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Micro Exam 4 > Afebrile Diarrhea caused by Parasites > Flashcards

Afebrile Diarrhea caused by Parasites Flashcards

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
Q

A Giardia outbreak could occur if

A

a central water source was contaminated

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26
Q

Giardia cysts are shed in stool for _____ after an infection

A

months

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27
Q

Risk factors for Giardia

A

Male, travelers, daycare, close contacts, ingestion of contaminated lake/river/pool water, hikers, poor sanitation, gay men

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28
Q

Giardia trophozoites are found in what area of the GIT

A

duodenum and upper jejunum

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29
Q

Life cycle of Giardia?

A

ingested cyst from contaminated source, develops to trophozoite in small intestine, attaches to villi w/ sucking discs, trophozoite dehydrates in large bowel and encysts

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30
Q

Giardia trophozoites cause

A

epithelial damage and villous atrophy

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31
Q

Giardia trophozoites cause damage which may cause infiltration of

A

lamina propria by plasma cells, lymphocytes, and PMNs

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32
Q

Symptoms due to Giardia are due to

A

mechanical blockage of fat and protein absorption

33
Q

Incubation period of Giardia is

34
Q

Symptoms of an acute Giardia infection

A

watery, foul-smelling diarrhea, steatorrhea with nausea and abdominal distention and flatulence, afebrile or low-grade fever, may lose ~10lbs on average

35
Q

Duration of an acute Giardia infection

A

duration of 3-4 days

36
Q

Symptoms of a Chronic Giardia infection

A

mild abdominal pain, distention, flatulence, greasy, foul-smelling stools, malabsorption, weight loss

37
Q

Duration of a Chronic Giardia infection

A

May persist for 2 years (patient may not even remember initial episode)

38
Q

What condition may result from a Giardia lamblia infection

A

reactive arthritis

39
Q

What cells will infiltrate the lamina propria in a Giardia infection?

A

plasma cells, PMN, and lymphocytes

40
Q

Diagnostic tests for Giardia

A

stool specimen examination, stool EIA, endoscopy, enterotest/string test, DFA, PCR

41
Q

How would you perform a stool specimen test for Giardia

A

3 samples: 1/day on alternate days

42
Q

How would you perform a enterotest/string test for Giardia

A

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
Q

Treatment for Giardia

A

Quinacrine, Metronidazole, Furazolidone, Albendazol

44
Q

Prevention for Giardia

A

Proper disposal of human feces, good hygienic practices, consumption of appropriately treated water

45
Q

Albendazol mechanism of action

A

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
Q

Furazolidone mechanism of action

A

cross-linking DNA, treat diarrhea and enteritis caused by bacteria or protozoan infections

47
Q

Quinacrine

A

Nitazoxanide (anti-protozoan)

48
Q

Characteristics of Cryptosporidium parvum

A

Obligate intracellular parasite, minimally invasive, 2 forms (oocyst and trophozoite)

49
Q

Characteristics of Cryptosporidium parvum oocyst

A

small, spherical, contain 4 motile sporozoites, ACID-FAST, extremely resistant to Cl-, drying, filtering, Giemsa +

50
Q

Most common cause of water borne outbreaks

A

Cryptosporidium parvum

51
Q

Most common cause of swimming pool infectious outbreak

A

Cryptosporidium parvum

52
Q

Reservoir of Cryptosporidium parvum is

A

humans and animals

53
Q

Risk Factors for Cryptosporidium parvum

A

Hikers/campers, travelers, SWIMMING POOLS, gay men

54
Q

Risk Factors for CHRONIC Cryptosporidium parvum infection

A

AIDS, T-cell compromised, hypogammaglobulinemia, IgA deficiency

55
Q

When will the Cryptosporidium parvum oocyst excyst?

A

in small intestines, in the presence of bile salts and proteases, into 4 motile sporozoites

56
Q

Cryptosporidium parvum - 4 motile sporozoites action:

A

attach and infect the superficial surface of the sm. intestine epithelium - Intracellular sporozoites divide asexually to form 8 merozoite

57
Q

Cryptosporidium parvum - 8 merozoites action:

A

are released into the intestinal milieu to infect other epithelial cells

58
Q

Cryptosporidium parvum - undergoes sexual reproduction to become

A

an oocyst, which is shed or autoinfects

59
Q

Cryptosporidium parvum - infiltrates in the lamina propria are primarily

A

Mononuclear

60
Q

In immunocompetent person, Cryptosporidium parvum infection is limited to

61
Q

Immunocompromised patients (AIDS): Cryptosporidium parvum organisms can be found

A

in any part of the GIT, liver, or pancreas

62
Q

Incubation period for Cryptosporidium parvum

63
Q

Symptoms of Cryptosporidium parvum infection in an immunocompetent person

A

Explosive, profuse, watery diarrhea; rarely will see n/v, anorexia, fever

64
Q

Duration of Symptoms of Cryptosporidium parvum infection in an immunocompetent person

A

5-10 days, but up to 19 days

65
Q

Symptoms of Cryptosporidium parvum infection in an immunocompromised person

A

Severe, cholera-like diarrhea (2 liters/day) for months

66
Q

Virulence factors for Cryptosporidium parvum

A

CT-like toxin: AC -> cAMP -> Cl- secretion

67
Q

Diagnosis of Cryptosporidium parvum is made primarily by

A

Fecal examination w/ presence of ACID-FAST OOCYSTs

68
Q

Other tests for diagnosis of Cryptosporidium parvum

A

DFA, ELISA, PCR

69
Q

Treatment for Cryptosporidium parvum

A

Supportive (Fluids/electrolytes) and Nitrazoxanide for > 1y/o

70
Q

Nitrazoxanide can be used for Cryptosporidium parvum in patients that

A

are >1 y/o; not effective for immunocompromised (NO Tx FOR AIDS pts)

71
Q

Where is Cytoisospora found primarily?

A

Tropic and sub-tropic areas primarily

72
Q

Clinically, Cytoisospora is identical to Cryptosporidium parvum, but what distinguishes the 2?

A

Cytoisospora responds to TMZ-SMX

73
Q

Characteristics of Cytoisospora

A

Protozoan, large ACID-FAST oocyst, sporoblast (2-cell stage)

74
Q

How would you treat an AIDS pt w/ Cytoisospora

A

TMZ-SMX and due to high relapse rate, maintain therapy

75
Q

Diagnostic tests for Cytoisospora?

A

Fecal exam: large, acid-fast oocyst, Charcot-Leyden crystals, no WBC/RBC

76
Q

What would be seen on a peripheral smear for a Cytoisospora infection

A

peripheral eosinophilia

77
Q

Blastocystis hominis Charcteristics

78
Q

Presentation of Blastocystis hominis

A

identical to Cryptosporidium parvum

79
Q

Treatment for Blastocystis hominis

A

None known

Micro Exam 4 (8 decks)

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