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Internal Parasite Management in Pasture-Based Sheep

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Internal parasites (GI worms) are the primary health problem affecting sheep. The barber pole worm (Haemonchus contortus) is the worm of primary concern. It is a blood-sucking parasite that causes blood and protein loss (anemia) and edema (“bottle jaw”). Worms have developed resistance to most of the anthelmintics (dewormers). Therefore, it is important to worm only as needed. Bringing sheep onto “virgin land” require careful consideration when managing parasites. Studies have found that they can survive on a site for 180 after sheep leave. Rotational grazing is important, not only to have an intensive controlled “mow”, but in controlling parasites.

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Internal Parasite Management in Pasture-Based Sheep

  1. 1. UrbanShepherds.org Internal Parasite Management in Pasture-Based Sheep Kathy Bielek kathy.bielek@gmail.com
  2. 2. UrbanShepherds.org Acknowledgements • Dr. William Shulaw (OSU Extension Veterinarian) • Rory Lewandowski (OSU Extension, Wayne County)
  3. 3. UrbanShepherds.org Cost of Parasites • Reduced milk production in ewes • Slower lamb growth • Appetite suppression • Reduced wool production and quality • Reduced fertility • Less immunity to other diseases • Lamb deaths
  4. 4. UrbanShepherds.org The “costs” of parasitism • “…thus acquisition of immunity in the young lamb has a higher priority than growth, but in the adult, expression of immunity will have lower priority than reproductive effort…” Sykes and Coop New Zealand Veterinary Journal 2001;49:222-226.
  5. 5. UrbanShepherds.org How do we “manage” internal parasites in sheep and goats? Approaches Conquer or Eliminate Co-exist Avoid
  6. 6. UrbanShepherds.org Conquer by Chemicals • Requires regular, by the calendar, drenching with a chemical dewormer. • Requires an effective chemical dewormer • Requires development of new chemical brought to market about every 5 years
  7. 7. UrbanShepherds.org Drug resistance: How Does It Develop? • Drug resistance develops as a genetic trait. •Once resistance is present, it is likely to be permanent. • Resistance develops when worms have frequent exposure to a drug. • A major cause of drug resistance is under dosing. • underestimating weight • incorrect dose calculation • incorrect dilution of products • improperly calibrated equipment • Treatment of ALL animals and movement to a “safe” or “clean” pasture
  8. 8. UrbanShepherds.org TREATMENT RESISTANCE SELECTION IN ADULT WORMS
  9. 9. UrbanShepherds.org 100% - and survivors of TX no refugia of unselected worms On the new pasture
  10. 10. UrbanShepherds.org 5% 95% Refugia: parasites not exposed to chemicals and selection pressure
  11. 11. UrbanShepherds.org Log of conc. ng/ml 0 10 20 30 40 50 60 70 from: Shoop et al. 1997. J Vet Pharmacol Therap. 20 (Suppl. 1), 12-14 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 moxidectin ivermectin 200 ug/kg oral dose 35 days of selection for resistance in larvae acquired from pasture
  12. 12. UrbanShepherds.org You may not think you have a problem • Resistance is relative – Not all worms on farm are resistant • Killing some worms may relieve disease symptoms – Clinically it appears that the treatment was effective
  13. 13. UrbanShepherds.org Drug Resistance All control programs that rely strictly on the use of chemical dewormers will eventually fail as a result of development of resistance. The question is how soon it will happen on YOUR farm, or how well can you develop strategies that minimize drug use.
  14. 14. UrbanShepherds.org Avoid Parasites if Possible • Especially useful when pasture options or acreage are limited • Fall lambing • Early wean, raise lambs in barn or feedlot • France: lactating ewes to pasture during the day, back to barn at night. Lambs remain in the barn. (Also Wooster bulletin from April, 1900) • Goats: Consider the use of browse and brush to avoid contact with the parasite.
  15. 15. UrbanShepherds.org Early weaning and dry lot
  16. 16. UrbanShepherds.org Management Concepts for co-existing • Nature bats last, worms will adapt. • Must co-exist with the parasites, they are not going away. • Lambs/kids are the weak link, most susceptible to parasite infections. In a pasture system, lamb and kid management is labor intensive. • Dry ewes/does have good level of resistance to parasite infections and require low level of management. • Option: minimize lamb/kid time on the farm or on pasture.
