Download T.Saginata. Gravid segment

Phylum:Platyhelminths(flat worm)
Class:Cestoidea(Tapeworms)
Subclass:Cestoda
General characters:
-Flattened and segmented worms
-Size from few mm to several meters
-No digestive system,no body cavity.
-Body is divided into 3 parts:
A-Scolex:
-suckers
-rostellum
-hooks
B-Neck
C-Strobila-proglottids(segments):a chain of
progressively developing segments:immature,
mature and gravid segment
-Adults are hermaphrodites as cuch segment
contains both male and female genital organs.
Classification of cestodes according to
habitat in man:
1-Intestinal:present as adults:
-Diphyllobothrium latum( fish tapeworm)
-Taenia saginata(Beef tapeworm)
-Taenia solium(Pork tapeworm)
-Hymenolepis nana(Dwarf tapeworm)
-Hymenolepis diminuta(Rat tapeworm)
-Dipylidium caninum(Dog tapeworm)
2-Exta-intestinal or tissue cestodes:these are
present as larvae:
-Sparganum-plerocercoides of Spirometra.
-Hydatid cyst of Echinococcus granulosis.
-Cesticercus cellulosae of Taenia solium.
-Cysticercoid of Hymenolepis nana.
-Coenurus cyst of Multiceps multiceps.
There are 2 medically important orders:
Pseudophyllidea and Cyclophyllidea:
Pseudophyllidea
Size
Few meters
Cyclophyllidea
Few mms to several
meters
Scolex shape
Suckers
Rostellum
Common genita
pore
Almond
Pseudo(2 grooves)
Absent
Globular
True 4 suckers
Present or absent
Venteral
Lateral
Vitelline glands
Small follicles on
the sides
Mass behind the
ovary
Uterus
With pores
Blind sac
Egg shape
Operculated
Non-operculated
No.of I.H
2
1 or 0
Examples -Dyphyllobothrium
latum.
-Spirometra spp.
-T.saginata
-T.solium
-Hymenolepis nana
-Hymenolepis diminuta
-Dipylidium caninum
-Echinococcus
granulosus
Order cyclophyllidea
Genus Taenia
Taenia saginata
(Beef tapeworm)
Host: Man
Habitat: Small intestine
Intermediate host: cattle
Geographical distribution:- world wide.
Morphology :
Size:- about 4 – 10 meters long.
Scolex:-Globular in shape with 4 cup shaped suckers. No
rostellum.
Mature segment:- Slightly broader than long (nearly squarish)
-Bilobed ovary
-Uterus: simple tube in the median plane.
-Compact vitelline glands.
-Vagina: opens in the genital atrium.
-Numerous testes.
Gravid segment:-Uterus consists of median longitudinal stem
with 15- 30 main uterine branches ( on each
side).
Egg:-30 × 40 µ in diameter.
-Spherical, with an outer brownish, redially
striated embryophore which surrounds a
hexacanth embryo or onchosphere.
-Color: yellowish brown.
-Contents: hexacanth embryo (onchosphere).
Scolex of T.saginata
Egg of Taenia spp.
Cysticercus bovis:-is the larval stage .
Life cycle:-Mature eggs and gravid segments are detached
separately and disintegrate liberating eggs.
Sometimes these segments creep out of the
anus by their own activity.
-Cattle is the intermediate host within it
cysticercus bovis develop.
4-The final host (man) is infected by ingestion of
undercooked beef containing viable
cysticercous bovis (the infective stage).
Pathogensis:-Most infected individuals are asymptomatic.
-Other cases show intestinal disorders, hunger
feeling, diarrhea, loss of weight and weakness.
-Appendicitis and intestinal obstruction.
-Moderate eosinophilia (20- 30 %)
-Segments of Taenia saginata migrating out of
the anus cause worry and anexiety. This may
be the first clue that the patient has tape
worm infection.
Diagnosis:
●Examination of stool to detect:-Eggs :- but rare and indistinguishable from
T.solium egg.
-Gravid segment
Control:1-Treatment of infected persons.
2-meat inspection in slaughter-houses.
4-Through cooking of beef.
Taenia solium
(Pork tapeworm)
Host: Man
Habitat: Small intestine
Intermediate host: Pig and accidentally man
Geographical distribution:- found in many
parts of the world where raw or poorly cooked
pork is eaten.
Morphology:Size:- about 2 – 4 meters long.
