Abstract
Background: Live bird markets (LBMs) serve as a natural reservoir for class I Newcastle disease virus (NDV) and play an important role in viral evolution and spread. LBMs and commercial farms are the main sources of daily poultry products. However, limited studies are available for the class I NDV circulating at LBMs and commercial farms. In this study, significant progress has been made in sample detection and genetic analysis at LBMs and commercial farms in Eastern China.Methods: A long-term epidemiological investigation at LBMs and commercial farms in Eastern China was conducted. We sequentially conducted the collection of samples, virus isolation, RNA extraction, RT-PCR, and phylogenetic analysis. We also analyzed class I NDVs deposited in NCBI during 2002–2018 from China in terms of the host, genotype, time, and functional domains.Results: Here we report that class I NDVs continue to circulate in LBMs. Class I NDVs were detected at a high prevalence in chickens (23/26) but were seldom detected in waterfowl (3/26) at LBMs. In contrast, class I NDVs were rarely detected in commercial chickens but were present in commercial waterfowl at a certain frequency before they were brought to the LBMs. This observation suggests that the mixture of poultry and the conventional housing at LBMs cause the spread of class I NDVs. Sequence analysis of Class I NDV genomes deposited in NCBI during 2002–2018 from China revealed a high prevalence of class I NDVs in terrestrial birds (82.7%), which was much higher than in water birds (17.3%). In addition, we found that the class I NDVs predominantly belonged to the sub-genotype 3c and rarely evolved into a new sub-genotype such as the 3d. Furthermore, the epidemic sub-genotype 3c seems to be under ongoing evolution.Conclusions: Our study provides evidence that the traditional feeding mode at LBMs causes the spread of class I NDVs and poses a great risk of NDV epidemics in the poultry industry in Eastern China. The sub-genotype 3c is circulating at LBMs and currently the terrestrial bird is the predominant host of class I NDVs.
Molecular and Serological Detection of Newcastle Disease Virus in Native Chickens from Selected Live Bird Markets in Batangas, Philippines
