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Platyhelminths 2 Cestoidea

Platyhelminths 2 Cestoidea. David Humber. Cestodes - Tapeworms. Endoparasites No mouth or alimentary tract Attachment organ - anterior Elongated body - divided into proglottids Adults in intestines of vertebrates Larval stages in 1 or 2 intermediate hosts. Tissue cestodes

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Platyhelminths 2 Cestoidea

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  1. Platyhelminths 2Cestoidea David Humber

  2. Cestodes - Tapeworms • Endoparasites • No mouth or alimentary tract • Attachment organ - anterior • Elongated body - divided into proglottids • Adults in intestines of vertebrates • Larval stages in 1 or 2 intermediate hosts

  3. Tissue cestodes (extra-intestinal) Echinococcus grqnulosa Echinococcus multilocularis Multiceps spp Spirometra mansonoides Diphyllobothrium spp Taenia solium Disease Hydatid disease (6k) Hydatid disease (rare) Coenurosis (rare) Sparganosis (rare) Sparganosis (?) Cysticercosis (?) CestoideaTissue & Intestinal

  4. Intestinal Cestodes Diphyllobothrium latum Taenia solium Taenia saginata Hymenolepis nana Hymenolepis diminuta Dipylidium canis Cases 16 million 5 million 76 million 36 million Rare Rare CestoideaTissue & Intestinal

  5. Intestinal CestodesTapeworms • Attached via a scolex to mucosa (small intestine) • Composed of proglottids forming a strobila • Each proglottid contains male & female reproductive organs • Immature >> Mature >> Gravid

  6. Tapeworms • Hymenolepis nana • Dwarf tapeworm (upto 40mm - largely children) • Taenia saginata - • Beef tapeworm (upto 25m) • Taenia solium • Pork tapeworm (upto 7m) World-wide distribution

  7. Hymenolepis nanaDwarf Tapeworm • Intermediate host not required • infection via intermediate insect host rare • commonest tapeworm in UK and US (<1%) • Eggs via oral-faecal route • Hatch in stomach/small intestine • Larvae (onchospheres) penetrate villi • Develop into cysticercoid stage • Migrate back into lumen

  8. Hymenolepis nanaDwarf Tapeworm • Maturation 2-4 weeks • Length dependent on parasitemia • Scolex - 4 suckers + short rostellum with hooks • Eggs released by disintergration of terminal proglottids • Eggs immediately infectious

  9. Hymenolepis nanaDwarf Tapeworm • Often asymptomatic even with high worm burden • headache, dizziness, anorexia, abdominal pain, diarrhea, low grade eosinophilia • Heavy infections via auto infection (in intestine) • Diagnosis by egg morphology(adults v rarely seen)

  10. Hymenolepis nanaControl • World-wide incidence 4% • Treatment usually Praziquantel previously Niclosamide (both single oral dose) • Health education • Rodent reservoir?

  11. Taenia saginataBeef Tapeworm • Commonest taenia infection (Ethiopia) • Ingestion of raw or poorly cooked beef • Larvz digested & evaginates in small intestine • Scolex 4 suckers no hooks • Proglottids 1-2k (lateral unterine branches 15-20)

  12. Taenia saginataBeef Tapeworm • Motile proglottids crawl through anus during day • Eggs identical to T. solium (viable upto 159 days) • Larvae (onchospheres) hatch in cattle intestine • Migrate through villi via lymphatics/blood to striated muscle • Develop into cysticerci (bladder worm)

  13. Taenia saginataBeef Tapeworm • Usually asymptomatic • hunger pains, weight loss • discomft & embarrassment at voiding proglottids • Diagnosis based on recover of gravid proglottid (uterine branches >15) • Praziquantel or niclosamide • Health education

  14. Taenia soliumPork Tapeworm • Recognised since biblical times • Risk of cysticercosis • Evagination > six hooked four suckers larva (onchophore) in small intestine • Attaches to mucosa (penetrates in cysticercosis) • Matures in 5-12 weeks • Usually long lived (25 years) single worm • Less than 1000 proglottids

  15. Taenia soliumPork Tapeworm • Usually asymptomatic similar to S. saginata • Low grade eosinophilia <15% • Treatment • praziquantel • niclosamide

