Giardia duodenalis (G. lamblia; G. intestinalis)

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Giardia duodenalis (G. lamblia G. intestinalis)

• Giardiasis.
• Most distinctive of the flagellates.
• Has both a trophozoite and cyst stage.

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Giardia duodenalis Trophozoite
Trophozoites are binucleated (looks like a face).
12-15 µm.  
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Giardia duodenalis Trophozoite
Trophozoites are binucleated (looks like a face).
12-15 µm. Ventral surface bears
adhesive disk to adhere to surface of intestinal
cell.  
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Giardia duodenalis Trophozoite
Trophozoites are binucleated (looks like a face).
12-15 µm. Ventral surface bears
adhesive disk to adhere to surface of intestinal
cell. 8 flagella (2 anterior, 2 posterior, 2
ventral, and 2 caudal) - all arise from
kinetosome.  
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Giardia duodenalis Trophozoite
Trophozoites are binucleated (looks like a face).
12-15 µm. Ventral surface bears
adhesive disk to adhere to surface of intestinal
cell. 8 flagella (2 anterior, 2 posterior, 2
ventral, and 2 caudal) - all arise from
kinetosome. Median bodies occur behind adhesive
disk - function is unknown.  
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Giardia duodenalis Trophozoite
Light microscope photos of trophozoites
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Giardia duodenalis

• Lives in the upper part of the small intestine
  (duodenum, jejunum, and upper ileum).
• Here the trophozoites attach to the epithelial
  cells.

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Giardia duodenalis Trophozoite
ventral
dorsal
Scanning EM view of trophozoite surface showing
the adhesive disk.
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• Feeds on mucous that forms in response to
  irritation.

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• Feeds on mucous that forms in response to
  irritation.
• Also absorbs vitamins and amino acids.

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• Feeds on mucous that forms in response to
  irritation.
• Also absorbs vitamins and amino acids.
• Interferes with absorption in host especially
  lipids.

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• Feeds on mucous that forms in response to
  irritation.
• Also absorbs vitamins and amino acids.
• Interferes with absorption in host especially
  lipids.
• Giardia can also interfere with vitamin/nutrient
  absorption.
• Vitamin A? vision
• Vitamin D? rickets Both of these are due to long
  standing infections.

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Cyst of Giardia duodenalis
The cyst forms as trophozoites become dehydrated
when they pass through the large intestine.

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Cyst of Giardia duodenalis

• The cyst forms as trophozoites become dehydrated
  when they pass through the large intestine.
• Morphology
• ovoid in shape 8-12 µm long x 7-10 µm wide
• thin cyst wall.
• Four nuclei present, often concentrated at on
  end.
• Flagella shorten and are retracted within cyst.
• Axonemes provide internal support.

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Cyst of Giardia duodenalis
Cyst may remain viable in the
external environment (usually water) for many
months.
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Cyst of Giardia duodenalis
Cyst may remain viable in the
external environment (usually water) for many
months. -14 billion cysts can be passed in 1
stool sample -Moderate infections 300 million
cysts.
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Cyst of Giardia duodenalis
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Symptoms

• Range from none? abdominal discomfort causing
  acute or chronic diarrhea and other GI signs.
• Gray, greasy, voluminous malodorous diarrhea!
• Flatulence.

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Giardia duodenalis

• Giardia trophs are attracted to bile salts so
  sometimes you can get infections in bile ducts
  and gall bladder, causing jaundice and colic.
• This is irritating but not life threatening
  infection like E. histolytica.

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Pathogenesis and Pathology

• Nutrient malabsorption and physical blockage and
  damage to microvilli.
• Trophs attach to small intestine? cause damage
  (mechanical and toxins).

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Giardia trophozoite
Trophozoite attaches to surface of epithelial
cells with its adhesive disk.
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Pathogenesis and Pathology

• 1) Fat/CHO digestion decreases and causes
  maldigestion.

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Pathogenesis and Pathology

• 1) Fat/CHO digestion decreases and causes
  maldigestion.
• 2) Absorption decreases due to villus blunting
  causing malabsorption.

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Pathogenesis and Pathology

• 1) Fat/CHO digestion decreases and causes
  maldigestion.
• 2) Absorption decreases due to villus blunting
  causing malabsorption.
• 3) Malabsorption and maldigestion causes
  diarrhea.

