case 2.ppt
TRANSCRIPT
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Case report: I2
:
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History A 25-year-old woman had recently
returned from a trip to the RockyMountains. She had been traveling with
a group of campers, who had obtained
theirdrinking waterfrom a lake. A few
days after returning home, she presented
to her internist suffering from profuse(
) watery diarrhea, crampy epigastric
pain, and foul()-smelling flatulence ().She discovered that most of the other
campers had reported symptoms similar
to her own.
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History Three stool specimens were submitted
for laboratory analysis.All specimens
were negative forenteric bacterialpathogens, and two were also negative
forparasites. Since the specimens for
ova and parasites were received in vialscontaining the preservatives polyvinyl
alcohol and 10% formalin, no wet mounts
() were made to detect motility. Apermanent trichromestain revealed rare,
oval protozoan trophozoites, measuring 9
to 20 jjum in length and 5 to 15 jjim in
width.
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History The broad anterior end of each
trophozoite( )contained aconcave area which covered half the
ventral surface. The structure of this
parasite gave the overall appearance of a
"smiling face" . Rare cysts, having fournuclei, and characteristic median bodies
and longitudinal fibers were also seen.
Typical cysts are demonstrated.
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Questions 1.
Which protozoan parasite is causing the
camper's infection?
Which form of this parasite is infectious?
A:
Giardia lamblia. (giardiasis) cyst
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Accidentally putting something into your mouthor swallowing something that has come intocontact with feces of a person or animal
infected with Giardia. Swallowing recreational watercontaminated
with Giardia. Recreational water includes waterin swimming pools, hot tubs, jacuzzis,fountains, lakes, rivers, springs, ponds, orstreams that can be contaminated with sewageor feces from humans or animals.
Eating uncooked food contaminated withGiardia.
Accidentally swallowingGiardia picked up fromsurfaces (such as bathroom fixtures, changingtables, diaper pails, or toys) contaminated withfeces from an infected person.
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3.
How can this infection be controlled and
prevented?
A:
Practice good hygiene.
Avoid water that might be contaminated.
Avoid food that might be contaminated. Avoid fecal exposure during sexual
activity.
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4.
How does this parasite attach itself to
the intestinal wall? A:
Giardia is a flagellated (having whip-like
appendages for locomotion) protozoanthat, in the trophozoite (active) form,
attaches itself with an adhesive disk
(ventral side) to the lining of the upperintestinal tract of the host
animal. There, it feeds and
reproduces.
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Which condition
might result as a consequence of this
attachment?
1.malabsorptive diarrhea
2.fatty, four-smelling stools after eating
3.milk allergy or lactose intolerance (
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5.
How is this infection treated?
The most common treatment for giardiasis ismetronidazole (Flagyl) for 5-10 days. Iteradicates the Giardia more than 85% of thetime, but it often causes gastrointestinal side
effects such as nausea and a metallic tasteas well as dizziness and headache.
The only drug approved for treating giardiasis
in the U.S. is furazolidone (Furoxone) for 7-10 days. It is approximately as effective asmetronidazole.
Ti id l i il bl t id th U S d i
http://www.medicinenet.com/script/main/art.asp?articlekey=751http://www.medicinenet.com/script/main/art.asp?articlekey=5489http://www.medicinenet.com/script/main/art.asp?articlekey=5489http://www.medicinenet.com/script/main/art.asp?articlekey=6114http://www.medicinenet.com/script/main/art.asp?articlekey=20628http://www.medicinenet.com/script/main/art.asp?articlekey=20628http://www.medicinenet.com/script/main/art.asp?articlekey=6114http://www.medicinenet.com/script/main/art.asp?articlekey=5489http://www.medicinenet.com/script/main/art.asp?articlekey=5489http://www.medicinenet.com/script/main/art.asp?articlekey=751 -
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Tinidazole is available outside the U.S. and ishighly effective at treating giardiasis(>90%). Italso can be given as a single dose and is welltolerated.
Quinacrine is very effective for treatinggiardiasis but is no longer available in the U.S.
Paromomycin and albendazole, thougheffective, are less effective than othertreatments.
Occasionally, treatment fails to eradicateGiardia. In such cases, the drug may bechanged or a longer duration orhigher dosemay be used. Combination therapy also maybe effective (e.g., quinacrine and
metronidazole).
http://www.medicinenet.com/script/main/art.asp?articlekey=5176http://www.medicinenet.com/script/main/art.asp?articlekey=5176 -
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6.
Describe the life cycle of this parasite.
At some time in its active life, the trophozoite
releases its hold on the bowel wall and floats
in the fecal stream. As it makes its journey, it
transforms into an egg-like structure called acyst, which is eventually passed in the
stool. Duration of cyst excretion, called
shedding, may persist for months. Once
outside the body, the cysts can be ingested
by another animal. Then, they hatch into
trophozoites due to stomach acid action and
digestive enzymes, and the cycle repeats.
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7.
Describe the pathogenesis of this infection.
A significant infestation can leave millions oftrophozoites stuck tight to the intestinallining. There, they cripple the guts ability to
secrete enzymes and absorb food, especiallyfats, thereby producing the diseasessymptoms. The symptoms typically appearone to two weeks after ingestion, with anaverage ofnine days, but four weeks is notuncommon. Symptoms can vanish suddenlyand then reappear. They may hide formonths. They may not appear at all.
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8.
How is the laboratory diagnosis of this infection made?
A:
Giardia lamblia is frequently diagnosed by visualizingthe organism, either the trophozoite or the cyst instained preparations orunstained wet mounts with
the aid of a microscope. A commercial fluorescent antibody kit is available to
stain the organism.
Organisms may be concentrated by sedimentation orflotation; however, these procedures reduce the
number of recognizable organisms in the sample. An enzyme linked immunosorbant assay(ELISA)
that detects excretory secretory products of theorganism is also available.
http://www.cfsan.fda.gov/cgi-bin/bbbglos?Enzyme-Linked=Immunosorbent=Assayhttp://www.cfsan.fda.gov/cgi-bin/bbbglos?Enzyme-Linked=Immunosorbent=Assay -
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9.
Discuss the epidemiology of this infection.
A: Giardiasis is more prevalent inchildren than in adults,
possibly because many individuals seem to have alasting immunityafter infection. This organism isimplicated in 25% of the cases ofgastrointestinaldisease and may be present asymptomatically. Theoverall incidence of infection in the United States isestimated at 2% of the population. This disease afflictsmany homosexual men, both HIV-positive and HIV-negative individuals. This is presumed to be due tosexual transmission. The disease is also common inchild day care centers, especially those in whichdiapering is done.
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10.
How does the structure of these
trophozoites account for the "smiling-face"
appearance?
A:
http://www.yosemite.org/naturenotes/images/Giardia.jpg -
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Thanks for your
attention !!!