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Giardia duodenalis (G. lamblia; G.
intestinalis)
– Giardiasis.
– Most distinctive of
the flagellates.
– Has both a
trophozoite and
cyst stage.
Giardia duodenalis Trophozoite
Trophozoites are
binucleated (looks like
a face). 12-15 μm.
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.
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.
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.
Giardia duodenalis Trophozoite
Light microscope photos of trophozoites
Giardia duodenalis
• Lives in the upper part of the small
intestine (duodenum, jejunum, and upper
ileum).
• Here the trophozoites attach to the
epithelial cells.
Giardia duodenalis Trophozoite
ventral
dorsal
Scanning EM view of trophozoite surface showing the
adhesive disk.
• Feeds on mucous that forms in response
to irritation.
• Feeds on mucous that forms in response to irritation.
• Also absorbs vitamins and amino acids.
• Feeds on mucous that forms in response to irritation.
• Also absorbs vitamins and amino acids.
• Interferes with absorption in host
especially lipids.
• 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.
Cyst of Giardia duodenalis
The cyst forms as trophozoites
become dehydrated when they
pass through the large intestine.
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.
Cyst of Giardia duodenalis
Cyst may remain viable in the
external environment (usually
water) for many months.
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.
Cyst of Giardia duodenalis
Symptoms
• Range from none abdominal
discomfort causing acute or chronic
diarrhea and other GI signs.
• Gray, greasy, voluminous malodorous
diarrhea!
• Flatulence.
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.
Pathogenesis and Pathology
• Nutrient malabsorption and physical
blockage and damage to microvilli.
• Trophs attach to small intestine cause
damage (mechanical and toxins).
Giardia trophozoite
Trophozoite attaches to surface of epithelial cells with its
adhesive disk.
Pathogenesis and Pathology
1) Fat/CHO digestion decreases and causes
maldigestion.
Pathogenesis and Pathology
1) Fat/CHO digestion decreases and causes maldigestion.
2) Absorption decreases due to villus blunting
causing malabsorption.
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.
Pathogenesis and Pathology
4) Physical damage: clubbing of villi; decreases
villus-to-crypt ratio; brush borders of cells are
irregular.
Epidemiology
• Get infected by ingesting cysts through
contaminated water.
Epidemiology
• Get infected by ingesting cysts through contaminated
water.
• Most common intestinal flagellate of
people.
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%.
Epidemiology
• Get infected by ingesting cysts through contaminated
water.
• Most common intestinal flagellate of people.
• World wide distribution; prevalence ranges from 2.467.5%.
• Reservoir hosts can play a significant
role.
Reservoir Hosts
Transmission from animals to humans is
controversial; dependent on strain or type involved.
Human Infections
• There are hot spots: Vacations and
Travels Camping.
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.
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.
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.
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.
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.
Adaptation to Parasitism
• Most parasites came from free-living
forms.
Adaptation to Parasitism
• Most parasites came from free-living forms.
• They became parasites when hosts
ingested them and they survived the
process.
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.
Adaptation to Parasitism
• This is not the case for blood and tissue
flagellates.
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.
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!
Blood and Tissue Flagellate
Anatomy and Life Stages
• There are seven ontogenetic stages, but
not all species have all seven.
• These stages are continuous.
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.
• You will be responsible for 4 of them.
• Remember not all 4 stages will be found
in each species life cycle.
Promastigote
anterior
Flagellum
Kinetosome
Kinetoplast
Nucleus
posterior
Epimastigote
anterior
Undulating
membrane
posterior
Trypomastigote
anterior
Undulating
membrane
posterior
Amastigote
anterior
Flagellum
Kinetosome
Kinetoplast
Nucleus
posterior
These are intracellular, stages that
occur within cells.
Leishmaniasis
• Infection with Leishmania spp.
– Disease of the Reticulo-Endothelial Cells.
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.
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.