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This PowerPoint presentation, "Parasites and their biology" is the first from a four-part webinar series on worms. The author is Susan Schoenian, University of Maryland Extension Sheep & Goat Specialist.

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  1. 1. I. Parasites and their biology<br />species, life cycles, pathogenicity, interactions<br />
  2. 2. Barber pole worms in abomasumImage source:<br />What is a parasite?<br />A (generally undesirable) living organism that exists by stealing the resources produced or collected by another living organism. <br />
  3. 3. There are two kinds of parasites.<br />Internal (endo) – a parasite that lives inside another organism.<br />External (ecto) – a parasite that lives on the blood of the host or lays eggs on their hide or in their nose.<br />External parasite: sheep ked (tick)Image from Colorado State University<br />
  4. 4. There are two general kinds of internal parasites.<br />Helminthsmulti-cellular<br />Nematodes<br />Cestodes<br />Trematodes<br />Protozoasingle cell<br />Coccidia <br />Giardia<br />Cryptosporidium<br />Haemonchus contortus (barber pole worm)<br />Image from University of Georgia<br />
  5. 5. 1. Helminths (parasitic worms)<br />NematodesRoundworms<br />CestodesTapeworms<br />TrematodesFlukes<br />Barber pole wormImage source: MicrobiologyBytes<br />
  6. 6. A. Nematodes (roundworms)Phylum Nematoda<br />Approximately 1 million<br />Over 28,000 described<br />Over 16,000 parasitic<br />Round<br />Elongated<br />Worm-like<br />Have digestive systems<br />Reproduce sexually<br />Mostly host-specific<br />Not all are pathogenic<br />Most significant kind of internal parasites that affect sheep and goats.<br />
  7. 7. ClassNematoda -> SuperfamilyStrongyloidea -> FamilyStrongylidae-> Genera StrongylePrimary parasites affecting sheep and goats: Strongyles<br />
  8. 8. Haemonchus contortusBarber pole worm<br />Most common in warm, moist climates with summer rainfalls.<br />Adapting to cooler climates.<br />Most deadly worm.<br />Blood sucker.<br />Prolific egg layer.<br />
  9. 9. Western Maryland Pasture-Based Meat Goat Performance Test (2009)<br />
  10. 10. Strongyle- type worms<br />Direct life cycles<br />Weather dependent<br />14 to 21 days<br />Eggs cannot be differentiated in fecal analyses.<br /> 75 – 95 µ m<br />Mixed infections common.<br />Have developed varying levels of resistance to anthelmintics.<br />L4, adult suck blood<br />L3<br />L1<br />L2<br />
  11. 11. Environmental-parasite interactions<br />Optimal conditions for development of Haemonchus larvae are 82⁰F and humidity above 70%.<br />Teladorsagia is better adapted to cooler, temperate climates. They fair poorly in very hot, dry summers.<br />Trichostrongylus spp. are more resistant to cold and desiccation than Haemonchus.<br />
  12. 12. Hypobiosisinhibited or arrested larval development<br />Period of delayed development whereby 4th stage larvae stop development and remain in the mucosa for 3 to 4 months.<br />Occurs when there is insufficient moisture or temperatures that are too cold for larval development.<br />Occurs in winter or summer, depending upon parasite and geographic location.<br />Probably involves some immune and environmental cues.<br />Survival mechanism<br />No host response<br />
  13. 13. Strongyles that cause occasional problems<br />BunostomumHookworm<br />Cooperiaspp.Small intestinal worm<br />Nematodirusthreadneck worm<br />OesophagastomumNodule worm<br />StrongyloidesCommon threadworm<br />TrichurisovisWhipworm<br />MuelleriuscapillarisDictyocaulusfilaria Lungworms<br />Paralaphostrongylus tenius Meningeal worm(brain, deer worm)<br />
  14. 14. Lungworms<br />Muelleriuscapillaris<br />Dictyocaulusfilaria<br />Direct or indirect life cycle<br />Prefer cool conditions<br />Diagnosis is difficult<br />Clinical signsPersistent coughing, respiratory distress, reduced weight gains<br />Recovery of 1st stage larvae from feces<br />Identify at post-mortem<br />Image source: UPENN Vet School<br />
