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Liz's Parasitology Course > World of Parasites > Flashcards

World of Parasites Flashcards

1
Q

Common name for platyhelminths

A

Flatworms

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2
Q

Common name for cestodes

A

Tapeworms

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3
Q

Common name for trematodes

A

Flukes

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4
Q

Common name for nematodes

A

Roundworms

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5
Q

Common name for arthropoda

A

Insects, spiders, mites, and ticks

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6
Q

These are single celled parasites that contain many phyla

A

Protozoa

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7
Q

What are flatworms, tapeworms, flukes, and roundworms known as?

A

Helminths

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8
Q

Impact of parasites in the U.S. and the world w/ regards to such issues as health, economics, etc.

A
  • Parasite infections outnumber humans
  • Tropics/temperate zones (3rd world) → life-threatening, hindrance to economic development
  • U.S. → increased #s due to: increased mobility, compromised patients, refugees, free trade, climate change
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9
Q

Factors that influence the prevalence of parasites in society

A
  • Geographic
  • Social customs
  • Host factors
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10
Q

How does geography influence the prevalence of parasites?

A
  • Climate
  • Modifications to environment
  • Vector population
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11
Q

How do social customs influence the prevalence of parasites?

A
  • Fecal disposal
  • Diet/food prep
  • Agricultural methods
  • Housing (rats, mosquitos)
  • Sexual practices (AIDS, etc.)
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12
Q

How do host factors influence the prevalence of parasites?

A
  • Nutritional state
  • Immune status → detrimetnal, possible immunological benefits
  • Genetics
  • Age
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13
Q

Life cycle for protozoa

A
  • Trophozoites

- Cysts

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14
Q

Life cycle for helminths

A
  • Egg
  • Larva
  • Adult stages
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15
Q

What protozoan stage would you find in formed stool?

A

Cysts (and eggs); trophs wall themselves up to form cysts as protection

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16
Q

What protozoan stage would you find in liquid stool?

A

Trophs (and eggs); these are more motile and fragile, commonly found higher up in the GI tract

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17
Q

What protozoan stage can be found in semiformed/soft stool?

A

Cysts, trophs, and eggs

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18
Q

What is the ratio of preservative to stool?

A

3 parts preservative: 1 part stool

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19
Q

This preservative serves as a fixative (mercuric chloride), is a resin for adhesion to the slide, and is used for PERMANENT smears.

A

PVA-polyvinyl alcohol

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20
Q

This preservative is used for concentrations or wet mounts, NOT smears.

A

10% buffered formalin

21
Q

Two methods of concentration are based on specific gravity

A

Flotation and sedimentation

22
Q

Preservative used in the flotation concentration technique

A

Modified Zinc Sulfate

23
Q

Specific gravity in concentration techniques

A

1.18-1.2

24
Q

Disadvantages of using the flotation technique

A

Dense eggs sink and operculated eggs rupture

25
Q

Advantages of doing flotation techniques

A

Allows detection of most eggs, larvae, and cysts; also eliminates debris (will settle to the bottom)

26
Q

Advantages of doing sedimentation concentration techniques

A

Allows detection of most eggs, larvae, and cysts by gravity or centrifugation

27
Q

Disadvantages of using sedimentation concentration techniques

A

Smaller eggs may not sediment; more fecal debris than flotation methods

28
Q

Advantages of doing permanent stains

A

Able to view internal structures (trophs or cysts)

29
Q

Most common/best permanent stain for viewing internal structures

A

Trichrome

30
Q

Specimen types collected for parasite identification

A
  • Gastrointestinal (most common)
  • Vaginal
  • Sputum
  • Aspirates (lung, liver, LNs, bone, etc.)
  • Biopsy (lung, cornea, skin, LN, GI, etc.)
  • Blood (thick, thin preparations)
31
Q

How many specimens are collected for fecal parasite identification?

A

Three fecal specimens on alternate days (6 for amoebiasis)

32
Q

Describe the transportation of fecal specimens collected for parasite identification

A

Clean, dry container

33
Q

Gross examination of fecal specimens

A
  • Blood (red, black)
  • Barium (white-clay) → Not acceptable!
  • Mucus
  • Adult worms
34
Q

Specimen processing of liquid fecal samples

A
  • Examine or preserve w/in 30 minutes, after collection

- Wet mounts, concentrations, permanent-stained smears

35
Q

Specimen processing of semi-formed/soft fecal samples

A
  • Examine or preserve w/in 1 hour after collection

- Wet mount, concentrations, permanent-stained smears

36
Q

Specimen processing of formed fecal samples

A
  • Usually not sent for parasite studies
  • Examine w/in 24 hours (or preserve them)
  • Concentrations, permanent-stained smears
37
Q

Why aren’t wet mounts observed w/ formed fecal samples?

A

No trophs will be found

38
Q

Describe the timing of fecal specimens collected for parasite identification

A
  • Before radiologic studies w/ barium (or 1-2 weeks post-barium)
  • Avoid medications (mineral oil, bismuth, antidiarrheal medications, some antibiotics, e.g., tetracycline)
  • Avoid contamination w/ water, urine
39
Q

Three identification techniques performed in an “O and P” examination

A
  1. Wet mount
  2. Concentrations
  3. Permanent stains
40
Q

Wet mounts

A

From direct specimen (not formed stool)
- Drop of physiologic saline
- Drop of iodine (one slide w/ and one w/o)
Screen w/ 10x objective (NEVER USE OIL)

41
Q

Concentration techniques

A

Separates parasites from fecal debris

Always performed from fresh or formalin-preserved stool (NEVER PVA)

42
Q

Trichrome stain

- Procedure

A
  • Fresh specimen is fixed or can use PVA preserved specimen (thin smear)
  • Requires experience
  • Stains takes hours (usually overnight)
43
Q

Trichrome stain

- Interpretation

A
  • Scan at low power (10x or 40x), then examin at 100x oil immersion (at least 300 fields)
  • Background debris = green
  • Protozoa = blue-green cytoplasm, red-purple nuclei, inclusions
  • Helminth eggs (may be distorted)
  • Larvae = dark red-purple
44
Q

What types of fecal specimens are used w/ a modified acid-fast stain?

A
  • Fresh stool or formalin fixed specimens

- Not PVA-preserved specimens!

45
Q

How quickly should blood smears be prepared?

A

< 1 hour

46
Q

Two types of blood smears that are prepared

A

Thick and thin

47
Q

Which type of blood smear is best for identification?

A

Thin smears

48
Q

Which type of blood smear has the best sensitivity?

A

Thick smears

Liz's Parasitology Course (8 decks)

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