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Phylum Platyhelminths Phylum Nematoda Turbellarians Free-living worms Monogenea Monogenetic flukes Trematodes Digenetic flukes Cestodes Tapeworms Helminths Dr.T.V.Rao MD 2

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Dr.T.V.Rao MD 3

Common features of Class Cestoda:

C ommon features of Class Cestoda 1. Adult worm is flattened ribbon-like, without body cavity. 2. The body is composed of a head, neck and segmented strobilus. The head has suckers, rostellum and hooklets or sucking grooves. The neck is the budding zone from which segments are formed. The strobilus consists of immature, mature and pregnant proglottides. 3. They are hermaphroditic. There is a set of female and male reproductive organs in every mature proglottid. 4. Digestive tract is absent. Nutrition is absorbed by villi of body surface. 5. They are biohelminths. Intermediate hosts are indispensable. Dr.T.V.Rao MD 4

Basics :

Basics Complex two-host life cycle Human beings are the only definitive host (small intestines - 2-4 meters long -800-1000 segments) Both humans and pigs can act as intermediate hosts (larvae or cysticerci) Most common in Latin America, Africa and India - 400,000 people have symptomatic neurocysticercosis in Latin America Dr.T.V.Rao MD 5


CESTODES Order pseudophyllidea : have scolex with bothria ; the sperm whale tapeworm, H. physesteris , can be > 30 m long; the genital pore and uterine pore are located on the mid-ventral surface, and the ovary is bilobed ("dumbbell-shaped"); each segment has 4-14 complete sets of genitalia, can be up to 45,000 segments in a worm Diphyllobothrium sp. Order cyclophyllidea : most important group of tapeworms of humans and domestic animals , multiple proglottid , scolex ("head") with four suckers. Proglottids have a yolk gland or vitellarium posterior to the ovary; can be small (a few mm's) or large (up to 10 m); mammals serve as intermediate hosts Family Taeniidae : Taenia saginata, Taenia solium , taenia multiceps; Echinococcus granulosus , E. multilocularis Family Hymenolepididae : Hymenolepis diminuta, Hymenolepis nana , Diphyllobotrium latum Dr.T.V.Rao MD 6

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Dr.T.V.Rao MD 7

Tapeworms: the Cestodes:

Tapeworms: the Cestodes They are flat in cross section Hermaprhoditic Live in the intestines with feces Life cycles are complex and can include multiple intermediate hosts No mouth, no digestive system They have suckers and teeth that grasp the host. Reproductive structures Behind a short neck are repeated parts of the worm, each containing reproductive structures with eggs and sperm, which can be released with the host's feces. The pieces give the worm a ribbon-like structure, beneficial for absorbing nutrients from the intestine. http://www.ndpteachers.org/perit/biology_image_gallery1.htm Dr.T.V.Rao MD 8

1. Body length:

1. Body length T. solium T. saginata Differences between T. solium and T. saginata Dr.T.V.Rao MD 9

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scolex neck strobila The body plan of adult cestodes includes a scolex (looks like the “head”), a neck and strobila that can extend for only a few proglottids or thousands The strobila is not truly metameric though as several organs like the excretory system extend through the entire worm Proglottid : each individual segment Most worms are very long: occupying the entire length of small intestine Tapeworms Dr.T.V.Rao MD 10


Morphology 1. Adult is flattened ribbon-like, creamy write in color, measures about 2-4 m and has 700-1000 proglottides. scolex : global, 1mm. With 4suckers, 1rostellum and 25-50 hooklets arranged in a double crown It consists of neck: it ’ s the narrowest part of the body and budding zone containing germinative tissue immature proglottides:width>length strobila mature proglottides: width=length gravid proglottides: width<length Dr.T.V.Rao MD 11

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Immature proglottides are transverse rectangle, located in the anterior part of the body and inner organs are developing. Mature proglottides are square in shape and located in the mid part of the body and have 150-200 testes, a centrally straight uterus and 3 lobes of ovary . Pregnant(gravid) proglottides are longitudinal rectangle, located in the posterior part of the body and contain a branched uterus filled with eggs. The number of main branches on each side of the uterus stem is 7-13. Dr.T.V.Rao MD 12

