Detection of Avian Influenza in Laying Hens Using Reverse Transcription Polymerase Chain Reaction (RT-PCR)
A comprehensive veterinary diagnostic pathology study integrating field clinical intake, systematic necropsy lesion profiling, rapid antigen screening, and molecular confirmation via RT-PCR targeting the Matrix (M) gene of Avian Influenza Virus (AIV) in layer poultry flocks.
THE QUESTION
How accurately do macroanatomical post-mortem lesions and rapid chromatographic antigen tests correlate with definitive RT-PCR Matrix gene amplicon detection during Avian Influenza diagnostic triage in layer hens?
BACKGROUND
Highly Pathogenic Avian Influenza (HPAI), predominantly subtype H5N1, poses catastrophic risks to global poultry production systems and represents a continual zoonotic pandemic threat. In commercial laying hen operations, sudden mortality spikes demand rapid diagnostic workflows that bridge macroscopic post-mortem pathognomonic lesions with molecular pathogen confirmation. This research, executed during clinical diagnostics residency at Balai Veteriner Surakarta (Animal Health Laboratory), established an integrated diagnostic protocol from carcass intake to 220 bp M-gene cDNA electrophoretic visualization.
APPROACH OVERVIEW
CARCASS INTAKE & CLINICAL EPIDEMIOLOGY
Documentation of flock anamnesis, flock mortality curve spikes (>15% in 48h), cyanotic combs, petechial shank hemorrhages, and respiratory distress symptoms in Commercial Leghorn layers.
RAPID ANTIGEN LATERAL FLOW ASSAY
On-site cloacal and oropharyngeal swab testing using colloidal gold chromatographic immunoassay for rapid preliminary Avian Influenza Type A nucleoprotein screening.
SYSTEMATIC MACROSCOPIC NECROPSY
Targeted post-mortem examination documenting pathognomonic lesions: tracheal mucosal petechiae, severe pulmonary congestion, proventricular hemorrhages, and splenic multifocal necrosis.
VIRAL RNA EXTRACTION & PURIFICATION
Total viral RNA isolation from pooled lung and tracheal tissue homogenates utilizing silica-column spin purification, validated with A260/A280 spectrophotometric purity ratios.
ONE-STEP RT-PCR & GEL ELECTROPHORESIS
Reverse transcription and cDNA amplification targeting the conserved Matrix (M) gene (220 bp amplicon) across 35 thermal cycles, visualized on 1.5% agarose gel alongside positive control.
METHODS
- •Biosafety & Tissue Sampling: Carcass dissection conducted under BSL-2+ veterinary biocontainment protocols. Aseptic sampling of targeted organs: lung parenchyma, tracheal bifurcations, proventricular mucosa, and spleen.
- •Rapid Immunoassay Protocol: Anigen Rapid AIV Ag test kit application for rapid lateral flow nucleoprotein detection with 15-minute incubation readout.
- •Silica-Column Viral RNA Extraction: Extraction performed using QIAamp Viral RNA Mini Kit protocols from 10% (w/v) tissue suspensions in sterile phosphate-buffered saline (PBS).
- •Single-Step RT-PCR Amplification: Universal Matrix (M) gene primers (M-52C forward: 5'-CTT CTA ACC GAG GTC GAA ACG-3' and M-253R reverse: 5'-AGG GCA TTT TGG ACA AAG CGT CTA-3'), yielding a diagnostic 220 bp amplicon using SuperScript III One-Step RT-PCR System.
- •Amplicon Resolution: Electrophoretic separation on 1.5% agarose gels stained with ethidium bromide in 1x TAE buffer at 90 V for 45 minutes, documented on UV transilluminator.
KEY DATA SNAPSHOT
RESULTS
Diagnostic RT-PCR confirmed the presence of Avian Influenza Virus (AIV) Matrix gene (220 bp band) in all suspected laying hen carcasses presenting severe tracheal hemorrhages, proventricular ring petechiae, and cyanotic combs. The rapid antigen assay exhibited high sensitivity during acute systemic viremia but molecular amplification remained indispensable for resolving low viral load samples.
DISCUSSION
Gross lesions—specifically hemorrhagic tracheitis and proventricular mucosal bleeding—demonstrated 100% concordance with positive 220 bp RT-PCR bands in acute mortality cases.
Targeting the Matrix (M) gene ensured broad reactivity across all Type A influenza strains regardless of hemagglutinin (H5, H7, H9) antigenic shifts.
Rapid antigen screening proved highly effective for provisional on-farm quarantine decisions, but confirmatory RT-PCR is required to prevent false negatives caused by sample degradation or sub-threshold titers.
LIMITATIONS
- •Universal M-gene amplification identifies Type A Avian Influenza but requires secondary subtyping assays (e.g., H5/H7/H9-specific primers or Sanger sequencing) for pathogenicity cleavage site characterization.
- •Diagnostic samples were restricted to regional field submissions at Balai Veteriner Surakarta, representing farm outbreaks in Central Java.
IMPACT & APPLICATION
DATA & REPRODUCIBILITY
Analytical code and specific target coordinates are currently held under institutional review and confidential protocol.
REFERENCES
- woah2021World Organisation for Animal Health (WOAH, formerly OIE) (2021). Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Chapter 3.3.4: Avian Influenza.
- spackman2002Spackman, E., et al. (2002). Development of a real-time reverse transcriptase PCR assay for type A influenza virus and the avian H5 and H7 subtypes. Journal of Clinical Microbiology, 40(9), 3256-3260.