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This presentation on Internal Parasite Control in Sheep was given at the Indianhead Sheep Breeders Association 17th Annual Shepherd's Clinic and Trade Show on February 12, 2011.

This presentation on Internal Parasite Control in Sheep was given at the Indianhead Sheep Breeders Association 17th Annual Shepherd's Clinic and Trade Show on February 12, 2011.

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  • 1. Internal parasite control in sheep
    SUSAN SCHOENIAN (Shāy-nē-ŭn)Sheep & Goat SpecialistWestern Maryland Research & Education -
  • 2. Internal parasites: the realities
    Internal parasites are the primary health problem affecting sheep in warm, moist climates.
    Except for goats, sheep are the most susceptible farm livestock to internal parasites.
    Though it varies by geographic location and individual farm, worms are rapidly developing resistance to the anthelmintics.
    Nowadays, successful worm control requires an integrated approach that does not rely solely on anthelmintics.
    Anthelmintic = dewormer
  • 3. What is a parasite?
    A (generally undesirable) living organism that exists by stealing the resources produced or collected by another living organismSource: Wiktionary
  • 4. There are two kinds of parasites.
    Internal (endo) - a parasite that lives inside another organism.
    External (ecto) - a parasite that lives on the blood of the host or lays eggs on their hide or in their nose.
  • 5. There are two general kinds of internal parasites.
    Parasites “tend” to be species-specific.
    1) Helminths (multi-cellular)
    Nematodes (roundworms)
    Cestodes (tapeworms)
    Trematodes (flukes)
    2) Protozoa (single cell)
    Nematodes (roundworms)
    • Over 20,000 species
    • 7. Long
    • 8. Round
    • 9. Not segmented
    • 10. Microscopic
    • 11. Sexual reproduction
    • 12. Male and female worms
    • 13. Haemonchus contortus Barber pole worm
    Scour worms
    • Trichostrongylus spp. Hair worm
    • 14. Teladorsagia
    Brown stomach worm
    • Oesophagostomum
    Nodule worm
    • Nematodirus spp.
    • Lungworms
    • 15. Meningeal worm
    • Blood sucker
    • 16. Found in abomasum
    • 17. Most pathogenic
    • 18. Causes anemia, bottle jaw, and death.
    • 19. Prolific egg producer
    • 20. Direct life cycle
    • 21. Requires warmth (60°F) and moisture to complete its life cycle
    • 22. Short 3 week life cycle
    Barber pole wormHaemonchus contortus
    • Found in abomasum and Intestines.
    • 24. Usually found in mixed infections with barber pole worm.
    • 25. Not as pathogenic as barber pole worm.
    • 26. Cause digestive problems (scouring) and ill thrift.
    • 27. Similar life cycle and pre- patent period as barber pole worm.
    • 28. Egg laying capacity varies.
    • 29. Eggs look the same as barber pole worm.
    “Scour” worms
    Image source: NADIS UK
    Tapeworms (cestodes)
    • Non- pathogenic
    • 37. Non disease-causing
    • 38. No benefit to treatment
    Flukes (trematodes)
    • Single-cell
    • 45. Spore-forming
    • 46. Microscopic
    • 47. Can reproduce sexually or asexually
    • 48. Species-specific
    • 49. Eimeria spp.
    • 50. Cause scouring
    • 51. Damage lining of small intestines.
    • 52. Treat with amprolium (Corid) or sulfa drugs.
    • 53. Prevent with coccidiostats.
  • Integrated parasite management
    Life cycle
    Host resistance
    Clean or safe pastures
    Multi-species grazing
    Pasture rest and rotation
    Alternative forages
    Nutritional management
    Zero grazing
    Genetic selection
    Manage refugia
    Targeted selective treatment
    Your approach to internal parasite control should be integrated or holistic.
  • 54. Parasite identificationWhat kind(s) of parasites are affecting your sheep?
    Fecal egg flotation
    • To differentiate between strongyle (stomach) and tapeworm eggs and coccidia oocytes.
