Cestodes - Parasitology


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Cestodes - Parasitology

  1. 1. CESTODES
  2. 2. General CharacteristicsMajority are long, segmented and tape-like are calledtapewormsDorso-ventrally flattenedSize varies from a few mm to several metersAdult worms are found in the intestinal canal of man andanimals“head” or scolex is provided with suckers and sometimeswith hooks that serve as organs of attachmentThere are 3 regions in an adult worm: Head: scolex Neck Strobila (body or trunk) Consist of a series of segment called proglottids
  3. 3. General CharacteristicsSexes are not separateBody cavity is absentAlimentary canal is entirely absentExcretory and nervous systems are presentReproductive system is present and complete in eachsegment According to maturity of reproductive organs, three types of segments of the strobila can be recognized from the fron backwards Immature: male and female organs are not differentiated Mature: male and female organs have become differentiated (male organs appear first) Gravid: uteri are filled with eggs (other organs are atrophied or have disappeared)
  4. 4. Classification of Cestodes Infecting ManI. Pseudophyllidean cestodes Possess false or slit-like grooves called bothria Adult worms in Intestine Diphyllobothrium latum: Fish Tapeworm Larval stages: Plerocercoid in Man Sparganum mansoni Sparganum proliferum
  5. 5. Classification of Cestodes Infecting ManII. Cyclophyllidean cestodes Possess cup-like and round suckers called acetabula Adult Worms in the Intestine Taenia saginata Taenia solium Hymenolepis nana Hymenolepis diminuta Dipylidium caninum
  6. 6. Classification of Cestodes Infecting ManAccording to HabitatII. Cyclophyllidean cestodes Possess cup-like and round suckers called acetabula Larval Stages in Man Hydatid cyst of Echinococcus granulosus and Echinococcus multilocularis Cysticercus cellulosa of Taenia solium Coenurus cerebralis of Multiceps multiceps Coenurus glomeratus of Multiceps glomeratus
  7. 7. Differences Between a Pseudophyllidean and a Cyclophyllidean Cestode Pseudophyllidean CyclophyllideanHead or scolex Bears 2 slit-like Bears 4cup-like grooves suckersuterus No branching Branching Convoluted uterine May or may not be tubes assume the present form of rosettesUterine pore present absentCommon genital pore Ventral; in the midline lateraleggs Operculated; gives Not operculated; do rise to ciliated larvae not give rise to ciliated larvae
  8. 8. Order Pseudophyllidea CharacteristicsLarge worms consisting of a long chain of segments“head” has two slit-like sucking grooves called bothriainstead of suckersUterine glands are widely scattered in the parenchymaand is composed of many aciniGenital pores are on the ventral surface of the segmentand are not marginalUterus opens to the exterior through which eggs comeoutEggs are operculated and can develop only in water;immature when oviposited and oncosphere gives rise tociliated embryoLarval development proceeds in two intermediate hosts: First larval stage is called procercoid Second larval stage is called plerocercoid
  9. 9. Diphyllobothrium latumCommon Name: Fish Tapeworm Broad TapewormMorphology Adult worm is yellowish grey in color Dark central markings in the strobila are due to the egg-filled uterus Measures 3 to 10 meters in length Life-span is for a period of 5 to 15 years http://www.revistaaquatic.com/aquatic/html/art1401/fig11.gif 3-01-08
  10. 10. Diphyllobothrium latumScolex is spoon-shapedor spatulateScolex bears 2 slit-likegrooves called bothria(1 on the dorsal surfaceand 1 on the ventralsurface)Scolex has no rostellumand no hookletsNeck is thin andunsegmented and ismuch longer than thehead
  11. 11. Diphyllobothrium latumMorphology 3,000 to 4,000 A mature segment is filled with male and female reproductive organs Terminal segments shrink and becomes empty as eggs are constantly discharged Dried up segments break off from the body in chains and are passed out in the host’s feces Uterus at the center of the segment appears in the form of a rosette
  12. 12. Diphyllobothrium latum http://pathmicro.med.sc.edu/parasitology/dip1.jpg 3-01-08
  13. 13. Diphyllobothrium latumOva Passed out in the host’s feces in large numbers Oval Bile stained Contains abundant granules and unsegmented ovum Inconspicuous operculum at one end and a small knob at the other end Does not float in saturated solutions of common salt A single egg gives rise to a single larva Not infective to man http://workforce.cup.edu/Buckelew/images/Diphyllobothrium%20latum%20egg.jpg 3-01-08
  14. 14. Diphyllobothrium latumlarva Passed first in water and then in the respective intermediate hosts 3 stage – First stage larva Coracidium Ciliated oncosphere that develops from egg in water – Second stage larva Procercoid Spindle-like solid body with cephalic invagination Found inside the cyclops (the first intermediate host) – Third stage larva Plerocercoid Head is invaginated in the neck Found in the fresh water fish, the second intermediate host
  15. 15. Diphyllobothrium latum
  16. 16. Diphyllobothrium latum
  17. 17. Diphyllobothrium latumFinal Host Man, dog, cat Small intestine1st I.H. Cyclops or Diaptomus2nd I.H. Fresh water fish, pike, trout, salmon, perchMode of Infection Ingestion of imperfectly cooked infected fish or roe containing plerocercoid larvaeInfection Diphyllobothriasis G.I. disturbances and anemiaDiagnosis Microscopic examination of feces for the characteristic operculated eggs