  17. 17. UrbanShepherds.org Hemonchus Telodorsagia (Ostertagia) Trichostrongylus Cooperia Nematodirus About one-half inch
  18. 18. UrbanShepherds.org
  19. 19. UrbanShepherds.org Referred to as “L3”
  20. 20. UrbanShepherds.org egg to L3 >3.5 days L3 to eggs in feces – 19 to 21 days complete cycle – 24 to 25 days L3s tolerate cold well
  21. 21. UrbanShepherds.org
  22. 22. UrbanShepherds.org Haemonchus contortus will survive • Adult female can produce 5000 eggs per day • If each animal has 500 female worms • 50 animals can contaminate your pastures with approximately 1 billion eggs per week!
  23. 23. UrbanShepherds.org On Farm Research:Lessons Learned • Lambs/kids are very susceptible to parasite infections • Overwintered larvae must be considered • Making more than one grazing pass across grass/legume paddocks with lambs/kids has the potential to significantly increase the worm load • Lambs/kids need some “safe” pastures
  24. 24. UrbanShepherds.org • Farm #1 – All dewormed 7/20/06 – Rotated across previously grazed pastures  Farm #2  All dewormed 7/16/06  Moved to clean pasture every week Factors influencing FEC counts: Pasture Management Matters Lamb ID Sire ID FAMACHA FEC Lamb ID Sire ID FAMACHA FEC 603 A 3 300 11 B 2 0 612 A 3 0 14 B 2 0 613 A 1 250 46 B 1 0 616 A 3 1100 5 B 1 50 638 A 2 300 10 B 1 0 639 A 3 500 49 B 1 0 640 A 3 3450 6 B 3 50 641 A 3 1800 24 B 2 0 645 A 3 250 29 B 2 150 646 A 3 3150 3 B 2 0 Sire A Average 3 1110 Sire B Average 2 25 Farm #2 - 8/19/06Farm #1 - 8/16/06
  25. 25. UrbanShepherds.org What is safe pasture for lambs? • Young lambs/kids do not have a developed immune system, any infective L3 larvae they ingest will get multiplied! • One where L3 larva concentration is low: managed so that minimal levels of L3 are ingested. • One where no L3 larvae have survived: a long enough time period has passed that L3 larvae have died. How long? Over-wintered larvae? • One that limits grazing height/How does grazing height influence parasite infection?
  26. 26. UrbanShepherds.org
  27. 27. UrbanShepherds.org Based on farm research results: • Over wintered larvae are a concern. Spring grazing (April/May) of pastures that were used the previous fall (Sept./October) increases the risk of parasite infection. • Lamb/kid nutrition on pasture is a challenge. Nutrition is an important component of parasite management. • There needs to be an effective chemical de-wormer that can be used selectively and as a rescue treatment.
  28. 28. UrbanShepherds.org Possible alternatives to preserve a refugia • treat selectively with FAMACHA, or body condition score; then move • leave heaviest 10-15% untreated; then move • treat all animals with a non-persistent dewormer and leave on contaminated pastures 3-5 days • move, wait a few days, then treat
  29. 29. UrbanShepherds.org Concept Behind Selective Treatment • Every animal in the flock does not have the same parasite numbers/level of infection • 20-30 % of animals harbor most of worms, responsible for most of egg output • Selective treatment targets these animals only • Tools: – FAMACHA – Fecal Egg Counts?
  30. 30. UrbanShepherds.org XXX Farm Daily Egg Output 0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 18000000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 all sheep numberofeggs 103,546,200 eggs per day for just 46 sheep Just 10 (21%) of the lambs excreted 77% of the eggs !! Fall 2000
  31. 31. UrbanShepherds.org 600 epg 50 epg 1150 epg 3150 epg 100 epg 1150 epg 0 epg 1050 epg 5550 epg 0 epg
  32. 32. UrbanShepherds.org The FAMACHA© System • Eye color is correlated with the level of anemia, and to a lesser degree, fecal egg shedding levels • Eye color is an indirect measure of the worm burden – applies to Hemonchus contortus ONLY
  33. 33. UrbanShepherds.org The FAMACHA© System • By selecting only the most heavily infected animals for treatment, we can significantly reduce the number of treated animals while still reducing pasture contamination and providing treatment to the animals that need it most. XXX Farm Daily Egg Output 0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 18000000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 all sheep numberofeggs This approach should slow the development of resistance to dewormers. Refugia
  34. 34. UrbanShepherds.org The FAMACHA© System • current recommendations are to treat: – non-lactating ewes in categories 4 and 5 – lactating ewes and lambs in category 3, 4, or 5 should be treated – goats in categories 3, 4 and 5 – all animals with “bottle jaw”
  35. 35. UrbanShepherds.org
  36. 36. UrbanShepherds.org FAMACHA • In Ohio, the parasite life cycle begins to ramp up in May. • Animals should be scored beginning in May. • If FAMACHA is the only strategy employed, it must be done at least every 14 days, or more frequently, by mid-June. • It can be used in large flocks, by examining subsets of animals.
