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Cestodes
Cestodes, or tapeworms, are flat segmented parasitic worms that infect the intestines of humans and other animals. They range in size from a few millimeters to several meters in length. The body consists of a head (scolex) and chain of segments (proglottids) that contain reproductive organs. Two major orders that infect humans are Pseudophyllidea and Cyclophyllidea. Pseudophyllidea have slit-like grooves instead of suckers, while Cyclophyllidea have cup-like suckers. Common tapeworms infecting humans include Diphyllobothrium latum (fish tapeworm), Taenia saginata (beef tapeworm), Taenia sol
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Cestodes
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- 2. General Characteristics Majority arelong, segmented and tape-like are called tapeworms Dorso-ventrally flattened Size varies from a few mm to several meters Adult worms are found in the intestinal canal of man and animals “head” or scolex is provided with suckers and sometimes with hooks that serve as organs of attachment There are 3 regions in an adult worm: Head: scolex Neck Strobila (body or trunk) Consist of a series of segment called proglottids
- 3. General Characteristics Sexes arenot separate Body cavity is absent Alimentary canal is entirely absent Excretory and nervous systems are present Reproductive system is present and complete in each segment 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. Classification of Cestodes Infecting Man I. 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. Classification of Cestodes Infecting Man II. 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. Classification of Cestodes Infecting Man According to Habitat II. 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. Differences Between aPseudophyllidean and a Cyclophyllidean Cestode Pseudophyllidean Cyclophyllidean Head or scolex Bears 2 slit-like Bears 4cup-like grooves suckers uterus No branching Branching Convoluted uterine May or may not be tubes assume the present form of rosettes Uterine pore present absent Common genital pore Ventral; in the midline lateral eggs Operculated; gives Not operculated; do rise to ciliated larvae not give rise to ciliated larvae
- 8. Order Pseudophyllidea Characteristics Large worms consisting of a long chain of segments “head” has two slit-like sucking grooves called bothria instead of suckers Uterine glands are widely scattered in the parenchyma and is composed of many acini Genital pores are on the ventral surface of the segment and are not marginal Uterus opens to the exterior through which eggs come out Eggs are operculated and can develop only in water; immature when oviposited and oncosphere gives rise to ciliated embryo Larval development proceeds in two intermediate hosts: First larval stage is called procercoid Second larval stage is called plerocercoid
- 9. Diphyllobothrium latum Common Name: Fish Tapeworm Broad Tapeworm Morphology 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. Diphyllobothrium latum Scolex isspoon-shaped or spatulate Scolex bears 2 slit-like grooves called bothria (1 on the dorsal surface and 1 on the ventral surface) Scolex has no rostellum and no hooklets Neck is thin and unsegmented and is much longer than the head
- 11. Diphyllobothrium latum Morphology 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. Diphyllobothrium latum http://pathmicro.med.sc.edu/parasitology/dip1.jpg 3-01-08
- 13. Diphyllobothrium latum Ova 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. Diphyllobothrium latum larva 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
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- 17. Diphyllobothrium latum Final Host Man, dog, cat Small intestine 1st I.H. Cyclops or Diaptomus 2nd I.H. Fresh water fish, pike, trout, salmon, perch Mode of Infection Ingestion of imperfectly cooked infected fish or roe containing plerocercoid larvae Infection Diphyllobothriasis G.I. disturbances and anemia Diagnosis Microscopic examination of feces for the characteristic operculated eggs
- 18. Order Cyclophyllidea Characteristics Large or small worms consisting of chains of segments Scolex is quadrate with four cup-like round suckers An apical rostellum with hooklets may be present Vitelline glands concentrated in a single mass Common genital pore is marginal (on lateral side of segment) No uterine opening for the exit of eggs from the gravid uterus Eggs only escape from the rupture or disintegration of ripe segments Eggs are not operculated and can develop only in the intermediate host, fully embryonated Oncosphere is never a ciliated embryo Larval development proceeds in one intermediate host
- 19. Taenia saginata Beef Tapeworm UnarmedTapeworm of Man Adult worms are white and semi-transparent Measures about 5-10 meters or sometimes up to 24 meters Live up to 10 years or more