    • 55. Can’t differentiate between strongyle (stomach) worm eggs except Nematodirus)
    Public lab
    Diagnostic lab
    Private lab
    Larval id
    To differentiate between strongyle (stomach) worms (H. contortus, Teladorsagia, and trichostrongyles)
    University of Georgia
    Other universities
    Lectin-staining test
    Determine percent of Haemonchus contortus eggs in a fecal sample
    Oregon State University
    University of Georgia
  • 56. Life cycle
    • Eggs hatch and develop into infective larvae (L3).
    • 57. Sheep ingest infective 3rd stage larvae (L3).
    • 58. Immature adults (L4) and adult worms suck blood.
    • 59. Adult worms lay eggs.
  • Host resistanceSheep and lambs vary in their susceptiiblity to parasitism.
    More susceptible
    Weaned lambs
    Bummer lambs
    Late-born lambs
    High-producing females
    Periparturient ewe
    Thin animals
    Geriatric sheep
    Unadapted breeds
    Stressed animals
    More resistant
    Mature sheep
    Dry ewes
    Pet sheep
    Mature wethers
    Sheep in good body condition
    Fat sheep
  • 60. Management
    Good sanitation
    Use feeders
    Clean water
    Avoid overgrazing
    Do not graze below 2 inches.
    Time lambing to minimize parasite infections.
  • 61. Pasture rest and rotation
    Pasture rotation is a recommended strategy for controlling internal parasites because it allows the use of cleaner (rested) pastures.
    Intensive rotational grazing may not help to reduce parasitism unless rest periods are long enough.
    Due to increased stocking rates, management intensive grazing may increase internal parasite problems in sheep and lambs.
    It takes about 2 months of rest for a contaminated pasture to become relatively “clean” for sheep grazing.
  • 62. Use of clean or safe pastures
    A pasture that has not been grazed by sheep (or goats) for the past 6 to 12 months.
    A pasture that has been grazed by adult cattle and/or horses for the past 6 to 12 months.
    New pasture
    A pasture that has been renovated with tillage.
    A pasture in which a hay or silage crop has been removed.
    A pasture that has been rotated with row crops.
    A pasture that has been burned.
  • 63. Alternative forages
    Livestock that browse have fewer parasite problems.
    Livestock grazing tall-growing forages will have less parasite problems.
    80% of parasite larvae is found in the first two inches of vegetative growth.
    Grazing tanniferous forages may reduce the effects of parasitism.
    Sericea lespedeza
    Birdsfoot trefoil
  • 64. Multi-species grazing
    Sheep and goats share the same parasites, but they are different from the parasites that affect adult cattle and horses.
    Producers who graze multiple species of livestock report fewer parasite problems with small ruminants.
    Cattle and horses “vacuum” sheep/goat pastures of infective worm larvae.
    Sheep, goats, and cattle have complementary grazing habits.
  • 65. Nutritional management
    Animals on a high plane of nutrition and in better body condition are better able to withstand worm burdens.
    Nutrition in early pregnancy (fat stores) can affect the immune response to internal parasites.
    Sheep receiving higher levels of protein prior to lambing have lower fecal egg counts.
    Supplementing grazing lambs with protein has been shown to reduce fecal egg counts.
    Nutritional supplementation is most likely to be beneficial when pregnant females and young animals are below optimal body condition at a time when pasture quality and/or quantity is limited.
  • 66. Zero grazing
    Sheep raised in confinement or dry lot (zero grazing) tend to have fewer worm problems.
    Sheep put in confinement or dry lot do not usually get re-infected with worms.
    Coccidiosis could still be a problem, if preventative measures are not taken.
    Good sanitation
    Proper feeders
  • 67. Genetic selection
    Breeds vary in their resistance to gastro-intestinal parasites.
    Resistant breeds: Gulf Coast Native, Katahdin, St. Croix, Barbado.
    There is as much difference within breeds as between breeds.
    The 80-20 ruleApproximately 20 percent of the flock sheds 80 percent of the eggs onto pasture.
    Parasite traits are moderately heritable.
    Selection for parasite resistance will not adversely affect the growth of lambs or fertility of ewes.
    Ability of host to resist infection
    Measured by fecal egg counts
    Ability of host to withstand challenge and/or infection.
