Production Diseases

What info do you need to justify a testing plan for 1 animal?

• pre-test probability

• test characteristics (sensitivity, specificity)

• your testing goal

• the owner’s goal + budget

What info do you need to justify a testing plan for a herd?

• pre-test probability

• test characteristics (sensitivity, specificity)

• which animals from the herd should be tested

Disease progression (infectious)

• pre-infection (exposure)

• infection

• migration within the body (may not be detectable)

• multiplication (in definitive hosts)

• symptomatic (may persist after pathogen clearance)

• long-term carrier

• recovery (pathogen cleared, no symptoms, may still be antibody +)

timeline determines where/how to detect the disease

Disease progression (non-infectious)

• pre-disease

• subclinical

• clinical (onset of signs)

• chronic

• recovery/management

Genetic testing

• PCR, Loop-Mediated Isothermal Amplification - version of PCR, sequencing (metagenomics vs viromics), pulsed field gel electrophoresis

• all tests search for pathogenic genome - does not necessarily mean that the pathogen is alive or causing symptoms

Antigen/antibody testing

• ELISA, fluorescent antibody, hemagglutination, Western blot, agar gel immunodiffusion assay, serum neutralization, MALDI-TOF

• confirms that animal has been exposed to a pathogen (by infection or vaccination), does not necessarily mean the animal is currently infected

Organism/cause testing

• culture, microscopy, imaging, endocrine, toxins

Secondary testing

• CBC/PCV, chemistry, FAMACHA (symptom/function test), treatment

• show how an animal has been affected by a disease

How to determine the best test to use?

• match stage of disease to sampling method (ex: blood, feces, biopsy, etc.) & test

Sample handling considerations

• temperature of storage (especially for live samples)

• sunlight exposure (especially for live/viral samples)

• chemical exposure (ex: disinfectants)

• air