The Cestodes (tape worm)

Nematode trematode

common features of Class Cestoda

1. Adult worm is flattened ribbon-like

2. Body wall: Tegument and

subtegument;

and no body cavity.

body wall construction：substantia corticalis：microvilli 、 cytomere 、 basal membrane①scratch intestinal mucosa②conduce(to)attachment③expand surface area of absorption ④possess sensory function⑤to resist digestion

subcutaneous stratum：annuliform muscle、 vertical muscle、oblique musclehelp the proglottid Slipping and falling off

3.The body is composed of a head, neck an

d segmented strobilus ( 链体 ). The head ha

s suckers, rostellum ( 顶突 ) and hooklets o

r sucking grooves. The neck is the budding

zone from which segments are formed. The

strobilus consists of immature, mature and

pregnant proglottides.

Strobila (链体 ):（ 1 ） Scolex (头节 ) - equipped with organs of attachment: suckers, hooks, grooves.（ 2 ） Neck （颈部） - germinal portion (3) Proglottids (节片 ) - immature, mature, gravid( 孕节 ).

4.  They are hermaphroditic. There is a set of female and male reproductive organs in every mature proglottid.

5. Digestive tract is absent. Nutrition is absorbed by villi of body surface.

Nematode trematode

6.  They are biohelminths. Intermediate hosts are indispensable.7.  All adult worms parasitize digestive tracts of mammals.

8. The developing stages in intermediate hosts are called metacestode ( 中绦期 ), such as cysticercus ( 囊尾蚴 ), hydatid cyst ( 棘球蚴 ), cysticercoid ( 似囊尾蚴 ), procercoid ( 原尾蚴） , plerocercoid （裂头蚴） .

PHYSIOLOGY AND PATHOGENESIS: 1. Surface absorption capabilities. 2. Highly developed reproductive functions. 3. Anaerobic metabolism (无氧代谢 ).

PHYSIOLOGY AND PATHOGENESIS: (2) 4. No external environment development. 5. All species are parasitic. 6. Pathogenic stage may be adult or the larvae.

Tapeworms are classified into two orders: (1).Cyclophyllidea ( 圆叶目 ): The head is spherical with suckers, hooklets. The uterus has no opening. One intermediate host is required. The eggs contain an oncosphere ( 六钩蚴 ). They are medically important, such as Taenia solium ( 链状带绦虫 ), Taenia saginata ( 肥胖带绦虫 ) and Echinococcus granulosus ( 细粒棘球绦虫 ).

Cyclophyllidea (圆叶目 )

(2). Pseudophyllidea (假叶目 ): The head is spear-like with sucking grooves. The uterus has an opening. Two or more intermediate hosts are required. The eggs contain a coracidium （钩球蚴） and have to get into water to develop. Human being occasionally get infection. This worms include Spirometra mansoni （曼氏迭宫绦虫） and Diphyllobothrium latum （阔节裂头绦虫） .

Pseudophyllidea (假叶目 ):

Cyclophyllidea (圆叶目 )

Pseudophyllidea (假叶目 ):

Taenia solium(pork tapeworm)

Adult worms live in human small intestin

e causing taeniasis (绦虫病 ). The larval stag

e (Cysticercus cellulose 猪囊尾蚴 ) lives in p

ig or human tissues causing human cysticer

cosis（囊尾蚴病或囊虫病） .

GENERAL INTRODUCTION:1. Worldwide distribution.2. Large tapeworm.

3. Taenia solium:  Laval infection cause serious clinical disease --- CYSTICERCOSIS.

Adult:

Taenia solium (pork tapeworm)

Adult of the Pork Tapeworm

averages 2 – 4 meters long.

I. Morphology

1.   Adult is flattened ribbon-like, creamy white in color, measures abo

ut 2-4 m and has 700-1000 proglottides.

scolex : global, 1mm. With 4suckers, 1rostellum （顶突） 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 th

e anterior part of the body and inner organs are developing.

Mature proglottides are square in shape and located in the m

id part of the body and have 150-200 testes, a centrally straight

uterus and 3 lobes of ovary .

Pregnant(gravid) proglottides are longitudinal rectangle, locat

ed in the posterior part of the body and contain a branched uter

us filled with eggs. The number of main branches on each side

of the uterus stem is 7-13.

scolex

Mature proglottid

India Ink Technique

• Note : less than 13 lateral uterine branches (one sid

e). In this species the uterus of the gravid proglottid has between 7 and 13 lateral branches on each side.

2.  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

3.Cysticercus cellulose. It is a semitransp

arent and elliptic bladder, like a white p

omegranate seed ( 石榴籽 )about 0.6-1

cm. There is fluid and a white scolex wit

h 4 suckers and hooklets in the bladder.

Under stimulation of bile

The scolex invaginates

in the bladder The scolex evaginates

Cysticerci in myocardium

II. Life cycle 1.  final host: man,

2.  Intermediate host: swine (or man),

3.  Infective stage: cysticercus and egg,

4.  Infective mode: eating raw bean-pork or egg

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.