  16. Taenia soliumCysticercosis • Onchospheres penetrate intestine (adult worm not usually found) • Distributed via mesenteric venules • Most organs including brain, eyes, sucutaneous and intramuscular • Sometimes multiple organs (geographical variations)

  17. Taenia soliumCysticercosis • Bladder worms upto 60ml in volume (usually around 5 x 800 mm) • Diagnosis • surgical removal • X ray - calcified larvae • CT scan or MRI for brain lesions • Fine needle aspirate • Serology/PCR

  18. Taenia soliumCysticercosis • Treatment • surgical removal • praziquantel (15 day course) • only treatment for cysticercus • albendazol (8 day course)

  19. Taenia solium Echinococcus grqnulosa Echinococcus multilocularis Diphyllobothrium spp Multiceps spp Spirometra mansonoides Tissue Cestodes

  20. Echinococcosis - Hydatid disease • Echinococcus granulosa • worldwide • Echinococcus multilocularis • Europe, Russia, China, Canada • Echinococcus vegeli • Central & South America

  21. Distribution

  22. Hydatidosis • Known since Hipporates 400BC • Most serious of the tapeworm infections

  23. Hosts • Definitive Host • Canids & felids • 59% dogs in Istanbul (E.granulosa) • Intermediate Host • humans +60 species • ungulate,marsupials, elephants,primates, • rodents for E. multilocularis

  24. Definitive host Egg production Worm lives 2+ years Cyst evaginates Intermediate host Hatch - onchosphere invades mucosa & penetrates capillaries Cysts form in liver & lungs Secondary metastasis 20+ years Secondary daughter cysts bud in E. multilocularis Lifecycle

  25. Clinical Features • Definitive Host • usually asymptomatic • Intermediate Host • dependent on burden & site • usually single - 50% in liver, 3% brain (E.g) • incubation +5 years • 6-10% diagnosed cases fatal • Eosinophilia in 25% cases

  26. Diagnosis • Parasitological • eosinophilia • palpation • Radiological (CT & MRI) & ultrasound • differente from tumor • Immunological • Skin test - Casoni test - 18% false +ves • Serology

  27. Treatment & Control • Surgery • drainage + 5 mins 10% formalin • Praziquantel or albendazol • steroids to prevent inflammation • aspiration + 95% ethanol • Health education • sanitation - dogs cats raw meat

  28. Diphylobothrium - Sparganosis • Diphylobothrium latum • Broadfish tapeworm • Definitive host • humans/dogs/cats/pigs/bears/otters, seals etc • First intermediate host • Copepods • Second intermediate host • trout/salmon/perch/pike

  29. Intestinal infections • Limited to fish eating areas • raw or improperly cooked • dumping untreated raw sewage • Adult worms (upto 10m) • attach to lining of intestine • Ovoid operculated eggs released • Eggs dormant in water (8-12 days) • motile coracidium hatches ingested by freshwater copepod

  30. Intestinal infections • Ciliated embryophore shed & naked hexacanth larva attaches by hooks • Bores through intestinal wall into haemocoel • Hexacanth metamorphose into procercoid (14-18 days) 500um in length

  31. Intestinal infection • In fish procercoid penetrates intestinal wall • migrates to muscles • develops into plerocercoid (20-40mm) in • 7-30 days with fully developed scolex • In definitive host attaches to mucosa • grows at 30 proglottids a day • Full sexual maturity in 3-5 weeks

  32. Sparganosis • Some species of Diphylobothrium and Spirometra • larva invade

  33. Nematode Infections

  34. Nematodes • Half million species • 50% free living • animal & plant parasites • Animal • vertebrate & invertebrate hosts • infection by ingestion • penetration

  35. Nematodes • Generally elongated, cylindrical & tapered at each end (99%) • fluid filled pseudocoelom logitudinal muscle only • no vasculature or respiratory system • usually sexual dimorphism (some parthenogenetic) • males usually smaller than females • most between 1mm and 150mm • colourless translucent to opaque with an elastic curticle

  36. Ascaris • Large intestinal round worm • mouth with I dorsal & 2 ventral lips • female 40cm male 30cm • Uterus of mature female 20+ million eggs • Sheds 200,000 golden brown ovoid eggs per day • Eggs resistant to desiccation

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