What Is Equine Influenza?
The term equine influenza refers to a highly contagious viral disease of the upper respiratory tract in equines. Its symptoms appear in the form of coughs, conjunctivitis, fever and nasal discharge, but it does not usually lead to death. Interestingly, it is estimated that 100% of horses that have not been vaccinated or exposed to the virus will become infected at some point.
In any case, although the rate of infection is alarming, the mortality rate from this infection does not exceed 4%. In other words, only foals and horses in poor health prior to infection are at real risk. If you want to know more about equine influenza, read on.
Is equine influenza due to a virus?
Equine influenza receives several names at the veterinary level, including horse flu . These terms may sound familiar to you, as they are also applicable in human medicine. No wonder: the pathogen belongs to the group of Influenza A viruses , which also cause disease in people, birds and other mammals.
As indicated by the Sinobiological portal , it is estimated that there could be 144 subtypes of the Influenza A virus , although only 2 of them seem to specialize in infecting horses. So far, strains H7N7 (equine-1) and H3N8 (equine-2) have been detected. However, it is believed that H7N7 could have disappeared from the natural environment, as it has been undetected for more than 20 years.
Thus, the main suspect in all cases of influenza in horses is the H3N8 subtype. However, it is known that this pathogen can also infect birds, dogs, cats and even seals, according to the BBC.
Characteristics of the virus
These microorganisms are very simple, like all viruses. Its genetic information consists of RNA segments, in turn protected from the environment by a lipid bilayer, which gives the pathogen its shape. Meanwhile, the virus type Influenza are categorized into different variants according expressing proteins in their membrane.
Since viruses lack almost all the characteristics necessary to be considered cells, they are rarely included in the group of living beings. In order to replicate themselves, they have to infiltrate their host’s cell, “hijack” its replicative machinery, and generate copies. When the new viruses enter the extracellular environment, the infected cell dies (lysis).
Symptoms of equine influenza
According to the MSD Veterinary Manual portal , the incubation period lasts from 1 to 3 days after infection. After this short interval, the following symptoms usually occur:
- High fever, up to 41 ° C.
- Serous nasal discharge.
- Strong, dry cough.
- General weakness and worse job performance.
- Difficulty breathing (dyspnea).
- Muscle pain and stiffness of the musculoskeletal system.
The most obvious clinical signs last very little – about 2 or 3 days – in immunocompetent horses, as they are able to cope with the infection quickly and get rid of it. However, as the virus invades the wall of the respiratory epithelium, local destruction of some bronchial structures may occur. Because of this, coughs sometimes last for a few more weeks.
Possible complications
Due to the damage caused by viral expansion and replication, it usually takes about 21 days for the respiratory epithelium to fully heal. During this stage, horses will be prone to being infected by other opportunistic pathogens, so they can manifest conditions such as pneumonia, pleuropneumonia and chronic bronchitis. Therefore, it is best to let the equine rest until it fully recovers.
How is contagion produced?
As the Frontiers of Microbiology journal indicates , this condition is transmitted through droplets, which can be ejected by the sick animal during a cough, sneeze or whinny. The effectiveness of this virus lies in its resistance, since it can be transmitted through the air over distances of 1 to 2 kilometers.
In addition, the microorganism remains viable for up to 3 days outside the host. Brushes, chairs, caregivers’ clothing, haystacks, waterers, and all facility materials may contain pathogens. If a healthy horse comes into direct contact with any of these elements, it will become infected.
Diagnosis of equine influenza
Ideally, it is necessary to call the vet when only one horse shows the clinical signs cited. In any case, due to the rapidity of contagion, surely a large part of the members of the stable – or all – become ill at the same time. This situation is more than enough to suspect an outbreak of equine influenza.
The first step is always to obtain samples of the oral and nasal mucosa of the animal. These samples are taken to the laboratory and, using genetic information amplification techniques – such as PCR -, the virus genome can be detected. Circulating blood antibody tests are also very useful for this task.
Treatment and prevention
Horses that do not develop serious clinical signs do not need specific treatment, only supportive care. In any case, the ideal is that each sick equine can remain 1 week of rest for each day of fever – in general, 3 weeks. Those with a high fever can be treated with non-steroidal anti-inflammatory drugs ( NSAIDs ), always in the doses specified by a veterinarian.
On the other hand, it may also be necessary to prescribe antibiotics to the animal, especially if the fever lasts more than 4 days and the runny nose is accompanied by purulent solutions. Thus, secondary infections that could endanger the life of the sick equine are avoided.
A very common disease
As we said at the beginning, up to 100% of unvaccinated horses become infected with equine influenza at some point in their life. Although the condition generates very annoying symptoms, in 2 or 3 weeks the pathology usually resolves itself and the horse will return to its previous state of health. The death rate does not exceed 4%, so it is not a fatal condition.
However, special care must be taken with immunosuppressed specimens and foals in the herd. These weaker animals can develop much more severe infectious diseases, so to protect them, the best option is to vaccinate everyone in the barn.
