parasitology study questions Flashcards
areas of the body which can be infected by parasites
oral cavity, esophagus, stomach, small and large intestine
5 different life stages seen in feces
eggs
oocysts
larvae
segments
adults
2 methods of preserving a sample for later evaluation
refrigerate or mix with 10% formalin
the minimum amount of fecal material needed for a fecal floatation
1 gram
Under what 2 conditions would a larger sample be needed to get accurate results?
diarrhea or undigested hay/hair
disadvantage of using a fecal wand to obtain a sample
too small of sample
How should fecal samples be labeled
Owner name, pet name, date, time
collected
If the client is collecting the sample, list 3 instructions you should give them
a. collect immediately after defecation
b. store in disposable container
c. approximately 1 gram needed
precautions when handling fecal samples
Wear gloves and ppe, wash hands frequently
5 things you should look for/evaluate as part of the gross exam
a. consistency
b. color and odor
c. presence of blood or mucous
d. foreign bodies
e. adult parasites
Which two adult parasites may be noticed in the fecal of small animals?
roundworms and tapeworms
If you skip the gross exam, what parasite might be missed? Why?
Tapeworm. The eggs are inside the segment and the segments don’t float. We often do break segments open in preparing the float, and if we do, we can see tapeworm ova or the dipyllidium egg packets with the ova inside.
what does bright red blood on the feces indicate
bleeding in large intestine or rectum
what does black or tarry feces indicate
bleeding in upper GI (stomach small
intestine)
what does clay (off white)colored feces indicate
excess fat present
2 situations where doing a direct smear would be a good idea
to visualize trophozoite-giardia and diarrhea
how to perform a direct fecal smear:
a. How much feces do you put on the slide?
b. What do you mix the feces with?
c. Should you use a coverslip?
d. What microscope settings do you use?
e. How much of the smear do you look at?
a. Small amount
b. Water or saline
c. YES
d. 10X and 40X
e. Entire coverslip
disadvantage of the performing only a direct fecal smear
not adequate because it is a small sample size and debris could be confused for parasite material
Is the direct fecal smear a good method when looking for nematode infections?
NO, The sample is so small that you are likely to get a false negative result because there will be only a few ova in that amount and they may be hidden under other debris.
parts of tapeworm that float
egg packets and ova
procedure to do a simple fecal floatation
Place approximately 2 g to 5 g (1-2 tsp) of feces in the paper cup.
Add 30 mL of flotation solution.
Use a tongue depressor to mix the feces and produce an evenly suspended emulsion.
Pour the suspension through the metal strainer into another cup
Pour into test tube sitting in a rack
Fill the test tube to form a convex dome (meniscus) at the rim. Do not overfill the vial. Fresh solution can be used to form this dome
Place a coverslip on top of the test tube.
Allow the coverslip to remain undisturbed for 10 to 20 minutes.
Pick the coverslip straight up and then place it on a glass slide, with the fluid side down.
why is centrifugation method recommended
removes excess debris, recovers more eggs and cysts in less time
procedure for doing the centrifugation method using a fixed head centrifuge
- More sensitive than simple flotation
- Recovers more eggs and cysts in less time
What is a swinging head centrifuge? How is the procedure different if you use one?
A centrifuge with rotating buckets the containers that hold the samples swing
outward when spinning. You can apply the coverslip during centrifugation.
purpose of doing a fecal sedimentation
Used when suspected ova are too large to be recovered with standard flotation
Fluke ova
procedure for doing fecal sedimentation
Mix 2 g to 5 g of feces in a cup with 30 mL of water.
Strain the fecal suspension through the cheesecloth, gauze, or tea strainer into a
50-mL conical centrifuge tube. (Suspending a funnel over the tube facilitates the
filling of the tube.)
Wash the sample with water until the tube is filled.
Allow the tube to sit undisturbed for 15 to 30 minutes.
Decant the supernatant off, and then resuspend the sediment in water.
Repeat Steps 4 and 5 two more times.
Decant the supernatant without disturbing the sediment.
Use a pipette to mix the sediment, and then transfer an aliquot to a slide.
Place a coverslip over the sediment, and systematically examine the slide with
100× magnification.
Repeat Steps 8 and 9 until all sediment has been examined.
When would we use cellophane tape to prepare a sample?
To gather pinworm and tapeworm segments
Baermann technique
- Used to recover larvae from fecal samples
- Requires the construction of a Baermann apparatus
- Large funnel, tubing, and collection tube
What stage of the parasite life cycle is the Baermann technique used to find?
larvae
how to do the Baermann technique
- Construct a Baermann apparatus. Put 30 g to 50 g of feces on top of the cheesecloth or Kimwipes, and fill the funnel with warm water (not hot) to a level above the fecal sample.
- Allow the apparatus to remain undisturbed for a minimum of 1 hour and up to 24 hours.
- Collect the fluid in the rubber tubing (or the stem of the glass), and transfer it to a Petri dish or a centrifuge tube.
- Examine the Petri dish for larvae with the use of a stereo microscope, or
centrifuge the solution to pellet the larvae. Remove the supernatant from the
centrifuge tube, and then place the pellet on a microscope slide. - Examine the slide for larvae, and identify them. The slide can be passed over the flame of a Bunsen burner several times to kill the larvae in an extended position before identification.
When would occult blood testing be performed on feces and what does the
test identify?
- Intestinal bleeding is suspected
- presence of hemoglobin
When would a fecal culture test be run?
Used to differentiate parasites whose eggs or larvae are not easily distinguished by a fresh fecal sample
Modifies McMasters technique
Provides an estimate of the number of eggs or oocysts per gram of feces
When mixing fecal solution, why is it important that the specific gravity be between 1.18 and 1.20?
If SG is too high all the junk will float on the “thick” solution and the ova will be
hard to find. If the SG is too low, ova we want to see will be heavier than the
solution and sink to the bottom where we won’t find them.
What objective is used when looking for ova?
10 X
How are the condenser, diaphragm and rheostat set when looking for ova?
set for the 10 X objective; diaphragm 10 X, rheostat down, condenser stays in place
What could happen if your lighting is too bright when you do the microscopic exam?
The light burns through the ova and you will not detect them
Name at least 2 different solutions used for fecal floatations.
Sodium nitrate
zinc sulfate
magnesium sulfate
sheathers solution
3 nematodes by their common and scientific name
Roundworm: Toxacaris or toxacara
hookworm: Ancylostoma
Whipworm: trichuris
What scientific family do Dipylidium and Taenia belong to?
cestodes
What is dipylidium and taenia’s common name?
tapeworm
how is dipylidium and taenia transmitted to dogs and cats
Intermediate host Dipylidium-flea
taenia-rabbit, mouse
scientific name of the coccidia found in dogs and cats?
isospora
is isospora a nematode, cestode, or protozoan?
protozoan
What is the proper term for the “egg” of isospora?
oocyst
biggest parasite ova we will learn this semester
dipylidium
smallest parasite ova we will learn this semester
coccidia
second smallest parasite ova we will learn this semester
taenia
embryonated
Developed into an embryo, the egg is passed hatches and reinfects within hours (whipworm)
Nematodes
hookworm, roundworm, whipworm
Cestodes
Dipylidium, taenia
Protozoa
coccidia (isospora)
