Biological Properties and Genetic Characterization of Novel Low Pathogenic H7N3 Avian Influenza Viruses Isolated from Mallard Ducks in the Caspian Region, Dagestan, Russia.

Marina Gulyaeva,Maria Alessandra De Marco,Eric Bortz,Kirill Sharshov,Marzia Facchini,Mauro Delogu,Ganna Kovalenko,Alimurad Gadzhiev,Kseniya Yurchenko,Ivan Sobolev,Tatiana Murashkina,Alexander Shestopalov

doi:10.3390/microorganisms9040864

Abstract

Avian influenza viruses (AIVs) are maintained in wild bird reservoirs, particularly in mallard ducks and other waterfowl. Novel evolutionary lineages of AIV that arise through genetic drift or reassortment can spread with wild bird migrations to new regions, infect a wide variety of resident bird species, and spillover to domestic poultry. The vast continental reservoir of AIVs in Eurasia harbors a wide diversity of influenza subtypes, including both highly pathogenic (HP) and low pathogenic (LP) H7 AIV. The Caspian Sea region is positioned at the intersection of major migratory flyways connecting Central Asia, Europe, the Black and Mediterranean Sea regions and Africa and holds a rich wetland and avian ecology. To understand genetic reservoirs present in the Caspian Sea region, we collected 559 cloacal swabs from Anseriformes and other species during the annual autumn migration periods in 2017 and 2018. We isolated two novel H7N3 LPAIV from mallard ducks whose H7 hemagglutinin (HA) gene was phylogenetically related to contemporaneous strains from distant Mongolia, and more closely Georgia and Ukraine, and predated the spread of this H7 LPAIV sublineage into East Asia in 2019. The N3 neuraminidase gene and internal genes were prototypical of AIV widely dispersed in wild bird reservoirs sampled along flyways connected to the Caspian region. The polymerase and nucleoprotein segments clustered with contemporaneous H5 HPAI (clade 2.3.4.4b) isolates, suggesting the wide dispersal of H7 LPAIV and the potential of this subtype for reassortment. These findings highlight the need for deeper surveillance of AIV in wild birds to better understand the extent of infection spread and evolution along spatial and temporal flyways in Eurasia.

Highlights

IntroductionIn particular mallards (Anas platyrhynchos), have been recognized as key reservoir hosts, in which most Avian influenza viruses (AIVs) subtypes are maintained by migratory and/or resident bird populations [2]
To characterize Avian influenza viruses (AIVs) genotypes circulating in the Caspian region, cloacal samples were collected from hunted wild birds belonging mainly (n = 429/559) to the Anseriformes order
LPAI AIV of the H7N3 subtype were isolated from numerous bird species [36]

Summary

Introduction

In particular mallards (Anas platyrhynchos), have been recognized as key reservoir hosts, in which most AIV subtypes are maintained by migratory and/or resident bird populations [2]. The long-distance spread of AIV in nature is intrinsically linked with the movements and migratory behaviors of birds. It is supposed that bird movements are minimally affected by low pathogenic (LP) AIV infection, resulting in the potential for virus shedding, spread, and reassortment during stopovers along the migration route [3]. Shifts from intraspecies to interspecies transmission and gene reassortment events represent additional aspects of AIV’s evolution strategy, enabling viral gene flow during the annual cycles of migratory behavior among wild bird species [6]

Methods

Results

Conclusion