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Veterinary Diagnostics > Serology/Immunodiagnostics > Flashcards

Serology/Immunodiagnostics Flashcards

1
Q

What is the difference between a molecular versus a serologic test?

A

Molecular: Direct (DNA or RNA) - PCR
Serologic: Indirect - antigen or antibody

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2
Q

What is Polymerase chain reaction (PCR)?

A

Synthesize and amplify specific target sequence of pathogens
-Nucleic Acid Extraction
-PCR Amplification (denature, anneal and extension)
-Fluorescence probes

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3
Q

What is Serology?

A

-ID antibody or antigen (IgG or IgM)
-Serum commonly used (plasma, feces, urine, saliva, CSF)
-Diagnose infection - blood type, host type or immunology

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4
Q

What is the lag phase?

A

Time post exposure to a pathogen before the body starts its primary response

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5
Q

Is IgM specific? What about IgG?

A

IgM is a general antibody that stalls the pathogen until the specific IgG can come in and clean up

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6
Q

What is different when it comes to the immune systems response between a primary and secondary exposure to a pathogen?

A

Primary: takes a bit longer to recognize and for IgG to kick in

Secondary: much faster response and IgG is prepped and already read to go

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7
Q

What does serostatus mean?

A

-Seropositive = sample contain antibodies and antigen (can report a titer)
-Seronegative = sample does not contain antibodies (not infected)

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8
Q

What is seroconversion?

A

Change from seronegative to seropositive - must be at least a 4 fold increase in titer between acute and convalescent sample- paired sample

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9
Q

How far apart should convalescent samples be taken for serology?

A

2-4 weeks apart

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10
Q

What kinds of serological tests are available?

A

ELISA, IFA, IHC, Agglutination, AGID, Virus neutralization, Complement Fixation

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11
Q

What should you remember about an Elisa test?

A
  • send out or in house (snap, out give microtiter)
    -can detect antibodies or antigens (can no distinguish vaccination versus exposure)
    -detection (Antigen capture, capture antibody, add sample captured and second antibody with color indicator dropped in) - opposite for antibody test
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12
Q

What is an example of an Elisa test?

A

Snap - tick born diseases

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13
Q

What is Direct Immunofluorescence Assay (IFA)?

A

Direct FA
-Detect antigen
-Fluorescent labeled antibody conjugated
-Poor sensitivity - no individual viral particles, accumulated antigen, need to permeabilize cells before staining

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14
Q

What kinds of tests are Direct IFA?

A

Giardia and Cryptosporidium (feces) and Rabies (brain tissue)

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15
Q

What is Indirect IFA?

A

IFA or IFAT
-Test antibody (tell serum antibody titer)
-More sensitive than DFA
-Similar to Elisa - serum diluted and antibody isfluorescent, highest dilution of serum that results in specific fluorescence repoted as antibody tier to infectious agent of interest

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16
Q

What can you detect with IFA?

A

Anaplasma and Ehrlicihia, lyme

17
Q

What makes immunohistochemistry different than IFA?

A

Conjugated with horseradish peroxidase
-Visualize with light microscope

18
Q

How does agglutination work?

A

Detect antibody or antigen
-clumping of bacteria, RBC or antigen/antibody coated latex particles
-bivalence antibodies - cross linkage
-Determine titer like IFA

19
Q

What can you test for with agglutination?

A

Brucellosis, leptospirosis, cryptococcus, blood typing, IMHA

20
Q

What is AGID?

A

Agar Gel Immunodiffusion
-Round wells in agar - middle filled with patient serum, positive control included, reagent diffuse through agar, meet a parciptate forms

21
Q

What do you run AGID to detect?

A

Coggins, Fungal (Aspergillus)

22
Q

Why do we use a viral antibody titer?

A

Determine viral antibody titer
-serial dilution to plasma
-incubate
add cell culture monolayer
-higherst dilution of serum that prevetns cytopathic efect is the antibody titer

23
Q

What may you run a virus neutralization test on?

A

DHPP, BVD

24
Q

How do you determine the antibody titer?

A

Highest dilution of antibody that will detectably interact with the antigen
-lowest concentration of antibody
-presented as inverse concentration
1:1000>1:10 (Think of it as dilution)

25
Q

How do you pick a diagnostic test?

A

Availability, type of pathogen, symptomatic or asymptomatic, time form exposure, treatment
-molecular more sensitive than serologic

26
Q

What are some testing limitations?

A

High sensitivity - if negative test you can rule out disease, if positive may or may not have disease (false positives)

High specificity- negative may or may not have disease, positive you rule in (false negatives)

27
Q

When you select a test remember there are tradeoffs for sensitivity and specififty. Cut off may have false results

A
28
Q

What is a protective titer?

A

Animals with an antibody titer that did not get clinically ill when exposed to disease (core vaccines have one)

29
Q

What are titers measuring and missing?

A

Measuring: Humoral Immunity
Missing: Cell Mediated Immunity

30
Q

Why can you not offer to vaccinate pets based on titers?

A

-Cell mediated immunity is critical too
-Limited to diseases where immunity challenge studies have occurred
-Legal requirements (rabies)
-Not all labs test for them and may not be accredited
-More expensive than vaccination

31
Q

What are the risks of using serologic assays in young animals?

A

-Maternal antibody
-length of time young animals retain maternal antibodies is species specific
-know when to recommend repeat testing
-Helpful for Lenti virus

32
Q

Why do you test for many serovars of lepto?

A

Cross reacts, largest one generally the culprit

33
Q

What is MAT Assay?

A

Microagglutination Test

34
Q

Describe how each pathogen on the 4dx test is identified:
E. Canis/E. ewingii
A. phagocytophilum/A.platys
C. Immitis (hearworm)
B. burgdorferi (Lyme)

A

E. Canis/E. ewingii (ehrliciosis): Antibody
A. phagocytophilum/A.platys (Anaplasmosis ): Antibody
C. Immitis (hearworm): Antigen
B. burgdorferi (Lyme): Antibody

35
Q

How do you know if the dog has chronic ehrliciosis?

A

PCR negative due to circulating levels of bacteria being low, dog has inadequate treatment of acute infection, diagnose with quantitive titer

Veterinary Diagnostics (13 decks)

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