teladorsagia- Clinical disease scouring and weight loss in yearling sheep • Pasture contamination in spring and early summer • Main way Haemonchus survives winter Nematodirus battus • Nematodirus battus • Has different epidemiology • Eggs shed by lambs one year, remain on pasture and infect next year lambs • Most hatching and release occurs period of chill followed temperature range of 10C-18C • Change in epidemiology some not now require chill • Cause clinical problems in autumn in lambs • Large numbers L3 hatch simultaneously • severe outbreaks diarrhoea typically 6-12 week old lambs in late spring/ early summer Disease caused by nematodes • Telodorsagia • Type 1- Lambs first grazing season, mid summer onwards • Type 2 -Yearlings winter months, emergence of hypobiotic larvae • Trischostrongylus • black scour • lambs or replacements late summer autumn winter • Haemonchus • • • • • Adults and lambs All parts UK sheep with 5000 nematodes can lose 250ml blood daily Acute regenerative anaemia Chronic hypoproteinaemia, anaemia bottle jaw Sheep Immunity to Nematodes • Provide been exposed to nematodes LAMB should be developing resistance to nematodes around 5-6 months old • Nutrition • Genetics • Stage of production • Peri-parturient immunosuppression • 2-4 weeks before lambing and 6-8 weeks after (end of lactation) • Less in single bearing ewes, reduced by high UDP. Control of nematode infections in sheep Nematode Control Principles 1. 2. 3. 4. Not possible to eliminate infections Balance between sufficient exposure to develop host immunity, but not too much to cause disease Over-reliance on anthelmintic but NOT sustainable!! Apply Sustainable Control Of Parasites in Sheep principles Management of Infectious/Parasitic Disease 1. 2. Biosecurity: preventing disease entry Reduce disease challenge 1. Management 1. 2. 3. 3. Hygiene/pasture management, Ventilation stocking rates 2. Test and cull infected animals 3. Drug treatments:- antibiotics/anthelmintics Improve animals resistance 1. Vaccinate 2. Management 1. 2. 3. 3. Improve nutrition Reduce stress Reduce concurrent disease Breeding ANTIHELMINTICS Antihelmintics Drugs • 5 groups, but lots of companies make them- do not worry about trade names, learn about groups activity and names of drugs within the groups • Benzimadazoles • Levamisole • Macrocytic Lactones • Amino-acetonitrile • Spiroindoles Treatment of PGE Anthelmintic Drugs 1. Benzimadazoles • Tubulin binding, prevents uptake of glucose, ovicidal, 2. Imidazothiazoles (levamisole) • Ganglion blocking drugs, paralysis not ovicidal 3. Macrocyclic lactones • Avermectins and milbemycin, • Block Cl- and GABA channels paralysis 4. Amino-acetonitrile AAD • ACH receptors, paralysis • Monopantel 5. Spiroindoles • Derquantel • nicotinic cholinergic paralysis • Comes with abamectin Special features • Benzimidazoles • • • • • • Broad spectrum round worms Tape worms( not highly clinically significant in sheep) Albendazole (also fluke) N battus Some hypobiosed larvae Most resistance –it may not work !! • Macrocytic Lactones • Round worms and mites • Moxidectin • Persistent activity Telodorsagia Haemonchus 5 weeks, one preparation 14-16 weeks • All injectable forms active against mange mites • Group 4 and 5 new generation • Do not keep for best, should be used regularly as part of worm control plan, especially at quarantine dose Resistance to Anthelmintic Drugs • Genes conferring anthelmintic resistance occur naturally within a whole population • Big genomes, polymorphic • Key Factors influencing the development of Anthelmintic Resistance in a population are • • • • Proportion of population exposed to treatment “in refugia” Treatment frequency over use Under dosing Biosecurity Anthelmintic Resistance • Resistance • defined as drug <95% efficacy How do we know if anthelmintic resistance is present? • Often undetected • Clinical signs • Lamb growth rates • EID regular weighing DLWG really useful • Diarrhoea • Death • Test for Anthelmintic resistance • FEC should be reduced to zero after administration of drug. If reduction is 95% or less resistance has been detected. (FECRT, LDT) Testing for Anthelmintic Resistance • Drench test • Cheap, farm practice useful indicator • FEC 7-14 days post treatment (depending on drug) • FECRT • • • • • 10 lambs per group Weigh and mark Pre-treatment FEC Accurate dose drug 7-14 days post treatment (depending on drug used) FEC • Calculate mean reduction in FEC >95% • https://www.scops.org.uk/internalparasites/worms/testing-forresistance/ Testing for Anthelmintic Resistance Other tests (specialist labs) • Egg hatch assay • Larval development test • Larval migration test • Adult motility • Larval Feeding Inhibition Assay • BZ and LV • Molecular markers for BZ Manage Resistance • Avoid over use • Reduce treatments • Adult sheep • target treatments • FEC weighing sheep grazing management • Scab control • Avoid under