Influenza Equina:soroprevalência do Vírus da Influenza Equina H3N8 Florida Clado 1 em equídeos de tração na região metropolitana de Belo Horizonte nos anos de 2010 a 2017

Abstract

Equine influenza, or equine flu, is one of the most prominent respiratory diseases affecting equids, causing significant economic impact and posing a serious threat to the equine industry during outbreaks. The spread of the disease among susceptible populations is a major concern. The equine industry in Brazil is vital to the economy, with horses, donkeys, and mules distributed across the country, playing roles in labor, sports, and leisure. Draft animals, such as cart horses, are important in urban dynamics and close to humans, factors that facilitate the spread of the disease and potential interspecies transmission. In Belo Horizonte, cart animals are essential for collecting debris, construction waste, and garbage, and are not vaccinated against equine influenza virus, making them a key population for epidemiological studies. This is the first retrospective seroprevalence study to analyze 745 samples from draft equids collected between 2010 and 2017 in the metropolitan area of Belo Horizonte, using hemagglutination inhibition tests for the H3N8 FC1 virus. The results showed 47.92% positive samples, with 62.76% showing high titers (≥640), 12.41% medium titers (160-320), and 24.82% low titers (40-80). These results confirm the endemic circulation of the virus in the region, aligning with previous findings. The presence of high titers in unvaccinated animals suggests active viral circulation, highlighting the need for epidemiological surveillance, especially in Belo Horizonte, where equestrian events are common and cart animals play a vital role in the city. The results also have implications for public health, given the potential for transmission between equines and humans. Although human infection cases are rare, the possibility of cross-species transmission is concerning. The lack of vaccination in this equid population increases the risk of virus spread. This study provides the first retrospective estimate of seroprevalence of equine influenza virus in draft equids in Belo Horizonte, highlighting the need for continuous surveillance and preventive measures to control the spread of the virus and protect both animal and human health.