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Micro Exam 4 > Afebrile Diarrhea caused by Parasites > Flashcards

Afebrile Diarrhea caused by Parasites Flashcards

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1
Q

Definitive Host

A

harbors sexual stage of the parasite

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2
Q

Intermediate Host

A

harbors asexual stage

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3
Q

Protozoan Cell Characteristics

A

unicellular, eukaryotes, ≥ 1 nucleus, motile by cilia, flagella, and/or pseudopodia, sexual or asexual reproduction

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4
Q

Helminths include

A

Nematode, Cestode, Trematode

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5
Q

Nematode

A

non-segmented roundworm

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6
Q

Cestode

A

flat, segmented bodies with a head (scolex) and a series of segments (# is variable) known as proglottids or commonly called tapeworms

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7
Q

Trematode

A

flukes, non-segmented flat worms

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8
Q

Infective stage for Giardia is

A

cyst

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9
Q

Infective sage for Cryptosporidium

A

oocyst

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10
Q

Reservoir for Giardia and Cryptosporidium

A

human and animals

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11
Q

Transmission of Giardia and Cryptosporidium occurs by

A

Ingestion of fecally-contaminated water/food (cyst and oocyst)

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12
Q

Cyst and Oocyst of Giardia and Cryptosporidium are resistant to

A

Cl- and drying

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13
Q

Giardia and Cryptosporidium are associated with

A

swimming-related outbreaks

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14
Q

What season would you see Giardia lamblia

Cryptospordia infections predominantly

A

warm summer-fall

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15
Q

Characteristics of Giardia

A

protozoan, extracellular, non-invasive, flagellated, denude villus tips

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16
Q

Giardia has 2 forms, they are

A

cyst and trophozoite

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17
Q

Characteristics of a Giardia cyst

A

infectious stage, large, oval, tough hyaline walls, & 4 nuclei

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18
Q

Giardia cysts are resistant and may survive

A

~3 mo in water or moist environments

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19
Q

Giardia cysts are formed by

A

trophozoite gradually dehydrates w/in feces of the lg bowel

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20
Q

Characteristics of a Giardia trophozoite

A

pear-shaped, 2 nuclei, 4 pairs of flagella, looks like a human face, motile (erratic tumbling, falling leaf)

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21
Q

In immunocompromised hosts, C. parvum may be found

A

in any part of the GIT

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22
Q

Given what you know about how a cyst is formed, which form of Giardia would you find in diarrhea? Solid stool?

A

trophozoite; cyst

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23
Q

Immunity towards Giardia is due to

A

Secretory IgA and B cell-independent mechanisms

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24
Q

The most common intestinal parasite of humans in the U.S. is?

