Class Cestoidea Tapeworms Chap' 20

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Class Cestoidea Tapeworms Chap. 20 21
Tapeworms are entirely endoparasitic. Adults
inhabit the ________________________________of
vertebrate definitive hosts. Life cycles involve
larval development in 1 or 2 intermediate
hosts. Of the two subclasses, cestodes of
medical and veterinary importance occur in the
SUBCLASS EUCESTODA
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General Tapeworm Morphology
Tapeworms are polyzoic and
consist of 3
regions a. b. c.
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General Tapeworm Morphology

• Scolex - anterior attachment structure
• Is is NOT a __________________________
• Structures for attachment differ in the 2
  important orders
• Order Pseudophyllidea - scolex contains
  slit-like suckers called _________________________
  ___
• Order Cyclophyllidea - scolex contains
  ______________________________ and a central
  domed area called the ____________________________
  _ with or without hooks
• Scolex is an important taxonomic structure.
• 2. Neck - undifferentiated region posterior to
  scolex

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General Tapeworm Morphology

• 3. Strobila - linear series of segments or
  proglottids
• Proglottids are continuously formed posterior to
  the neck region in a process called
  strobilization.
• As new proglottids are formed, the older
  proglottids move posteriorly and become sexually
  mature.
• immature proglottids
• mature proglottids
• gravid proglottids -

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General Tapeworm Morphology

• Gravid proglottids cont
• Male and female organs in gravid proglottids
  degenerate as the uterus fills with eggs.
• Gravid proglottids often detach from the
  strobila
• - disintegrate during passage through the
  digestive tract releasing eggs in the feces
• - or are released intact in the feces.

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Tapeworm Tegument

• Structure of the tapeworm tegument is similar
  to that of trematodes.
• 1. Syntegument - outer anucleate syncytial
  cytoplasmic layer containing mitochondria and
  secretory bodies.
• Major difference involves the presence of
  _____________________________ on the surface
• microvilli-like projections but with a dense
  core
• increase absorptive area.
• Glycocalyx covers the microtriches.
•  

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Tapeworm Tegument
2. Cytotegument - nucleated cell bodies lying
beneath the tegumental
muscles and connected to syntegument.

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Tapeworm Tegument
Microtriches showing the dense core
Tapeworm tegument
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Functions of the Tapeworm Tegument
1. Because tapeworms lack a digestive tract,
_________________________________ are absorbed
through tegument.   2. Tegument protects the
tapeworm from host _______________________________
_______ This is especially important as
adults live in the small intestine where
digestive enzymes occur. 3. Tegument protects
the tapeworm from ________________________________
_____________. This is important in larval
forms that live in many habitats in host
body.    
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Parenchyma
System of loose cells filling space in the
proglottid. Many parenchymal cells contain
_____________________________________ - a
characteristic structure in tapeworms. These are
circular structures consisting of concentric
rings. Possible functions are (1)
___________________________________________
(2) ______________________________________________
Calcareous corpuscles are

best seen in living specimens.  
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Reproductive Organs
Tapeworms are _________________________________-
each proglottid is a reproductive individual with
both male and female organs. Male system develops
first Structures begin to form in the immature
proglottids and are fully developed in mature
proglottids. Structures are many testes (
varies from 3 to 100's) vasa efferentia vas
deferens (often highly coiled) cirrus sac with
cirrus common genital pore
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Reproductive Organs
Female system - structures form and become
functional in mature
proglottids. Structures are 1 ovary
vitellaria - scattered or compact Mehlis'
gland uterus (contains eggs in branches)
vagina (carries sperm to ootype)   common genital
pore Most of the female organs disappear

in gravid proglottids except for the

egg-filled uterus.
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Taxonomy of the Class Cestoidea
Contains 13 orders but only 2 orders contain
tapeworms of medical and veterinary
importance.   Order Pseudophyllidea  
Order Cyclophyllidea
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Order Pseudophyllidea - Chapter 21
Contains some of the largest tapeworms known -
lengths of 10-30 feet are common Characteristics
of the order  1. scolex contains
_______________________________ -

slit-like adhesive organs   
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Order Pseudophyllidea - Chapter 21
Characteristics of the order cont 2. male and
female genital
openings are
separate and
located
midventrally in the
proglottid   3.
__________________________
are scattered
throughout the proglottid 4. gravid proglottid
is not shed
eggs are released through
________________________________  
??
Uterine pore
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Order Pseudophyllidea
Characteristics of the order cont 5. life
cycles are complex involving 3 hosts  first
intermediate host - ____________________
second intermediate host -
_______________________
definitive host - _________________________   Two
species of medical importance
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Diphyllobothrium latum
Common name - the BROAD FISH TAPEWORM broad -
indicates that the proglottids are wider than
long fish - indicates that the definitive host
is infected by eating raw or poorly cooked
fish DISTRIBUTION - _________________distribution
(not tropical) Occurs in northern Europe, Asia,
and North America In North America, it is common
in the Arctic and the Great Lakes Region In
Wisconsin?
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Adult of Diphyllobothrium latum

• Scolex with bothria
• Little difference between mature and gravid
  proglottids
• proglottids are ________________________
• uterus is _____________________________
• Strobila reaches length of 30 feet

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Adult of Diphyllobothrium latum

• Eggs are shed from gravid proglottids through
  uterine pore (difficult to see)
• up to 1,000,000 eggs released/day
• egg in feces is diagnostic - has
  ________________________________ and
  _______________________________________