    For barber pole worm: measured by packed cell volume.
  • 68. Slow down drug resistanceRufugia are worms that have not been exposed to anthelmintic treatment.
    Do not deworm on a regular schedule.
    Do not deworm all animals in a group.
    Do not return treated animals to a clean pasture.
    Give all anthelmintics orally at the proper dose.
    Do not underdose.
    Deworm new animals with anthelmintics from two different chemical classes.
    Without refugia, worms will eventually be resistant to all anthelmintics.
  • 69. Targeted selective treatmentFive Point check©
  • 70. FAMACHA© eye anemia score
  • 71. Body condition score (BCS)
  • 72. Dag Scores
  • 73. Bottle jawSub-mandibular edema
  • 74. Nasal discharge
  • 75. Fecal egg countseggs per gram of feces
    Indicate “potential” parasite burden in animal.
    Indicate potential parasite contamination.
    Use to determine level of drug efficacy.
    Use to determine genetic differences in parasite resistance.
  • 76. Limitations of fecal egg counts
    Fecal egg counts are not always well-correlated with disease.
    Presence of eggs or does not mean that the animal is clinically parasitized and needs treatment.
    Absence of eggs or oocytes (coccidia) does not mean that the animal is parasite-free and not needing treatment.
  • 77. Fecal egg count interpretatoin
  • 78. Three classes of anthelmintics
    Nicotinic agonists
    Macrocylic lactones
  • 79. Benzimidazoles (BZD)
    White dewormers
    Water soluble
    Broad spectrum
    Wide margin of safety
    Efficacy against tapeworms
    Efficacy against liver flukes (albendazole)
    Widespread resistance
    Resistance is caused by dominant gene
    Fenbendazole [Rx]SafeGuard®, Panacur®
    Oxyfendazole [Rx]Synanthic®
  • 80. Nicotinic agonists
    Clear drench
    Water soluble
    Broad spectrum of activity
    Not effective against arrested larvae
    Narrower margin of safety
    Resistance reported
    Resistance is caused by a recessive gene
    Morantel and Pyrantel
    Not effective against larval stages
      Imidazothiaoles (IMID)
    LevamisoleProhibit®, Levasol®
     Tetrahydropyrimidines (TETR)
    Morantel [Rx]Rumatel®
    Pyrantel [Rx]Strongid®
  • 81. Macrocylic lactones (ML)
    Doramectin [Rx]Dectomax®
    MoxidecinCydectin® Quest® [Rx]
    Broad spectrum
    Wide margin of safety
    Effective against external parasites
    Persistent activity
    Widespread resistance, reported especially ivermectin
    Resistance is caused by dominant gene
  • 82. Improving (maintaining) the efficacy of treatment
    Weigh animals to determine proper dose.
    Do not underdose.
    Use proper drench technique.
    Fast animals prior to treatment.
    Give multiple anthelmintics [Rx]
    Synergetic effect
    Manage for refugia
  • 83. How do you know if you have anthelmintic resistance on your farm?
    1) DrenchRite® Larval Development Assay
    2) Fecal Egg Count Reduction Test (FECRT)
    An in vitro test for the detection of resistance to all anthelmintic groups.
    Need pooled fecal sample from 10 or more animals (minimum of 6)
    at least > 350 epg >500 epg preferred
    Animals with FAMACHA© scores of 3, 4, or 5 are more likely to have higher egg counts if barber pole worm is the primary parasite.
    Comparison of before and after fecal egg counts
    Benzimidizoles7 days post-treatment
    Levamisole 7 days post-treatment
    Avermectins14 days post-treatment
    Should include “control” (untreated) animals in testing.
  • 84. The future of parasite control
    “natural” anthelmintics
    Copper oxide wire particles
    Copper sulfate
    Pine bark
    Sericea lespedeza (leaf meal)
    Vaccine development
    They are testing a promising vaccine in Australia
    The European community has received a historically large grant to help develop vaccines for gastro-intestinal parasites in livestock.
    New anthelmintics
    Startect®derquantel + abamectin
  • 87. Small Ruminant Program
    Thank you for your attention.
    Any questions?