A

Giardia

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25
A Giardia outbreak could occur if
a central water source was contaminated
26
Giardia cysts are shed in stool for _____ after an infection
months
27
Risk factors for Giardia
Male, travelers, daycare, close contacts, ingestion of contaminated lake/river/pool water, hikers, poor sanitation, gay men
28
Giardia trophozoites are found in what area of the GIT
duodenum and upper jejunum
29
Life cycle of Giardia?
ingested cyst from contaminated source, develops to trophozoite in small intestine, attaches to villi w/ sucking discs, trophozoite dehydrates in large bowel and encysts
30
Giardia trophozoites cause
epithelial damage and villous atrophy
31
Giardia trophozoites cause damage which may cause infiltration of
lamina propria by plasma cells, lymphocytes, and PMNs
32
Symptoms due to Giardia are due to
mechanical blockage of fat and protein absorption
33
Incubation period of Giardia is
9-15 days
34
Symptoms of an acute Giardia infection
watery, foul-smelling diarrhea, steatorrhea with nausea and abdominal distention and flatulence, afebrile or low-grade fever, may lose ~10lbs on average
35
Duration of an acute Giardia infection
duration of 3-4 days
36
Symptoms of a Chronic Giardia infection
mild abdominal pain, distention, flatulence, greasy, foul-smelling stools, malabsorption, weight loss
37
Duration of a Chronic Giardia infection
May persist for 2 years (patient may not even remember initial episode)
38
What condition may result from a Giardia lamblia infection
reactive arthritis
39
What cells will infiltrate the lamina propria in a Giardia infection?
plasma cells, PMN, and lymphocytes
40
Diagnostic tests for Giardia
stool specimen examination, stool EIA, endoscopy, enterotest/string test, DFA, PCR
41
How would you perform a stool specimen test for Giardia
3 samples: 1/day on alternate days
42
How would you perform a enterotest/string test for Giardia
patient swallows a capsule-coated weight with an attached string, string is taped to cheek, weight capsule dissolves and weight is passed, string remains partially in stomach and sm. Intestine for 4 hours before being removed
43
Treatment for Giardia
Quinacrine, Metronidazole, Furazolidone, Albendazol
44
Prevention for Giardia
Proper disposal of human feces, good hygienic practices, consumption of appropriately treated water
45
Albendazol mechanism of action
vermicidal, causes degenerative alterations in the tegument and intestinal cells of the worm by binding to the colchicine-sensitive site of tubulin, inhibiting polymerization or assembly into microtubules. Leading to impaired uptake of glucose and depletes the glycogen stores. Degenerative changes in the ER, mitochondria of the germinal layer, and lysosome release, results in decreased ATP production. Diminished energy results in immobilization and eventually death of the parasite.
46
Furazolidone mechanism of action
cross-linking DNA, treat diarrhea and enteritis caused by bacteria or protozoan infections
47
Quinacrine
Nitazoxanide (anti-protozoan)
48
Characteristics of Cryptosporidium parvum
Obligate intracellular parasite, minimally invasive, 2 forms (oocyst and trophozoite)
49
Characteristics of Cryptosporidium parvum oocyst
small, spherical, contain 4 motile sporozoites, ACID-FAST, extremely resistant to Cl-, drying, filtering, Giemsa +
50
Most common cause of water borne outbreaks
Cryptosporidium parvum
51
Most common cause of swimming pool infectious outbreak
Cryptosporidium parvum
52
Reservoir of Cryptosporidium parvum is
humans and animals
53
Risk Factors for Cryptosporidium parvum
Hikers/campers, travelers, SWIMMING POOLS, gay men
54
Risk Factors for CHRONIC Cryptosporidium parvum infection
AIDS, T-cell compromised, hypogammaglobulinemia, IgA deficiency
55
When will the Cryptosporidium parvum oocyst excyst?
in small intestines, in the presence of bile salts and proteases, into 4 motile sporozoites
56
Cryptosporidium parvum - 4 motile sporozoites action:
attach and infect the superficial surface of the sm. intestine epithelium - Intracellular sporozoites divide asexually to form 8 merozoite
57
Cryptosporidium parvum - 8 merozoites action:
are released into the intestinal milieu to infect other epithelial cells
58
Cryptosporidium parvum - undergoes sexual reproduction to become
an oocyst, which is shed or autoinfects
59
Cryptosporidium parvum - infiltrates in the lamina propria are primarily
Mononuclear
60
In immunocompetent person, Cryptosporidium parvum infection is limited to
jejunum
61
Immunocompromised patients (AIDS): Cryptosporidium parvum organisms can be found
in any part of the GIT, liver, or pancreas
62
Incubation period for Cryptosporidium parvum
7-10 days
63
Symptoms of Cryptosporidium parvum infection in an immunocompetent person
Explosive, profuse, watery diarrhea; rarely will see n/v, anorexia, fever
64
Duration of Symptoms of Cryptosporidium parvum infection in an immunocompetent person
5-10 days, but up to 19 days
65
Symptoms of Cryptosporidium parvum infection in an immunocompromised person
Severe, cholera-like diarrhea (2 liters/day) for months
66
Virulence factors for Cryptosporidium parvum
CT-like toxin: AC -> cAMP -> Cl- secretion
67
Diagnosis of Cryptosporidium parvum is made primarily by
Fecal examination w/ presence of ACID-FAST OOCYSTs
68
Other tests for diagnosis of Cryptosporidium parvum
DFA, ELISA, PCR
69
Treatment for Cryptosporidium parvum
Supportive (Fluids/electrolytes) and Nitrazoxanide for > 1y/o
70
Nitrazoxanide can be used for Cryptosporidium parvum in patients that
are >1 y/o; not effective for immunocompromised (NO Tx FOR AIDS pts)
71
Where is Cytoisospora found primarily?
Tropic and sub-tropic areas primarily
72
Clinically, Cytoisospora is identical to Cryptosporidium parvum, but what distinguishes the 2?
Cytoisospora responds to TMZ-SMX
73
Characteristics of Cytoisospora
Protozoan, large ACID-FAST oocyst, sporoblast (2-cell stage)
74
How would you treat an AIDS pt w/ Cytoisospora
TMZ-SMX and due to high relapse rate, maintain therapy
75
Diagnostic tests for Cytoisospora?
Fecal exam: large, acid-fast oocyst, Charcot-Leyden crystals, no WBC/RBC
76
What would be seen on a peripheral smear for a Cytoisospora infection
peripheral eosinophilia
77
Blastocystis hominis Charcteristics
Protozoan
78
Presentation of Blastocystis hominis
identical to Cryptosporidium parvum
79
Treatment for Blastocystis hominis
None known

Micro Exam 4 (8 decks)

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