Equine respiratory infections : what to do when your horse starts coughing ?
By the bioMérieux Editors | Reading time: 3 min
If you already had a sick horse, you know the situation can escalate quickly.
At the first signs of a respiratory disease, distinguishing a simple cough from a severe infection which will evolve into respiratory distress, and even the appearance of neurologic symptoms can be a challenge. These seemingly inoffensive symptoms can signify a much more critical issue. If not detected in time and treated correctly, a respiratory disease can be disabling for your horse for its entire life, damaging its health along with its sportive carrier.
Be aware of the threats
Horses are obligatory nasal breathers, relying solely on their nasal passages for breathing. Therefore, any problem with their upper respiratory system can significantly impact their overall health, performance and wellbeing.
Overall, respiratory diseases result in significant economic losses due to decreased athletic performance, reduced breeding potential, and the cost of ongoing treatment and medication.
More common than you might think
The reality is that respiratory diseases among horses are more commonplace than you might assume. Indeed, up to 80% of horses will experience a respiratory infection at some juncture in their lives, underscoring the prevalence of the issue.
Adding to this concern, the surge in equine rhinopneumonitis and equine flu outbreaks, growing both in frequency and intensity each year, raises a clear call for vigilance.
Equine Flu is caused by Equine Influenza A Virus (EIV) with 2 different subtypes - H7N7 and H3N8. Flu affects usually horses up to 2-3 years old. After an incubation period of one to three days, the main symptoms include fever, decreased appetite, nasal discharge, cough and increased respiratory rate. In most serious cases, complications such as myocarditis, myositis, limb edema and encephalitis may occur.
What are the alarming symptoms?
- Hyperthermia, Submandibular lymphadenopathy
- Abscess formation of the cervical lymph nodes
- Cough, nasal discharge
- Respiratory distress, laboured breathing
- Lethargy, reduced stamina
- Discomfort, pain, distress
- Decreased appetite, weight loss.
Rhinopneumonitis is caused by Equine Herpesviruses (EHV) like EHV-1 & EHV-4. These highly contagious viruses are widely spread globally, affecting up to 80% of young horses in their first year. While morbidity rate is up to 90%, mortality is quite low. Nevertheless, after an incubation period of ten days in average, the clinical presentation ranges from fever with benign pharyngitis, to serious complications such as abortion for both viruses, or myeloencephalopathy for EHV1.
Strangles is caused by Streptococcus equi equi, a facultative anaerobic gram positive coccus. After an incubation period of two to ten days, the pathogenesis of this disease includes several phases. After an initial fever, depression and anorexia, horses may develop a classic form with 7 to 14 days of nasal discharge, submandibular lymphadenitis, abscesses of the lymph nodes ; or atypical forms with various symptoms such as guttural pouch empyema, abscesses, and pulmonary metastases. The mortality rate is expected to be low, but chronic cases with bacterial persistence can be challenging and lead to complications like abscesses or recurrent outbreaks.
Infectious Rhinitis is caused by viruses such as Equine Rhinitis Viruses A & B or Equine Adenovirus 1. The clinical presentation including fever, loss of appetite, peripheral edema, conjunctivitis, cough, abortion or leukopenia. Despite the better prognosis associated with these pathogens, it is crucial to distinguish such cases in order to ensure the appropriate management of infected horses and the implementation of biosecurity measures.
Respiratory diseases in horses can occur all year, but autumn and winter are especially critical for epidemics. In these periods, you need to watch out for potential symptoms and take preventive measures.
The most common and contagious pathogens responsible for Equine Respiratory Diseases are:
- Equine Influenza A Virus,
- Equine Herpesviruses (EHV-1 & EHV-4)
- Streptococcus equi equi,
- Equine Rhinitis viruses A & B,
- Equine Adenovirus 1.
Lessons from Valencia: A Wake-Up Call
In Valencia (Spain), the 2021 outbreak of Equine rhinopneumonitis caused by Herpesvirus 1 (EHV1), which resulted in the deaths of 18 horses, was a stark reminder of the complexities and challenges of managing a highly contagious respiratory pathogen within a community of horses. (full report from FEI available here)
Originating from diverse corners of Europe, these equine travelers carried with them a hidden threat that swiftly erupted into an outbreak, showcasing the intricate web that is equine health management.
In this context, horses who live in large barns or attend competitions are particularly at risk. Biosecurity measures are central to minimize the impact and the spread of pathogens.
How are respiratory diseases transmitted ?
- Direct contact with an infected horse through nose-to-nose contact, through coughing, sneezing, or nasal discharge.
- Aerosol transmission of infectious droplets through the air, particularly in crowded or poorly ventilated areas.
- Indirect contact with contaminated objects, such as water troughs, feed buckets, or shared equipment.
→ Be mindful to reduce direct and indirect contacts between horses when there is an infection in your barn.
An Early Call to Action: Identifying the root cause
When caused by an infectious pathogen, the horse may recover in one or two weeks, but it may nonetheless have dramatic consequences. When the first signs of a respiratory issue appear, proactive steps are essential.
A thorough examination by a veterinary practitioner is crucial. This clinical assessment may be accompanied by in vitro diagnostic tests, an indispensable tool to pinpoint the disease's origin (infectious vs inflammatory) and chart a suitable course of treatment and management.
In the management of equine infectious respiratory diseases, you must keep in mind that early intervention is your horses' strongest ally.
Respiratory diseases present a great challenge to our equine companions. Equine herpesvirus 1 and 4, Influenza A and Streptococcus equi equi are pathogens that are responsible for the most dangerous respiratory diseases in horses.
Hyperthermia, serous nasal discharge, anorexia, and cough are the main symptoms, yet, it hides the true depth of the problem. It's not just the horse's wellbeing that is at stakes, but also the management of the stable yard and an entire economy when an epidemic outbreak occurs.
Vigilance, early detection, and comprehensive diagnostics is the milestone to restrain the spread, and to offer our horses a path to swift recovery. The importance of management and diagnosis in respiratory diseases for horses cannot be overstated.
Take home message about respiratory diseases in horses
- Equine herpesvirus 1 & 4, Influenza A and Streptococcus equi equi are the main pathogens behind the most severe respiratory infections.
- Symptoms include hyperthermia, serous nasal discharge, anorexia and cough. But they are non specific and only reveal part of the threat.
- Beyond the horse’s health, outbreaks disrupt stable yard management and have economic consequences for the whole equine sector.
- Vigilance, early detection and accurate diagnosis are key to limiting the spread and enabling rapid recovery.
→ Stay alert : every day without a diagnosis is a day lost in the fight against respiratory outbreaks.
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