Outbreaks of avian influenza H6N2 viruses in chickens arose by a reassortment of H6N8 and H9N2 ostrich viruses

Abstract

The first recorded outbreak of avian influenza (AI) in South African chickens (low pathogenicity H6N2) occurred at Camperdown, KwaZulu/Natal Province (KZN) in June 2002. To determine the source of the outbreak, we defined the phylogenetic relationships between various H6N2 isolates, and the previously unpublished gene sequences of an H6N8 virus isolated in 1998 from ostriches in the Leeu Gamka region (A/Ostrich/South Africa/KK98/98). We demonstrated that two distinct genetic H6N2 lineages (sub-lineages I and II) circulated in the Camperdown area, which later spread to other regions. Sub-lineages I and II shared a recent common H6N2 ancestor, which arose from a reassortment event between two South African ostrich isolates A/Ostrich/South Africa/9508103/95 and (H9N2) /Ostrich/South Africa/KK98/98 (H6N8). Furthermore, the H6N2 sub-lineage I viruses had several molecular genetic markers including a 22-amino acid stalk deletion in the neuraminidase (NA) protein gene, a predicted increased Nglycosylation, and a D144 mutation of the HA protein gene, all of which are associated with the adaptation of AI viruses to chickens. The H6N2 NS1 and PB1 genes shared recent common ancestors with those of contemporary Asian HPAI H5N1 viruses. Our results suggest that ostriches are potential mixing vessels for avian influenza viruses (AIV) outbreak strains and support other reports that H6 viruses are capable of forming stable lineages in chickens.

Phylogenetic Analysis of H6 Influenza Viruses Isolated from Rosy-Billed Pochards (Netta peposaca) in Argentina Reveals the Presence of Different HA Gene Clusters

“…Importantly, AIVs of the H6 subtype are some of the most abundant AIVs detected in wild bird populations worldwide (13,15,22). H6 AIVs have crossed the species barrier and caused outbreaks in domestic poultry in Eurasia, North America, and Africa (1,2,11,12,24). In Southeast Asia, H6 AIVs have established stable lineages, which are hard to eradicate and likely contribute to the genetic diversity of influenza viruses in local domestic poultry (6,10).…”

Replication and transmission of mammalian-adapted H9 subtype influenza virus in pigs and quail

“…H9N2 viruses have also been identified as the donor, as well as recipient, of the internal genes to the highly pathogenic IAV H5N1 and the newly emerged H7N9 and H10N8 viruses that have infected humans in Asia Liu et al, 2013;Wu et al, 2013). Homosubtypic and heterosubtypic H9N2 reassortants have been isolated from both birds and swine in nature (Abolnik et al, 2007;Cong et al, 2007;Wang et al, 2012;Wu et al, 2015;Yu et al, 2008Yu et al, , 2011. Under experimental conditions, H9N2 viruses also demonstrate compatibility for reassortment, especially with regard to human seasonal H3N2 and H1N1pdm viruses, with many reassortants showing increased infectivity, transmissibility and pathogenicity in mice and ferrets (Kimble et al, 2011(Kimble et al, , 2014Qiao et al, 2012;Sorrell et al, 2009;Sun et al, 2011;Wan et al, 2008) We previously reported that a reassortant virus having surface genes from an avian H9N2 virus (A/guinea fowl/ Hong Kong/WF10/1999) and internal genes from a human H3N2 virus (A/Memphis/14/1998) -herein referred to as 2WF10 : 6M98 -were transmitted only to direct-contact (DC) ferrets (Wan et al, 2008).…”

H6 Influenza Viruses Pose a Potential Threat to Human Health

“…An H6 influenza virus was first isolated from a turkey in Massachusetts in 1965, and since then H6 viruses have been isolated with increasing frequency from wild and domestic aquatic and terrestrial avian species (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). A surveillance study from Europe and the Americas found that H6 was the most abundantly detected influenza virus subtype and that it had a broader host range than other subtypes (25).…”

“…A surveillance study from Europe and the Americas found that H6 was the most abundantly detected influenza virus subtype and that it had a broader host range than other subtypes (25). Although the H6 viruses isolated to date have largely caused asymptomatic infections in waterfowl, infection of chickens with H6 viruses has been associated with decreased egg production, upper respiratory tract infection, morbidity, and increased mortality (10)(11)(12)(13). Several studies have shown that certain H6 viruses can infect and cause illness in mice and ferrets (26,27).…”