Overview

ELISA (Enzyme-Linked Immunosorbent Assay) is a common laboratory technique used to detect and measure antibodies or antigens in a sample. In the poultry industry, ELISA can be used for a variety of applications, such as:Diagnosing infectious diseases: ELISA can be used to detect antibodies to common poultry diseases like Newcastle disease, Avian Influenza, and Infectious Bronchitis Virus.Monitoring vaccination programs: ELISA can be used to measure the levels of antibodies in poultry after vaccination to ensure that the vaccination program is effective.Detecting foodborne pathogens: ELISA can be used to detect bacteria like Salmonella and E. coli in poultry products.This course will provide students with a comprehensive understanding of the ELISA technique and its applications in the poultry industry. Students will learn about the principles of ELISA, different types of ELISA assays, and how to interpret ELISA results. The course will cover the use of ELISA for diagnosing infectious diseases in poultry, monitoring vaccination programs, and detecting foodborne pathogens.Prerequisites:Basic knowledge of poultry diseases and immunologyLearning Outcomes:Upon successful completion of this course, students will be able to:Explain the principles of ELISADescribe different types of ELISA assaysInterpret ELISA resultsApply ELISA techniques for diagnosing poultry diseasesEvaluate the use of ELISA in monitoring vaccination programsDiscuss the application of ELISA for detecting foodborne pathogens in poultry productsimmunologyAntigen (Ag): any foreign substance that elicits animmune response (i.e., the production of specificantibody molecules) when introduced into the tissuesof a susceptible animal and is capable of combiningwith the specific antibodies formed.AAntigens are generally of highmolecular weight and commonlyare proteins orpolysaccharides.• Antigens that give strong immuneresponses are stronglyimmunogenic.• The small site on an antigen towhich an antibody binds is calledan epitope.• Most common antigens areviruses and bacteriaAntibody (Ab): an immunoglobulincapable of specific combinationwith the antigen that caused itsproduction in a susceptible animal.• Antibodies are produced inresponse to the invasion of foreignmolecules(antigens) in the body.• Antibodies exist as one or more copies of a Y-shaped unit.The Difference BetweenBlocking and Indirect ELISA TestsIndirect ELISAA broad range of Ab variants willbind to the plate.• The conjugate is an anti-speciesIgG conjugate which will bind toall alreadybound Ab.• Highly sensitive, but a smallpossibility to have nonspecific Abbinding to theplate, resulting in false positiveresults.indirect ELISA Blocking ELISA Can only be used for specificspecies depending upon whichconjugate is usedin the test.• The amount of bound conjugate isproportional to the Ab level in thesample.• Quantitative results can becalculated (S/P)Blocking (Competitive)ELISA A broad range of Ab variants willbind to the plate.• The conjugate is a monoclonal Ab(specific Ab) which will bind toonly a specificepitope on the coated plate if thisspace is not already occupied by anAb fromthe sample.• Highly specific, it doesn't matterif any nonspecific binding hashappened toother parts of the plate as this willnot be detected by the conjugateIndirectly proportional to the Ablevel in the sample (the moreantibodies presentin the sample, the less colordevelopment in the test wells)• Not species-dependent as theconjugate binds directly to the Agon the plate Immunoassays play a vital role inthe control and prevention ofpoultry diseases. They allow forearly detection of outbreaks, whichhelps to prevent the spread ofdisease and minimize economiclosses. They are also used tomonitor the effectiveness ofvaccination programs and toensure the safety of poultryproducts.Poultry diagnostics is the processof identifying the cause of illness ordisease in poultry. This is crucial forensuring the health and well-beingof birds, preventing the spread ofdisease, and maintaining the safetyof poultry products for humanconsumption.Diagnostic Process:Poultry diagnostics typically involves amulti-step process:1.Clinical Observation: This involvesobserving the flock for signs of illness,such as lethargy, decreased appetite,respiratory problems, diarrhea, orunusual behavior.Diagnostic Process:1.Sample Collection: Samples, such as blood, tissues, or feces, may becollected from sick birds or the environment for further testing.2.Laboratory Analysis: Various laboratory tests are employed to identifythe causative agent of the disease. These tests may include:1. Immunoassays: As mentioned earlier, these tests detect thepresence of antibodies or antigens associated with specificpathogens.2. Bacteriology: This involves culturing bacteria from samples toidentify the specific bacterial species causing the disease.3. Virology: This involves isolating and identifying viruses present inthe samples.4. Parasitology: This involves identifying parasites that may be presentin the bird or its environment.5. Necropsy: In some cases, a post-mortem examination of deceasedbirds may be performed to identify signs of disease and aid indiagnosis.Importance of Poultry Diagnostics:Accurate and timely poultry diagnostics is crucial for several reasons:•Early diagnosis and treatment: Identifying the cause of illnesspromptly allows for the implementation of appropriate treatmentmeasures, improving the chances of a successful recovery andminimizing bird mortality.•Disease control and prevention: Early detection of outbreaks helpsprevent the spread of disease within the flock and to other flocks. Thisis particularly important for highly contagious diseases like avianinfluenza.•Food safety: Diagnosing and controlling diseases in poultry flocksensures the safety of poultry products for human consumption byminimizing the risk of foodborne illnesses.•Monitoring flock health: Regular diagnostic testing helps monitor theoverall health of the flock and identify potential problems early on.Different Diagnostic Techniques:Several diagnostic techniques are employed inpoultry diagnostics, each with its own advantagesand limitations:1. Immunoassays: As discussed earlier, these arehighly specific and sensitive tests that canrapidly detect pathogens or antibodies inpoultry.2. Polymerase chain reaction (PCR): This is ahighly sensitive technique used to detect thepresence of specific DNA sequences ofpathogens.3. Histopathology: This involves examining tissuesamples under a microscope to identifymicroscopic changes associated with disease.4. Serology: This involves measuring the levels ofantibodies in the blood to assess exposure tospecific pathogensELISA Test KitsRapidly detects and quantifies antigens or antibodies against bacteria, virusesand other pathogens• Robust and user-friendly• One of the most sensitive and reproducible test methods availableELISA Test KitsTest a large number of samples at the same time• Automate the procedure using robotics or other types of automated equipment• Use software to calculate and report results Test Kit Components• Coated Plates• Positive and Negative Control• Sample Diluent• Conjugate• Substrate (TMB)• Stop• Wash SolutionELISA Test Usage• Highly sensitive screening tool• Results need to be interpreted on a flock level with knowledge of flock health.• ELISAs give a very low number of false-positive results.• Unexpected positives should be confirmed by another test system (HI, Culture,IPMA, Western Blot, Complement Fixation, PCR, VI).• The test will not tell you if the detected Ab are maternal Ab, from vaccination orfrom infection (i.e., Differentiating Infected from Vaccinated Animals [DIVA] test).Good Laboratory Practices• Receiving kits- Inspect for damage- Record date received and when used- Store properly per kit insert instructions- Note kit expiration date• General reagent handling- Follow kit insert (check often for revisions)- Warm up reagents (2-3 hours)- Mix reagents- Avoid contamination (no "back pour", use designated reagent reservoirs)Reagent Handling

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