Page 695 - The Veterinary Care of the Horse

to breathe in enough of the drug. Dexamethasone and prednisolone are commonly used.

Once the symptoms are controlled, inhaled medication is preferable as there is less risk of
VetBooks.ir side effects which include laminitis, Cushings-type signs and suppression of the immune
system. Immunosuppression increases the risk of the horse succumbing to bacterial infection.

The inhaled corticosteroids include beclomethasone dipropionate and fluticasone propionate.
A number of systems for delivering the drug are now available (Figure 15.18).

OTHER MEDICATION

Disodium cromoglycate is sometimes used as a prophylactic treatment to prevent the
disease occurring when a horse that is known to be susceptible to RAO is unavoidably

exposed to allergens. It is administered by nebulization. The response to this treatment is not
consistent. It appears to work for some horses but not for others. This medication is not
effective in horses already showing clinical signs.

Mucolytics are drugs that help to break up the mucus so it is more easily cleared from the

airways. The efficacy of these drugs in horses has not been proved.
Antibiotics are rarely necessary as secondary bacterial infection is uncommon.

Prognosis

If managed correctly, the changes in the lungs are reversible. However, once a horse or pony

has been sensitized, the symptoms will recur if it is exposed to environmental allergens. The
airways also become hyper-responsive to other irritants in the atmosphere such as noxious
gases. The condition tends to become worse with age and causes reduced exercise tolerance.

The prognosis is therefore guarded.

SUMMER PASTURE ASSOCIATED OBSTRUCTIVE

PULMONARY DISEASE (SPAOPD)

A number of horses and ponies develop the signs of recurrent airway obstruction (RAO)
while out at grass with no exposure to hay and straw. The condition tends to occur between

the spring and early autumn months, with complete remission of symptoms during the winter,
and is known as summer pasture associated obstructive pulmonary disease (SPAOPD). A

number of affected animals also have RAO so they experience respiratory problems all year
round. Once affected, the symptoms tend to recur in subsequent years. The incidence of

SPAOPD increases with age.