Life Cycle of Taenia solium

Attach to intestinal mucosascolex evaginates adults grivad proglottides develop into fall off duodenum In human small intestine and are 2-3 months discharged in feces man eats cysticercus in raw pork

───────────────────────────── swine ingests eggs In intermediate hosts man gets infection

60-70days

develop into cysticercus onchosphere hatch

in all parts of the body larval migration in duodenum penetrate intestinal wall into blood stream

III. Pathogenesis and Clinical Manifestations

1.   Taeniasis: It is caused by the adult resi

ding in small intestine of the man. The adult

irritates the small intestine causing discomf

orts, such as abdominal pain, anorexia, chr

onic indigestion, diarrhea, emaciation and e

tc. The patient is usually no obvious sympt

om, only complaining passing proglottides.

2.   Cysticercosis: It is caused b

y the cysticerci living in human t

issues. The manifestations vary

with the number of cysticerci an

d the tissues and organs involve

d. Cysticercosis is divided into f

our types.

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

(1) Subcutaneous type:

(2) muscles type:

Note this cysticercus in the tongue

The cysticercus is usually found in the vitreous body or subretina. Visual disturbance often occurs. The died body of worm may provokes local inflammation causing blindness.

(3) Ocular type:

(4) Brain type: The symptoms are related to the site of infection. The patients may manifest headache, nausea, vomiting, epilepsy ( 癫痫 ), paralysis ( 瘫痪 ), weakness in limbs, diplopia （复视） , dizziness, mental disorder. Epilepsy is the most frequent symptoms of brain cysticercosis.

Brain type

IV. Diagnosis 1.Taeniasis: Confirmative diagnosis of ta

eniasis is made by finding gravid proglotti

des or egg in stool. (1) direct fecal smear

(2) brine floatation technique **(3) cello

phane-tape technique

the examination of a transparent plastic adhesive tape previously applied to the perianal region

Showing some eggs of Taenia spp. and

an egg of E.vermicularis.

Scotch-tape smear

2. For cysticercosis (1) Specific diagnosis is difficult to establish, the history and adult worm infection attribute to strong suspicion. (2) Biopsy to subcutaneous lesions. (3) computerized axial tomography

(CT) or (MRI). are used for the diagnosis of brain type and ophthalmoscope examination is used for ocular form.

3.   Immunological tests are for reference only. IHA, ELISA, Dot-ELISA McAb-CAg.

V. Treatment and prevention

1. Treatment of Taeniasis: (1) Chinese herb med

icine: pumpkin seed and areca nut ( 槟榔 ) . The r

ecognition of a scolex in the patient’s stool after t

he application of taenifuge is important. When th

e entire worm has been expelled, the therapy is s

uccessful, otherwise the strobila regrow. (2) Prazi

quantel may be used.

2. Treatment of cysticercosis: Surgical removal is required for ocular and superficial cysticercoses. Praziquantel may be used to treat brain cysticercosis , but the patients should take praziquantel in hospital.

3.   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.

VI. 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.

Taenia saginata(肥胖带绦虫，牛带绦虫，牛肉绦虫或无钩绦虫 )

Adult worms live in human small intesti

ne causing taeniasis. Larval stage (Cysti

cercus bovis) lives in cattle tissues. This

disease is prevalent all over the world.

1. Body length

T. solium T. saginata

Differences between T. solium and T. saginata

2. scolex

T. solium T. saganita

Mature proglottids of Taenia sp.

3. Mature proglottid

T. solium T. saginata

4. Gravid proglottid

.

T. solium•In this species the uterus of the gravid proglottid has between 7 and 13 lateral branches on each side.

T. saginatathe uterus of the gravid proglottid has between 15 and 30 lateral branches on each side

5. cysticercus

Cysticercus cellulose Cysticercus bovis

COMPARASON OF THE TWO TAPEWORMS:

T. solium T. saginata

1. Size 2-4m 4-8m

2. Scolex Rostellum

& hooks No

3. Mature Proglottid:

Ovary 3 lobes 2 lobes

4. Gravid proglottid :

Lateral Uterine Branches<13 >15

COMPARASON OF THE TWO TAPEWORMS: (2)

T. solium T. saginata 5. Intermediate Host: Swine & Humans, Cattle 6. Disease caused : Taeniasis & cysticercosis, Taeniasis only 7. Infective stage: Egg & Cysticercus, Cysticercus Only8. Mode of infection : Cross or autoinfection, Cross only

COMPARASON OF THE TWO TAPEWORMS: (3)

T. solium T. saginata

9. Diagnosis :

Gravid proglottid, Gravid proglottid

Egg may be found in stool, Egg may be found in stool,

Perianal egg exam Perianal egg exam

T. solium T. saginata

10. Clinical significance:

Much more important, Less important

11. Chemotherapy:

Should be instant , Not so urgent

COMPARASON OF THE TWO TAPEWORMS: (3)

II. Life cycle The intermediate host is cattle and cysticercus

bovis can not live in human. The others same as those of T. solium.