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Pathogenesis and Pathology

• 4) Physical damage clubbing of villi decreases
  villus-to-crypt ratio brush borders of cells are
  irregular.

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Epidemiology

• Get infected by ingesting cysts through
  contaminated water.

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Epidemiology

• Get infected by ingesting cysts through
  contaminated water.
• Most common intestinal flagellate of people.

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Epidemiology

• Get infected by ingesting cysts through
  contaminated water.
• Most common intestinal flagellate of people.
• World wide distribution prevalence ranges from
  2.4-67.5.

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Epidemiology

• Get infected by ingesting cysts through
  contaminated water.
• Most common intestinal flagellate of people.
• World wide distribution prevalence ranges from
  2.4-67.5.
• Reservoir hosts can play a significant role.

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Reservoir Hosts
Transmission from animals to humans is
controversial dependent on strain or type
involved.
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Human Infections

• There are hot spots Vacations and Travels?
  Camping.

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Human Infections

• There are hot spots Vacations and Travels?
  Camping.
• Colorado ski resorts are notorious for outbreaks?
  drinking from Mountain Springs, washing
  utensils/drinking water that is not treated.

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Human Infections

• There are hot spots Vacations and Travels?
  Camping.
• Colorado ski resorts are notorious for outbreaks?
  drinking from Mountain Springs, washing
  utensils/drinking water that is not treated.
• Day care centers.

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Diagnosis

• Trophs in diarrheic feces cysts in formed feces.
• At least 3 exams (one every other day) before
  judge negative.
• ELISA tests detect soluble antigen.

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Treatment and Prognosis

• Drug of choice is Flagyl.
• Giardia thrives in people? not necessarily hard
  to treat, but keeping those who were infected
  from becoming reinfected.

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Blood and Tissue Flagellates Phylum Euglenoidea

• Known as Hemoflagellates or Kinetoplastids.
• Some have forms that live in the alimentary canal
  of insects such as flies, bugs, etc.

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Adaptation to Parasitism

• Most parasites came from free-living forms.

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Adaptation to Parasitism

• Most parasites came from free-living forms.
• They became parasites when hosts ingested them
  and they survived the process.

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Adaptation to Parasitism

• Most parasites came from free-living forms.
• They became parasites when hosts ingested them
  and they survived the process.
• They were then selected for and adapted to
  colonize hosts.

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Adaptation to Parasitism

• This is not the case for blood and tissue
  flagellates.

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Adaptation to Parasitism

• This is not the case for blood and tissue
  flagellates.
• Because most insect species have flagellates that
  live within them and these share characters with
  human blood and tissue flagellates.

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Adaptation to Parasitism

• This is not the case for blood and tissue
  flagellates.
• Because most insect species have flagellates that
  live within them and these share characters with
  human blood and tissue flagellates.
• Therefore biting insects probably gave these
  parasites to us!

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Blood and Tissue Flagellate Anatomy and Life
Stages

• There are seven ontogenetic stages, but not all
  species have all seven.
• These stages are continuous.

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Life-cycle stages of trypanosomatidae. A.
promastigote b. ophistomastigote c.
epimastigote d. trypomastigote e.
choanomastigote f. amastigote g. paramastigote
K. kinetoplast N. nucleus F. flagellum.
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• You will be responsible for 4 of them.
• Remember not all 4 stages will be found in each
  species life cycle.

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Promastigote
anterior
Flagellum Kinetosome Kinetoplast Nucleus
posterior
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Epimastigote
anterior
Undulating membrane
posterior
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Trypomastigote
anterior
posterior
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Amastigote
anterior
Flagellum Kinetosome Kinetoplast Nucleus
posterior
These are intracellular, stages that occur within
cells.
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Leishmaniasis

• Infection with Leishmania spp.
• Disease of the Reticulo-Endothelial Cells.

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Leishmaniasis

• Infection with Leishmania spp.
• Disease of the Reticulo-Endothelial Cells.
• Reticulo-Endothelial System- is diffuse in the
  body and made up of all phagocytes except for
  leucocytes.

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Leishmaniasis

• Infection with Leishmania spp.
• Disease of the Reticulo-Endothelial Cells.
• Reticulo-Endothelial System- is diffuse in the
  body and made up of all phagocytes except for
  leucocytes.
• Macrophage is a standard reticulo-endothelial
  cell.