Equine Influenza Virus—A Neglected, Reemergent Disease Threat

Abstract

Equine influenza virus (EIV) is a common, highly contagious equid respiratory disease. Historically, EIV outbreaks have caused high levels of equine illness and economic damage. Outbreaks have occurred worldwide in the past decade. The risk for EIV infection is not limited to equids; dogs, cats, and humans are susceptible. In addition, equids are at risk from infection with avian influenza viruses, which can increase mortality rates. EIV is spread by direct and indirect contact, and recent epizootics also suggest wind-aided aerosol transmission. Increased international transport and commerce in horses, along with difficulties in controlling EIV with vaccination, could lead to emergent EIV strains and potential global spread. We review the history and epidemiology of EIV infections, describe neglected aspects of EIV surveillance, and discuss the potential for novel EIV strains to cause substantial disease burden and subsequent economic distress.

Divergent Influenza-Like Viruses of Amphibians and Fish Support an Ancient Evolutionary Association

“…Finally, it is interesting to speculate on whether these influenza-like viruses are host specialist or generalist viruses. Influenza A-D viruses have extensive host ranges, including an array of mammalian species, particularly those associated with food production (i.e., cattle and swine), and in the case of IAV, wild and food production associated birds (i.e., poultry) [6][7][8][9][20][21][22]. Salamander influenza-like virus also appears to be a multi-host virus, being found in four salamander species raised in laboratory colonies, with the greatest abundance in the Mexican walking fish and plateau tiger salamander.…”

“…Until recently, influenza viruses had been limited to a small group of pathogens with public health importance for humans, particularly those of pandemic and epidemic potential-influenza A virus (IAV, Alphainfluenzavirus) and influenza B virus (IBV, Betainfluenzavirus). Influenza A virus is an important, multi-host virus best described in humans, pigs, horses and birds [6][7][8][9]. These viruses are epidemic in humans and are closely monitored for pandemic potential.…”

Peer Review #2 of "Genetic and serologic surveillance of canine (CIV) and equine (EIV) influenza virus in Nuevo León State, México (v0.1)"

“…The vaccination against EIV is not mandatory, thus, the immune status against equine influenza virus is unknow. However, the incidence of EIV in 23 states of United States during 2015 supports the possibility of an outbreak within the equine population (Sack et al, 2019). This population of animals are exposed to multiple risk factors such as work injuries, the contact with waste, and interaction with different animal species (Rimbaud et al, 2006).…”

“…At present, CIV is currently distributed in at least 30 states of the United States (Voorhees et al, 2017, CDC, 2019. The detection of Equine Influenza Virus (EIV) occurs in sporadic outbreaks around the world, where essentially, the disease is distributed among unvaccinated horses in precarious animal health conditions (Gaíva et al, 2014;Singh et al, 2018;Sack et al, 2019). Several factors could contribute to the emergence of the Influenza A virus in companion animals such as the absence of vaccination (Gaíva et al, 2014), co-infection with other respiratory agents (Metzger and Sun, 2013) and co-existence with infected animals in poor health conditions (Holt et al, 2010;Hayward et al, 2010).…”

Evaluating 5.5 Years of Equinella: A Veterinary-Based Voluntary Infectious Disease Surveillance System of Equines in Switzerland

“…While notifiable diseases are being monitored via active surveillance and/or mandatory notification (passive surveillance), non-notifiable diseases are often poorly or not tracked at all. Most endemic diseases belong to this second category, and in most countries, it is up to the equine industry to manage them (5). To improve early detection of notifiable and non-notifiable diseases, surveillance systems based on voluntary notifications have been developed.…”