Lecture 3: Diagnostic Techniques Flashcards
Possible diagnostic samples (6)
Feces
Vomit
Blood
Urine
Skin scrapes
Formalin fixed tissue samples
Qualitative exam techniques: feces (5)
Direct visualization
Direct smear
Concentration techniques = Fecal flotation, Fecal sedimentation, Baermann
When to use direct visualization of endoparasites (and examples of parasites that can be seen)
If adult endoparasites are expelled in feces or vomitus
Toxocara canis roundworms, stomach worm, tapeworm proglottids
Direct fecal smear: how to perform, when not useful, when most useful
Drop of saline + small amount of feces + coverslip
NO = most GI parasites
YES = observe motility of Protozoal parasites that have motile stages
Fecal flotation: requirements and why this is important
Flotation solution must have higher/heavier specific gravity than most common parasites eggs/cysts
Higher specific gravity = eggs/cysts will float to top of solution
Fecal flotation: how to perform
Flotation solution = zinc sulfate or sucrose
Mix fecal debris in flotation solution then place coverslip over tube, eggs/cysts float and attach to coverslip
When to use fecal sedimentation (including species)
Detect eggs/cysts that are too heavy or delicate to concentrate by fecal flotation
Non nematode eggs = trematode, acantocephalan
Protozoal cysts = amoebae, ciliates, giardia species
Is fecal sedimentation sensitive for nematode eggs or coccidian oocysts?
No
When and for what species is Baermann technique useful (and what does this technique rely on)
Recovering nematode larvae from samples
Some lung worms and strongyloides species
Relies on motility
Is Baermann technique recommended as a primary diagnostic test for evaluation of parasites in feces
No
Baermann technique: main components
Diagnostic sample covered in water
Isolate motile larvae through straining
2 examples of when Baermann is not useful and instead flotation is preferred
Lethargic larvae
Or if larvae are not produced
Direct smear: when to use, cons
Protozoal GI infection with motile stages
Not very sensitive —> don’t use as primary diagnostic tool
Fecal flotation: when to use, cons
Nematode infection that produces eggs/cysts
If eggs/cysts are too heavy to float
Fecal sedimentation: when to use, cons
Infections with trematodes or acanthocephalans; amoebae, ciliates, giardia species
Not sensitive for nematode eggs or coccidian oocysts (cryptosporidium)
Baermann: when to use, cons
If Motile larvae present in feces (lung worms, strongyloides)
Only useful for isolating motile larval stages
Other Qualitative exam techniques (3)
Immunoassays
PCR
Culture of eggs or larvae
Immunoassays: when to use, what is detected specifically
GI protozoal parasites = giardia, cryptosporidium
Endoparasites antigens in feces
PCR: what is detected, when to use, variation
Endoparasite DNA in feces
Giardia and cryptosporidium
Can be qualitative or quantitative (real time)
Culture of eggs/larvae: target, when to use
Morphological differences in Eggs of nematode species
L3
Strongyles in large animals
Quantitative exam techniques (2)
Dilution egg counts = Cornell McMaster
Concentration egg count
When are quantitative exam methods used over qualitative methods
Better understand level of burden
Large animals always have low levels of egg shedding unless actively being treated
What parasites are targeted for quantitative exam methods
Trichostrongyle/strongyles in ruminants and horses
Cornell McMaster dilution egg counting technique: goal, requires what equipment, what does it provide
Quantify eggs within diluted fecal sample that is further diluted 1:1 in fecal flotation solution
Specialized microscope chamber slide
Estimate of eggs/gram of feces
Cornell mcmaster dilution egg counting technique: why dilute with flotation solution (2)
Decrease number of eggs you must count = enhance accuracy
Allow eggs to float to top of chamber = bringing them to same microscope field, floating above heavier fecal debris
When to use concentration egg count vs Cornell McMaster
If you suspect low levels of infection and don’t want to dilute sample
Concentration egg count: definition (combo of what?), end up with
Combo of cornell-McMaster and fecal flotation
Minimum estimate of eggs/gram of feces
Types/classifications of eggs (4)
Nematode
Trematode
Cestode
Protozoan cysts and oocysts
4 types of nematode eggs
Ascaridoid
Strongyle type
Trichinelloid/trichuroid
Oxyurid
Ascaridoid eggs aka
Roundworm eggs
Ascaridoid eggs: general characteristics (3)
Light brown to brown
Round to oval
Thick wall
Canine roundworm: genus and species, type of egg
Toxocara canis
Ascaridoid
4 main Ascaridoid eggs
Toxocara species/canine roundworm
B. Procyonis/Racoon roundworm
Parascaris equorum
Ascaris suum
Strongyle type eggs: general characteristics (3)
Elongated oval, thin wall
Clear/colorless
Embryonated (spheres pushed together)
Examples of Strongyle type eggs (3)
Ancylostoma
Strongylus
Haemonchus contortus
Oxyurid eggs aka
Pinworms
Oxyurid eggs: general characteristics (2)
Colorless shell
Small operculum/cap on one end
Is there a public health concern if horse has pinworms and why
No, not transmitted between species
Trichinelloid/trichuroid eggs aka
Whipworms
Trichinelloid/trichuroid eggs: general characteristics (3)
Bipolar plugs/bioperculated
Elongate to barrel shaped
Smooth thick wall
What kind of test would be best to identify Trichinelloid eggs
Fecal flotation
Capilllarids look like what kind of worms
Whipworms
Trematode eggs: general characteristics (2)
Brown egg
With operculum
Best test to identify trematode eggs and why
Fecal sedimentation
Heavy eggs
Cestode eggs: general characteristics (3)
Embryonated
6 hooked onto sphere inside thick, striated shell
Protistan cycsts and oocysts: general characteristic
Smaller than most eggs
2 main genera of protistan cysts
Entamoeba
Giardia
3 main genera of protistan oocysts
Isospora
Eimeria
Cryptosporidium
ID techniques for blood parasites (3)
Direct blood smear
Immunoassays for canine heart worm Ag/Ab
Microfilaria concentration techniques = modified knott’s, millipore filter test
Direct blood smear: how to do, what is identified
Drop of whole blood on slide —> create smear —> dry, fix, stain
Circulating Microfilariae, Protozoa, rickettsia (bacteria)
Immunoassays (blood parasite): used to detect
Ag or Ab
Dirofilaria immitis
Of the Microfilaria concentration techniques, which is preferred
Modified knott’s
2 Microfilaria recognized in blood of dogs in North America
D. Immitis
Acanthochilonema reconditum
If animal is positive for D. Immitis on immunoassay, what is next step
Perform concentration test to visualize Microfilaria
Modified knott’s/millipore filter test: why/how used, when used, concern about using test
Concentrate/filter blood to increase likelihood Microfilaria will be visualized
Lyses RBCs
Done after positive immunoassay
False negatives —> Microfilaria not present in all HW infected dogs
Techniques for detecting ectoparasites (4)
Direct visualization/ID
Skin scraping
Cellophane tape prep
Skin histopathology
Direct visualization: how/when to use
Use external traits (ornamentation, mouth parts)
Ticks, lice, mites
Skin scraping: when to use, how to do, what follows to diagnose
If suspect mite infestation (demodex, scabies)
Have to scrape deeply because mites embedded in skin/hair follicles
Dx with skin histopathology
Cellophane prep: when to use
Trap/catch mites or lice that are close to surface
Histopathology usually done when
Post Mortem
