Abstract
Low-pathogenicity avian influenza viruses (LPAIV) introduced by migratory birds circulate in wild birds and can be transmitted to poultry. These viruses can mutate to become highly pathogenic avian influenza viruses causing severe disease and death in poultry. In March 2019, an H7N3 avian influenza virus—A/Spot-billed duck/South Korea/WKU2019-1/2019 (H7N3)—was isolated from spot-billed ducks in South Korea. This study aimed to evaluate the phylogenetic and mutational analysis of this isolate. Molecular analysis revealed that the genes for HA (hemagglutinin) and NA (neuraminidase) of this strain belonged to the Central Asian lineage, whereas genes for other internal proteins such as polymerase basic protein 1 (PB1), PB2, nucleoprotein, polymerase acidic protein, matrix protein, and non-structural protein belonged to that of the Korean lineage. In addition, a monobasic amino acid (PQIEPR/GLF) at the HA cleavage site, and the non-deletion of the stalk region in the NA gene indicated that this isolate was a typical LPAIV. Nucleotide sequence similarity analysis of HA revealed that the highest homology (99.51%) of this isolate is to that of A/common teal/Shanghai/CM1216/2017 (H7N7), and amino acid sequence of NA (99.48%) was closely related to that of A/teal/Egypt/MB-D-487OP/2016 (H7N3). An in vitro propagation of the A/Spot-billed duck/South Korea/WKU2019-1/2019 (H7N3) virus showed highest (7.38 Log10 TCID50/mL) virus titer at 60 h post-infection, and in experimental mouse lungs, the virus was detected at six days’ post-infection. Our study characterizes genetic mutations, as well as pathogenesis in both in vitro and in vivo model of a new Korea H7N3 viruses in 2019, carrying multiple potential mutations to become highly pathogenic and develop an ability to infect humans; thus, emphasizing the need for routine surveillance of avian influenza viruses in wild birds.
Highlights
Avian influenza is an infectious disease caused by the influenza A virus, which is widespread in migratory birds and mammals, including humans [1]
The first report of a H7 subtype avian influenza viruses (AIVs), which was studied in northern Italy in 1878 by Perroncito, who labelled the disease caused by this virus as a “fowl plague” [4], long-term (1976–2012) surveillance reports from North American regions indicate that the H7 subtype high-pathogenic AIVs (HPAIVs) mostly infect migratory birds [5,6]
Samples were isolated from feces of waterfowls in South Korea on 15 March 2019
Summary
Avian influenza is an infectious disease caused by the influenza A virus, which is widespread in migratory birds and mammals, including humans [1]. AIVs have been identified on the basis of surface proteins, hemagglutinin (HA; H1–16 in birds and H17–18 in bats), and neuraminidase (NA; N1–9 in birds and N10–11 in bats) subtypes [2]. They have been categorized into two groups based on their virulence: low-pathogenic AIVs (LPAIVs) and high-pathogenic AIVs (HPAIVs) [3]. The first report of a H7 subtype AIV, which was studied in northern Italy in 1878 by Perroncito, who labelled the disease caused by this virus as a “fowl plague” [4], long-term (1976–2012) surveillance reports from North American regions indicate that the H7 subtype HPAIVs mostly infect migratory birds [5,6]. During that period, H7N1 and H7N3 species of the HPAIV H7 subtype caused outbreaks due to poultry/migratory birds [5], which spread to South/Latin American (Mexico and Canada), Europe (Italy), and South-Central Asian (Pakistan) regions [7,8]
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