  15. 15. Meningeal worm <br />White-tailed deer are the normal host.<br />Infection typically causes no clinical disease in deer.<br />Severe neurological disease occurs when infected snails or slugs are ingested by other cervids or ungulates.<br />Gastropods serve as intermediate host. <br />Parasite migrates to spinal cord and brain.<br />10 to 14 days after ingestion of infected snail or slug<br />
  16. 16. TREAMENT<br />CLINICAL SIGNS<br />Variable<br />Mimic other neurologic disease<br />Weakness<br />Lameness<br />Circling<br />Blindness<br />Head tilt<br />Abnormal behavior<br />Paralysis<br />Death<br />High doses of anthelmintics<br />Ivermectin for five days<br />Fenbendazole for five days<br />Anti-inflammatory drugs<br />No controlled studies have confirmed or refuted the efficacy of various treatment recommendations.<br />
  17. 17. Prevention<br />Limit deer access to pasture.<br />Eliminate deer via lethal means.<br />Deer-proof fencing for small operations.<br />Make pastures less appealing to deer.<br />Feed in enclosed areas.<br />Reduce exposure to infected snails and slugs.<br />Do not allow access to pastures that contain thick vegetation or moist shaded areas that are favorable snail and slug habits.<br /><ul><li>Prophylactic treatment with anthelmintics (every 10-14 d).</li></li></ul><li>B. Cestodes (tapeworms)<br />Flat <br />Segmented<br />Hermaphrodites<br />Indirect life cycle<br />Some cause symptoms in intermediate host<br />
  18. 18. Tapeworms affecting sheep and goatsGenus Moniezia<br />Indirect life cycle<br />Pasture mites serve as an intermediate host.<br />6 weeks<br />Segments visible in feces.Only worm visible in feces<br />Generally thought to be non-pathogenic and of little consequence.<br />Usually no benefit to treatment<br />Treat with albendazole (Valbazen®), fenbendazole (Safe-Guard®), or praziquantel.<br />
  19. 19. Sheep measles (Ovine cysticercosis)<br />Sheep tapeworm of dogs<br />Transmitted to sheep eating forages contaminated with tapeworm eggs shed by canines.<br />Sheep and goats host larval stage of parasite<br />No clinical signs in sheep or goats.<br />Causes development of cysts in skeletal and heart muscle.<br />Cause of carcass condemnation.<br /><ul><li>Control point: dogs</li></ul>Image source: Optimal Livestock Services, LLC<br />
  20. 20. C. Trematodes (flukes)<br />Flat <br />Oval shape<br />Indirect life cycle<br />Hermaphrodites <br />Image source:<br />
  21. 21. Liver flukes<br />Fasciola hepatica(common liver fluke)<br />Gastropods serve as intermediate host.<br />In U.S., found mainly in Gulf states, California, and Pacific Northwest.<br />Symptoms include pale mucous membranes, bottle jaw, and weight loss.<br />Treat with albendazole (Valbazen®).<br />Image source: Agricultural Research Council in South Africa<br />
  22. 22. 2. Protozoan parasites<br />Eimeria spp.Coccidia<br />Giardia<br />Cryptosporidium sp. <br />Toxoplasmagondii<br />Image source: FAO United Nations<br />
  23. 23. Eimeria spp. - Coccidia<br />Single cell<br />Life cycle<br />Complicated<br />Many stages<br />Oocytes -> sporulation (hatching)<br />Sexual and asexual reproduction<br />21 days <br />10 species known to infect sheep and goats<br />Host specific<br />Not all are pathogenic<br />Damage cells of small intestines<br />Subclinical<br />Clinical (diarrhea)<br />
  24. 24. Internal parasites of sheep and goats<br />Barber pole worm<br />Teladorsagia (Ostertagia)Trichostronyglus spp.<br />Roundworms<br />Tapeworms<br />Helminths<br />Other strongylesLungworms<br />Meningeal worm<br />Liver flukes<br />Coccidia<br />Protozoa<br />
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  26. 26. Small Ruminant Program<br />Thank you for your attention.<br />Any questions?<br />SUSAN<br />Next webinar: Integrated parasite management (May 12) <br />