3 – Diagnostics

Question 1

Fecal floatation

Answer 1

• Light eggs/oocysts float in high specific gravity
• Debris go down

Question 2

Fecal floatation characteristics

Answer 2

• Qualitative
• Quantitative
• Passive
• Centrifugal

Question 3

Fecal flotation is good for

Answer 3

• Helminth eggs (especially nematodes
• Some protozoal oocysts

Question 4

Limitations of fecal floatation

Answer 4

• False negative: sensitivity issues
• False positives: specificity issues

Question 5

Why might you get false negatives w/fecal floatation?

Answer 5

• Intermittent shedding
• Prepatent period
• Environment
• Single sex nematode infections
• Aged feces
• May not detect segments, larvae
• Technical errors (wrong solution, small sample)

Question 6

Why might you get false positives w/fecal floatation?

Answer 6

• Pseudoparasites
• Coprophagia (spurious)
• Parasites in prey species
• INDISTINGUISHABLE eggs

Question 7

Strongly-type egg

Answer 7

• 70 possible species

Question 8

Taeniid-type egg

Answer 8

• 12 possible species

Question 9

How do you get the most out of a fecal floatation?

Answer 9

• Request multiple samples from right animals
• Request fresh samples
• Annual check
• Get a detailed dietary and travel history
• Train personnel
• Order RIGHT tests
• Field test: understand limitations

Question 10

Fecal sedimentation can be used for

Answer 10

• Larvae (ex. Baermann larval sedimentation)
• Fluke eggs
• *for eggs to dense to float (ex. trematode eggs in large animals)
  o Often operculate

Question 11

Baermann larval sedimentation

Answer 11

• Live larvae in fresh feces submerged in water, wriggle out and sink
• Need to specifically ask for this one
• Ex. lungworms (dogs, livestock)

Question 12

Other ways to recovery and determine morphology

Answer 12

• Perianal tape method
• Total worm count
• Skin scarping/parasite collection
• Tissue digestion
• coproculture

Question 13

Perianal tape method

Answer 13

• Pinworms (nematodes) in large animals
• Cyclophilid cestodes in small animals
• Eggs adhered to perianal region

Question 14

Total worm count

Answer 14

• Worm burden in GI tract
• Ruminant GIN
• Echinococcus sp (cestodes) – canids
• GI tract lavage

Question 15

Skin scraping/parasite collection

Answer 15

• Ticks, lice, fly maggots
• Mites: deep/superficial scraping

Question 16

Tissue digestion

Answer 16

• Larvae and adult helminths
• Host tissues/organs
• Digest solution
• Ex. Trichinella spp

Question 17

Coproculture

Answer 17

• Nematodes: identical eggs
• Eggs cultured to develop into L3

Question 18

What is used in Protozoan infections?

Answer 18

• Fecal smear

Question 19

Fecal smear: protozoan infections

Answer 19

• Simple, quick, low sensitivity
• False negatives are common (due to not shedding all the time)
• Ex. protozoal trophozoites and cysts

Question 20

Other technique to isolate eggs/larvae for detection and ID

Answer 20

• coproPCR (fecal samples)
• PCR (blood and urine)
• *presence or absence of DNA does not always mean presence or absence of parasites

Question 21

PCR steps

Answer 21

1. Denaturing: strands separate
2. Annealing: primers bind template
3. Extension: synthesize new strand

Question 22

Antigen tests

Answer 22

• Specific parasite-associated compounds
• Blood or fecal suspension
• SNAP tests=commercially available, no equipment
• Ex. coproantigen tests

Question 23

Antibody tests

Answer 23

• Due to host immune response
• Regulatory or large-scale screening (ex. horse competitions)
• Blood, saliva, CSF: protozoans

Question 24

Antibody tests: positive test

Answer 24

• EXPOSURE
  o Clinical interpretation, in parallel tests
  o Blood, saliva, CSF: protozoans
• *regulatory or large-scale screening

Question 25

Histology and immunohistochemistry

Answer 25

• Tissue helminths, protozoa
• NOT COMMON

Question 26

Histological sections collected at

Answer 26

• Necropsy/biopsy

Question 27

Immunohistochemistry

Answer 27

• Detection of antibodies in histological sections