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Chronic Obstructive Pulmonary Disease of Horse (COPD)

Chronic Obstructive pulmonary Disease (COPD) is a disease of horses characterized clinically by decreased work performance, chronic coughing, abnormal lung sounds and varying degree of pulmonary and cardiac dysfunction.

Pathologically, there are varying degrees of bronchitis, bronchiolitis and pulmonary emphysema. The disease was formerly known as (heaves), pulmonary emphysema or (bracken wind).

Causes:

Chronic bronchiolitis which is present in affected horses is due to a hypersensitivity reaction to the allergens found in barn, dust, moldy and dusty feeds.
Micropolyspores of fungi and Asperigillus fumigatus are recognized as common causes of Chronic Obstructive Pulmonary Disease of Horse.

Clinical findings:

The disease occurs most commonly in adult horses 5-10 years old. The usual history is that the horse has been stabled for several weeks or months and has a chronic cough.
The animal may have had an infectious disease 1-2 months previously, recovered form acute illness but began coughing recently. There may be a history of reduced exercise tolerance in some horses, but this is not the major feature initially.
On clinical examination, the horse is usually bright and alert, the temperature and appetite is usually normal.
Coughing is common and may consist of a single cough every few seconds or there is may be a paroxysm of coughing.
An intermittent, bilateral nasal discharge is a common signs which may consist of serous fluid, mucous, mucopurulent, or bloody or a combination of their bilateral blood stained. Race horses with early COPD may develop exercise induced pulmonary hemorrhages, the so called (bleeder) and exhibit epistaxis.
The resting respiratory rate is decreased with an increase in depth of respiration. In advanced cases the expiration which are normally biphasic become exaggerated.
During expiration there is normal collapse of the rip cage followed by a clearly visible contraction of abdominal muscles of the flank. In long-standing cases, this results in the so called (heaves line) which is a trough that follows along the costal arch. In advanced cases the nostrils may be visibly dilated during inspiration and the force of the expiratory effort causes of the anus to protrude.
In COPD, the heart rate is commonly within the normal range or only slightly increased. In advanced cases, pulmonary arterial hypertension may result in an increase in heat rate up to 50-60/min. The heart rate is significantly higher during exercise than in clinically healthy once.
Auscultation of the lung in the early stage of the disease, may reveal only a slight increase in the amplitude of normal breath sounds. The abnormal sounds may be audible in the resting horses but they can be accentuated by 10-15/min. exercise for a long time. Also the placement of plastic bag over the horse nostrils for one minute, will cause the horse to hyperventilate and abnormal sounds may become clearly audible.
The course of the disease is dependent on the removal of the continual presence of the precipitating factors. If the cause is removed in the early stage, complete recovery may occur.
The degree of improvement will depend on how much emphysema is functional and how much is structural. In the continual presence of the precipitating causes relapse occurs commonly or the disease become progressively and affected horses become severely incapacitated, with good management and adequate housing, riding animals, and hunters or show jumpers can remain useful for many years.
The prognosis for race horses with exercise-induced epistaxis is less hopeful, because even a small degree of persistent emphysema is a serous handicap of a race horse.
Most horses even with advanced Chronic Obstructive Pulmonary Disease do not die form the disease, but usually euthanitized.


Clinical pathology and special examinations:
Affected horses have an increased respiratory and expiratory flow rate, a decreased dynamic compliance, an increased in the maximum changes in the intrapleural pressure and elevated values for the effort of breathing.
Precipitins against fungi have been identified in the serum of the affected horses and allergic skin tests have also been used.
Cytological examination of transtracheal washing can aid in the differential diagnosis from infectious diseases of the lungs.
The presence of eosinophils in the tracheal fluid samples suffers an allergic cause, however, their absence dose doesn't exclude allergy as a cause.
Endoscopic examination of the upper respiratory tract can aid in detection of horse with evidences of pulmonary hemorrhages secondary to this disease.
Also, in the horse with advanced bronchitis, an excess of mucous may be seen in the pharynx, larynx or upper trachea.
Radiography of the thorax may be useful in differentiating Chronic Obstructive Pulmonary Disease of Horse from others.

The important clinical features of COPD of Horse

Include the following:
1-Mature horse 5-10 years old.
2-History of prolonged confinement and exposure to a dusty environment.
3-Chronic coughing for several days or week.
4-Reduced exercise tolerance.
5-Dyspnoea.
6-Wheezing and cripitant lung sounds.
7-An obvious expiratory effort following exercise.
8-Lack of toxemia.

The disease should be differentiated form acute pneumonia in which there is toxemia, fever, coughing and increased bronchial tones on auscultation. A tracheal wash will reveal the presence of exudates.



Treatment and control:
1-The best treatment for early cases is the provision of fresh air.
2-Ideally, the horse should be kept permanently in the open air, if not actually on pasture. A
partly covered and well protected outside yard is also suitable. During the winter months,
blankets may be necessary for horses kept outdoors.
3-For horses, which must be housed, the boxes should be well ventilated. Every effort must be
made to ensure that stable dust is kept to a minimum. All dust should be removed from roof
rafters, windows and feed boxes.
4-If hay is fed, it should be of the best quality and must be throughout wetted with water prior to
feeding. The feeding of hay as wet stuffs at ground level will encourage the horse to keep its
head down for long periods where advanced cases of pulmonary emphysema in the horse are
unlikely to recover but with proper care and feeding as outlined above they can be maintained
as breeding animals for months and even years. Many drugs including corticosteroids,
antihistaminics, expectorants, inhalants, bronchodialtors and antibiotics have been used for the
treatment of the COPD.
5-Of corticosteroids, dexamethasone is used at a dose are of 25 mg per animal intramuscularly
every 2nd day for up to 2 weeks, this may give a remarkable results. Bronchodilators atropine
sulfate can be used.
6-Administration of these bronchodilators by inhalation or atropine injection intravenously at a
rate of 0.02 mg/kg body weight will result in a marked decrease in intrathoracic pressure, a
decrease in respiratory rate, an initial decrease followed by an increase in arterial oxygen
partial pressure and clinical improvement.