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.

1. Internal parasite control in sheep SUSAN SCHOENIAN (Shāy-nē-ŭn)Sheep & Goat SpecialistWestern Maryland Research & Education Centersschoen@umd.edu - www.sheepandgoat.com

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) Coccidia Giardia Cryptospordium

7. Long

8. Round

9. Not segmented

10. Microscopic

11. Sexual reproduction

12. Male and female worms

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 cycleBarber pole wormHaemonchus contortus

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

31. Ribbon-like

32. Flat

33. Segmented

34. Hermaphrodites

35. Intermediate host

37. Non disease-causing

39. Oval-shape

40. Leaf-like

41. Hermaphroditic

42. Require intermediate host: snail, slug

43. Damage liver

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.

55. Can’t differentiate between strongyle (stomach) worm eggs except Nematodirus)Do-it-yourself Public lab Diagnostic lab Private lab Veterinarian 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

57. Sheep ingest infective 3rd stage larvae (L3).

58. Immature adults (L4) and adult worms suck blood.

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 Chicory 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 Coccidiostats

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. Resistance Ability of host to resist infection Measured by fecal egg counts Resilience 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 Benzimidizoles Nicotinic agonists Macrocylic lactones

79. Benzimidazoles (BZD) characteristics 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 products Fenbendazole [Rx]SafeGuard®, Panacur® AlbendazoleValbazen® Oxyfendazole [Rx]Synanthic®

80. Nicotinic agonists characteristics Levamisole 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 products Imidazothiaoles (IMID) LevamisoleProhibit®, Levasol® Tetrahydropyrimidines (TETR) Morantel [Rx]Rumatel® Pyrantel [Rx]Strongid®

81. Macrocylic lactones (ML) products Avermectins IvermectinIvomec® Doramectin [Rx]Dectomax® Milbemycins MoxidecinCydectin® Quest® [Rx] characteristics 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.

85. Pumpkin seed

86. Diatomaceous earthPine bark Sericea lespedeza (leaf meal) Others Future 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 Zolvix®Monepantel Startect®derquantel + abamectin

87. Small Ruminant Program Thank you for your attention. Any questions? Susan Schoeniansschoen@umd.eduwww.sheepandgoat.com