A novel indirect ELISA for serological surveillance of fowl adenovirus in chickens: utilizing a regionally relevant field strain

Fowl adenoviruses are significant avian pathogens that cause considerable economic losses globally, associated with diseases such as inclusion of body hepatitis, hydropericardium syndrome, and gizzard erosion. There is a critical need for rapid, sensitive, and high-throughput diagnostic tools for seroepidemiologic surveillance and evaluating vaccine efficacy, as the traditional diagnostic methods are limited due to the high viral diversity, which often hinders the effectiveness of group-specific targeted commercial ELISAs, as the antigens may not align with regionally prevalent serotypes. This study details the development and validation of an indirect ELISA designed for the detection of anti-Fowl adenoviruses antibodies in chickens, utilizing an antigen derived from a field strain of Fowl adenoviruses from Türkiye and propagated in cell culture. The assay was validated using 109 serum samples, benchmarked against the commercial BioCheck Fowl adenoviruses-1 ELISA CK132 kit. The developed ELISA demonstrated an optimal sample dilution of 1:400 and a cutoff value of 0.125. It achieved a sensitivity of 90.20 % and a specificity of 100 %. A Cohen’s kappa index of 0.675 indicated good agreement with the reference method. Furthermore, the assay exhibited good precision, with intra-assay coefficients of variation (CV %) ranging from 6.24 % to 11.03 % and an inter-assay CV % of 16.20 %, both within acceptable limits. This novel ELISA, employing a regionally relevant field strain, offers a cost-effective and specific tool for Fowl adenoviruses serological surveillance and vaccine monitoring, particularly beneficial in regions where circulating strains vary from vaccine strains.