  18. 18. Order Cyclophyllidea CharacteristicsLarge or small worms consisting of chains of segmentsScolex is quadrate with four cup-like round suckersAn apical rostellum with hooklets may be presentVitelline glands concentrated in a single massCommon genital pore is marginal (on lateral side ofsegment)No uterine opening for the exit of eggs from the graviduterusEggs only escape from the rupture or disintegration ofripe segmentsEggs are not operculated and can develop only in theintermediate host, fully embryonatedOncosphere is never a ciliated embryoLarval development proceeds in one intermediate host
  19. 19. Taenia saginataBeef TapewormUnarmed Tapewormof ManAdult worms are whiteand semi-transparentMeasures about 5-10meters or sometimesup to 24 metersLive up to 10 years ormore
  20. 20. Taenia saginata1,000 to 2,000 proglottidsCommon genital pore is marginallysituatedVagina is provided with asphincter muscleGravid proglottid consists of auterus and a central longitudinalstem with 15 – 30 branches oneach sideHighly branched proglottidsGravid proglottid contains 97,000to 124,000 ovaGravid segments are expelledsingly and force their way throughthe anal sphincterFree gravid proglottid crawls out ofthe anal orifice and oviposits onthe perianal skin
  21. 21. Taenia saginata
  22. 22. Taenia saginataOva Liberated by rupture of ripe proglottids No uterine opening Spherical Thin, outer transparent shell Inner embryophore is brown, thick walled and radially striated Has an oncosphere with 3 pairs of hooklets Does not float in saturated salt solutions Eggs are resistant and remain viable for 8 weeks Infective only to cattle
  23. 23. Taenia saginataFinal Host: ManIntermediate Host: cattle, cow buffaloMode of Infection; eating beef containing CysticercusbovisPathogenesis Taeniasis Passage of proglottids in stool Mild irritation at site of attachment Epigastric pain Hunger fangs Weakness Weight loss Loss of appetite Pruritis Obstruction in intestine but also in bile and pancreatic ducts and appendix because proglottids are actively motile
  24. 24. Taenia saginataDiagnosis Identifying characteristic eggs, proglottids or scolex Usual specimen is gravid proglottids ( lateral branches 15-20) Concentration techniques for eggs (eggs rarely passed out in stool) Perianal swabsTreatment Praziquantel 5-10mg/kg single doseCriteria for cure Recovery of the scolex Negative stool examination 3 months after treatment
  25. 25. Taenia soliumPork Tape wormArmed Tapeworm of ManTaeniasis is common amongthose eating raw or insufficientlycooked “measly pork”Uncommon among non-porkeaters
  26. 26. Taenia soliumScolex is globular inoutline with 4 circularsuckersScolex has arostellum armed witha double row ofalternating large andsmall hookletsRostellar hooklets areshaped like daggersor Arabian poniards
  27. 27. Taenia solium
  28. 28. Taenia solium
  29. 29. Taenia soliumAdult worms measure2-3 metersAdult worms live up to 25years
  30. 30. Taenia solium800-900 proglottidsCommon genital pore ismarginal and thick lippedVaginal opening is notguarded by a muscularsphincterGravid segments areexpelled passively inchains of 5-6 at a timeand not singly.Gravid proglottidscontains approx. 30,000to 50,000 eggs
  31. 31. Taenia soliumOva– Same as those of Taenia saginata– Infective to man as well as pigs– Thick brown striated embryophore surrounding a hexacanth embryo
  32. 32. Taenia soliumFinal Host: ManIntermediate Host: PigMode of infection; eating measly porkcontaining Cysticercus cellulosaeDiagnosis: stool examination forproglottids/eggs
  33. 33. Taenia soliumPathogenesis Mild, non-specific abdominal complaints Proglottids are not as motile as T. saginata so organ obstruction is less likely.Cysticercosis Multiple Develop in any organ or tissue Neurocysticercosis (most serious zoonotic disease) Chorioretinitis vasculitis
  34. 34. Taenia soliumDiagnosisIntestinal Identifying the characteristic proglottids, eggs or scolexCysticercosis Computed Axial Tomography Magnetic Resonance ImagingTreatment Praziquantel: 5-10 mg/kg single dose for children and adults Niclosamide not available locallyCriteria for cure: Recovery of scolex Negative stool exam 3 months after treatment
  35. 35. Comparison Between T. saginata and T. solium Taenia saginata Taenia soliumlength 5-10 meters 2-5 metersHead or scolex Large, quadrate, no Armed; with rostellum; rostellum and hooks with hookletsNumber of proglottids 1,000 to 2,000 Below 1000Expulsion Expelled singly and may Explelled passively in be forced through the chains of 5 or 6 anal sphincteruterus Highly branched with 15- Lateral branches 5-10 on 30 lateral branches on each side, thin, dendritic each side; thin; and vaginal sphincter is dichotomous absenttestes 300-400 follicles 150-200 follicles
  36. 36. Echinococcus granulosusTaenia echinococcusDog TapewormHydatid WormMan harbors the larval form and not theadult worms which however is found in theintestine of dogs and canines
  37. 37. Echinococcus granulosusAdult worms are small(3-6 mm in length)It is composed of a Scolex Neck Strobila3 segments(occassionally 4) Immature Mature Gravid
  38. 38. Echinococcus granulosusScolex bears 4suckers and aprotrusible rostellumwith 2 circular rows ofhooks.
