Spatiotemporal Analysis of the Genetic Diversity of Seal Influenza A(H10N7) Virus, Northwestern Europe

Abstract

Influenza A viruses are major pathogens for humans, domestic animals, and wildlife. In addition to the continuous circulation of influenza A viruses among various host species, cross-species transmission of influenza A viruses occurs occasionally. Wild waterfowl and shorebirds are the main reservoir for most influenza A virus subtypes, and spillover of influenza A viruses from birds to humans or other mammalian species may result in major outbreaks. In the present study, various sequencing methods were used to elucidate the genetic changes that occurred after the introduction and subsequent spread of an avian influenza A(H10N7) virus among harbor seals of northwestern Europe by use of various samples collected during the outbreak. Such detailed knowledge of genetic changes necessary for introduction and adaptation of avian influenza A viruses to mammalian hosts is important for a rapid risk assessment of such viruses soon after they cross the species barrier.

Influenza A (H10N7) Virus Causes Respiratory Tract Disease in Harbor Seals and Ferrets

“…The whole spectrum of virus-associated histological changes, the distribution of viral antigen and the target cell tropism of Seal/H10N7 in harbor seals are unknown. This study provides a more comprehensive description of histological, IHC, virological, bacteriological and parasitological findings in 16 naturally infected seals that were described previously by Bodewes and co-workers [3,5]. Since the zoonotic potential of Seal/ H10N7 is unknown, especially people handling ill seals, performing necropsies, or disposing carcasses may be at risk.…”

“…Sequence analyses indicated that Seal/H10N7 virus was most closely related to LPAIV [1][2][3]5]. Humans infected with H10N7 from live poultry developed conjunctivitis and mild upper respiratory symptoms [37] and marine biologists working with stranded seals or with experimentally infected seals during the outbreak of LPAI H7N7 in 1979 developed purulent conjunctivitis associated with similar H7N7 influenza virus infection [38].…”

“…After retrieval from the coast the carcasses were kept at +4°C or were deep frozen (-80°C) until necropsy (Table 1). A short report about the findings and molecular identification of the virus has been published previously [3,5]. A complete necropsy was performed on each seal.…”

“…16 as described previously [14]. Real-time RT-qPCR targeting the influenza A virus matrix gene was performed on lung and tracheal swab samples collected from the seals as described previously [3,5].…”

“…In 2014 and the beginning of 2015, there was an epidemic of a novel H10N7 influenza A virus (Seal/H10N7) among harbor seals (Phoca vitulina) resulting in increased mortalities along the coasts of Sweden, Denmark, Germany and The Netherlands [1][2][3][4][5]. Most probably this epidemic was caused by a spill-over of a low pathogenic avian influenza virus (LPAI) originating from wild aquatic birds, since this Seal/H10N7 is genetically closely related to various influenza viruses detected in wild birds [3,5].…”