Serologic and molecular evidence of avian metapneumovirus subtypes A and B in unvaccinated broiler breeder flocks in Egypt (2024-2025).

Abstract

BACKGROUND: Avian metapneumovirus (aMPV) is an economically significant respiratory pathogen of poultry that affects performance, egg production, and fertility of breeder flocks. Despite its impact, aMPV continues to be ill-defined in Egypt with no integrated surveillance studies conducted in breeder flocks. Therefore, the current study was designed to provide the first integrated molecular and serological evaluation of aMPV circulation in broiler breeders in Egypt. METHODS: Between 2024 and 2025, a total of 6,000 serum samples and 800 tracheal swabs were collected from 60 unvaccinated broiler breeder flocks across twelve Egyptian governorates. Sera were obtained at 16 weeks (rearing phase) and 35 weeks (production phase) of age and screened for aMPV subtypes A and B by ELISA. Tracheal swabs collected during the production phase were pooled into 80 composite samples and tested for the viral RNA by reverse transcription quantitative real time PCR (RT-qPCR). RESULTS: Serological analysis revealed widespread aMPV exposure, with governorate-level seroprevalence ranging between 64.4% (Luxor) and 89% (Giza). Antibody titers increased between 16 and 35 weeks of age, reflecting cumulative viral exposure. Molecular testing detected aMPV RNA in 67 (83.75%) of pooled swab samples. Subtype B was the predominant genotype detected solely in 65 (81.25%) sample pools and in co-detection with subtype A in 2 pools (2.5%). Serological and molecular findings were generally aligned, with flocks positive for aMPV RNA often exhibiting higher antibody titers. CONCLUSION: These findings indicate that aMPV, particularly subtype B, is likely endemic across the Egyptian broiler breeder flocks. The study highlights critical knowledge gaps and emphasizes the need for viral isolation, sequencing, and controlled evaluation of biosecurity and vaccination strategies.