Detection of the epidemic of the H3N8 subtype of the equine influenza virus in large-scale donkey farms

Yu Yongfeng,Sun Xiaobo,Xia Nan,Zhang Jingwen,Liu Wenqiang

doi:10.1080/23144599.2020.1739844

Yu Yongfeng, Sun Xiaobo + Show 3 more

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https://doi.org/10.1080/23144599.2020.1739844

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Abstract

ABSTRACT To monitor the occurrence of equine influenza in large-scale donkey farms in Liaocheng City, Shandong Province, serological investigation and sequence analysis of HA/M protein gene of equine influenza virus (EIV) were carried out. Samples (n = 65) of the lung and nasal swab were collected in six different large-scale donkey farms and detected with RT-PCR for HA and M protein gene. The homology and evolution of HA and M genes were analysed with known sequences. Antibody titres of serum samples (n = 120, unvaccinated) level was determined by the HI test. The average seropositive rate was 32.5% (39/120) with great diversity among different populations. The positive rate of EIV HA/M protein gene was 21.5% (14/65) by RT-PCR. The equine influenza H3N8 virus was confirmed by gene sequencing, and the homology of the sequence was 99.77% with isolates from Northeast China (equine/heilongjiang/1/2010), consistent with the input of donkeys. This suggested that EIV has become an important threat to large-scale donkey farms in Liaocheng and threats from the input area must be vigilant.

Highlights

Equine influenza virus (EIV) is an acute and contagious infectious disease of horses, donkeys and other equine family caused by the equine influenza A virus of genus Orthomyxovirus [1]
According to the Hemagglutination inhibition (HI) test, the positive rate of 120 serum samples from 6 farms ranged from 20% to 45%, with an average of 32.5% (Table 1.) The statistical results showed that the positive rate of antibody in six fields was higher, and the positive rate of female donkey was the highest in different populations, which was 45% (Table 2.)
Since 2015, hundreds of large-scale donkey farms have been built in Liaocheng City, Shandong Province, and extended to Hebei, Shanxi Province and other regions, which are completely different from traditional free culture

Summary

Introduction

Equine influenza virus (EIV) is an acute and contagious infectious disease of horses, donkeys and other equine family caused by the equine influenza A virus of genus Orthomyxovirus [1]. Influenza A viruses are subtyped according to their surface glycoprotein haemagglutinin (HA) and neuramindase (NA). There are two major subtypes, H7N7 and H3N8, which have been isolated from horses [3]. World Health Organization (OIE) regulates that horse flu is a legally reported animal epidemic. It is classified as the third category of animal epidemic disease in China [4]. The characteristic clinical symptoms of influenza virus infection in equine animals include high fever, cough, serous nasal juice and female abortion. The epidemic of EIV is extremely strong, once infected, it will quickly spread to the whole population. Especially the cross-border transport of horse races, is the main reason for the spread of horse flu from one country to another [6]

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