Diagnostic parasitology techniques Flashcards
what does endoparasites break down into? (broad)
protozoa - unicellular
helminths - multicellular worms
what are the key characteristics of ectoparasites?
jointed appendages
what are common protozoal parasites in veterinary medicine?
flagellates, amoeba, ciliates, apicomplexans
what are the common helminth parasites in veterinary medicine?
trematodes (flukes), cestodes (tapeworms), nematodes
what are the common ectoparasites in veterinary medicine?
ticks, mites, lice, fleas, flies/bots
what are the possible diagnostic samples you may encounter?
feces
sputum/vomitus
blood
urine
skin scrapes
formalin-fixed tissues samples -> histopathology
what does a qualitative test tell you?
wether an animal is infected
what does a quantitative test tell you?
tells you the amount affected
what are qualitative tests to diagnose endoparasites for feces?
direct visualization
direct smear
concentration techniques - fecal flotation, fecal sedimentation, baermann, immunoassays, polymerase chain reaction (PCR), culture of eggs or larvae
how do you get a parasitologist to tell you what the parasite it?
save in 70% ethanol and submit to veterinary diagnostic lab
what type of parasites get expelled in the feces or vomitus?
adult endoparasites
how do you prepare a direct fecal smear?
drop of saline + small amount of fecal material + coverslip
what has a risk for false negatives and is not a great tool for detecting most GI parasites?
direct fecal smear
what test is most useful when observing the motility of protozoal parasites that have motile stages?
direct fecal smear
what must the fecal flotation have for the most common parasites eggs/cysts to float?
higher/heavier specific gravity than most common parasites eggs/cysts
what is a good test for nematode eggs?
fecal flotation
what test is used to detect eggs/cysts that are too heavy to concentration by fecal flotation?
fecal sedimentation
what test is most useful for non-nematode eggs and certain protozoal cysts?
fecal sedimentation
what are some non-nematode eggs that fecal sedimentation are useful for?
trematode or acanthocephalan
what are some certain protozoal cysts that fecal sedimentation are useful for?
amoebae, ciliates, Giardia spp.
what is the fecal sedimentation not sensitive for?
nematode eggs or coccidian oocysts
what is the baermann technique useful for?
nematode larvae
How does the Baermann technique recover nematode larvae?
nematode larvae will wiggle out of biological material, cannot swim against gravity and will fall through the water to the area of clamped off tubing
what is the baermann technique useful for identifying?
lung worms and Strongyloides spp.
what is this test called?
Baermann technique
what is this test called?
fecal sedimentation
what test would you do when you suspect a protozoal GI infection that has motile stages?
direct smear
what test would you do when you suspect a nematode infection that produce eggs/cysts?
fecal flotation
what test would you do when you suspect infections with trematodes or acanthocephalans, amoebae, ciliates, Giardia spp.?
Fecal sedimentation
what test would you do when you suspect motile larvae is present in the species (lung worm or Strongyloides spp. infections)?
Baermann
what are the cons of a direct smear?
not very sensitive, don’t use as a primary diagnostic tool
what are the cons of a fecal flotation?
some eggs/cysts are too heavy to float (use fecal sedimentation in this case)
what are the cons of fecal sedimentation?
not very sensitive for nematode eggs or coccidian oocysts (ex. Cryptosporidium spp.)
what are the cons of Baermann test?
only useful for isolating motile larval stages
what is an immunoassay for feces?
detection of parasite antigens in feces
what is a PCR for feces?
detection of parasite DNA, can be quantitative depending on test
what is the immunoassay most commonly used for?
GI protozoal parasites - Giardia & Cryptosporidium
what are PCRs most commonly used for?
GI protozoal parasites - Giardia & Cryptosporidium spp.
Which PCR is qualitative or quantitative?
rt - qualitative
q - quantitative
what does a lower Ct indicate?
higher burden
what L3 larvae commonly infect large animals?
trichostronglyes & strongyles
what egg is this?
Trichostrongyle egg - Teladorsagia circumcincta - brown stomach worm
what egg is this?
Strongyle egg - Strongylus vulgaris
what are quantitative tests for endoparasites in the feces?
-dilution egg counts (Cornell-McMaster dilution technique)
why use a quantitative test and not qualitative test in large animals?
they almost always have low levels of egg shedding unless they are actively being treated, so question is not are they infected but to what degree
what is dilution egg counts mostly used for?
trichostrongyle/strongyles in ruminants and horses
what does the Cornell-McMaster dilution egg counting technique do?
provides an estimate of eggs/gram of feces
How is the Cornell-McMaster dilution egg counting technique done?
quantify’s eggs within a diluted fecal sample that is further diluted (1:1) in fecal flotation solution
Why dilute the cornell-mcmater dilution egg counting technique with flotation solution?
