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Questions and Answers
Which organ is most commonly affected by large cysts?
Which organ is most commonly affected by large cysts?
What is a possible consequence of spontaneous rupture of cysts?
What is a possible consequence of spontaneous rupture of cysts?
Which of the following is NOT a method for diagnosing cysts?
Which of the following is NOT a method for diagnosing cysts?
What characterizes nematodes?
What characterizes nematodes?
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Which measure is NOT part of the prevention and control of cysts?
Which measure is NOT part of the prevention and control of cysts?
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What is the primary definitive host for Echinococcus granulosus?
What is the primary definitive host for Echinococcus granulosus?
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Which structure is characteristic of the adult Echinococcus granulosus?
Which structure is characteristic of the adult Echinococcus granulosus?
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How does the hydatid cyst develop in humans?
How does the hydatid cyst develop in humans?
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What is the typical size range of a hydatid cyst?
What is the typical size range of a hydatid cyst?
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Which of the following components is NOT found in a hydatid cyst?
Which of the following components is NOT found in a hydatid cyst?
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What is the mode of infection for Echinococcus granulosus?
What is the mode of infection for Echinococcus granulosus?
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Which of the following statements about the eggs of Echinococcus granulosus is true?
Which of the following statements about the eggs of Echinococcus granulosus is true?
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What layer of the hydatid cyst secretes the laminated layer and produces scolices?
What layer of the hydatid cyst secretes the laminated layer and produces scolices?
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Study Notes
Echinococcus granulosus (Hydatid worm)
- Geographic distribution: Worldwide
- Definitive hosts: Dogs, foxes, wolves
- Intermediate hosts: Man, cattle, pigs, sheep
- Adult worms: Size: 3-6mm
- Scolex: Globular with 2 rows of hooks
- Strobila: Formed of 3 segments (immature, mature, gravid)
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Eggs: Similar to Taenia eggs
- Size: 28-40 μm
- Shape: Spherical
- Shell: Thick, distinct radii
- Color: Yellowish brown
- Content: Mature hexacanth embryo with three pairs of hooklets
Life Cycle
- Adults live in the small intestine of definitive hosts (dogs and other canines)
- Eggs pass in feces and are swallowed by intermediate hosts (man, sheep, cattle)
- Oncosphere hatches in the intestine, penetrates the intestinal wall
- The onchosphere spreads to different organs and develops into hydatid cysts
Hydatid Disease (Echinococcosis/Hydatidosis)
- Definition: A pathological condition where human tissues carry hydatid cysts (larval stage of Echinococcus granulosus)
- Mode of infection: Ingestion of contaminated food/water/vegetables with Echinococcus granulosus eggs, or handling infected dogs (contaminated hairs)
Hydatid Cyst
- Size: 1-10 cm
- Shape: Spherical, enclosed in a fibrous capsule
-
Wall: Two layers
- Outer: Laminated, non-cellular
- Inner: Cellular germinal layer secreting laminated layer and producing scolices, brood capsules, and daughter cysts
Hydatid Cyst Contents
- Individual scolices: Microscopic
- Brood capsules: Cysts formed by invagination of the germinal layer
- Daughter cysts: Cysts formed from the mother cyst layers; contain scolices, brood capsules, and even grand-daughter cysts
- Hydatid fluid: Liquid component
- Hydatid sand: Detached scolices, brood capsules, and daughter cysts in the hydatid fluid
Clinical Picture
- Depends on cyst size, location, and number
- Large cysts cause pressure atrophy of affected organs
- Common affected organs: Liver (70%), lung (20%), others include brain, bone, spleen, kidney, muscles, heart, eyes (10%)
- Spontaneous rupture of cysts leads to severe allergic reactions (anaphylactic shock)
- Bacterial infection can lead to abscess formation
Diagnosis
- X-ray
- Ultrasound
- Scolices in sputum or urine
- Puncture or aspiration of hydatid fluid
- Eosinophilia
- Serological tests
- PCR
- Intradermal test (Casoni test)
Treatment
- Surgical removal of the cyst
- Albendazole in inoperable cases and after surgery
Prevention and Control
- Health education
- Avoid contamination of food with dog feces
- Fly control
- Periodic examination and treatment of pet dogs
- Infected organs in slaughterhouses should be destroyed
General Characteristics of Nematodes (Class Nematoda)
- Elongated, cylindrical, pointed ends
- Unsegmented
- Variable in size: 5mm – 1 meter
- Separate sexes (female longer than male)
- Body wall: Tough cuticle, inner longitudinal muscle layer
- Body cavity present
- Movement: Longitudinal muscle contraction
- Alimentary canal: Well-developed, mouth, esophagus, intestine, rectum, subterminal anus
- Nervous system: Rudimentary, circular nerve ring (brain)
- Excretory system: Rudimentary
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Description
Test your knowledge about Echinococcus granulosus and its life cycle. This quiz covers the hydatid worm's geographic distribution, definitive and intermediate hosts, and the details of hydatid disease. Explore the fascinating aspects of this parasite and its impact on human health.
