Evaluation of transmission potential and pathobiological characteristics of mallard originated Avian orthoavulavirus 1 (sub-genotype VII.2) in commercial broilers

• Published in: Microbial pathogenesis 2019-12, Vol.137, p.103785-103785, Article 103785
• Main Authors: Habib, Momena, Yaqub, Tahir, Aziz-ul-Rahman, Sohail, Tayyebah, Shahbaz, Muhammad, Shehzad, Wasim, Munir, Muhammad, Shabbir, Muhammad Zubair
• Format: Article
• Language: English
• Subjects: Animals; Avian orthoavulavirus 1; Chickens - virology; Ducks - virology; Genome, Viral; Genotype; Greenish diarrhea; Macroscopic changes; Newcastle Disease - pathology; Newcastle Disease - transmission; Newcastle Disease - virology; Newcastle disease virus - classification; Newcastle disease virus - genetics; Newcastle disease virus - isolation & purification; Newcastle disease virus - physiology; Phylogenetic analysis; Phylogeny; Poultry Diseases - pathology; Poultry Diseases - transmission; Poultry Diseases - virology; Sub-genotype VII.2; Water fowls
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/j.micpath.2019.103785

Newcastle disease (ND), caused by Avian orthoavulavirus 1 (AOAV-1), affects multiple avian species around the globe. Frequent disease outbreaks are not uncommon even in vaccinates despite routine vaccination and, in this regards, viruses of diverse genotypes originating from natural reservoirs (migratory waterfowls) play an important role in a disease endemic setting. Though genomic characterization of waterfowl originated viruses has been well-elucidated previously, there is a paucity of data on clinico-pathological assessment of mallard-originated sub-genotype VII.2 in commercial chickens. Hence, the current study was designed to evaluate its transmission potential, tissue tropism and micro- and macroscopic lesions in commercial broilers. Based on complete genome and complete F gene, phylogenetic analysis clustered the study isolate within genotype VII and sub-genotype VII.2 in close association with those reported previously from multiple avian species worldwide. The study strain was found to be velogenic on the basis of typical residue pattern in the F-protein cleavage site (112R-RQ-K-R↓F117), sever disease induction in chicken, tissue tropism and subsequent clinico-pathological characteristics. Giving a clear evidence of horizontal transmission, a 100% mortality was observed by 4th and 6th day post infection (dpi) in chickens challenged with the virus and those kept with the challenged birds (contact birds), respectively. The observed clinical signs, particularly the greenish diarrhea, and macroscopic lesions such as pinpoint hemorrhages in proventriculus and caecal tonsils were typical of the infection caused by an AOAV-1 in chickens. The virus exhibited a broad tissue tropism where genomic RNA corresponding to study virus was detected in all of the tissues collected from recently mortile and necropsied birds. The study concludes that mallard-originated Avian orthoavulavirus 1 is highly velogenic to commercial chicken and therefore ascertain continuous disease monitoring and surveillance of migratory/aquatic fowls to better elucidate infection epidemiology and subsequent potential impacts on commercial poultry. •Phylogenetic analysis of mallard originated AOAV-1 strain revealed clustering within sub-genotype VII.2.•Assessment of infection potential of strain indicated highly virulent for commercial poultry.•Viral RNA was detected in all tissues collected form necropsied bird.