What is Recurrent Airway Obstruction (Heaves)?
Recurrent airway obstructions in horses, perhaps more commonly known as heaves, has historically been called chronic obstructive pulmonary disease or COPD, but recently, the veterinary community has gone toward referencing it as recurrent airway obstruction or RAO to avoid confusion with the human COPD condition as there are many differences between the human version and this one in horses. Though the estimates differ in various areas of the country and in different climates, this disease is estimated to affect approximately 12 to 20 percent of adult horses, usually over the age of 9 years old, and can affect either gender and any breed of equine.
Recurrent airway obstruction (or heaves) in horses is defined as a noninfectious airway condition in horses also known as RAO (recurrent airway obstruction) characterized by narrowing of the airway, mucus production and bronchial spasms. This condition has historically been referred to as chronic obstructive pulmonary disease or COPD in horses.
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Symptoms of Recurrent Airway Obstruction (Heaves) in Horses
Here are some of the symptoms you may notice in your horse with heaves:
- Occasional cough - one of the first symptoms noted
- Higher breathing rate
- Nasal discharge
- Flaring of nostrils
- Exercise intolerance
- Weight loss if condition is severe
- Anorexia if condition is severe
- Fever is present only if a bacterial pneumonia is present
These symptoms will likely present in milder forms and, as the disease progresses, the symptoms will worsen. As a result of the blockage of the airway, the horse works harder to breathe and you may also notice enlargement of abdominal muscles and perhaps even a heave line at the lower edge of the ribs.
This severe equine asthmatic condition is found in two basic types:
- Barn-associated type - This type affects horses who live in kept stalls and are fed hay
- Summer pasture-associated obstructive pulmonary disease (SPAOPD) - Also called summer heaves
At this time, horses with these types of recurrent airway obstruction are labeled as having equine asthma.
Causes of Recurrent Airway Obstruction (Heaves) in Horses
As noted above, this condition is considered the horse version of asthma and is similar to that condition of which humans suffer in that it is comprised of both allergic and inflammatory elements. This disease is found in both males and females and usually in equines who are over 9 years old. Exacerbation of symptoms for the barn-associated type seems to occur in winter and summer, while symptoms for the pasture associated type are generally more prevalent in summer and early fall. Here are some of the irritants which cause RAO:
- Mold, organic dust and endotoxins found in hay and straw - Endotoxins are toxins inside individual cells (also called intracellular toxins)
- The same irritants can be found in fodder found in pastures during the summer and early fall months
- Exacerbation of causes occurs when the heat and humidity increases
Some of the things which might be causing RAO, of either type, in your horse seem to be related to hay and straw, though there is some support to a hereditary component. It has been found that if both parents are healthy horses, the rate of RAO occurrence is about 10 percent, while that percentage goes up to about 44 percent if both parents are also affected.
Diagnosis of Recurrent Airway Obstruction (Heaves) in Horses
The majority of the time, your veterinarian will likely be able to diagnose this condition in your equine by your history and his evaluation. However, there may be times in which he may wish to utilize some specific testing to confirm his assessment. The additional testing might include:
- Endoscopy of the trachea and airway
- Bronchoalveolar lavage
- Testing of lung function
- Thoracic radiographs
- Ultrasound examination of the tissues
- Cytology to look for abnormal white blood cell counts to indicate inflammation presence
The purpose of the radiographs (x-rays) will definitely be needed for any equine who doesn’t appear to be responding positively to the treatment plan developed by your veterinary professional. They may also be needed to distinguish inflammation in the lungs of the equine. Your vet will determine the stage of severity of the disease by the types of inflammatory cells, if any, which are found in the airway fluids.
While samples of the airway fluids can be collected directly from the windpipe, the more reliable samples will be obtained via the bronchoalveolar lavage (BAL) as they will be less likely to have originated in other parts of the airway than in the segment being sampled. There are differences in the sampling locations between the tracheal aspirations and the BAL and those differences are not interchangeable when cytological evaluation and interpretation is done.
Treatment of Recurrent Airway Obstruction (Heaves) in Horses
The main element in the treatment plan will be to reduce the equine’s exposure to mold, dust and endotoxins. There will likely be a period of trial and error in which you will be involved with trying some of the suggestions listed below to see which ones work best for your horse.
- Keeping the equine in the pasture is one of the best options for reducing dust and mold exposure in the barn-associated RAO, feeding fresh grasses with supplements of feed pellets
- Since the organic dust and mold come from the hay and straw which are commonly fed and used for bedding, switching from round bale hay and straw would likely benefit since this method of baling holds more of the allergens
- Keeping the stalls cleaned and as free of dust as possible; this might mean changing the bedding from straw and sawdust to perhaps wood chips, rubber matting or newspaper
- Remove the equine from the barn when cleaning his stall to reduce exposure to the allergens during the cleaning process
- Stable and stall ventilation (evaluation of the environment may reveal insufficient ventilation for the stalled equine)
- If you have an equine who has been found to be sensitive to these airborne irritants, do not keep them near roads which are dry and dusty or near paddocks
- For those horses who are found to have pasture-associated RAO, avoid pasturing them except in the winter
It is important to note that this condition cannot be cured and will remain a lifelong condition however, it must also be noted that mild to moderate degrees of recurrent airway obstruction can be managed successfully with environmental and dietary changes alone. If your horse is moderate to severely affected, you may need to completely remove him from hay as a food source and replace it with pelleted nutrition in addition to the environmental changes noted above. Any medications recommended by your veterinary professional will not provide long term benefits. Severely affected animals will suffer from lung and respiratory damage for the rest of their lives.
Recovery of Recurrent Airway Obstruction (Heaves) in Horses
This is a lifelong condition for your horse. If the condition is severe, there may be some limitations to what he can do in regard to exercise, work and racing performance but he may still be useful as a pleasure horse. For those horses who are suffering from mild to moderate conditions, the potential for them to return to very near full measures of usefulness is very good. If you are a dedicated owner who is attentive to detail and committed to doing what is necessary, changing the environment and dietary regimens of your equine for the rest of his life, your horse may be able to recover and return to his previous routines even though he will never be cured of the condition. You, as the owner, have a great deal of control over the prognosis of your equine by exercising strict compliance with the environmental and dietary recommendations of your veterinary professional.