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Adult of Diphyllobothrium latum
DEFINITIVE HOSTS - _______________________________
__________________ Common hosts include bears,
dogs, cats, foxes, mink, raccoons, walruses,
seals, and humans. Adults show low host
specificity.  
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Life Cycle of Diphyllobothrium latum
1. Adult tapeworm occurs in the
___________________________of carnivore or human
definitive host. 2. Eggs are shed in the feces
into water. 3. Eggs embryonate in water and a
___________________________ hatches from each egg
after several weeks.
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Life Cycle of Diphyllobothrium latum
Coracidium consists of outer ciliated embryophore
and inner oncosphere containing six hooks
embryophore
oncosphere
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Life Cycle of Diphyllobothrium latum
4. Free-swimming coracidium is eaten by
________________ 1st intermediate host. 5. In
copepod's midgut, embryophore ruptures and
_________________________uses its 6 hooks to
penetrate midgut. Oncosphere migrates to the
copepod hemocoel. 6. In the hemocoel, the
oncosphere elongates to become the
_________________________
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Life Cycle of Diphyllobothrium latum
7. Infected copepod is eaten by a
___________________ 2nd intermediate host (Almost
any fish including minnows will work) 8.
Procercoid burrows through the fish gut and
migrates to the muscles where it transforms into
a ________________________(scolex and neck)
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Life Cycle of Diphyllobothrium latum
9. Larger fish - northern pike, walleye, perch,
salmon, trout - eat smaller infected fish.
Plerocercoid will live in these fish but
undergoes no further development These fish are
________________________ and increase chances of
reaching the definitive host.  
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Life Cycle of Diphyllobothrium latum
10. Carnivore or human definitive host is
infected by eating raw or poorly cooked fish
containing plerocercoids. Worms attach to the
wall of the small intestine and become sexually
mature in 1 to 2 weeks
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Life Cycle Stages of Diphyllobothrium latum

Copepod first intermediate host containing the
procercoid
Fish second intermediate host containing the
plerocercoid
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Diphyllobothrium latum infections
Fish in the Great Lakes are common second
intermediate hosts and are heavily parasitized
with plerocercoids - up to 50-75
prevalence Bears are common definitive hosts due
to their fish-eating habits. Dogs and cats become
definite hosts when fed scraps of fish.  

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Diphyllobothrium latum infections
Humans become infected by ________________________
____________________________ -
gefilte fish (Scandanavian) - sushi
and sashimi (Japanese) - cerviche
(Latin American)  
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Pathology of Diphyllobothrium latum
Human infections cause 1. ______________________
_____________________ (diarrhea,
nausea, intestinal cramps). 2. some cases result
in ____________________________________   - adult
D. latum absorbs high levels of
__________________   - lack of this causes
decreased rbc production and anemia Parasite is
never life threatening.
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Diagnosis Treatment of Diphyllobothrium latum
DIAGNOSIS - ID egg in feces -
egg has
distinct operculum
and abopercular
knob     TREATMENT drugs ______________________
_____________ are effective in eliminating adult
tapeworms
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Diphyllobothrium mansonoides
Causative agent of a human disease called
______________________________________ -
disease results when humans become
___________________ _____________________________
___________________ - old name for
plerocercoid was sparganum - hence the name
sparganosis   - humans are NEVER
definitive hosts    
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Diphyllobothrium mansonoides
Adult tapeworm is morphologically similar to D.
latum.  
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Life Cycle of Diphyllobothrium mansonoides

1. Adult tapeworm occurs in the small intestine
of a ___________________ definitive host.  2.
Eggs are shed in water and a _____________________
_____ hatches.  3. Coracidium is eaten by
_______________________ and procercoid develops.
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Life Cycle of Diphyllobothrium mansonoides

4. Copepod is eaten by second intermediate host
- can be almost ___________ ______________________
__. Common hosts are fish, frogs, snakes, and
mice.  5. Plerocercoid ( sparganum) occurs
primarily in the _________________________________
__________ 6. Cat becomes infected by eating
infected second intermediate.
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Life Cycle Stages of Diphyllobothrium mansonoides

Plerocercoid beneath the skin (subcutaneous
location) in a mouse second intermediate host
Procercoid in copepod first intermediate host

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Human Infections of Diphyllobothrium mansonoides
Humans can serve as accidental hosts of the
_______________________ Humans are infected by 3
methods 1. _____________________
_______________________ _______________________
_______________________ Procercoid penetrates
intestinal wall and migrates into the
subcutaneous regions as the plerocercoid.


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Human Infections of Diphyllobothrium mansonoides
2. __________________ ___________________________
_________________________________ Plerocercoid
migrates to subcutaneous tissues and undergoes no
further development.


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Human Infections of Diphyllobothrium mansonoides
3. __________________ ___________________________
____________________________________
Plerocercoid crawls out of this host into
human.  


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Human Infections of Diphyllobothrium mansonoides
A few cases have involved finding plerocercoids
in the __________________ from this
method of infection.  


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Human Infections of Diphyllobothrium mansonoides
Parasite is rare - only about 40 cases of human
sparganosis have been reported in the
U.S. Parasite is diagnosed and treated by
__________________________________________________
___

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Diphyllobothrium mansonoides
Unusual occurrence is the production of a
chemical called __________________
________________________________ This chemical
acts much like _______________________________
and causes a great increase in size of a
mammalian second intermediate host (mice). This
hormone, however, does not effect humans.