On‐Site Rapid and Specific Detection of Novel Emerging Goose Astrovirus Using a Nanobody‐Based Colloidal Gold Immunochromatographic Strip

In recent years, outbreaks of gouty goose disease in goslings caused by a novel goose astrovirus (nGAstV) have occurred across major poultry-producing regions in Eastern China, with a mortality rate of approximately 50%. To date, there is a lack of rapid detection kits for early-stage disease control to reduce economic losses. In this study, two nanobodies (Nb-58 and Nb-60) that reacted with the nGAstV P2 protein were screened and identified using phage display technology and immunological experiments to develop colloidal gold immunochromatographic strips (CGISs) for nGAstV detection. CGIS did not cross-react with goose parvovirus (GPV), goose circovirus (GCV), H9N2 avian influenza virus (H9N2 AIV), Newcastle disease virus (NDV), avian leukemia virus (ALV), or infectious bursal disease virus (IBDV), indicating its strong specificity. The detection threshold of the CGIS was more than 640-fold diluted nGAstV (~10^1.57 TCID₅₀), which was comparable to a Ct value of 26.82, thereby showing high sensitivity. CGIS, with high stability, could be stored for at least 6 months at 25 and 4°C. The repeatability test showed that nGAstV could be readily detected in different CGIS batches. The coincidence rates of CGIS and conventional reverse transcription-polymerase chain reaction (RT-PCR) in 51 clinical tissue samples and 60 cloacal swab samples were 100% and 95.24%, respectively. In conclusion, the present study identified two specific Nbs and developed a reliable CGIS for the rapid detection of nGAstV in the field setting.