CESTODES by 6MgQeS

VIEWS: 394 PAGES: 86

									CESTODES
     General Characteristics
Majority are long, 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
     General Characteristics
Sexes are not 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)
    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
   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
 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
  Differences Between a Pseudophyllidean
       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
        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
    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
Diphyllobothrium latum
Scolex is spoon-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
     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
Diphyllobothrium latum




   http://pathmicro.med.sc.edu/parasitology/dip1.jpg 3-01-08
      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
        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
Diphyllobothrium latum
Diphyllobothrium latum
       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
         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
          Taenia saginata
Beef Tapeworm
Unarmed Tapeworm
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
                 Taenia saginata
1,000 to 2,000 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
Taenia saginata
               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
              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
             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
         Taenia solium
Pork Tape worm
Armed Tapeworm of Man
Taeniasis is common among
those eating raw or insufficiently
cooked “measly pork”
Uncommon among non-pork
eaters
            Taenia solium
Scolex is globular 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
Taenia solium
Taenia solium
              Taenia solium
Adult worms measure
2-3 meters
Adult worms live up to 25
years
              Taenia solium
800-900 proglottids
Common genital 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
             Taenia solium
Ova
– Same as those of
  Taenia saginata
– Infective to man as
  well as pigs
– Thick brown striated
  embryophore
  surrounding a
  hexacanth embryo
          Taenia solium
Final Host: Man
Intermediate Host: Pig
Mode of infection; eating measly pork
containing Cysticercus cellulosae
Diagnosis: stool examination for
proglottids/eggs
              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
                 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
              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
  Echinococcus granulosus
Taenia echinococcus
Dog Tapeworm
Hydatid Worm
Man harbors the larval form and not the
adult worms which however is found in the
intestine of dogs and canines
   Echinococcus granulosus
Adult worms are small
(3-6 mm in length)
It is composed of a
     Scolex
     Neck
     Strobila
3 segments
(occassionally 4)
     Immature
     Mature
     Gravid
   Echinococcus granulosus
Scolex bears 4
suckers and a
protrusible rostellum
with 2 circular rows of
hooks.
   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
  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
Echinococcus granulosus
Echinococcus granulosus
   Echinococcus granulosus
Definitive Host
     Dog
     Wolf
     Fox
     Jackal
Intermediate Host
     Sheep
     Pig
     Cattle
     Horse
     Goat
   Echinococcus granulosus
Definitive Host
     Dog
     Wolf
     Fox
     Jackal
Intermediate Host
     Sheep
     Pig
     Cattle
     Horse
     Goat
  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
Echinococcus granulosus
Echinococcus granulosus




 Encysted scolices of Echinococcus granulosus
 in lung "hydatid sand"
Echinococcus granulosus




 Encysted scolices of Echinococcus granulosus
 in lung "hydatid sand"
Echinococcus granulosus




 Encysted scolices of Echinococcus granulosus
 in lung "hydatid sand"
  Echinococcus granulosus
Diagnosis
    Radiographic findings
    Immunodiagnosis
    Antibody detection
          IHA
          IFA
          EIA

Antigen detection
  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
       Hymenolepis species
Genus is derived 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
        Hymenolepis nana
Dwarf Tapeworm
Smallest tapeworm 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”
         Hymenolepis nana
Adult
Found in the 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
         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
            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
Hymenolepis nana
        Hymenolepis nana
Mode of transmission 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
          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
        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
      Hymenolepis nana
Epidemiology
   Countries with warm temperature
         Southern USA
         Latin America
         Mediterranean
         East Asia
         Philippines
     Hymenolepis diminuta
Rat tapeworm
Common parasite 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
        Hymenolepis diminuta
Adult
    Larger than
    Hymenolepis nana

    Measures 60 cm in
    length
    Hymenolepis diminuta
Scolex
    Unarmed
    rostellum
    4 suckers
Hymenolepis diminuta
    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
      Hymenolepis diminuta
Ova
  Larger than H.
  nana
  Outer shell is
  yellowish in color
  Inner
  embryohore has
  2 knob-like
  thickenings
  No polar
  filaments
         Hymenolepis diminuta
cysticercoid of Hymenolepis
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,
Hymenolepis diminuta
     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
      Hymenolepis diminuta
Treatment
Praziquantel
25mg/kg body weight 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%
       Dipylidium caninum
Double Pored Dog Tapeworm

Presence of bilateral genital pores in each
segment (di: 2; pylis: gate): 2 entrances

Common intestinal parasite of dogs
     Dipylidium caninum

Adult
    10-70 cm in
   length
    Pale reddish
      Dipylidium caninum
Scolex
   Small and
   globular
   4 deeply cupped
   elliptical suckers
   Protrusible/retra
   ctile rostellum
   Rostellum has 1-
   7 rows of rose
   thorn shaped
   hooklets
Dipylidium caninum
     Dipylidium caninum

Strobila
   200
   proglottids
   narrow
     Dipylidium caninum
Mature
proglottids
   2 sets of male
   and female
   reproductive
   organs
   Bilatera
   genital pores
      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
Dipylidium caninum




     Proglottids
Dipylidium caninum
         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
      Dipylidium caninum
Intermediate hosts

    Ctenocephalides canis : dog flea
    Ctenocephalides felis : cat flea
    Pulex irritans : human flea
    Trichoedectes canis : dog flea
      Dipylidium caninum
Pathogenesis
   Dipylidiasis
   Rarely multiple
   Symptoms are minimal
        Slight intestinal discomfort
        Epigastric pain
        Diarrhea
        Anal pruritus
        Allergic reactions
       Dipylidium caninum
Treatment
Praziquantel
5-10 mg/kg body weight single dose
Epidemiology
USA
Rhodesia
Argentina
China
Philippines
Dipylidium caninum

								
To top