III. Pathogenesis:

Usually only single worm is present and the patient is no symptom. Some patients may complain of migrating proglottids from anus with pruritus at the perianal region. Abdominal discomfort, nausea, vomiting, constipation or diarrhea may occur.

IV. Diagnosis Finding of gravid proglottids or eggs at the perianal region b

y cellophane tape method.

V. Epidemiology:

T. saginata has a world-wide distribution. Human infection is acquired from consumption of raw beef containing the cysticercus bovis. Cattle become infected from grazing on the ground polluted by human feces containing the eggs of the parasite. It is important to have latrines and manure pits far away from the pastures.

VI. Treatment:

Same as tha of T. solium

** Echinococcus granulosus(dog tapeworm)

There are three developmental stage in lyfe cycl

e including egg, larva and adults. Adult worms

live in the small intestine of dogs, wolves and

other canines. The larval stage lives in the tiss

ues of herbivores or men, so man is a intermed

iate host of Echinococcus granulosus. It cause

s echinococcosis (hydatid disease or hydatido

sis). Hyditid cyst chiefly lives in the liver of hu

man body.

The globular scolex bears a rostellum with 24-40 hooklets and 4 sukers.

Slender neck. Immature proglottid Mature proglottid Gravid proglottid consists

of uterus with irregular lateral branches filled with eggs.

All kinds of proglottids only one.

Adult morphology

Egg The egg,34 to 41um in diameter, has a brown,thick,radially striated embryophore surrouding an oncosphere,six-hooked embryo, and is similar in appearance to those of Taenia worms

Hydatid fluid

Hydatid cyst

Protoscolex

Brood capsules

Daughter cysts

Granddaughter cysts

Laminated layer

Germinal layer

contents

Cyst wall

hydatid sand

Hydatid Cyst:

Hydatid cyst Largest larval stage of all tap

eworms

Protoscolex

Notice the scolex armed with suckers and hooklets.

Life cycle

The definitive hosts are dogs, wolves, and other canines. The adult inhabits their small intestine. The eggs discharged from the ruptured proglottid, pass to outside with feces. The intermediate hosts are sheep, cattle, goats, camels, horses and human beings.

Life cycle

When the intermediate hosts ingests eggs, they hatch in the duodenum and penetrate the intestinal mucosa and are carried by the blood to the liver, brain, heart, bones, kidneys and other tissues. When they are earten by a definitive host such as dogs, each of the individual protoscolex may develop into an adult worm in about 7 to 8 weeks. Then the adult worm may discharge eggs.

Conclusion of life cycle

1.Definitive host: dogs, wolves, and other canines.

2.Intermediate host: herbivores and humans.3.Infective stage: protoscloex (to definitive host)

egg (to intermediate host)

4.Route of transmission: protoscolex are eaten by definitive host, eggs are ingested by intermediate host.

Pathogenesis and syptomatology

The common pathogeneses are:a) Local compression and excitation:

the cyst acts as a sapce-occupying lesion,produces damage on adjacent tissues, example for liver,lung,brain,kidney and so on

Hydatid cyst in liver

Cyst in liver, there may be hepatomegaly, right upper quadrant pain, jaundice, hepatic mass, etc.

Hydatid cyst in lungsCyst in lungs may

give rise to cough,shortness of breath, hemoptysis( 咯血 ), or chest pain.

Hydatid cyst in brainCysts within the central nervous system will produce serious damage. The common symptoms are headache, nausea, vomiting,epilepsy, dizziness,mental confusion,and weakness in limbs.

Hydatid cyst in kidneyCysts live in th

e kidney may induce circulating antigen-antibody complexes deposit in the kidney,initiating inflammation

Pathogenesis and syptomatology

b) Secondary hydatid cyst inflammation:

Rupture of hydatid cyst may release the fluid, lead to dissemination of infection and produce secondary hydatid cysts, or provoke inflamation.

Pathogenesis and syptomatology

C) Allergic reaction: the cyst fluid contains parasite antigens, which can sensitize the host, so pruritus and urticaria occur usually. If the cyst ruptures spontaneously or during trauma or surgical removal,life-threatening anaphylaxis can occur.

Pathogenesis and syptomatology

d) Poisoning and gastrointestinal dysfunction

The patient may present with anorexia, loss of body weight, maldevelopment due to the toxin of parasite.

Laboratory diagnosis

observe the protoscolex with microscope in sputum, 尿液、腹水或胸水

IHA 、 ELISA Dot-ELISAChest X-ray, CT, MRI and ultrasonography( 超声 )

The end

See you next time

plerocercoid 裂头蚴(spirometra mansoni)

cysticercus 囊尾蚴

hydatid cyst 棘球蚴

procercoid 原尾蚴(Diphyllobothrium latum)

cysticercoid 似囊尾蚴(hymenolepis nana)

head has suckers, rostellum and hooklets

neck budding zone from which segments are formed

strobilus

immature proglottides

mature proglottides

pregnant proglottides

Laminated layer

Germinal layer

Protoscolex

Brood capsules

Daughter cysts

Granddaughter cysts