Assessment of Equine Influenza Virus Status in the Republic of Korea from 2020 to 2022

Abstract

Equine influenza virus (EIV) causes acute respiratory disease in horses and belongs to the influenza A virus family Orthomyxoviridae, genus Orthomyxovirus. This virus may have severe financial implications for the horse industry owing to its highly contagious nature and rapid transmission. In the Republic of Korea, vaccination against EIV has been practiced with the active involvement of the Korea Racing Authority since 1974. In this study, we monitored the viral RNA for EIV using PCR, as well as the antibody levels against ‘A/equine/South Africa/4/03 (H3N8, clade 1)’, from 2020 to 2022. EIV was not detected using RT-PCR. The seropositivity rates detected using a hemagglutination inhibition assay were 90.3% in 2020, 96.7% in 2021, and 91.8% in 2022. The geometric mean of antibody titer (GMT) was 83.4 in 2020, 135.7 in 2021, and 95.6 in 2022. Yearlings and two-year-olds in training exhibited lower positive rates (59.1% in 2020, 38.9% in 2021, and 44.1% in 2022) than the average. These younger horses may require more attention for vaccination and vaccine responses against EIV. Continuous surveillance of EIV should be performed to monitor the prevalence and spread of this disease.

First Molecular Detection and Epidemiological Analysis of Equine Influenza Virus in Two Regions of Colombia, 2020–2023

“…The high positivity rate in our sample could be explained by the fact that the studied population consisted of symptomatic individuals [ 20 ] and that the sampling period coincided with the 2021–2022 outbreak, which had a global distribution, largely in America, Europe, and Asia [ 7 ]. Furthermore, in 2022, there was an increase in rainfall in Colombia, mainly between April and May [ 38 ], the months in which the outbreak was reported, which may explain the high degree of virus transmission because sick and healthy horses have closer contact, mostly with young susceptible individuals [ 39 , 40 ].…”

“…[ 4 ]; it has an enveloped capsid and contains eight negative sense genomic segments of single-stranded RNA. The surface proteins hemagglutinin (HA) and neuraminidase (NA) determine the EIV subtype [ 5 , 6 , 7 ]. Currently, only EIV H3N8 causes significant economic losses in the equine industry [ 2 ].…”