parasitology lab notes


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parasitology lab notes

  1. 1. Lab 4: Cestodes The Tapeworms!
  2. 2. General anatomy of a tapeworm <ul><li>Tapeworms are long, segmented, flattened & ribbonlike </li></ul><ul><li>On extreme anterior end is the scolex or the head. This is the holdfast organelle. </li></ul><ul><li>The scolex has 4 suckers called acetabula </li></ul><ul><li>Some tapeworms are armed with rostellum , backward-facing hooks that help anchor the worm in the small intestine. </li></ul><ul><li>Posterior to scolex is the strobila or the neck – this is where the proglottids , or segments, are formed. </li></ul><ul><li>The proglottids closest to the scolex are immature, those farthest are gravid - the oldest. </li></ul>
  3. 3. Tapeworm Reproduction <ul><li>Tapeworms are hermaphroditic, the proglottids contain both male & female sex organs. </li></ul><ul><li>Cross-fertilization & self-fertilization occur between/within individual proglottids </li></ul><ul><li>Gravid proglottids are “spent” and contain only a uterus filled with egg packets. They may break off and exit via feces or around anus. Can be seen with the naked eye. </li></ul><ul><li>Proglottids rupture in external environment & release thousands of hexacanth embryos. </li></ul><ul><li>Hexacanth embyros have six hooks. </li></ul>Better picture on page 72 of textbook
  4. 4. Dipylidium canninum: “cucumber seed tapeworm” <ul><li>Most common tapeworm of both dogs & cats because the intermediate host is the flea </li></ul><ul><li>Fleas often contain the infective metacestode (larval) stage: cysticercoid </li></ul><ul><li>Scolex is armed & has prominent proboscis covered w/ hooks </li></ul><ul><li>Terminal proglottids are motile and look like moving cucumber seeds on the stool or around anus </li></ul>
  5. 5. Dipylidium canninum: “cucumber seed tapeworm” (cont’d) <ul><li>Terminal proglottids contain thousands of egg packets, each containing 20-30 hexacanth embryos </li></ul><ul><li>Prepatent period is 14-21 days </li></ul>
  6. 6. Dipylidium canninum: Life cycle Dog, cat becomes infected by ingesting fleas that are infected with cysticercoid larval stage Also important to note that these are ZOONOTIC!
  7. 7. Dipylidium canninum: Control <ul><li>Flea control is the number one way to prevent tapeworm infection </li></ul><ul><li>Treatment is usually with a single dose of praziquantel (Droncit) </li></ul>
  8. 8. Taenia spp. <ul><li>2 nd most common type of tapeworm seen in clinics </li></ul><ul><li>Segments are more rectangular shaped </li></ul><ul><li>Also zoonotic </li></ul><ul><li>Intermediate hosts are rodents & rabbits </li></ul><ul><li>Seen more frequently in cats than in dogs </li></ul>
  9. 9. Taenia spp.: Anatomy <ul><li>Scolex is armed with 2 rows of hooks or acetabula </li></ul><ul><li>Also manifests with motile terminal proglottid segments that may appear on feces or around anus </li></ul>
  10. 10. Taenia spp. <ul><li>Terminal proglottids contain eggs with hexacanth embryos (not egg packets!) </li></ul><ul><li>Striated eggshell, slightly oval shaped & contain single oncosphere with three pairs of hooks </li></ul>
  11. 11. Taenia spp.: Life Cycle <ul><li>Metacestode (larval) stage </li></ul><ul><li>is cysticercus: bladder worm </li></ul><ul><li>found in intermediate host </li></ul><ul><li>Embryos develop into </li></ul><ul><li>cysticercus in peritoneal </li></ul><ul><li>cavity of intermediate host </li></ul><ul><li>One cysticercus=one adult </li></ul><ul><li>tapeworm </li></ul><ul><li>More pathogenic to </li></ul><ul><li>intermediate host than to </li></ul><ul><li>definitive host </li></ul>
  12. 12. Echinococcus granulosis & E. multilocularis: Hydatid disease tapeworms <ul><li>E. granulosis = dogs, encysts in viscera & brain </li></ul><ul><li>E. multilocularis = cats, encysts in lungs & alveoli </li></ul><ul><li>Has only 3 proglottids, very small </li></ul><ul><li>Eggs are very similar to Taenia spp. – adult must be identified </li></ul><ul><li>EXTREME ZOONOTIC POTENTIAL!!!!! </li></ul>
  13. 13. Echinococcus granulosis & E. multilocularis <ul><li>Hydatid cysts result in thousands of scolex </li></ul><ul><li>Size is impingent on organs </li></ul><ul><li>Damages area where it resides (brain, liver, lung) </li></ul><ul><li>Neoplastic lesions can grow as large as a human head </li></ul><ul><li>Can kill host if burst open, causes anaphylaxis </li></ul><ul><li>Wild herbivores are intermediate hosts </li></ul>
  14. 14. Anoplocephala spp.: Equine tapeworms <ul><li>Most common equine tapeworm </li></ul><ul><li>Lives in small & large intestine, occasionally in stomach </li></ul><ul><li>Proglottids are wider than they are long </li></ul><ul><li>Intermediate host is grain mite & occasionally beetles </li></ul>
  15. 15. Monezia spp. <ul><li>Infect intestinal tract of cattle, sheep & goats </li></ul><ul><li>Scolex is unarmed </li></ul><ul><li>Proglottids are very short & wide </li></ul><ul><li>Eggs are square or triangular shaped, possess a pyriform apparatus (pear-shaped) </li></ul><ul><li>Intermediate host is oribatid grain mites </li></ul><ul><li>Can cause GI stasis in calves </li></ul><ul><li>Can cause ulcerative lesions </li></ul><ul><li>where attached </li></ul>
  16. 16. Diphyllobothrium latum: Broadfish tapeworm <ul><li>Pseudotapeworm w/ zoonotic potential </li></ul><ul><li>Continually release eggs until exhausts uterine contents </li></ul><ul><li>Terminal proglottids become senile rather than gravid and detach in chains </li></ul><ul><li>Eggs are light brown, oval & possesses single operculum at one pole </li></ul><ul><li>Eggs are unembryonated when passed in feces </li></ul>
  17. 17. Diphyllobothrium latum <ul><li>Tapeworm of fish-eating mammals </li></ul><ul><li>Has 2 intermediate hosts, copepod & fish </li></ul><ul><li>Encysts in fish muscle </li></ul><ul><li>Larvae develop on intestinal wall </li></ul>
  18. 18. Identify!
  19. 19. Identify!
  20. 20. Identify!