  37. 37. UrbanShepherds.org TECHNIQUE
  38. 38. UrbanShepherds.org How not to do it !!!
  39. 39. UrbanShepherds.org Always use the card !!!
  40. 40. UrbanShepherds.org score 5/5/08 6/5/08 6/23/08 7/8/08 1 0.77 0.36 0.29 0.09 2 0.23 0.64 0.65 0.42 3 0.00 0.00 0.05 0.42 4 0.00 0.00 0.02 0.05 5 0.00 0.00 0.00 0.02 FAMACHA percentages over time FAMACHA scores by group and over time - 2008 early weaned
  41. 41. UrbanShepherds.org FAMACHA correlation with FEC is good but not perfect FAMACHA average median range in number Score FEC FEC FEC 10 2 6,930 6,000 1,100 to 15,000 30 3 9,998 7,925 2,000 to 26,000 19 4 20,120 19,100 6,000 to 35,000 59 lambs scored and sampled July 4, 2011
  42. 42. UrbanShepherds.org FAMACHA Limitations • Requires some type of handling system • Labor intensive • Can disrupt grazing rotations • Needs a record keeping system that can track trends • Extends effectiveness of chemicals but does not eliminate resistance already present • Limited to Haemonchus contortus detection
  43. 43. UrbanShepherds.org
  44. 44. UrbanShepherds.org
  45. 45. UrbanShepherds.org But wait, I heard that Garlic works as a dewormer….. • Where is the information coming from? • How was it evaluated? Cause and effect are not so easy, there can be confounding factors. Nutrition is one. • To have confidence, should be the result of scientifically designed and replicated studies. This includes control groups and statistical analysis.
  46. 46. UrbanShepherds.org literature review/results of designed studies • Diatomaceous earth (DE): No scientific evidence • Copper Oxide Wire Particles (COWP):yes, some trials indicate effectiveness. Should be used under veterinarian supervision. However: potential toxicity, this is extra label use, and effectiveness may be limited. • Garlic: No • Sericea lespedeza pellets: Some trials indicate effectiveness, but possible nutrition effect? • Papaya seeds: No • Wormwood species: Artemisia absinthium in some trials showed some positive effects • Others???
  47. 47. UrbanShepherds.org Resources • OSE Veterinary Extension – Decision making support tool – http://vet.osu.edu/extension/decision-tree • OSU Veterinary Extension Fact Sheets – http://vet.osu.edu/extension/beef-sheep-resources • OSUE - Small Ruminant Pastures, Parasites, and Profits: Putting it all together – three 90 minute programs •http://vet.osu.edu/extension/sare/parasite_control Scroll down to mid page
  48. 48. UrbanShepherds.org Additional Resources – University of Maryland Extension: http://www.sheepandgoat.com/ click on parasites heading • American Consortium for small Ruminant Parasite Control • http://www.wormx.info/index.html
  49. 49. UrbanShepherds.org Animal Health Regulations • USDA-National Organic Program http://www.ams.usda.gov/AMSv1.0/nop http://www.ams.usda.gov/AMSv1.0/nopgeninfo • Food Animal Residue Avoidance Database http://www.farad.org/ • U.S. Food and Drug Administration http://www.fda.gov/ http://www.fda.gov/AnimalVeterinary/default.htm • FDA Requirements: – Use of unlicensed drug is prohibited – Veterinary Client - Patient Relationship – Producer must not administer drugs in violation of FDA guidelines
  50. 50. UrbanShepherds.org Conclusion • Currently there is not an easy answer to internal parasite control. • Each farm must use various “tools” to put together a integrated parasite control strategy + monitoring program • The management strategy on your farm depends upon your goals, your market and the size of your flock • Recognize economic factors. Pasture is the cheapest feed. Grains are expensive. Indoor facilities are costly, require more labor and a manure management plan.
  51. 51. UrbanShepherds.org Questions?

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