2 Airway diseases in horses Acute, chronic or allergy-related coughs are now one of the most common health problems affecting horses. There can be many reasons why respiratory diseases develop. These include: • Stabling problems: Too much dust in the stable, lack of exercise, too little fresh air (harmful gases such as ammonia) • Previous infections that may not have been picked up on or treated correctly • Allergies to fungal spores from hay and straw or to pollen from flowers • Viruses, bacteria (occasionally also parasites) • Genetic predisposition In most cases, several causes simultaneously lead to a weakening of the immune system, resulting in respiratory diseases. Prompt diagnosis, rapid treatment from the vet and supportive measures can help to cure many diseases of the airways. A healthy horse has its own type of self-purifying mechanism. Horses' airways are lined with fine ciliated hairs (cilia) and these are in turn moistened by a fluid secretion. Inhaled harmful substances, such as dust particles, stick to the uppermost layer of this secretion and are transported up the airways and outwards thanks to the wave-like movement of the hairs, and are eventually coughed out. Inflamed or irritated airways, however, can interfere with this mechanism. Mucus production is stimulated and this thick mucus is no longer able to be coughed up and transported away, which in turn leads to airway problems. Any impairment of the self-cleaning mechanism can, if it persists, lead to severe, chronic lung damage. Initially, a distinction is made in horses between acute and chronic cough, also known as equine asthma. Acute bronchitis Acute coughs are commonly caused by viral infections, but often a secondary infection can develop from bacteria. In bronchitis, the following symptoms are usually seen, for example: • Cough • Nasal discharge • Loss of appetite • Reduced performance, fatigue • Fever (normal temperature for adult horses: 37.0 °C - 38.0 °C) • Swelling of the lymph nodes in the head area The first signs of a cough should not be ignored. Occasional coughing, especially at the start of a physical situation such as when trotting, may be indicative of a developing disease. The rapid initiation of therapeutic measures can prevent the condition from becoming chronic. Equine asthma Several factors often play a role at the same time as triggers for a chronic cough. In many cases, it is preceded by acute bronchitis that has not been treated consistently. The irritated mucous membranes that this condition brings with it provide the perfect breeding ground for infection with viruses or bacteria. In addition to cold and dry air, especially in the winter months, the daily care of the horses (mucking out, bedding, sweeping and feeding) is a challenge for the entire respiratory system. Horses kept indoors during the winter are particularly affected (permanent exposure to dust, ammonia gases, mould spores and lack of exercise). Typical symptoms of equine asthma (previously also called COB) are: • Cough (in the morning and/or at the beginning of a work phase) • Reduced performance through to apathy • Increased respiratory rate (normal value: 8-16 breaths per minute) • Nostril flaring at rest • Little nasal discharge • Difficulty breathing up to increased abdominal breathing (heave line) • Blue discolouration of the mucous membranes due to oxygen deficiency Performance needs intact respiratory organs! Without treatment, an acute cough can develop into equine asthma.