RAO / COPD
INFLAMMATORY AIRWAY DISEASE (IAD) IN PLEASURE HORSES
IAD is used to describe airway inflammation without concurrent infection
It has various synonyms which include the following. For ease it will be referred to as IAD throughout this article.
RAO – recurrent airway obstruction
COPD – chronic obstructive pulmonary disease
SPA/OPD – summer pasture associated obstructive pulmonary disease
It remains the most common form of chronic coughing in horses. Disease risk relates to:
- Genetic susceptibility
- Airborne environment
Symptoms may include:
- Poor performance
- Nasal discharge
- Heaves line
- Higher resting respiratory rate (20 instead of 8-12/minute)
- Poor recovery from exercise
Diagnosis is based on clinical signs and endoscopic examination.
An endoscope camera (see picture below) is put into the horse’s airway. This allows us to visualise the airway and to take samples from the horse’s trachea. Sterile saline is put down the airway and then aspirated back. The resultant sample will be analysed in a laboratory.
The above results are an example of a tracheal wash sample from horse that had a history of a cough, increased respiratory rate and mild nasal discharge. An elevated neutrophil count, which is a particular type of white blood cell, is indicative of IAD.
What happens to a horse’s airways when they have IAD….?
To better understand the treatment aims of IAD, it is important to understand what happens to the airways of a horse with the condition. In response to the irritant e.g. dust or spores, the following will happen:
- Bronchospasm (the small airways start to constrict or narrow)
- Increased mucus production (this fills up the airways)
- Influx of inflammatory cells
- Coughing will further exacerbate this inflammation
There are three cornerstones to management of horses with IAD,
- DRUG THERAPY
- Relief of BRONCHOSPASM
- Reduction of INFLAMMATION
- Dust free bedding e.g. shavings
- Switch from hay to haylage
- Soak/steam hay
- Turn out as much as possible
- Feed from the floor
Sometimes environmental management alone is enough to control the clinical signs depending on severity. Alternative measures involve the use of drugs and this will depend on how severe the clinical signs are as to what method is used. There are three main routes for treatment.
Oral drug therapy
Ventipulmin® granules are commonly dispensed as a first line treatment for suspected cases of IAD. It is only effective in a small number of horses and usually has to be substituted or used in conjunction with other treatments. The drug, clenbuterol, is a bronchodilator and aims to open up the airways when they start to narrow due to bronchospasm.
Equisolon® (prednisolone) is a steroid powder that is licensed for use in horses to treat the inflammation that occurs with RAO. They aim to reduce to the inflammation that is present in the lower airways. With the use of steroids in horses, there is always a small risk of inducing laminitis. Talk to your vet about the risks with your pony or horse.
Injectable drug therapy
In more severe cases, injectable drug therapy will be initiated to get a good clinical response before either oral or inhaled therapies are continued. These may include:
Colvasone® – this is a steroid that can be given into the vein or muscle to reduce inflammation within the lower airways
Atrocare® – this is atropine; it results in bronchodilation (widening of the small airways). Its effect is almost immediate and will be used in horses in respiratory distress, usually in combination with the other two injectable drugs.
Inhaled drug therapy
Inhaled therapy is highly effective for the treatment of IAD. It allows a higher concentration of drug to reach the location and minimises potential side effects.
A spacer device has to be used in horses, which allows the drug to be transported from the inhaler to the airways. Horses generally tolerate their use very well. There are various drugs in the inhaled form that can be used.
Steroid – in general this is the drug that the horse will be treated with starting at a higher dose, usually 14 puffs twice daily, lowering as the clinical signs improve.
Bronchodilator – e.g. Salbutamol or Atropine, these tend to be used if the horse becomes a lot worse or is in respiratory distress. If there has been no improvement, then the vet will have to be called to initiate systemic therapy.