Immunology - Diagnostic Approaches Flashcards
Problems solved with laboratory diagnosis (6)
Exotic disease
Zoonosis
Vet health programs
Eradication
Certificates of freedom
Prevention of virus transfer to recipients
Types of diagnosis (5)
Differential
Presumptive (clin signs alone)
Definitive (based on lab tests)
Pathologic (necropsy/biopsy)
Undetermined
What do clinical pictures tell us?
Clinical signs, duration, onset, year, species, organ system
Top 3 to consider when sampling
Timing
Type
Quality
Others to consider when sampling
Quantity
Transport to lab
Appropriate samples (6)
Blood
Feces
Skin follicles
Discharge from eye/nose
Vesicle fluid
Tissues collected from necropsy
Fresh tissues taken postmortem
Any tissue w gross lesions
Lung
Tissue pool - liver, spleen, kidney
Intestines or feces
Brain
What determines the type of diagnostic test?
Type of sample
Clinical screening/questions
Availability of test
Intended use
Performance characteristics of tests
Sensitivity
Specificity
Positive or negative predictive values
Reliability
Ways to detect organisms
Visual
Detecting protein
Detecting DNA or RNA
Tests for visualization
Light or electron microscopy
Potential pathogens found using visual tests
Virus, parasite, bacteria
Tests for detecting protein
ELISA, IFA, IHC
Tests for detecting DNA or RNA
PCR, NGS
Advantages of electron microscope
Visualization of virus
Rapid
Detects viruses that can’t be isolated
Live virus not required
Disadvantages of electron microscopy
Expensive
High number of virus required
Specialized training
Needle in a haystack
Virus isolation advantages
Sensitive
Specific characterization of virus
ID of unknown viruses
Disadvantages of virus isolation
Not widely available
Slow results
Specialized training
Costly
Antibody-antigen test (protein)
ELISA
Immunoflorescence (IFA)
Immunohistochemistry (IHC)
Function of elisa
Antigen capture
Conjugated primary & secondary antibody
Substrate gives color reaction
What does ELISA stand for?
Enzyme linked immunosorbent assay
Immunofluorescent antibody test
Cell culture or tissues
Antibody has fluorescent tag
Requires high viral titer
Immunohistochemistry
Uses paraffin-embedded tissues mounted on glass slides
Sections are incubated, tagged in substrate
Substrate gives color reaction
Allows detection of antigen in lesion or targeted cells
Advantages of antibody based tests
Rapid
Sensitive
Easy to use
Can detect different serotypes
Disadvantages of antibody based tests
Not available of all organisms
Can be difficult to interpret
Genomic detection
PCR
In-situ hybridization
Next generation sequencing
PCR
In-situ hybridization
Visualize virus in tissue or site
Determine which virus is responsible for pathologic lesions
Next generation sequencing
Whole genome sequencing
Detection of unknown viruses
Advantages of DNA based tests
Rapid
Sensitive
Specific
Relatively cheap
Potentially applicable to all viruses
Disadvantages of dna based tests
Sensitive - detection X=X causation
Risk of DNA contamination
Must know what to look for
