Dr.T.V.Rao MD 1

TINEA SOLIUMDr.T.V.Rao MD

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Phylum Platyhelminths

Phylum Nematoda

Turbellarians Free-living worms

Monogenea Monogenetic flukes

Trematodes Digenetic flukes

Cestodes Tapeworms

Helminths

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Common 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.

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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

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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

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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

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1. Body length

T. solium T. saginata

Differences between T. solium and T. saginata

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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

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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

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• Faecal-borne infection1) Tapeworm larval cyst (cysticercus) is ingested with poorly

infected meat2) Larva escapes the cyst and attaches to the mucosa by the

scolex3) 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

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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

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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） .

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Gross appearance of Tinea Solium

scolex

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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.

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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.

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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

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• 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

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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

Egg, The eggs of Taenia saginata

and T. solium are indistinguishable

morphologically. The eggs are

spherical, diameter 31 to 43 µm, with

a thick radially striated brown

embryophore ( 胚膜 ). Inside each is

an oncosphere ( 六 钩 蚴 ) with 6

hooklets.

t

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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.

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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.

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Dr.T.V.Rao MD 29Egg or gravid proglottides

Ingested by pig and human

Oncospheres

Intestine Raw or undercook pork

cysticerci Cysticer-

cosis

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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)

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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

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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

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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

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CLINICAL MANIFESTATIONS

Symptoms can be different depending on where infection with cysticerci occurs how many the cysts are there

Most cases are asymptomatic. • Incubation: months~5ys

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Subcutaneous type

• The subcutaneous nodules are usually found in head, limbs, neck, abdomen and back. They are movable and painless.

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Cysticercosis in the tongue

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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.

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Major cause of Morbidity due to Brain Involvement

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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.

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• 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?

• 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• 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

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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.

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

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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

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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