- 20. Taenia saginata 1,000 to2,000 proglottids Common genital pore is marginally situated Vagina is provided with a sphincter muscle Gravid proglottid consists of a uterus and a central longitudinal stem with 15 – 30 branches on each side Highly branched proglottids Gravid proglottid contains 97,000 to 124,000 ova Gravid segments are expelled singly and force their way through the anal sphincter Free gravid proglottid crawls out of the anal orifice and oviposits on the perianal skin
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- 22. Taenia saginata Ova 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. Taenia saginata Final Host:Man Intermediate Host: cattle, cow buffalo Mode of Infection; eating beef containing Cysticercus bovis Pathogenesis 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. Taenia saginata Diagnosis 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 swabs Treatment Praziquantel 5-10mg/kg single dose Criteria for cure Recovery of the scolex Negative stool examination 3 months after treatment
- 25. Taenia solium Pork Tapeworm Armed Tapeworm of Man Taeniasis is common among those eating raw or insufficiently cooked “measly pork” Uncommon among non-pork eaters
- 26. Taenia solium Scolex isglobular in outline with 4 circular suckers Scolex has a rostellum armed with a double row of alternating large and small hooklets Rostellar hooklets are shaped like daggers or Arabian poniards
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- 29. Taenia solium Adult wormsmeasure 2-3 meters Adult worms live up to 25 years
- 30. Taenia solium 800-900 proglottids Commongenital pore is marginal and thick lipped Vaginal opening is not guarded by a muscular sphincter Gravid segments are expelled passively in chains of 5-6 at a time and not singly. Gravid proglottids contains approx. 30,000 to 50,000 eggs
- 31. Taenia solium Ova – Sameas those of Taenia saginata – Infective to man as well as pigs – Thick brown striated embryophore surrounding a hexacanth embryo
- 32. Taenia solium Final Host:Man Intermediate Host: Pig Mode of infection; eating measly pork containing Cysticercus cellulosae Diagnosis: stool examination for proglottids/eggs
- 33. Taenia solium Pathogenesis 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. Taenia solium Diagnosis Intestinal Identifying the characteristic proglottids, eggs or scolex Cysticercosis Computed Axial Tomography Magnetic Resonance Imaging Treatment Praziquantel: 5-10 mg/kg single dose for children and adults Niclosamide not available locally Criteria for cure: Recovery of scolex Negative stool exam 3 months after treatment
- 36. Comparison Between T. saginata and T. solium Taenia saginata Taenia solium length 5-10 meters 2-5 meters Head or scolex Large, quadrate, no Armed; with rostellum; rostellum and hooks with hooklets Number of proglottids 1,000 to 2,000 Below 1000 Expulsion Expelled singly and may Explelled passively in be forced through the chains of 5 or 6 anal sphincter uterus 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 absent testes 300-400 follicles 150-200 follicles
- 37. Echinococcus granulosus Taenia echinococcus DogTapeworm Hydatid Worm Man harbors the larval form and not the adult worms which however is found in the intestine of dogs and canines
- 38. Echinococcus granulosus Adult wormsare small (3-6 mm in length) It is composed of a Scolex Neck Strobila 3 segments (occassionally 4) Immature Mature Gravid
- 39. Echinococcus granulosus Scolex bears4 suckers and a protrusible rostellum with 2 circular rows of hooks.
- 40. Echinococcus granulosus Ova Ovoid in shape Resemble Taenia ova Hexacanth embryo with 3 pairs of hooks Infective to: Man Cattle Sheep and other herbivorous animals
- 41. Echinococcus granulosus Larva 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
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- 44. Echinococcus granulosus Definitive Host Dog Wolf Fox Jackal Intermediate Host Sheep Pig Cattle Horse Goat
- 45. Echinococcus granulosus Definitive Host Dog Wolf Fox Jackal Intermediate Host Sheep Pig Cattle Horse Goat
- 46. Echinococcus granulosus Pathogenesis Echinococcosis 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
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- 48. Echinococcus granulosus Encystedscolices of Echinococcus granulosus in lung "hydatid sand"
- 49. Echinococcus granulosus Encystedscolices of Echinococcus granulosus in lung "hydatid sand"
- 50. Echinococcus granulosus Encystedscolices of Echinococcus granulosus in lung "hydatid sand"
- 51. Echinococcus granulosus Diagnosis Radiographic findings Immunodiagnosis Antibody detection IHA IFA EIA Antigen detection
- 52. Echinococcus granulosus Treatment 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
