Parasitology

Question 1

What are the two purposes of testing for parasites in small animals?

Answer 1

(Identifying the cause of clinical signs and monitoring asymptomatic animals as a part of preventative medicine programs)

Question 2

List the advantages and disadvantages of morphological parasite tests.

Answer 2

(Advantages → inexpensive, allows examination for multiple parasites; disadvantages → requires trained technicians, requires larger samples than immunologic or molecular tests)

Question 3

If fecal samples are unable to be examined within a few hours, where should they be stored?

Answer 3

(The fridge)

Question 4

A direct saline smear can only be used for what stage of protozoan parasites?

Answer 4

(Trophozoites, bc they move, cannot use this method for other parasites or protozoan cysts)

Question 5

What are the two protozoans that affect small animals that have trophozoites that can be seen on a direct smear?

Answer 5

(Giardia and Tritrichomonas)

Question 6

Why should fecal samples be mixed thoroughly prior to taking your sample for testing?

Answer 6

(Because parasites are not uniformly distributed in feces)

Question 7

(T/F) Higher density liquids will likely have more debris floating at the top when compared to lower density liquids.

Answer 7

(T, but lower density liquids will float eggs less efficiently depending on their weight)

Question 8

For a direct smear, the sensitivity is low/moderate/high (choose) while the specificity is low/moderate/high (choose).

Answer 8

(Sensitivity is low and specificity is moderate aka your false negative chance is high and your false positive chance is moderate)

Question 9

Do centrifugal or passive flotation exams have a higher sensitivity?

Answer 9

(Centrifugal, if you do not have the ability to centrifuge your fecal floats you might as well just send them out)

Question 10

What flotation solution is commonly used for Giardia infections?

Answer 10

(Zinc sulfate, will float in the others bc the cysts are so light but Sheather’s and sodium nitrate can destroy the cysts)

Question 11

What are pseudoparasites?

Answer 11

(Things that look like parasites but aren’t)

Question 12

What are spurious parasites?

Answer 12

(Things that are parasites of other animals but that show up in samples because or coprophagy or predation)

Question 13

When a fecal float and antigen test are combined, the combined sensitivity is higher when compared to the sensitivity of each individual test, why is that?

Answer 13

(Bc an animal is considered positive if it is detected positive for any (one) or both of the tests → you are decreasing the chance of a false negative because being false negative on both tests is less likely)

Question 14

When a fecal float and antigen test are combined, the combined specificity is lower when compared to the specificity of each individual test, why is that?

Answer 14

(Bc an animal is considered negative if it is detected negative for both tests → your probability to get a false positive increases)

Question 15

What is specificity most affected by?

Answer 15

(Reader error)

Question 16

A lot of things can look like parasites, what is often the easiest way to rule out something being a pseudoparasite?

Answer 16

(Weird size, parasites are a predictable size)

Question 17

What are sedimentation tests used for?

Answer 17

(Parasite stages with high density that won’t float readily → fluke eggs)

Question 18

What parasitic characteristic is being taken advantage of when performing a Baermann test?

Answer 18

(Hydrotropism)

Question 19

What is the benefit to using iodine to kill a larva found with a Baermann test as opposed to heat?

Answer 19

(Iodine can help to visualize structures of the larva)

Question 20

What are some of the nematode morphological characteristics that are used to distinguish between different species?

Answer 20

(Esophagus bulb, buccal capsule length, genital primordium, and the tail (kink or not))

Question 21

(T/F) If you see a larva with a kink tail in a fecal sample obtained from a dog, you can assume it is likely a spurious parasite due to coprophagy.

Answer 21

(T, only canine parasite with a kink tail is Angiostrongylus vasorum which has only been found in Newfoundland and Canada, may one day be an issue but not right now)

Question 22

Blood stains are most effective in diagnosing acute/chronic (choose) infections of haemoprotozoan.

Answer 22

(Acute)

Question 23

How can you increase the sensitivity of a skin scrape for diagnosing Sarcoptes?

Answer 23

(Take multiple samples from multiple sites and repeat every few days)

Question 24

If you find a worm in feces or vomit of a small animal, it is most likely what genus?

Answer 24

(Toxocara spp.)

Question 25

(T/F) Cats that are antibodies positive for Toxoplasma are unlikely to be shedding oocysts.

Answer 25

(T, period of oocyst production usually occurs before antibodies are detectable)

Question 26

(T/F) Both IgG and IgM can be detected in chronic Toxoplasma infections.

Answer 26

(T)

Question 27

What is the test of choice for chronic hemaprotozoan infections?

Answer 27

(Serology, PCR may not detect organism if levels are very low and PCR is generally more expensive)

Question 28

What is the test of choice for Echinococcus?

Answer 28

(PCR → only reasonable option)

Question 29

Give an example of when PCR is useful for determining more information about a parasite you are testing.

Answer 29

(Babesia → PCR can ID species which can impact tx; Giardia → PCR can ID assemblage)

Question 30

What are the reasons that you cannot assume that an animal shedding a certain number of coccidia oocysts has coccidiosis?

Answer 30

(Symptoms (diarrhea mainly) may precede high oocyst shedding, clinically normal animals can have high oocyst counts, and some species of Coccidia do not cause dz which you cannot tell microscopically what species you are looking at)

Question 31

What things can influence fecal egg counts?

Answer 31

(Immunity, season, fecal consistency (egg #s will be lower in diarrheic feces), and luck (eggs are not evenly distributed in feces))

Question 32

Does a low limit of detection increase or decrease sensitivity and increase or decrease negative predictive value?

Answer 32

(Increases sensitivity and increases negative predictive value)

Question 33

How can you increase the accuracy versus the precision of a fecal egg count?

Answer 33

(Accuracy → homogenize the fecal sample as much as possible to evenly distribute eggs/oocysts in the sample; precision → increases as you increase the volume of feces examined)

Question 34

What are the three ways to evaluate if there is anthelmintic resistance in a parasite population?

Answer 34

(FECRT, in vitro drug bioassays, and molecular testing)

Question 35

Which of the following treatment protocols have been successful in tx of persistent hookworm infections?
A - Febental/pyrantel/praziquantel + moxidectin
B - Fenbendazole alone
C - Fenbendazole + pyrantel + moxidectin
D - Emodepside alone
E - Moxidectin + imidacloprid

Answer 35

(A, C, D)