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Parasitology > Diagnostics > Flashcards

Diagnostics Flashcards

1
Q

Fecal Flotation

A

-Basically the light eggs/oocysts will float in high specific gravity AND the debris will go down

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2
Q

ways to diagnose- fecal flotation

A
  1. Qualitative- used in small animal; present/absent
  2. Quantitive - used for large animals; fecal egg counts.
    >informed decision: sometimes more is not necessarily worse than one parasite of a higher pathogenicity
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3
Q

Two ways that fecal flotation is conducted

A
  1. Passive- gravity based; clinics and fieldwork (mini-FLOTAC, Fecalyzer, McMaster)
  2. Centrifugal- high sensitivity labs (ex. Wisconsin)
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4
Q

What does fecal flotation show?

A

-Helminth eggs (especially nematodes)
-Some protozoal oocysts

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5
Q

What features help to differentiate nematode eggs?

A

-shape
-symmetry
-presence of plugs
-shells
-size
-presence of morula

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6
Q

What are features that can help differentiate cestode eggs?

A

**not shed all the time- lucky to see them!
- they are heavy and don’t float well

Features:
-hooks in egg
-shell/capsule
-geometric shape
-presence of single or multiple in eggs

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7
Q

Limitations of fecal flotation

A

Can result in false negatives (sensitivity) or false positives (specificity)

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8
Q

What causes false negative in fecal flotation?

A
  • intermittent shedding
    -prepatent period
    -environment
    -single sex nematode infections
    -aged feces (hatched eggs)
    -may not detect segments, larvae
    -technical errors (wrong solution, small sample, diarrhea, non homogenized)
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9
Q

What causes false positives in fecal flotation?

A

-pseudoparasites
-coprophagia (spurious)- dog ate cow feces and is now displaying parasite (but probably just when right through)
-parasites in prey species
-indistinguishable eggs**

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10
Q

Tips for doing a fecal flotation

A

-get multiple samples
-fresh samples (kept cold)
-annual check
-detailed dietary and travel history to help narrow down what you could expect
-train personnel how to store and ship
-order right tests
-understand limitations of field testing

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11
Q

Fecal sedimentation

A

-used for eggs too dense to float or detecting larvae (ex. Baermann larval sedimentation)

-often used for trematode eggs in large animals

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12
Q

Baermann larval sedimentation

A
  • live larvae in fresh feces submerged in water wriggle out and sink
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13
Q

How do you determine the presence of trematode eggs?

A

-often operculate (lets miracidia out)
-sizes
-shape

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14
Q

Tests to recover and determine morphology of parasites

A

1.Perianal tape method
2.Total worm count
3. Skin scraping/parasite collection
4. Tissue digestion
5. Coproculture

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15
Q

When would you use perianal tape method?

A
  • Pinworms (nematodes) in large animals
    -Cyclophilid cestodes in small animals
  • Eggs adhered to the perianal region
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16
Q

When would you use worm count?

A
  • Worm burden in GI tract
    -Ruminant GIN
    -Echinococcys sp (cestodes) in canids
    -GI tract lavage
17
Q

When would you use skin scraping/parasite collection?

A

-ticks, lice, fly maggots
-mites (deep/superficial scraping)

18
Q

When would you use tissue digestion?

A

-Larvae and adult helminths that reside in host tissues/organs
-digest solution

eg.Trichinella spp

19
Q

When would you use coproculture?

A

-Nematodes have many identical eggs. Let the eggs culture to develop into L3 where you can then determine species/morphology

20
Q

Fecal smear

A

-used to determine protozoan infections (trophozoites and cysts)
-simple, quick
-low sensitivity (because shedding is not occurring all the time)

21
Q

PCR

A

-use DNA sample and combine with primers (for specific type of parasite). Put in thermal cycler (Denaturing, Annealing, Extension)
-Specific primers will confirm on gel the presence/absence of different parasites

22
Q

What samples can you do PCR in?

A

-feces
-blood
-urine
-isolated eggs/larvae

23
Q

If DNA present or absent, does this mean that parasite is actually there or not there?

A

No

24
Q

Antigen tests

A

-SNAP tests- commercially available, no equipment
- looking for specific parasite-associated compounds
-use blood or fecal samples
-antigen binds to positive spot and pathogen specific coloured particle binds to determine positive

25
Q

Antibody tests

A

-host immune response to a parasite through production of specific antibodies
>positive test just means exposure!

-uses blood, saliva, CSF to detect protozoans

-regulatory or large-scale screening

26
Q

Histology and immunohistochemistry

A

-detect tissue helminths and protozoa
-use histological sections collected at necropsy to look for antibodies

27
Q

Importance of effective diagnostics

A

-screening or surveillance
-treatment/control strategies
-adoption of preventative measures
-access risk of infections of other animals in herd/household or humans

Parasitology (12 decks)

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