- 53. Hymenolepis species Genus isderived from the membranous character of the egg shell “hymen” 3 testes in each mature segment Uterus is sac-like and transverse Eggs possess two membranes’ outer membrane is thin and transparent larval stage is called cysticercoid Small bladder containing the invaginated head proximally and a solid, elongted portion as a caudal appendage There are 2 species; Hymenolepis nana Hymenolepis diminuta
- 54. Hymenolepis nana Dwarf Tapeworm Smallesttapeworm infecting man Found worldwide Mainly among children Only human tapeworm that can complete its life cycle in a single host Man can harbor both the adult and larval stages of the parasite Exception to the general rule that “Helminths do not multiply inside the body of the definitive host”
- 55. Hymenolepis nana Adult Found inthe ileum Delicate strobila 25 mm to 45 mm Worms may be presenr in large numbers from 1,000 to 8,000 Short life span, about 2 weeks Up to 200 proglottids Transverse uterus 3 testes
- 56. Hymenolepis nana Scolex 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
- 57. Hymenolepis nana Ova 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
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- 59. Hymenolepis nana Mode oftransmission is thru Direct Host ingests eggs that hatches in the duodenum Indirect 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
- 60. Hymenolepis nana Pathogenesis 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 occur Regulatory immunity will eventually limit the infection
- 61. Hymenolepis nana Diagnosis Demonstration of characteristic ova in the stool Proglottids are not recovered because they undergo degeneration prior to passage Treatment Praziquantel – 25mg/kg single dose – Drug dosage is higher than that of taeniasis because of resistant cysticercoids in intestinal tissue
- 62. Hymenolepis nana Epidemiology Countries with warm temperature Southern USA Latin America Mediterranean East Asia Philippines
- 63. Hymenolepis diminuta Rat tapeworm Commonparasite of rats and mice Accidental human infections Differs from Hymenolepis nana in morphology and life cycle because it requires an intermediate host 2 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
- 64. Hymenolepis diminuta Adult Larger than Hymenolepis nana Measures 60 cm in length
- 65. Hymenolepis diminuta Scolex Unarmed rostellum 4 suckers
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- 67. Hymenolepis diminuta Proglottid 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
- 68. Hymenolepis diminuta Ova Larger than H. nana Outer shell is yellowish in color Inner embryohore has 2 knob-like thickenings No polar filaments
- 69. Hymenolepis diminuta cysticercoid ofHymenolepis diminuta. The suffix indicates it is like a cysticercus but this larva has no bladder but instead has a tail. The dark body within the spherical portion is the scolex. The longer the tail, the more mature the cysticercoid. This stage is found inside an insect such as the mealworm,
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- 71. Hymenolepis diminuta Pathogenesis Hymenolepiasis Worm burden in rodents is relatively low In man, highest worm burden is 19 Clinical manifestations are minimal and non-specific
- 72. Hymenolepis diminuta Treatment Praziquantel 25mg/kg bodyweight single dose Epidemiology World wide Common among children due to ingestion of infected grain beetles, dried fruits, flour and cereals Prevalence of H. diminuta in Philippine rats is about 8%
- 73. Dipylidium caninum Double PoredDog Tapeworm Presence of bilateral genital pores in each segment (di: 2; pylis: gate): 2 entrances Common intestinal parasite of dogs
- 74. Dipylidium caninum Adult 10-70 cm in length Pale reddish
- 75. Dipylidium caninum Scolex Small and globular 4 deeply cupped elliptical suckers Protrusible/retrac tile rostellum Rostellum has 1- 7 rows of rose thorn shaped hooklets
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- 77. Dipylidium caninum Strobila 200 proglottids narrow
- 78. Dipylidium caninum Mature proglottids 2 sets of male and female reproductive organs Bilatera genital pores
- 79. Dipylidium caninum Gravid proglottids Have size and shape of pumpkin seeds Filled with capsules or packets of 8-15 eggs enclosed n an embryonic membrane
- 80. Dipylidium caninum Proglottids
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- 82. Dipylidium caninum Ova 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
- 83. Dipylidium caninum Intermediate hosts Ctenocephalides canis : dog flea Ctenocephalides felis : cat flea Pulex irritans : human flea Trichoedectes canis : dog flea
- 84. Dipylidium caninum Pathogenesis Dipylidiasis Rarely multiple Symptoms are minimal Slight intestinal discomfort Epigastric pain Diarrhea Anal pruritus Allergic reactions
- 85. Dipylidium caninum Treatment Praziquantel 5-10 mg/kgbody weight single dose Epidemiology USA Rhodesia Argentina China Philippines
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