Development of a Non-Invasive Indirect ELISA for Detecting IgY Against a Novel Avian Metapneumovirus Subtype C in Egg Yolks of Laying Ducks

Abstract

Simple Summary This study addresses the urgent need for reliable immunological assays for novel avian metapneumovirus subtype C (aMPV/C), a re-emerging pathogen causing hydrosalpinx fluid syndrome and substantial economic losses in China’s laying duck industry. In the absence of licensed vaccines or antiviral drugs, rapid diagnosis and timely culling of infected ducks remain the primary control measures. We developed a cost-effective indirect ELISA (iELISA) using purified whole inactivated aMPV/C as the coating antigen. The assay demonstrated high specificity (no cross-reactivity with other major duck pathogens), excellent repeatability (CVs < 10%), and high sensitivity (detection limit of 1:200). Clinical evaluation of 151 egg yolk samples from three duck breeds revealed an overall aMPV/C-specific IgY positivity rate of 58.3%, with breed-specific rates ranging from 34.4% to 67.5%. The iELISA showed 97.8% concordance with the immunofluorescence assay (45/46 samples). This work provides a reliable, high-throughput tool for large-scale surveillance of aMPV/C in laying ducks, directly supporting disease monitoring and control efforts in the poultry industry.