Equine-Like H3 Avian Influenza Viruses in Wild Birds, Chile.

Nicolas Bravo-Vasquez,Pamela Freiden,Victoria Meliopoulos,Bridgett Sharp,Amy Davis,Angela Danner,Jiangwei Yao,Stacey Schultz-Cherry,Christopher Hamilton-West,Sean Cherry,Pedro Jimenez-Bluhm,Leonardo Estrada,Brandi Livingston

doi:10.3201/eid2612.202063

Abstract

Since their discovery in the United States in 1963, outbreaks of infection with equine influenza virus (H3N8) have been associated with serious respiratory disease in horses worldwide. Genomic analysis suggests that equine H3 viruses are of an avian lineage, likely originating in wild birds. Equine-like internal genes have been identified in avian influenza viruses isolated from wild birds in the Southern Cone of South America. However, an equine-like H3 hemagglutinin has not been identified. We isolated 6 distinct H3 viruses from wild birds in Chile that have hemagglutinin, nucleoprotein, nonstructural protein 1, and polymerase acidic genes with high nucleotide homology to the 1963 H3N8 equine influenza virus lineage. Despite the nucleotide similarity, viruses from Chile were antigenically more closely related to avian viruses and transmitted effectively in chickens, suggesting adaptation to the avian host. These studies provide the initial demonstration that equine-like H3 hemagglutinin continues to circulate in a wild bird reservoir.

Highlights

Since their discovery in the United States in 1963, outbreaks of infection with equine influenza virus (H3N8) have been associated with serious respiratory disease in horses worldwide
The H3N8 EIV-like polymerase acidic (PA), nucleoprotein (NP), and nonstructural (NS) genes have been identified in avian influenza viruses (AIV) isolated from South American wild birds since the mid-2000s; the most recent isolation was in Argentina during 2016 [10,11,12]
Six of the H3 viruses, A/ cinnamon teal/Chile/C19368/2016 (H3N8), A/redfronted coot/Chile/5/2013 (H3N6), A/yellow-billed pintail/Chile/C2014/2015 (H3N8), A/red-gartered coot/Chile/C16030/2016 (H3N4), A/yellow-billed pintail/Chile/C30974/2017 (H3N8), and A/yellowbilled pintail/Chile/C34473/2017 (H3N8), were isolated from different regions of Chile (Figure 1), had highest nucleotide homology with the HA gene of the 1963 H3N8 EIV lineage, and had lower homology to the H3 of AIVs found in other regions (Figure 2; Appendix Figure 1, https://wwwnc.cdc.gov/EID/ article/26/12/20-2063-F1.pdf)

Summary

Introduction

Since their discovery in the United States in 1963, outbreaks of infection with equine influenza virus (H3N8) have been associated with serious respiratory disease in horses worldwide. We isolated 6 distinct H3 viruses from wild birds in Chile that have hemagglutinin, nucleoprotein, nonstructural protein 1, and polymerase acidic genes with high nucleotide homology to the 1963 H3N8 equine influenza virus lineage. Viruses from Chile were antigenically more closely related to avian viruses and transmitted effectively in chickens, suggesting adaptation to the avian host These studies provide the initial demonstration that equine-like H3 hemagglutinin continues to circulate in a wild bird reservoir. The H3N8 EIV-like polymerase acidic (PA), nucleoprotein (NP), and nonstructural (NS) genes have been identified in avian influenza viruses (AIV) isolated from South American wild birds since the mid-2000s; the most recent isolation was in Argentina during 2016 [10,11,12]. An EIV-like H3 hemagglutinin (HA) has yet to be identified in AIVs from wild birds

Methods

Results

Conclusion