Molecular surveillance of Newcastle disease virus in apparently healthy chicken and ducks reared at domestic-wild bird interface regions of Kerala

Newcastle disease (ND) is a highly pathogenic infectious disease of poultry, causing significant economic losses globally. Wild birds act as natural reservoir of Newcastle disease virus (NDV) and spread the virus to domestic poultry. Frequent exposure of backyard poultry to wild birds andor their excretions increases the risk of acquiring infection from wild birds. In the present study, tracheal andor cloacal swabs were collected from a total of 242 apparently healthy chicken and ducks from the backyards. The samples were tested for the presence of NDV using matrix (M) gene based quantitative real time polymerase chain reaction (RT-qPCR), where all the samples were found negative. Virus isolation was attempted using specific pathogen free- embryonated chicken eggs (SPF-ECEs). Out of 242 samples, 22 samples (9.09) showed haemagglutination (HA) across different passages. Genome of NDV could not be amplified in any of these HA-positive samples by using M gene-based RT-qPCR, and L- and F- genes based conventional reverse transcription polymerase chain reaction (RT-PCR). This indicates the presence of haemagglutinating agent other than NDV in the samples. Further studies are needed to identify the haemagglutinating agent detected in this study. All the samples in the present study were negative for NDV which might be due to absence of active infection during sample collection and vaccination status of the birds.