dosing • • • • • Weigh and dose by group Gun calibration Dosing technique Yard 24 hours post treatment NO GOATS • Leave unexposed population • “in refugia” • Dilution post treatment • Biosecurity • Don’t bring in new strains “In refugia” • If we dose the sheep with anthelmintic when the majority of worm population is in the sheep, ie when free living population is lowest rapidly select for resistance. • Autumn, winter, early spring • Often co-incides with lambing time and sheep scab treatments • Ewes dose at lambing only do triplets, thin ewes, young ewes (ie don’t treat fit singles and fit twin bearing ewes) “In refugia” Post treatment dilution of resistant worms • Don’t dose and move • Treat animals with anthelmintics then move onto low risk pasture, clean pasture will only be populated with resistant strains • Dose and return to contaminated pasture Sustainable Control of Parasites in Sheep Helping sheep farmers to maximise productivity by sustainably controlling parasites https://www.scops.org.uk/ SCOPS Principles 1. 2. 3. 4. Always make sure treatment is fully effective Reduce dependence on anthelmintics using management and monitoring Avoid bringing in resistant worms and/or other parasites by following a robust quarantine routine. Test for anthelmintic resistance Minimise the selection for worms that are resistant to anthelmintics when you treat sheep. 1. Always make sure treatment is fully effective • Avoid Under-dosing • Pick the heaviest sheep in group, weigh it • If big range in sizes then sub group • Dose to the heaviest • Check dosing gun • Dose correctly (technique video • Test for resistance • Choose correct product for task 1. Choose correct product for task • 5 classes of wormers • Most are broad spectrum • Use all of them (rotate through different groups) • Quarantine / biosecurity use new classes • Avoid combination products e.g flukicide and nematode antihelminitic unless actually required • Check for Resistance Management of Infectious/Parasitic Disease 1. 2. Biosecurity: preventing disease entry Reduce disease challenge 1. Management 1. 2. 3. 3. Hygiene/pasture management Ventilation stocking rates 2. Test and cull infected animals 3. Drug treatments:- antibiotics/anthelmintics Improve animals resistance 1. Vaccinate 2. Management 1. 2. 3. 3. Improve nutrition Reduce stress Reduce concurrent disease Breeding 2. Reduce reliance on anthelmintics Adult sheep • Generally should have acquired immunity to nematodes by time sheep adult • Reduce pasture contamination for lambs at lambing time. • Lambing Dose • Mainly done to reduce pasture contamination for lambs • Leave portion untreated (only treat thin sheep, triplet bearing ewes, shearlings ewe lambs, ie not fit singles, twin bearing ewes ) • Tupping time dose to ewes- NOT routine to dose everything! • Only treat thin ones, ideally FEC first 2. Reduce reliance on anthelmintics Grazing lambs • Weaned lambs move lambs on to lower risk pastures e.g aftermath, cattle grazing, group by age • Leave ewes on higher risk ones ie pastures used by ewes and lambs in spring • • • • • • Mixed grazing other species Good plane of nutrition (protein) Manage concurrent disease (coccidiosis) Genetic selection (EBV for resistance to nematodes) Bioactive forages Don’t use suppressive frequent dosing regimes target use of anthelmintics to when actually required • FEC • LWG monitoring • Forecasts • FAMANCHA FEC Interpretation • Count depends on species • Egg production by nematodes varies by time of year • Nematodirus egg counts not strongly related • Aid to diagnosis not necessarily 100% • Use history clinical signs time of year, pasture risk 2. Reduce reliance on anthelmintics • Use FEC to guide dosing. • Sample every 2-4 weeks • Fresh dung less than 1 hour old • Take at least 10 individual samples per group. For larger groups 10% is ideal (can use pooled samples) • Sheep should be healthy and have had full access to pasture and/or feed before sampling, otherwise the FEC will be difficult to interpret. • Samples taken must be completely random. • Make sure the air is expelled from the bag and keep the sample cool (preferably hygienically in a fridge) and get it to the practice or lab within 48 hours • Interpret according to clinical signs for sheep • Not suitable for nematodirus monitoring 2. Reduce reliance on anthelmintics • Nematodirus • Cant use FEC to target treatment as false negatives due to larval stages causing disease • Use low risk pastures for lambing and in spring • Use forecast • Preventative dosing with BZ wormer (white drench) Famancha test for haemonchosis • Use pallor of eye mucous membranes • Other clinical signs • • • • • Weakness Collapse Hyperpneoa Tachycardia Sudden death Estimating Pasture Risk SCOPS SPRING HIGH MEDIUM LOW Ewes and lambs grazed previous year Grazed only by adult non lactating sheep the previous year Crops Adult non lactating sheep in spring