Parasitology Flashcards
What diagnostic test is recommended for nematode larvae?
baermann test as it is the most sensitive
what is the purpose of testing for parasites in small animals?
- identify cause of clinical signs (most commonly)
- monitoring asymptomatic animals – preventative medicine programs or treating small animals
what 3 tests/samples can be used for morphological detection of macroscopic parasites?
- necropsy
- stool, vomit (helminths)
- arthropods themselves (ex. lice)
What 3 tests/samples can be used for morphological detection of MICROSCOPIC parasites?
- feces
- blood and other fluids
- skin debris or scrapings
What 2 types of tests are used for immunologic detection of parasites in small animals? (very generally, not specific names)
- antigen tests
- antibody tests
What 2 test are used for molecular detection of parasites in small animals?
- PCR
- sequencing
What are the advantages and disadvantages of morphologic tests for parasite detection?
(morphologic tests are standard for most parasites and are generally the first tests done)
advantages:
-inexpensive materials
-allows dg for multiple parasites
disadvantages:
- requires trained technicians
- requires larger samples
Why must we use fresh samples for fecal exams?
old samples may have maggots, soil nematodes, or hatched nematode parasite eggs
what is the minimum size appropriate for fecal samples?
3 grams
Why should you NOT ship fecal flotation slides?
parasites will be destroyed by the flotation solution
Direct saline smears using very fresh feces are only used for __________.
trophozoites such as giardia and tritrichomonas because they move.
NOT for protozoan cysts
The standard procedure for fecal analysis is _________________.
fecal flotation test
when doing a routine fecal float, you should always do what with the sample?
centrifuge and mix sample thoroughly before taking sample for your test because parasites are not uniformly distributed in the feces.
With regard to fecal float solutions, higher density solutions float _________, whereas lower densities float __________ less efficiently.
higher density solutions float more debris, whereas lower density solutions float some eggs less efficiently.
___________ is the ability to identify true positives (a measure of false negatives)
sensitivity
__________ is the ability to identify true negatives (a measure of false positives)
specificity
what is the sensitivity and specificity of direct fecal smears?
sensitivity = low
specificity = moderate
if we have a low sensitivity, then we cannot decrease the # of false negatives which is our goal usually.
how can you improve sensitivity and specificity?
combine with other tests.
T/F: the sensitivity of a fecal float is higher than direct smear
true
sample volume is more
patency of infection
parasites that you are trying to detect are usually easier detected
What is the specific gravity of zinc sulfate fecal flotation solution?
1.18 - 1.20
What is the specific gravity for sheathers sugar fecal float solution?
1.25-1.28
What is the specific gravity of sodium nitrate (fecasol) solution?
1.2
Which parasites have “heavier” eggs?
taenia sp
physaloptera sp.
which parasite is the “lightest”?
giardia cysts
which fecal solution is required to detect giardia?
zinc sulfate
what 2 fecal solutions are best to detect the MOST parasites?
- sheathers sugar solution
- zinc sulfate
T/F: centrifugal flotation tests are better than passive
true
How can you improve the sensitivity of fecal exams?
- use larger samples
- repeat the test (esp if girdia, trichuris, lungworms)
- combine with other tests (zinc sulfate float and antigen for giardia if diarrhea)
_________ are things that look like parasites but are not.
pseudoparasites
________ are things that are parasites of other animals and show up in your sample because of coprophagy or predation.
spurious parasites
If you suspect you have seen pseudoparasites or spurious parasites, what should you do?
repeat sample in 3-4 days and ensure there is no foreign material ingested during that time period.
Specificity is MOST affected by…
reader error
common errors: pseudoparasites (pollen grains, fungal spores, plant and animal hairs, air bubbles, yeasts) and spurious parasites (coprophagy, predation)
Many things may LOOK like parasites, but the easiest way to rule it out is looking at ________.
size
helminths = > 40 um
protozoa = < 60 um
What are some NEW technologies that improve parasite diagnosis?
- fecal Dx antigen test (IDEXX) (hooks, rounds, whips, diplydium)
- KeyScreen GI Parasite PCR (Antech) (20 parasites – hooks, rounds, whips, protozoa, giardia, coccidia, tapes, A. caninum benzimidazole resistance and zoonotic potential of giardia)
- Vetscan Imagyst System (Zoetis) (cytologic and fecal diagnostics using scanner with AI technology)
What are the reasons we do annual fecal exams in healthy dogs?
- detects parasites that are not treated by monthly products
- owner compliance is not good
- positive tests emphasizes importance of environmental management
- emerging drug resistance
Which of the following is FALSE about sedimentation tests?
A. used for parasite stages that have high density and wont float readily
B. feces mixed with zinc sulfate solution, then allowed to settle for a few minutes, then the fluid poured off leaving sediment, then repeat several times.
C. rarely performed in small animal
D. limited concentration of feces
B. feces mixed with zinc sulfate solution, then allowed to settle for a few minutes, then the fluid poured off leaving sediment, then repeat several times.
the feces are mixed with WATER, not zinc sulfate solution.