  39. 39. Echinococcus granulosusOva Ovoid in shape Resemble Taenia ova Hexacanth embryo with 3 pairs of hooksInfective to: Man Cattle Sheep and other herbivorous animals
  40. 40. Echinococcus granulosusLarva Found within the hydatid cyst developing inside the intermediate host Represents the structure of the scolex of the future adult worm Young larva are transformed into a hollow bladder (hydatis , drop of water) Brood capsules develop within the cysts and may contain thousands of scolices On entering the final host, the scolex armed with a rostellum and 4 suckers become adult worms
  41. 41. Echinococcus granulosus
  42. 42. Echinococcus granulosus
  43. 43. Echinococcus granulosusDefinitive Host Dog Wolf Fox JackalIntermediate Host Sheep Pig Cattle Horse Goat
  44. 44. Echinococcus granulosusDefinitive Host Dog Wolf Fox JackalIntermediate Host Sheep Pig Cattle Horse Goat
  45. 45. Echinococcus granulosusPathogenesisEchinococcosis Pathology is caused by the developing larval cyst in the intermediate host Most common site of involvement is the liver Echinococcus granulosus cyst: Unilocular hydatid cyst Echinococcus multilocularis: alveolar cyst Some may be asymptomatic for years Rupture of cyst in the lungs may present coughing accompanied by allergic reactions
  46. 46. Echinococcus granulosus
  47. 47. Echinococcus granulosus Encysted scolices of Echinococcus granulosus in lung "hydatid sand"
  48. 48. Echinococcus granulosus Encysted scolices of Echinococcus granulosus in lung "hydatid sand"
  49. 49. Echinococcus granulosus Encysted scolices of Echinococcus granulosus in lung "hydatid sand"
  50. 50. Echinococcus granulosusDiagnosis Radiographic findings Immunodiagnosis Antibody detection IHA IFA EIAAntigen detection
  51. 51. Echinococcus granulosusTreatment Surgical resection: not 100% effective Solicidal agent Hibitane 95% ethanol Hypertonic 30% Normal Saline Solution PAIR technique for inoperable cyst Puncture, Aspiration, Injection, Reaspiration Intervention Albendazole
  52. 52. Hymenolepis speciesGenus is derived from the membranous character of theegg shell “hymen”3 testes in each mature segmentUterus is sac-like and transverseEggs possess two membranes’ outer membrane is thinand transparentlarval stage is called cysticercoidSmall bladder containing the invaginated head proximallyand a solid, elongted portion as a caudal appendageThere are 2 species; Hymenolepis nana Hymenolepis diminuta
  53. 53. Hymenolepis nanaDwarf TapewormSmallest tapeworm infecting manFound worldwideMainly among childrenOnly human tapeworm that can complete its lifecycle in a single hostMan can harbor both the adult and larval stagesof the parasiteException to the general rule that “Helminths do not multiply inside the body of the definitive host”
  54. 54. Hymenolepis nanaAdultFound in the ileumDelicate strobila25 mm to 45 mmWorms may be presenr inlarge numbers from 1,000to 8,000Short life span, about 2weeksUp to 200 proglottidsTransverse uterus3 testes
  55. 55. Hymenolepis nanaScolex Subglobular 4 suckers Provided with a short retractile rostellum armed with a single row of 20-30 hooklets Rostellar hooklets are shaped like tuning forks
  56. 56. Hymenolepis nanaOva Spherical or oval Floats in saturated solutions of common salt 2 distinct membranes Outer membrane is thin transparent and colorless Inner embryophore that encloses an oncosphere with 3 pairs of lancet shaped hooklets Intermembranous space is filled with yolk granules and 4-8 polar filaments emating from little knobs at either end of the embryophore
  57. 57. Hymenolepis nana
  58. 58. Hymenolepis nanaMode of transmission is thruDirect Host ingests eggs that hatches in the duodenumIndirect pathway Accidental ingestion of infected arthropod intermediate host like rice and flour beetles in which cysticercoid arve are released nd develop into adult worms in the small intestine of the host