Cattle or conservation in first half of grazing season For Nematodirus carried ewes and lams in the previous spring Cattle or conservation in previous year Store lambs previous autumn winter LATE JUNE Ewes and lambs in spring Cattle or 3. Biosecurity/Quarantine Strategies • Really important way for resistance to spread • All brought on sheep • Dose • Monopantel (Zolvix) and/ or Derquantel and Abamectin (Startec) • Plus Moxidectin, Doramectin (to treat scab) • Hold off pasture 24-48 hours allow treatment to work • Return to contaminated pasture • VIDEO • https://www.youtube.com/watch?v=mOmOhEXmAL0&list=PLtI mzmj0GoB5p-rIFrzl0YFozWzHgk-ly&index=10 4. Minimise the selection for resistance to anthelmintics when you treat sheep. • Don’t dose and move • Dose leave on contaminated pasture couple days then move • Only treat thin, triplet bearing and young sheep at lambing • Avoid long acting products if possible Example Nematode Parasite Control Plans No blueprint No one size fits all General idea of how to approach different systems for parasite control January Lambing Risks Control • Housed, finished inside • Housed • Or • Housed then finished outside early season (Spring – May/June) • no contact with nematodes no drenching necessary ewes or lambs • Finished outside • Nematodirus risk (April/May) • Low risk pasture • Watch forecast • Dose BZ • Main season worms (June onwards) • Assess risk for main season worms depending on when turned out to pasture, how long for and pasture risk Feb March Lambing Creep Fed at Grass Risk Control • Housed for lambing then turned out March finished by July • Nematodirus • Nematodirus risk (April/May) • Tend to be high stocking concurrent coccidiosis • May or may not be finished and sold before main season worms (Telodorsagia/Trichostrongyles/ Haemonchus season) • Low risk pasture • Watch forecast • Dose BZ • Main season worms (June onwards) • Assess risk for main season worms depending on when turned out to pasture, how long for and pasture risk • • • • • Low risk pasture Good plane nutrition Other strategies to reduce risk FEC/LWG monitoring Monitor for resistance March- May Lambing Risks Control • Lamb in March • Outside grazing from March April, finished July onwards (often through to autumn) • Nematodirus • Telodorsagia/Trichostrongyle s/Haemonchus season (July onwards) • Nematodirus risk (April/May) • Low risk pasture • Watch forecast • Dose BZ • Main season worms (June onwards) • • • • • Low risk pasture Good plane nutrition Other strategies to reduce risk FEC/LWG monitoring Monitor for resistance Store Lambs Risk Control • Variety sources • High burdens on grass • Changes in nutrition • Grazing summer to late autumn then maybe housed • High risk for worms • High risk for anthelmintic resistance • Quarantine treatments • Low risk pasture • Good nutrition levels • Monitor for resistance (drench test post treatments) • Close monitoring • FEC or LWG throughout autumn and winter Hill Flocks Risk Control • Stocking rates are low generally so low risk but when brought down to low ground can be high stocking rates and high risk worms • Reduced opportunities to handle • Often routinely dosed when sheep are handled • Consider when in high risk pastures and use this to plan dosing regimes lambs and ewes Tapeworm –Intermediate hosts (Cestode infections) Common Name Intermediate Host Name Final Host Name Clinical Significance Sheep Tapeworm Soil Mite Sheep Monezia expansa ? pathogenic Thin Necked Bladder Worm Sheep (Cysticercus tenucollis) Dog (Taenia hydatigena) Liver damage, condemnations at slaughter house Sheep Bladder Worm Sheep (Cysticercus ovis) Dog (Taenia ovis) Cysts cause muscle damage and condemnation at S/H Gid Worm Sheep (Coenuris cerebralis) Dog (Taenia multiceps) Neurological disease in sheep (depends on location) Hydatid Sheep (Echinococcus granulosus Dog (Echinococcus granulosus) Cysts in liver and lungs S/H condemnation Zoonosis Tapeworm Control Parasite Control Sheep Control in Dog Control in Dog Sheep Monezia expansa Worm with Benzimadazoles N/A Dog (Taenia hydatigena) None Treat praziquantel every 6 weeks Do not allow dogs to stray onto pasture Do not allow access to sheep carcasses Dog (Taenia ovis) None Treat praziquantel every 6 weeks Do not allow dogs to stray onto pasture Do not allow access to sheep carcasses Dog (Taenia multiceps) Surgical removal of cysts Treat praziquantel every 6 weeks Do not allow dogs to stray onto pasture Do not allow access to sheep carcasses Dog (Echinococcus granulosus) None Treat praziquantel every 6 weeks Do not allow dogs to stray onto pasture Do not allow access to sheep carcasses Tapeworm (Cestode) Infections in Sheep • Monezia expansa • Sheep is final host • ? Pathogenic , farmers notice because of segments in poo • Treat BZ References • Sustainable Control of Parasites in Sheep • http://www.scops.org.uk/ • Know Your Anthelmintics Handout on CANVAS