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Edwardsiella tarda infection in fish results in economic losses in aquaculture industries worldwide. Besides, this pathogen is also a zoonotic agent causing gastrointestinal disease in humans. Detection of virulence factors expressed by E. tarda is a key for molecular diagnosis. This study aimed to design SYBR® Green-based quantitative PCR (qPCR) primer for E. tarda virulent protein C (EvpC) gene. A sequence of EvpC with accession number AY424360.4:6500-6991 obtained from GenBank NCBI was selected as the basis for qPCR primer design. qPCR primers were designed using Primer3 online software. Further analysis related to the secondary structure of each primer was carried out using Beacon Designer Free Edition. Five pairs of qPCR primers were successfully designed with Primer3. Based on the results of Primer3 and Beacon Designer analysis, F primer pair 1 (5'-GAATCCACCGACGATAAGCACAAA-3') and R primer pair 1 (5'-GACACGCAGCACCGACATCA-3') were the most favorable primer set since this primer met the criteria in terms of length, melting temperature, GC content, and self complementarity. In addition, this primer set had the highest (closest to zero) -ΔG value of cross dimer, self dimer, and hairpin. It can be concluded that SYBR® Green-based qPCR primer set for EvpC has been successfully designed. However, laboratory optimization experiments are essential for this designed primer set. [ABSTRACT FROM AUTHOR]

The surveillance of migratory wild birds (MWBs) for avian influenza virus (AIV) allows detecting the emergence of highly pathogenic AIV that can infect domestic poultry and mammals, new subtypes, and antigenic/genetic variants. The current AIV surveillance system for MWBs in the United States is based on virus isolation (VI) followed by sequencing isolates. This system primarily focuses on the early detection of H5 and H7 AIVs. However, it is suboptimal in assessing diverse AIV subtypes at any given time because of the low VI success rate. To improve such a shortfall, a SYBR® Green-based real-time reverse transcription-polymerase chain reaction (rtRT-PCR) panel was developed for direct HA subtyping of AIVs in oropharyngeal-cloacal (OPC) swabs from MWBs. Under optimal conditions, the PCR panel detected AIVs of all 16 different HA subtypes with an average limit of detection of 102.6 copies/reaction (2 μl of extract). In testing 90 OPC swabs from 13 MWB species, the PCR provided a significantly faster turnaround of results and demonstrated the presence of more subtypes and concurrent infection among MWBs compared to what the current surveillance testing algorithm showed. In conclusion, newly developed SYBR® Green rtRT-PCR panel can be a useful tool for monitoring MWBs for AIVs. • PCR-based subtyping detected more AIV subtypes than virus isolation (VI)-based method. • PCR-based subtyping is able to detect concurrent infections in samples undetected by VI • PCR-based subtyping is rapid and less labor intensive than the current VI and sequencing-based testing algorithm. • PCR-based subtyping can be applied to AIV surveillance for migratory wild birds [ABSTRACT FROM AUTHOR]