-dilution decreases # of eggs you must count -> enhances accuracy
-flotation solution allows eggs to float to top of chamber ->bringing them to the same microscope field, floating above heavier fecal debris
what are the 4 common types/classifications of eggs?
nematode, trematode, cestode, protistan cysts and oocysts
what does nematode eggs break down into?
ascaridoid(roundworm), strongyle-type, trichuroid (whipworm), oxyurid (pinworms)
what are ascaridoid eggs also called?
roundworm eggs
what are the general characteristics of ascaridoid eggs?
light brown to brown, round to oval, thick wall
what species are these? (each seperate)
which species is this?
which species is this?
what species is this?
Toxocara canis - canine roundworm
what is an ocular larval that migrates in humans
Toxocara canis
what species is this?
Baylisacaris procyonis - raccoon roundworm
what is a neurotropic parasite that has cerebral larval migration
Baylisacaris procyonis - racoon roundworm
what are the general characteristics of strongyle-type eggs?
elongated oval, thin wall, clear (colorless), embryonated
what type of egg is this?
Strongyle-type
what are the general characteristics of oxyurid egg (pinworms)?
colorless shell and a small operculum (cap) on one end
what type of egg is this?
Oxyurid egg - pinworms
what are the arrows pointing to?
Is there a public health significance if a horse has pin-worms?
no, can’t be zoonotic
what are the general characteristics of trichuroid egg (whipworm eggs)?
bipolar (bioperculated), elongated to barrel-shaped, smooth thick wall
what egg is this?
Trichuroid egg
what type of technique would work best to isolate trichuroid eggs?
fecal flotation
what egg looks a lot like trichuroid eggs?
capillarids
how do capillarids and whipworms differ?
capillarids - bipolar plugs less prominent, slight curved appearance, can have pitted/irregular shells
what are the general characteristics of trematode eggs?
brown egg with an operculum
what type of egg is this?
trematode egg
what are the arrows pointing to?
what type of technique would you use to isolate trematode eggs?
fecal sedimentation
what are the general characteristics of cestode eggs?
embryonated, 6-hooked oncosphere present inside a thick, striated shell
what type of egg is this?
Cestode eggs
what are the arrows pointing to?
what are the general characteristics protistan cysts and oocysts?
smaller than most other eggs, still relatively varied in size
what are these?
protozian cysts
what are these?
oocysts
what are possible pseudo-parasites?
air bubble, plant pollen, fungal spore
what are each of these?
what are some techniques for identifying blood parasites?
-direct blood smears
-immunoassays for detecting Dirofilaria immitis antigen or antibody
-microfilaria conc. techniques: modified knott’s, millipore filter test
what is typically used to identify circulating microfilariae, protozoa, and rickettsiae (bacteria)?
direct blood smear
what to do immunoassays detect?
antigen or antibody
what are two microfilaria conc. techniques? which is preferred?
modified knott’s (preferred)
milipore filter test
Aside from D. immitis what is the only filarid recognized in the blood of dogs in north america?
Acanthochilonema reconditum
how do you differ between A. reconditum and D. immitis?
why are microfilaria concentration techniques done?
to concentrate/filter the blood to increase the likelihood microfilaria will be be visualized, typically involved lysing RCBs
do you do a microfilaria concentration technique before or after a positive immunoassay?
after
can you use microfilaria concentration techniques as stand alone tests?
no risk for false negatives
why might you get false negatives with microfilaria concentration techniques?
microfilariae not present in all HW-infected dogs
what are the techniques for detecting ectoparasites?
direct visualization/identification, skin scraping, cellophane tape prep, skin histopathology
what can direct visualization help to differentiate between with ectoparasites?
ticks, lice, and mites
when do you use skin scrapings?
if you suspect a mite infestation
what do you use to do skin scrape?
scalpel blade, mineral oil, slide
why do you have to scrape so deeply?
some mites embed in the skin and some deep in hair follicles - need to diagnose via skin histopathology
when do you use cellophane prep?
trapping/catching mites/lice that are close to the surface
why is histopathology/postmortem important?
knowing a parasites life-cycle and anatomic predilection site is half the battle when trying to identify parasites grossly in vet species
what are these?
what are broad classifications of parasites?
endoparasites and ectoparasites
