Byrne, A. M. | bioRxiv Science

bioRxiv2021

Systemic infection with highly pathogenic H5N8 of avian origin produces encephalitis and mortality in wild mammals at a UK rehabilitation centre

Europe has experienced extensive outbreaks of highly pathogenic avian influenza (HPAI) during the autumn/winter 2020/21 season. These avian influenza A viruses are highly transmissible and have infected over 1000 commercial and backyard poultry premises in Europe in this period causing high mortality. The impact on wild bird populations has also been significant, with over 400 detections in at least 47 different species reported across Europe as being positive with the H5N8 virus. Although different H5Nx combinations within the H5 clade 2.3.4.4b have been detected, the H5N8 subtype has predominated both in wild birds and domestic poultry outbreaks. In the UK there have been 22 outbreaks of H5N8 in domestic poultry and captive birds and more than 300 wild bird detections involving H5N8 over the autumn/winter 2020/21 period to April 2021. Here we detail the series of events surrounding the detection of an H5N8 influenza A virus of avian origin in five swans, a fox and three seals in a wildlife rehabilitation centre.

microbiology↗

bioRxiv2021

Co-infection of chickens with H9N2 and H7N9 avian influenza viruses leads to emergence of reassortant H9N9 virus with increased fitness for poultry and enhanced zoonotic potential

An H7N9 low pathogenicity avian influenza virus (LPAIV) emerged through genetic reassortment between H9N2 and other LPAIVs circulating in birds in China. This virus causes inapparent clinical disease in chickens, but zoonotic transmission results in severe and fatal disease in humans. We evaluated the consequences of reassortment between the H7N9 and the contemporary H9N2 viruses of G1 lineage that are enzootic in poultry across the Indian sub-continent and the Middle East. Co-infection of chickens with these viruses resulted in emergence of novel reassortant H9N9 viruses carrying genes derived from both H9N2 and H7N9 viruses. These reassortant H9N9 viruses showed significantly increased replication fitness, enhanced pathogenicity in chicken embryos and the potential to transmit via contact among ferrets. Our study highlights that the co-circulation of H7N9 and H9N2 viruses could represent a threat for the generation of novel reassortant viruses with greater virulence in poultry and an increased zoonotic potential. O_FIG O_LINKSMALLFIG WIDTH=197 HEIGHT=200 SRC="FIGDIR/small/438444v1_ufig1.gif" ALT="Figure 1"> View larger version (96K): org.highwire.dtl.DTLVardef@1f425cborg.highwire.dtl.DTLVardef@1dd3ba2org.highwire.dtl.DTLVardef@1762348org.highwire.dtl.DTLVardef@1064cb7_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG In BriefH9N2 viruses have a high propensity to reassort with other avian influenza viruses. We found that co-infection of chickens with H9N2 and H7N9 led to the emergence of reassortant viruses including the H9N9 subtype. Some reassortant H9N9 viruses exhibited increased replication fitness, increased pathogenicity in the chicken embryo, greater avidity for human and avian cell receptors, lower pH fusion and contact-transmission to ferrets. This study demonstrated the ability of viruses that already exist in nature to exchange genetic material, highlighting the potential emergence of viruses from these subtypes with increased zoonotic potential. There are nine H9 influenza A subtypes carrying different neuraminidase (NA) genes, including H9N9 viruses, while they are not common they do exist in nature as wildtypes (CDC). HighlightsO_LICo-infection of chickens with H7N9 and H9N2 led to emergence of reassortant H9N9 viruses C_LIO_LIReassortant H9N9 viruses had an increased replication rate in avian and human cells C_LIO_LIReassortant H9N9 viruses had a lower pH fusion and significantly higher receptor binding to 2,3 sialoglycans C_LIO_LIReassortant H9N9 replicated in ferrets at similar levels compared to H7N9 and transmitted via direct contact C_LIO_LIFerrets exposed to reassortant H9N9 by aerosol contact were also found to be seropositive C_LIO_LIExperimental simulation of events that may occur naturally with circulating viruses has demonstrated the risk of emergence of viruses with increased zoonotic potential. C_LI

microbiology↗