Infectious diseases

What Is the Horse Flu? - Understanding Equine Influenza

María Besteiros
By María Besteiros, Expert veterinary assistant and canine/feline hairdresser.. Updated: January 30, 2024
What Is the Horse Flu? - Understanding Equine Influenza

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Equine Influenza is a contagious and common respiratory disease that affects horses worldwide. This informative resource aims to shed light on the symptoms and various treatment approaches for this concerning ailment, equipping horse owners, caregivers, and enthusiasts with essential knowledge to safeguard the health and well-being of their beloved equine companions.

The following AnimalWised article explores equine influenza, including its symptoms, effective treatment, and preventive measures.


  1. What is equine influenza?
  2. Transmission and spread of equine influenza
  3. Treatment for equine influenza
  4. Prevention of equine influenza
  5. Is equine influenza a zoonosis?

What is equine influenza?

Equine flu, also known as influenza or equine influenza, stands as one of the most prevalent diseases affecting horses worldwide.

This respiratory pathology is triggered by the equine influenza virus, characterized by its highly contagious nature and relatively low fatality rate. Transmission occurs through direct contact between horses, contaminated equipment or utensils, and even through the air.

One of the most concerning aspects of this virus is that infected horses can shed it even before exhibiting any symptoms. Consequently, equines that have not been vaccinated against the virus are highly susceptible to infection, leading to the swift development of equine flu epidemics.

The equine influenza virus primarily targets the mucosa of the respiratory tract, causing inflammation within days of infection. As the symptoms start to manifest, they bear a striking resemblance to those of human flu. Horses afflicted with the virus may display a range of clinical signs, including:

  • Fever
  • Lethargy
  • Decreased activity
  • Loss of appetite
  • Dry cough
  • Respiratory distress
  • Swollen mandibular ganglia
  • Edema in the paws
  • Runny nose
  • Eye discharge
  • Muscle pains
  • Weakness

How long does equine influenza last?

The duration of the disease typically spans around ten days, but certain symptoms such as persistent coughing may linger for a longer period, especially if the affected horse fails to get adequate rest. Therefore, it is crucial to promptly isolate any horse showing signs of the infection, even before confirming the diagnosis, particularly if multiple horses cohabit in the same space.

Enhance your understanding of your horse's behavior and communication by delving into this other article on horse body language and communication.


What Is the Horse Flu? - Understanding Equine Influenza - What is equine influenza?

Transmission and spread of equine influenza

Equine influenza spreads through various means, primarily due to its highly contagious nature. The virus can be transmitted and spread through the following routes:

The most common mode of transmission is direct contact between infected and susceptible horses. Horses that are shedding the virus, even before showing symptoms, can pass it on to others during close contact, such as nose-to-nose interactions or sharing feed and water troughs.

The equine influenza virus can become aerosolized when infected horses cough or sneeze. This allows the virus to spread through the air over short distances, making it easy for horses in close proximity to inhale infectious respiratory droplets.

The virus can survive on surfaces such as tack, grooming equipment, water buckets, and feed bins. If these items are not properly cleaned and disinfected after use on an infected horse, they can serve as vehicles for transmitting the virus to healthy horses. Though not a zoonosis, humans can play a role in indirectly transmitting the virus between horses. Contaminated clothing, hands, or equipment can transfer the virus from an infected horse to a healthy one.

Equine influenza can easily spread in places where horses congregate, such as shows, competitions, racetracks, and boarding facilities. The close proximity of many horses increases the risk of transmission.

It's important to note that equine influenza is not only highly contagious but also relatively fast-spreading. Horses infected with the virus can shed it for up to a few days before showing symptoms, making early detection and isolation critical in preventing outbreaks.

Treatment for equine influenza

When a horse exhibits clinical signs similar to equine influenza, it is essential to seek veterinary confirmation, as these symptoms can overlap with other respiratory diseases. Among the key clinical signs that raise suspicion of equine influenza is the presence of a dry cough, which serves as a distinctive marker of the infection. To ascertain the diagnosis, veterinarians typically collect a sample from the horse's nasal passages to detect the presence of the equine influenza virus.

Upon a confirmed diagnosis, immediate isolation becomes imperative, considering the ease with which the virus spreads among horses. Isolation not only helps contain the infection but also minimizes the risk of transmission to other healthy horses. Alongside isolation, specific measures need to be implemented to aid the horse's recovery:

  • The affected horse should be granted complete rest, adhering to the veterinarian's recommendation, until the horse receives a clean bill of health.

  • Providing the horse with a clean and well-ventilated environment is crucial for a swift recovery. Optimal living conditions facilitate healing and alleviate potential complications.

  • Encouraging the horse to eat is of paramount importance during recovery. Offering easily consumable food options ensures the horse's nutritional needs are met, bolstering its immune system and supporting recovery.

  • Depending on the severity of the infection and any potential complications, the veterinarian may prescribe anti-inflammatories to manage symptoms effectively. If a secondary bacterial infection is present, administering antibiotics becomes necessary. These measures are particularly crucial, as complications stemming from secondary bacterial infections can exacerbate the condition, potentially leading to fatal outcomes, especially in horses with compromised immune systems.

With timely intervention and attentive care, we can help our equine companions overcome this ailment and restore them to their lively and vibrant selves once again.

Prevention of equine influenza

Understanding the limitations of equine influenza immunity is crucial for responsible horse owners and caregivers. Although a horse may recover from a previous infection, it does not gain lifelong immunity. Consequently, if the horse comes into contact with the virus again, it remains susceptible to contracting the disease.

To bolster their horse's protection against equine influenza, owners must diligently follow the veterinarian's advice and administer the equine influenza vaccine as prescribed.

Vaccination serves as a vital preventive measure, especially for horses that partake in shows, competitions, or exhibitions. While the vaccine does not guarantee absolute immunity or cover all virus strains, it significantly reduces the severity of symptoms if the vaccinated horse does contract the disease. Regular booster shots, typically administered yearly, or even more frequently for horses at higher risk of exposure, are imperative to maintain vaccine efficacy.

For horse owners welcoming a new equine companion into their stable, ensuring the horse is free of equine influenza and up-to-date with vaccinations is of utmost importance. Regular disinfection of equipment and vehicles used by the horse, as well as frequent handwashing when handling the horse, constitute essential preventive measures. The equine influenza virus is susceptible to common disinfectants, making routine disinfection practices a valuable tool in reducing the risk of infection.

In environments where large groups of horses congregate, such as competition settings, the risk of contagion amplifies. Consequently, meticulous hygiene practices and vaccination become all the more critical in such scenarios.

What Is the Horse Flu? - Understanding Equine Influenza - Prevention of equine influenza

Is equine influenza a zoonosis?

The equine influenza virus falls within the group of influenza A viruses. While it is highly contagious among horses, it is essential to note that it is not a zoonosis, meaning it is not naturally transmitted from horses to humans. Although there have been experimental cases where humans were infected with the virus, individuals have shown the ability to develop antibodies without actually contracting the disease. Nonetheless, the primary focus of our efforts must remain on preventing contagion between equines.

By directing our efforts towards preventing the spread of equine influenza among horses, we can safeguard their health and well-being effectively. Implementing measures such as regular vaccination, isolation of affected horses, good hygiene practices, and periodic disinfection of equipment and facilities can significantly reduce the risk of outbreaks and protect the equine population from this highly contagious respiratory disease.

Discover the intriguing world of horses and their significance in our society through our other article on horse origin and evolution.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to What Is the Horse Flu? - Understanding Equine Influenza, we recommend you visit our Infectious diseases category.

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What Is the Horse Flu? - Understanding Equine Influenza