  59. 59. Hymenolepis nanaPathogenesis Symptoms are produced due to patient’s immunological response to the parasite Asymptomatic for light worm burden Headache Dizziness Anorexia Pruritus of the nose and anus Abdominal pain Pallor Desquamation of intestinal epithelial cell or as serious as necrosis may occurRegulatory immunity will eventually limit theinfection
  60. 60. Hymenolepis nanaDiagnosis Demonstration of characteristic ova in the stool Proglottids are not recovered because they undergo degeneration prior to passageTreatmentPraziquantel– 25mg/kg single dose– Drug dosage is higher than that of taeniasis because of resistant cysticercoids in intestinal tissue
  61. 61. Hymenolepis nanaEpidemiology Countries with warm temperature Southern USA Latin America Mediterranean East Asia Philippines
  62. 62. Hymenolepis diminutaRat tapewormCommon parasite of rats and miceAccidental human infectionsDiffers from Hymenolepis nana in morphologyand life cycle because it requires anintermediate host2 Hosts Larval stage: cysticercoid is passed in fleas Adult stage: in rats and mice and accidentally in humans especially children who accidentally ingest infected fleas
  63. 63. Hymenolepis diminutaAdult Larger than Hymenolepis nana Measures 60 cm in length
  64. 64. Hymenolepis diminutaScolex Unarmed rostellum 4 suckers
  65. 65. Hymenolepis diminuta
  66. 66. Hymenolepis diminutaProglottid 8,00 – 1,000 Mature proglottids of Hymenolepis diminuta from the laboratory rat. The three spherical bodies are testes which surround the ovaries, ootype and vitelline glands. The genital pores are on the left margin
  67. 67. Hymenolepis diminutaOva Larger than H. nana Outer shell is yellowish in color Inner embryohore has 2 knob-like thickenings No polar filaments
  68. 68. Hymenolepis diminutacysticercoid of Hymenolepisdiminuta.The suffix indicates it is like acysticercus but this larva hasno bladder but instead has atail. The dark body within thespherical portion is the scolex.The longer the tail, the moremature the cysticercoid.This stage is found inside aninsect such as the mealworm,
  69. 69. Hymenolepis diminuta
  70. 70. Hymenolepis diminutaPathogenesis Hymenolepiasis Worm burden in rodents is relatively low In man, highest worm burden is 19 Clinical manifestations are minimal and non-specific
  71. 71. Hymenolepis diminutaTreatmentPraziquantel25mg/kg body weight single doseEpidemiologyWorld wideCommon among children due to ingestion ofinfected grain beetles, dried fruits, flour andcerealsPrevalence of H. diminuta in Philippine rats isabout 8%
  72. 72. Dipylidium caninumDouble Pored Dog TapewormPresence of bilateral genital pores in eachsegment (di: 2; pylis: gate): 2 entrancesCommon intestinal parasite of dogs
  73. 73. Dipylidium caninumAdult 10-70 cm in length Pale reddish
  74. 74. Dipylidium caninumScolex Small and globular 4 deeply cupped elliptical suckers Protrusible/retrac tile rostellum Rostellum has 1- 7 rows of rose thorn shaped hooklets
  75. 75. Dipylidium caninum
  76. 76. Dipylidium caninumStrobila 200 proglottids narrow
  77. 77. Dipylidium caninumMatureproglottids 2 sets of male and female reproductive organs Bilatera genital pores
  78. 78. Dipylidium caninumGravidproglottids Have size and shape of pumpkin seeds Filled with capsules or packets of 8-15 eggs enclosed n an embryonic membrane
  79. 79. Dipylidium caninum Proglottids
  80. 80. Dipylidium caninum
  81. 81. Dipylidium caninumOva Passed out in the feces along with the proglottids Released by contraction of proglottids or disintegration outside the host Spherical Thin shelled With a hexacanth embryo
  82. 82. Dipylidium caninumIntermediate hosts Ctenocephalides canis : dog flea Ctenocephalides felis : cat flea Pulex irritans : human flea Trichoedectes canis : dog flea
  83. 83. Dipylidium caninumPathogenesis Dipylidiasis Rarely multiple Symptoms are minimal Slight intestinal discomfort Epigastric pain Diarrhea Anal pruritus Allergic reactions
  84. 84. Dipylidium caninumTreatmentPraziquantel5-10 mg/kg body weight single doseEpidemiologyUSARhodesiaArgentinaChinaPhilippines
  85. 85. Dipylidium caninum