Diagnostic Methods

Question 1

Describe where you would find parasites.

Answer 1

*feces, vomit, sputum, pigeon milk, blood, muscle biopsy, skin, necropsy
-nematodes = eggs, larvae, adults
-cestodes = proglottids, oncosphere
-trematodes = eggs, adults
-Protozoa = oocysts, cysts, trophozoites, gamonts
-insects/Acari = eggs, larvae, adults, nymphs

Question 2

Describe the different types of fecal methods.

Answer 2

1. Direct smear
2. Flotation
   >simple, centrifuge, kits, machines
3. Sediment
4. Baermann (larvae)

Question 3

Describe what impacts fecal results.

Answer 3

-worm burden
-fecal consistency = diarrheas egg count is diluted by water (less than normal feces)
-worm behavior (ex. Whip worm release eggs at same time)
-method used

Question 4

Describe the direct smear method.

Answer 4

-minimal feces required
-fast, inexpensive
-detects movement (when stain not used) fresh feces
-heavy & light eggs/cysts
-low infections missed
-small object hard to see

Question 5

Describe flotation solutions.

Answer 5

*flotation solution & sensitivity are directly related (can cause distortions)
-SG of water is 1
-most parasite eggs are 1.05-1.24
-.1 difference in egg & solution (higher) = ideal
-double centrifuge + sheathers sugar = most sensitive

Question 6

Describe simple flotation.

Answer 6

Steps:
-mix feces with solution
-strain
-fill tube with pos meniscus
-coverslip
-wait 5-10min

CONS:
-cant use high SG solutions
-cant use viscous solutions = decrease ability to detect some parasites

Question 7

Describe the steps of single VS double centrifugation.

Answer 7

Single:
-mix feces with solution
-strain
-fill tube w pos meniscus
-coverslip
-centrifuge
Double:
-mix feces w water
-strain
-fill tube & centrifuge
-pour off supernatant
-add solution, mix, fill tube
-coverslip
-centrifuge

Question 8

Describe the benefits of centrifuge flotation.

Answer 8

-high SG solutions
-high viscosity
-99% floats
-you can determine the egg per gram = quantitive

Question 9

Describe flotation kits.

Answer 9

-simple float
-centrifuge
-flotation solution
-increase cost
-decrease fecal handling

Question 10

Describe automated flotation methods.

Answer 10

-special reader & algorithm based ID
-learns & adds parasites
-removes operator error

Question 11

Describe sedimentation.

Answer 11

use a kit OR
-mix feces & water
-filter
-pour into tube (wait 5 min)
-remove supernatant (pipette)
-resuspend sediment
-repeat
*most sensitive to heavy/lg eggs = trematode (fluke) eggs

Question 12

Describe the baewrmann technique.

Answer 12

-detects larvae
-water, feces, gauze, gravity
-temp & humidity
-freshness of feces
-a lot of time

Question 13

Describe McMaster egg counting.

Answer 13

-livestock
-limited sensitivity
-nematode eggs, cestodes, Protozoa
-100x mag & no stains
-decision tool to treat = eval control prog
-sensitivity depends on:
>flotation solution
>ratio of feces to flotation solution
>time
*FECPAK designed for farmers
*flotation method + scanner
*read the pic
*cant tell eggs or sm/lg strongyles apart

Question 14

Describe blood smears.

Answer 14

-direct smear (w/ or w/o stains)
-mf = concentrate parasites via knotts test
-Protozoa

Question 15

Describe the scotch tape method.

Answer 15

-pinworms in horses
-cestodes
-hair/fur mites

Question 16

Describe ectoparasites (arthropods).

Answer 16

-adult fly, tick, louse or larval stage in 70% alcohol for ID
-lice: predilection sites, nits
-mites: skin scape, tape, otoscope, comb, environment

Question 17

Describe necropsy.

Answer 17

-detect zoonotic parasites in meat
-lg poultry production system
-parasites that dont release eggs (wrong host)
*pooled sample digestion method
*squash preparation method

Question 18

Describe antigen detection.

Answer 18

-feces, blood, serum, saliva
-parasite associated compounds
>must have enough parasites
-correct sex of parasite for some antigens
-false pos occur after clearing the infection (antigen disappears after 24-72h)

Question 19

Describe some immunodiagnostic methods.

Answer 19

-patient side tests (snap test)
-lateral flow immunochromatographic assay
*hw/giardia antigen test

Question 20

Describe fecal antigen for gastro-intestinal nematodes (dogs & cats).

Answer 20

-trichuris, toxocara, hooks
-enzyme linked immunosorbent assay for coproantigen detection
-not related to sex of parasite
-made by immature adults & adults = detection prior to PPP
-doesnt distinguish hook/roundworm species
-only in labs
-detect single sex infections
-can assist in differentiating infection from coprophagia

Question 21

Describe antibody detection.

Answer 21

-feces, blood, serum, saliva
-antibodies made by host immune system
-sufficient exposure time
-titer = understand life cycle
-confirms exposure & not infection
-differences in immunoglobulins & aid in understanding exposure, infections, length of infection

Question 22

Describe PCR.

Answer 22

-species specific RNA or DNA visible
-amplifies DNA/RNA sequences
-specific & sensitive
-limited for some species
-expensive & timely
-Protozoa & nematodes
-labs
-useful when parasite burdens are low
-common in livestock/horses (not for regular diagnosis)

Question 23

Describe fecal PCR for gastro-intestinal nematodes (dogs & cats).

Answer 23

-20 parasites
-unclear on species differentiation
-determines giardia assemblage (zoonotic or not)
-determines benzimidazole resistance for ancylostoma caninum