My horse is coughing

Respiratory

Coughing, poor air, dust sensitivity — respiratory topics are closely tied to management and the immune system.

Immune System & Allergies

Allergic reactions, recurring infections, constant sensitivity — the immune system is closely connected.

An acute cough is a symptom of suddenly arising airway irritation, often as part of a viral or bacterial infection of the upper and lower airways. It can be harmless and brief, but with fever, breathing difficulty or impaired general condition it may indicate a more serious infection and is often contagious in the stable.

Anaphylaxis is an acute, generalised allergic overreaction of the immune system (usually IgE-mediated) with massive histamine release. Within minutes it can threaten circulation and breathing and is a life-threatening emergency. Typical triggers are injections (medicines, vaccines, sera), insect stings or, more rarely, feed components.

In DDSP, the rear edge of the soft palate displaces over the epiglottis and temporarily obstructs the airways, especially at fast work. Typical is a gurgling breathing sound on exhalation with a sudden drop in performance; many horses start normally and only break down at high speed.

Chronic inflammatory airway disease caused by dust/mould allergens, with bronchospasm and increased mucus.

In EIPH, bleeding from small lung vessels into the airways occurs under high exertion, triggered by very high pressures in the pulmonary capillaries during intense work. It mainly affects racehorses and high-performance horses and often goes unnoticed, as only some horses show visible nosebleeds.

In a true feed allergy, the immune system reacts to a feed component, usually with skin or digestive symptoms. In horses, however, it is rare and often overdiagnosed — many supposed allergies are non-immunological intolerances or have other causes. Proof is demanding and best achieved through a controlled elimination diet.

Lymphangitis is a painful inflammation of the lymph vessels and surrounding tissue, usually in one hind leg, with marked swelling. Triggers are often bacterial infections via small skin lesions (e.g. with mud fever), more rarely non-infectious/immune-mediated processes. It runs acutely, is very painful and tends to recur.

Pemphigus foliaceus is the most common autoimmune skin disease of the horse. The immune system forms antibodies against connecting proteins of its own epidermal cells, so that skin layers detach and pustules, crusts and scales form. The changes often start on the head, legs or lower abdomen and can spread.

In photosensitisation, the skin overreacts to sunlight because light-active substances (photosensitisers) in the skin release UV energy and damage tissue. Mainly unpigmented, white skin areas are affected. A primary form (photosensitisers directly from plants) is distinguished from a secondary, liver-associated form, in which a damaged liver no longer sufficiently excretes a chlorophyll breakdown product (phylloerythrin).

Pleuropneumonia is a severe bacterial infection of the lung and pleura, in which inflammation and fluid/pus accumulate in the chest cavity. It often occurs after long transports with a fixed, raised head (shipping fever) and is a potentially life-threatening disease that must be treated quickly by a vet.

Purpura haemorrhagica is an immune-mediated, necrotising inflammation of small blood vessels (type III hypersensitivity). It classically appears about two to four weeks after a strangles infection (Streptococcus equi) or, more rarely, after vaccination/other infections, when the immune system damages the vessel walls with cross-reacting complexes. Typical are extensive oedema and pinpoint mucosal bleeding.

In roaring, the nerve supply to the laryngeal muscles — usually on the left side — is impaired, so that a vocal-fold cartilage does not open sufficiently on inhalation. This narrows the airways under exertion and produces the typical whistling breathing sound; large horses are especially affected.

Hereditary, severe defect of the immune defence in the Arabian foal: through a mutation in the DNA-PKcs gene (PRKDC) functional B and T lymphocytes are not formed. SCID is inherited autosomal-recessive; affected foals are practically defenceless against infections after the maternal antibodies from the colostrum are used up. The disease is not curable, affected foals usually die in the first months of life.

In sinusitis, one or more of the air-filled paranasal sinuses become inflamed, often with an accumulation of secretion or pus. It arises primarily after airway infections or secondarily through diseased cheek-tooth roots whose tips reach into the maxillary sinus.