Basics of the infection cycle:

Basics of the infection cycle Faecal-borne infection Tapeworm larval cyst (cysticercus) is ingested with poorly infected meat Larva escapes the cyst and attaches to the mucosa by the scolex Feces are contaminated with eggs (persist for several days in the environment) - consumed by pigs (eggs are hatched and form cysticerci Humans are the only definitive host Pigs - intermediate host (cysticercal stage) However; Humans - also can be the intermediate host - causing cysticercosis (Neurocysticercosis) if they ingest eggs

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The scolex is the part of the worm that anchors it to the intestinal epithelium and prevents that the worm is passed with the digested food Morphology of tapeworms: The scolex Scolex of Diphyllobothrium latum . The scolex structure varies between species of tapeworms. a. Diphyllobothrium latum has a scolex with elongated, slit-like attachment organs (bothria) b. Taenia saginata has four muscular SUCKERS. c. Taenia solium has similar muscular SUCKERS and a ROSTELLUM with rows of chitinous hooks. Scolex of Taenia Solium . http://www.denniskunkel.com/product_info.php?products_id=813 Scolex of Taenia Saginata Dr.T.V.Rao MD 14

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TAENIA SOLIUM The Lancet (2003) 361: 547 T. solium has a scolex (A) with four suckers and a double crown of hooks, a narrow neck, and a large strobila (2-4 m) (B) consisting of several hundred proglottids. About 2 months after ingestion, proglottids begin to detach from the distal end and are excreted in the feces. Each segment contains 50-60,000 fertile eggs. Taenia pisiforme, Scolex. Hakenkranz ähnlich dem der T. solium (Mit freundlicher Genehmigung Roche AG): http://www.infektionsnetz.at/test/bilder/mikroskop/taenia_pisiforme_r.jpg The armed scolex of T. solium (note hooks on top of scolex). CDC Dr.T.V.Rao MD 15

Taenia solium(pork tapeworm):

Taenia solium(pork tapeworm) Adult worms live in human small intestine causing taeniasis The larval stage (Cysticercus cellulose lives in pig or human tissues causing human cysticercosis ) . Dr.T.V.Rao MD 16

Gross appearance of Tinea Solium:

Gross appearance of Tinea Solium Dr.T.V.Rao MD 17

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scolex Dr.T.V.Rao MD 18

Morphology of Tape worm:

Morphology of Tape worm In most cestodes the scolex is tiny when compared to the strobila which makes up most of the actual “worm” The strobila consists of a linear series of proglottids Tape worms are hermaphrodites and each proglottid carries a set of female and male reproductive organs These segments are released and are eliminated with the feces of the host. Dr.T.V.Rao MD 19


Strobila *(Magnifications are based on a 35mm slide image of 24mm in the narrow dimension.) http://www.denniskunkel.com/product_info.php?products_id=813 In most cestodes the scolex is tiny when compared to the strobila which makes up most of the actual “worm” The strobila consists of a linear series of proglottids Tape worms are hermaphrodites and each proglottid carries a set of female and male reproductive organs These segments are released and are eliminated with the feces of the host. Dr.T.V.Rao MD 20


Strobila Strobilation : asexual process of forming segments New proglottids are continuously formed in the neck just below the scolex (A) Along the length of the worm the proglottids increase in size and maturity, developing from premature (B) to mature (C, carrying fully functional and active sexual organs), to the “gravid” stage (D) in which essentially the entire proglottid is filled with the uterus and eggs Dr.T.V.Rao MD 21

The tegument:

Custodies do not have a mouth or any form of intestine The entire uptake of nutrients occurs through multinucleate syncytial tegument. In reflection of this important role in uptake the absorptive surface is highly enlarged by small microvilli or microtriches Microfilaments (actin polymers) are the molecular backbone of microtriches The tegument Dr.T.V.Rao MD 22

Developmental stages: the egg:

Diagram of oncosphere of Hymenolepis diminuta , dorsal view With very few exceptions vertebrates are the final host harboring the adult tape worms Many invertebrates and vertebrates are parasitized as intermediate hosts The embryonate egg contains the oncosphere a larva that will penetrate the intestinal wall after eggs are swallowed by intermediate host The oncospheres of eucestoda have three pairs of hooks which makes it easy to identify them Developmental stages: the egg The egg of the pseudophyllidean tapeworm (left) has a thin shell wall and an operculum, which on hatching opens to release the free swimming larvae. In contrast, the egg of the cyclophyllideans tapeworms (right) has a very thick, resistant egg shell, with no operculum. The eggs of T. saginata and solium are similar. CDC Eggs larval stages (IH) adult forms (DH) Eggs Dr.T.V.Rao MD 23

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Egg , The eggs of Taenia saginata and T. solium are indistinguishable morphologically. The eggs are spherical, diameter 31 to 43 µ m, with a thick radially striated brown embryophore ( 胚膜 ). Inside each is an oncosphere ( 六钩蚴 ) with 6 hooklets. t Dr.T.V.Rao MD 24

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.Cysticercus cellulose . It is a semitransparent and elliptic bladder, like a white pomegranate seed about 0.6-1cm. There is fluid and a white scolex with 4 suckers and hooklets in the bladder. Dr.T.V.Rao MD 25

Life cycle:

Life cycle 1. final host: man, 2. Intermediate host: pig (or man), 3. Infective stage: cysticercus and egg, 4. Infective mode: eating raw bean-pork, 5. Site of inhabitation: adult in small intestine; cysticercus in tissues, 6. Infective mode of cysticercosis: endogenous, exogenous auto-infection and foreign source; 7. Life span: more than 25 years; cysticercus can survives 5-6 years in human body. Dr.T.V.Rao MD 26

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Dr.T.V.Rao MD 27

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Dr.T.V.Rao MD 28

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Egg or gravid proglottides Ingested by pig and human Oncospheres Intestine Raw or undercook pork cysticerci Cysticer- cosis Dr.T.V.Rao MD 29

Human infection - taeniasis:

Human infection - taeniasis The scolex attaches to the mucosa and begins forming segments (proglotids) After two months of infection, gravid proglotids begin to detach from the distal end - excreted in the feces Each segment contains 60,000 eggs Worm causes only minor inflammation to the intestine (mild symptoms - abdominal pain, distension, diarrhea and nausea - or none at all) Dr.T.V.Rao MD 30

Human infection - cysticercosis:

Human infection - cysticercosis Faecal-oral contamination with T. solium eggs from tapeworm carriers Internal autoinfection is also possible The invasive oncosphere (embryos) in the eggs are liberated by the action of gastric acid and cross the bowel wall (remember - cysticerci are too big to cross the bowel wall) They establish at small terminal vessels (muscles, brain, eye) where they grow to about the size of 1 cm in 2-3 months Dr.T.V.Rao MD 31

Human cysticercosis:

Human cysticercosis Muscle - small, palpable, movable nodules - chests and arms - mild or no symptoms Ophthalmic cysticercosis - intraocular cysts floating freely in the vitreous humor - decreased visual acuity Neurocysticercosis - most symptoms are because of the inflammatory reaction associated with cyst degeneration (that may take years to happen) - epilepsy, hydrocephalus, encephalitis, meningitis Dr.T.V.Rao MD 32

Human cysticercosis:

Human cysticercosis Muscle - small, palpable, movable nodules - chests and arms - mild or no symptoms Ophthalmic cysticercosis - intraocular cysts floating freely in the vitreous humor - decreased visual acuity Neurocysticercosis - most symptoms are because of the inflammatory reaction associated with cyst degeneration (that may take years to happen) - epilepsy, hydrocephalus, encephalitis, meningitis Dr.T.V.Rao MD 33


CLINICAL MANIFESTATIONS S ymptoms can be different depending on where infection with cysticerci occurs how many the cysts are there Most cases are asymptomatic. Incubation: months~5ys Dr.T.V.Rao MD 34

