3 – Diagnostics Flashcards
Fecal floatation
- Light eggs/oocysts float in high specific gravity
- Debris go down
Fecal floatation characteristics
- Qualitative
- Quantitative
- Passive
- Centrifugal
Fecal flotation is good for
- Helminth eggs (especially nematodes
- Some protozoal oocysts
Limitations of fecal floatation
- False negative: sensitivity issues
- False positives: specificity issues
Why might you get false negatives w/fecal floatation?
- Intermittent shedding
- Prepatent period
- Environment
- Single sex nematode infections
- Aged feces
- May not detect segments, larvae
- Technical errors (wrong solution, small sample)
Why might you get false positives w/fecal floatation?
- Pseudoparasites
- Coprophagia (spurious)
- Parasites in prey species
- INDISTINGUISHABLE eggs
Strongly-type egg
- 70 possible species
Taeniid-type egg
- 12 possible species
How do you get the most out of a fecal floatation?
- 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
Fecal sedimentation can be used for
- Larvae (ex. Baermann larval sedimentation)
- Fluke eggs
- *for eggs to dense to float (ex. trematode eggs in large animals)
o Often operculate
Baermann larval sedimentation
- Live larvae in fresh feces submerged in water, wriggle out and sink
- Need to specifically ask for this one
- Ex. lungworms (dogs, livestock)
Other ways to recovery and determine morphology
- Perianal tape method
- Total worm count
- Skin scarping/parasite collection
- Tissue digestion
- coproculture
Perianal tape method
- Pinworms (nematodes) in large animals
- Cyclophilid cestodes in small animals
- Eggs adhered to perianal region
Total worm count
- Worm burden in GI tract
- Ruminant GIN
- Echinococcus sp (cestodes) – canids
- GI tract lavage
Skin scraping/parasite collection
- Ticks, lice, fly maggots
- Mites: deep/superficial scraping
Tissue digestion
- Larvae and adult helminths
- Host tissues/organs
- Digest solution
- Ex. Trichinella spp
Coproculture
- Nematodes: identical eggs
- Eggs cultured to develop into L3
What is used in Protozoan infections?
- Fecal smear
Fecal smear: protozoan infections
- Simple, quick, low sensitivity
- False negatives are common (due to not shedding all the time)
- Ex. protozoal trophozoites and cysts
Other technique to isolate eggs/larvae for detection and ID
- coproPCR (fecal samples)
- PCR (blood and urine)
- *presence or absence of DNA does not always mean presence or absence of parasites
PCR steps
- Denaturing: strands separate
- Annealing: primers bind template
- Extension: synthesize new strand
Antigen tests
- Specific parasite-associated compounds
- Blood or fecal suspension
- SNAP tests=commercially available, no equipment
- Ex. coproantigen tests
Antibody tests
- Due to host immune response
- Regulatory or large-scale screening (ex. horse competitions)
- Blood, saliva, CSF: protozoans
Antibody tests: positive test
- EXPOSURE
o Clinical interpretation, in parallel tests
o Blood, saliva, CSF: protozoans - *regulatory or large-scale screening
Histology and immunohistochemistry
- Tissue helminths, protozoa
- NOT COMMON
Histological sections collected at
- Necropsy/biopsy
Immunohistochemistry
- Detection of antibodies in histological sections
