Parasitology- Diagnostics

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  1. Describe the double centrifugation fecal floatation protocol?
    • 1. 1-2g fresh feces mixed with 7mL water; emulsify.
    • 2. Remove large particulates by running through screen filter.
    • 3. Centrifuge, decant, keep pellet.
    • 4. Add float solution to 1/4, mix completely; then fill to ~1mm from the top of the tube.
    • 5. Centrifuge.
    • 6. Add more solution until you get a meniscus and place a coverslip on top for 10 min.
    • 7. Add coverslip to glass slide and examine.
  2. How does fecal flotation isolate the ova?
    during the wash step, eggs sink in water (to pellet); during the float step, eggs float in solution b/c specific gravity is greater
  3. After the wash step, where are the majority of the eggs?
    at the bottom, in the pellet
  4. Why must you decant as much of the wash solution as possible?
    if you leave too much water (wash solution), it will dilute the float solution and the eggs will not float (the specific gravity will be too low)
  5. How do you measure the specific gravity of float solution? Why is this important?
    Hydrometer; some larger eggs require a higher specific gravity to float
  6. What are the pros and cons of salt-based floatation solutions?
    better for visualizing giardia spores; fast to crystallize and will distort ova quickly
  7. What are the pros and cons to sugar-based floatation solutions?
    better if you wait a while before analyzing slides or storage slides because it won't distort like salt; not as good for visualizing small protozoa
  8. What is the optimum floatation solution SG? Why?
    ≥1.24 because even the largest eggs, Physaloptera (1.23), will float
  9. What parasites are fecal floatations useful for identifying?
    most parasite eggs (1.2 or less in density- not Taenia or Physaloptera), some larval stages (lungworms that were coughed up and swallowed)
  10. What are fecal floatations NOT useful for identifying?
    heavy eggs (trematodes), some protozoa (not trophozoites- they don't float), not good for moat larvae
  11. What parasites are identified with the Baermann test?
    lungworm infections- larvae
  12. What is a crucial point for successful use of the Baermann test?
    feces MUST be FRESH
  13. What parasites can be identified with a fecal smear?
    protozoa (Giardia, trichomonads, amoebae), Crypto if stained with acid fast stain
  14. Why isn't fecal smear recommended for routine fecal analysis?
    very low sensitivity- won't get rounds, whip,s and hooks
  15. Why can't you use water when performing a direct fecal smear?
    water will be taken up into trophozoites, causing them to burst... MUST use saline
  16. What are fecal quantitative egg counts used for?
    strongylid-type parasites [large animals]; want to know "parasite load" (how many strongylid type ova per gram feces); tells you who to treat, if there is drug resistance, pasture management is going well/poorly, predict disease occurance
  17. What are the strongylid-type parasites of horses? (2)
    cyanthostomes and large strongyles
  18. What are the strongylid-type parasites of ruminants?
    [Strongyles] Haemonchus, Ostertagia, Trichostrongylus, Cooperia
  19. What are the 2 most important types of fecal quantitative egg counts? What is each used for?
    McMaster's (not good for low numbers), Stoll's (detects low numbers of ova)
  20. What is the equation for fecal egg count reduction test?
    %FECR= ([pretreatment FEC- posttreatment FEC]/ pretreatment FEC) x 100
  21. How do you interpret a fecal egg count reduction test?
    fully effective anthelmintics >95% reduction; suspect if %FECR <90%
  22. What parasites can be isolated with simple sedimentation?
    heavy ova that don't float well, like flukes and some nematodes
  23. What is the modified Knott's test used to detect?
  24. Image Upload 1
    • Large ova- Nematodirus
    • Small Ova- Trichostrongyle
  25. Image Upload 2
    Pearsonema (formerly Capillaria) plica; infects bladder wall, with anterior portion woven into mucosa; eggs passed in urine and found on urine sediment; earthworms are intermediate host of L1; treated with Ivermectin or fenbendazole
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Parasitology- Diagnostics
2016-01-21 22:40:01
vetmed parasitology

vetmed parasitology
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