Virology

Question 1

define viruses

Answer 1

small, obligate intracellular, infectious agents that need to infect living cells to replicate, composed of RNA or DNA

Question 2

when is the best time to take a sample from an appropriate site to detect a virus?

Answer 2

as soon as the animal exhibits clinical signs because the virus load is at its maximum at the onset of clinical signs and then rapidly decreases after

Question 3

list the different immunoassays for antigen detection

Answer 3

ELISAs
Lateral Flow Assay
Fluorescent antibody testing
immunohistochemistry

Question 4

ELISA and Lateral assays work by having a capture __ for the __ of interest

Answer 4

ELISA and Lateral assays work by having a capture __ for the __ of interest

Question 5

describe how a sandwich ELISA works

Answer 5

1. capture antibody for a pathogen is placed in well plate
2. sample is added
3. antibody is added and binds to antigen-antibody complex
4. secondary antibody with fluorescent tag binds to the first antibody and changes color, indicating the presence of the antigen

Question 6

what are some pros and cons of ELISA and lateral flow assays?

Answer 6

They’re fast and cheap but may produce false negative if there is a low viral load so consider retesting if you have strong clinical suspicions

Question 7

a cat comes in with signs of FIV so you snap test it and the result is negative. what should you do?

Answer 7

retest the cat in 60 days ( 30 for FeLV) if there is a risk of recent exposure since it takes 30d to develop antigenemia

Question 8

parvovirus has its highest viral shedding between __ to __ days post infection. What should do with a negative test with high suspicion?

Answer 8

14-17 days post infection

retest in 1-2 days and test littermates

Question 9

Direct immunofluorescent Assay (IFA)

Answer 9

This is when there is an antibody with a fluorescent tag that that is specific for the antigen of interest. This technique, sensitive and specific but requires a very high viral load

Question 10

Immunohistochemistry (IHC)

Answer 10

This technique uses paraffin embedded tissues mounted on glass slides where the sections are incubated with specific antibodies tagged with an enzyme. A substrate is then added and if the antigen of interest is present then there will be a color change in the cells. Ex. Parvo virus causes crypt necrosis and would have viral antigen in the crypt epithelium.

Question 11

PCR requirements

Answer 11

For PCR you need to know which virus you are testing for because DNA primers and probes are specific to the target DNA. There also needs to be enough good quality target DNA and RNA to amplify it.

Question 12

T/F: a virus must be alive to detect antigen

Answer 12

F, but timing of the sample collection is still important

Question 13

what type of viruses is PCR useful for ?

Answer 13

viruses that can’t be easily cultured/isolated

Question 14

T/F: PCR can differentiate between a live and inactive virus

Answer 14

F, you need to evaluate the clinical picture and other test results

Question 15

sequencing looks at the the whole genome for __

Answer 15

detection of unknown viruses

Question 16

Virus isolations

Answer 16

the goal is to grow/culture this virus from a diagnostic sample and then identify it but this process is quite time consuming

Question 17

cytopathic effects of virus isolation

Answer 17

evidence of viral replication in cell culture

Question 18

virus isolation has a high __ but is __

Answer 18

virus isolation has a high efficacy but is inefficient

Question 19

presence of IgM on serology indicates __ while a 4x increase in __ indicates acute infection

Answer 19

presence of IgM on serology indicates acute infection while a 4x increase in IgG indicates acute infection

Question 20

serology tests are __ specific and does not require __

Answer 20

species, infectious virus or antigen

Question 21

Indirect IFA

Answer 21

virus infected cells on a glass mciroscope used to capture antibodies in sample specific to a virus of interest -> fluorescent tag