Subcutaneous type:

Subcutaneous type The subcutaneous nodules are usually found in head, limbs, neck, abdomen and back. They are movable and painless. Dr.T.V.Rao MD 35

Cysticercosis in the tongue:

Cysticercosis in the tongue Dr.T.V.Rao MD 36

Brain type: Neurocysticercosis :

Brain type : Neurocysticercosis The symptoms are related to the site of infection. The patients may manifest headache, nausea, vomiting, epilepsy , paralysis , weakness in limbs, diplopia , dizziness, mental disorder. Epilepsy is the most frequent symptoms of brain cysticercosis. Dr.T.V.Rao MD 37

Major cause of Morbidity due to Brain Involvement :

Major cause of Morbidity due to Brain Involvement Dr.T.V.Rao MD 38


Diagnosis 1.Taeniasis: Confirmative diagnosis of taeniasis is made by finding gravid proglottides or egg in stool. (1) direct fecal smear (2) brine floatation technique (3) cellophane-tape technique 2. Cysticercosis: Biopsy of subcutaneous nodules, X-ray ,CT 0r MR are used for the diagnosis of brain type and ophthalmoscope examination is used for ocular form. 3. Immunological tests are for reference only. Dr.T.V.Rao MD 39

Diagnosis - Taeniasis:

Diagnosis - Taeniasis Visualization of Taenia eggs was the only diagnosis until recently - has poor sensitivity and difficult to differentiate from taenia saginata . Best diagnosis - coproantigen detection ELISA (detect taenia specific molecules in the feces - 95% sensitivity and 99% specificity) Options: not efficient and cheap test vs. efficient and expensive test

Diagnosis - cysticercosis:

Diagnosis - cysticercosis Depends on the targeted organ: CNS - CSF immunology, neuroimaging (the scolex can be seen) Muscle - imaging, bx Eye - imaging (ultrasound) (serological exam - ELISA)

Why Taeniasis/Cysticercosis is a significant public health issue?:

Why Taeniasis/Cysticercosis is a significant public health issue? It accounts for 10% of acute neurological admissions in endemic areas It produces significant livestock production losses to pig owners An interesting model of zoonotic disease that can be applied to other infections diseases

Treatment - cysticercosis:

Treatment - cysticercosis Neurocysticercosis is the main problem The problem of the cyst is the inflammatory reaction Use of parasiticide (praziquantel or albendazole) - debatable - aim is to reduce inflammation and scar tissue palliative treatment to control inflammation - corticosteroids, antihistamines

Treatment and Epidemiology :

Treatment and Epidemiology Treatment of cysticercosis: Surgical removal is required for ocular and superficial cysticercosis. Praziquantel may be used to treat brain cysticercosis , but the patients should take Praziquantel in hospital. Prevention: (1) Health education (2) Avoid eating raw bean-pork. (3)avoid pigs eating human stool. (4) sanitary inspection of slaughter and sanitary disposal of night soil. Dr.T.V.Rao MD 44


Epidemiology This disease is prevalent all over the world except Muslim and Jew areas. The infection of T. solium is closely associated with the method of pig-raising and the sanitary condition. Affect millions of individuals - 2.5 million people worldwide carry the T. solium and 20 million are infected with the cysticerci Endemic villages - up to 25% are seropositive and 10-18% have CT findings suggestive of Neurocysticercosis

How can we prevent cysticercosis ?:

How can we prevent cysticercosis ? Control the sources of infection Control transmission ways Educate the populations Avoid eating raw or undercooked pork Wash hands after using the toilet and before handling food Wash and peel all raw vegetables and fruits before eating Dr.T.V.Rao MD 46


Eradication Pros: human is the only carrier, there a relatively simple treatment Other issues: 1) Technical - lack of a simple diagnosis, lack of an easily available treatment (costs) 2) Societal: poor community cooperation and sanitary education 3) Political: low priorities and debatable strategy CDC - eradication cannot be achieved in the near future - only regional elimination

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Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World Email doctortvrao@gmail.com Dr.T.V.Rao MD 48

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