Scolex:-With 4 cup-shaped suckers and
rostellum armed with 2 crowns of hooks .
Mature segment:-Similar to that of T.Saginata.
Gravid segment:-Resembles that of T.Saginata
but differs in :1)Smaller in size.
2)Number of main uterine branches are 713 on each of the uterine tube.
Scolex of T.solium
Egg:-Similar to that of T.Saginata.
Cysticercus cellulosae:-It is larval stage T.solium.
Life cycle:-Similar to that of T.Saginata
-Infection with the adult worm is initiated by
ingestion of raw or poorly cooked pork
containing encysted T.solium larvae.
-Man, the final host, may be also infected with
cysticerci so act as intermediate and definitive
host.
More importantly a human who carries an adult
T.solium in the intestine is liable to ingest eggs
passed in its own faeces. This type of self
infection is called external auto-infection which is
common. Also regurgitation of gravid segments
or eggs to the stomach exposes them to gastric
juice and may result in hatching of onchosphere
on return to the intestine. This type is called
internal auto-infection
cysticercosis .
●Which is more dangerous, T.solium or T.saginata ?
•
Pathology:- Presence of the adult worm
usually causes no problems other than:-Intestinal disorders, hunger pain, weakness.
-Diarrhea alternating with constipation usually
accompanies with increased appetite.
-Anaemia, eosinophilia may reach 25-30%.
Diagnosis:1-Examination of stool to detect gravid
segments
2-Eggs rarely present in stool and are similar
to those of T.Saginata.
Control:
1)Treatment of infected patients.
2)Meat inspection in slaughter houses.
3)Avoid eating insufficiently cooked pork
Cysticercosis
Definition:- This is the invasion of human
tissues by the larval stage of Taenia solium
(cysticercus cellulosae).
Mode of infection:- Man acquires infection on
ingestion of T.solium egg by one of the following
ways:1-Ingestion of raw vegetables or water
contaminated by infected faeces containing eggs
of T.soluim.
2-Auto infection:-Internal auto-infection as a result of
regurgitation of eggs released by disintegration
of gravid segment into the stomach by reverse
peristalsis.
-External auto infection as a result of hand to
mouth way.
3-Infected food handlers may disseminate the eggs
to food.
Pathogenesis:
1-The cyst produces a foreign body
inflammatory reaction which usually ends in
fibrosis and calcification.
2-Manifestations depend upon the tissue
invaded and the number of cysticerci.
3-The commonest sites are subcutaneous
tissues, muscles, brain, heart, liver, lung and
peritoneum.
4-The number of cysticerci vary from one to
several thousands.
5-Most seriously neurocysticercosis may develop
when the cysticerci localize in central nervous
system producing mental disturbances or
clinical signs of epilepsy or intracranial
hypertension.
Diagnosis:1-Biopsy.
2-X-ray may show calcifications later in the
course of the disease.
3-CT (computerized tomography) scans and
ultrasound may be helpful in identification.
4-Serological methods as IHA and ELISA may be
of help.
Prevention:
1- Human faeces should not be used as manure.
2-Proper washing of raw vegetables
3-Prompt treatment of infected persons to
eliminate the danger of auto infection with
cysticerci.
4-Infected persons should not take emetics or
nauseating drugs.
Cysticercus racemosus:Refer to an aggregate of cysts formed near
the base of the brain looks like a bunch
of grapes and may represent special type
of cysticercosis.
Treatment:
1-Praziquantel: 5-10mg ∕ kg in both adults and children.
2-Niclosamide:2g chewed thoroughly in adults. In
children 50mg/kg.
Treatment kills adult worms but NOT eggs. This is fine
for T.saginata but may not for T.solium in which the
praziquantel is the drug of choice.
3-Nitazoxanide is effective in praziquantel and
niclosamide resistant strains.
4-Cysticerci in some parts of the body may be surgically
removed.
Also,
care must be taken during treatment for
adults so that vomiting is not included which
may cause reverse peristalsis.
N.B:
T. saginata differ from T. solium in that:
1-Egg of T. saginata is more elliptic while egg of T. solium
is spherical.
2-Gravid segment oT.saginata is opaque while that of T.
solium is transparent (this can differentiate between
them without staining).
3-Scolex of T.saginata is without rostellum or hooks.
4-Staining of the mature segment of T.saginata will show:
- testis more numerous and none of them present
posterior to the vitelline gland.
-ovary has two lobules.
-cirrus sac is small.
-the vagina has a sphincter.