Cestodes

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Cestodes

• Gregory L. Brower, D.V.M., Ph.D.
• Cell Biology and Anatomy
• School of Medicine
• Columbia, South Carolina

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Cestodes (Tape Worms)

• Taenia solium (pork tapeworm) - Cysticercus
• Taenia saginata (beef tapeworm)
• Diphyllobothrium latum (fish tapeworm)
• Echinococcus granulosus (unilocular hydatid)
• Echinococcus multilocularis (alveolar hydatid)
• Hymenolepis nana (dwarf tapeworm)
• Hymenolepis diminutia
• Dipylidium caninum

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General Structure of Tapeworm

• Head region (scolex) contains suckers and hooks
  used to attach to a host organism.
• Proglottids square body segments used for
  reproduction.

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Tapeworm Structure

• Scolex - Attachment organ
• Zone of Proliferation - Undifferentiated area
  behind the scolex (neck region)
• Strobilia - Chain of segments (proglottids)
• Immature proglottids - developing reproductive
• Mature proglottids mature reproductive organs.
• Gravid proglottids contain eggs in the uterus.

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Immature Segment

• note that the reproductive organs are just
  beginning to differentiate.
• (Carmine stained)

Developing reproductive organs
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Mature Segments (Proglottids)

• Tapeworms are Hermaphroditic

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TaeniasisGeographic Distribution

• Worldwide, depending on dietary habits, and
  quality of cattle and pork farming.

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Taenia saginata and T. soliumScolex And
Proglottids
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Taenia solium (Pork Tapeworm) Morphology

• Adult Worm
• 2-4 m long,
• 700-1000
• segments
• Scolex
• Neck
• Immature segment
• Mature segment
• Gravid segment

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Cystcercus cellulosae in Muscles of Pigs
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Cysticercus cellulosae

• It is soybean-like in shape, with the
  small scolex invaginated into the translucent
  cyst (left).
• The scolex evaginated from the cyst (right).

Cysticercius cellulosae
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Taenia eggs

• The eggs of Taenia saginata and T. Solium are
  morphologically indistinguishable.

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Taeniasislife cycle
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Life Cycle
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TaeniasisSymptoms
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Cysticercosis
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TaeniasisDiagnosis

• Symptoms
• History of eating undercooked beef or pork
• Recovery of proglottids and/or eggs in the stool

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CysticercosisDiagnosis

• CNS and/or symptoms involving other organs
• History of ingesting food with T.solium eggs
• Radiographic localization of cysticercal lesions
  in tissues

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CysticercosisDisease
Cerebral cysticercosis
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CysticercosisDisease

• Cardiac cysticercosis

Ocular cysticercosis
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TaeniasisTreatment and Prevention

• Treatment
• Praziquantel scolex expulsion is essential
• Prevention
• Adequate cooking of meat
• Freezing meat below 10º C

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Fish TapewormDiphyllobothrium latum
Distributed worldwide freshwater (great lakes)
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Diphyllobothrium latum Morphology
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Diphyllobothrium latum Life Cycle
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DiphyllobothriasisSymptoms
Site
Symptoms
Pathogenesis
gastro-intestinal
abdominal discomfort, rarely severe cramping
pain, diarrhea alternated by constipation,
vomiting
related to worm burden
weight loss, vitamin B-12 deficiency
physical mass and inflammation
general
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DiphyllobothriasisDiagnosis

• symptoms
• history of eating raw fish
• recovery of proglottids and/or eggs in the stool

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DiphyllobothriasisTreatment

• Praziquantel is the drug of choice
• Avoid uncooked fish from infested waters
• Freezing for 24 hours and pickling kills the tape

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Hymenolepis nana (Dwarf Tape Worm)Morphology
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Hymenolepis nana (Dwarf Worm)Life Cycle
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Hymenolepis nana (Dwarf Worm)Symptoms

• Lighter infections mild abdominal disturbance
• Heavier infections enteritis

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Hymenolepis nana (Dwarf Worm)Diagnosis,
Treatment And Control
Diagnosis rodent infestation ova in the
feces Treatment and Control Praziquantel is the
drug of choice rodent population control
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Echinococcus granulosus (hydatid)Geographic
Distribution
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Echinococcus granulosus (hydatid)Case History

• 32-year-old Kenyan woman presented in Boston with
  a 3-month history of cough that was initially
  productive of thick, gray sputum that had
  gradually become blood-tinged. She had low-grade
  fevers. Chest radiography revealed an apparent
  elevation of the right hemidiaphragm. CT scan the
  chest with contrast medium revealed a low-density
  cystic mass measuring 13 by 13 by 10 cm in the
  right lower hemithora.

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Echinococcus granulosus (hydatid)Case History

• Ultrasound-guided aspiration of the contents of
  the cyst yielded clear, colorless fluid
  containing a protoscolex of Echinococcus
  granulosus. Three days later, cystectomy was
  performed, with the use of specific precautions
  to prevent local spread of disease. After
  adequate antiparasitic treatment, follow-up
  radiography demonstrated reexpansion of the right
  lung. The patient has returned to her normal
  level of activity, and there is no evidence of
  recurrent disease.

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Echinococcus granulosus (hydatid)Morphology
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Echinococcus granulosus Life Cycle
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Echinococcus granulosus Symptoms
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Echinococcus granulosus Diagnosis

• Endemicity
• Symptoms
• X-ray and CT scan
• Serology
• Skin (Casoni) test

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Echinococcus granulosus Treatment and Control

• Surgical removal of the cyst
• Praziquantel
• Avoidance or treatment of infected canine

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Echinococcus multilocularis (hydatid)Geographic
Distribution
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Echinococcus multilocularis

• Similar to E. granulosus, except
• Secondary hosts and reservoir are rodents.
• The egg produces multilocular cysts.
• The cestode is more resistant to chemotherapy.

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Echinococcus multilocularis Treatment and
Control

• Surgical removal of the cyst
• Resistant to praziquantel Albendazole has some
  effect
• Avoidance control of rodent population

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Hydatid Cysts
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