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RAO D I AGNOS I S
How do you treat a
horse with RAO?
As always prevention is better than cure. In
fact this is a condition for which there is no
cure, once a horse has developed signs they
are more likely to have another attack (the
clue is in the name - RECURRENT airway
obstruction). It is not something horses
grow out of, rather, RAO tends to get worse
with age.
The most important treatment for affected
horses is environmental management to
reduce their exposure to dust and allergens.
Additional treatments used include clenbuterol
which is given in feed and can help widen
the airways by relaxing the smooth muscle
around the bronchioles (airways) making it
easier for the horse to breathe. Steroid
anti-inflammatories are very effective in the
management of severe and long term cases,
these may be given by mouth in tablet form,
by injection (especially if the horse is having
a bad attack) or by inhaler, in the same way
that human asthmatics medicate themselves.
A variety of equine inhaler spacer masks are
available to use with the multi-dose inhalers.
Although the presenting sign in horses is a
cough, the use of cough medicines is of
little benefit.
Well controlled and with proper treatment
many horses can return to work at the levels
they did previously, but exposure to the
allergens (e.g. dusty hay) for even a short
period of time can cause a relapse.
Figure 1
- A section of lung showing the small
airways that become narrowed in RAO
Figure 2
- Endoscopy: a small flexible camera
is inserted into the windpipe
How do vets diagnose
RAO?
To help your vet in their diagnosis they will
ask questions about the signs your horse
is showing and how he is kept. They will
examine the horse and listen to his chest,
at rest and perhaps after exercise or using
a rebreathing bag to exaggerate lung
sounds. Sometimes the vet will want to
use an endoscope (flexible camera) to
look down the horse’s airways or take
samples of the lung secretions by flushing
sterile saline into the airway and then
sucking it straight back out. This is called
a tracheal wash or bronchoalveolar
lavage (BAL) depending on the technique
used. The samples obtained are
examined under the microscope to look
for certain cells characteristically found in
horses suffering from RAO.
TOP TIPS...
for management of
horses with RAO:
●
if stabled make sure the horse can put
his head out over a stable door or
window to the outside and fresh air;
●
ensure stables are well ventilated
(cobwebs mean there is not enough
air movement); leave top doors and
windows open; clean out and disinfect
stables regularly to prevent the build-up
of dust;
●
if a horse must be stabled FOR ANY
PERIOD OF TIME, do not bed on
straw or sawdust; suitable beddings
are dust-free shavings, shredded paper
or other baled dust-free beddings;
don’t deep litter beds; make sure that
horses in the next stable or the same
air space are also on dust free beds;
●
do not stable horses with heaves next
to hay or straw stores or dusty arenas;
●
feed dust-free forage - haylage,
pelleted feeds or very good quality
hay with no visible dust or mould that
has been soaked in water for at least
15 minutes before feeding; change
the water used for soaking hay daily;
●
feed soaked hay from the ground,
do not use hay nets or elevated hay
racks; this will reduce the level of
dust in the air.
if at all possible have your horse
living out all the time;
A recent paper was presented at the
British Equine Veterinary Association
Congress in Birmingham in September
2012 describing a complicated genetic
basis for the inheritance of RAO. One
of the genes implicated is the same as
the gene associated with asthma and
allergic skin disease in humans. Although
susceptibility to the disease appears to
be inherited, it is not down to one single
gene and so it is unlikely that a single test
for the disease will be developed.
Furthermore, families of RAO affected
horses were shown to have an increased
susceptibility to developing insect bite
hypersensitivity and urticaria or hives,
again an allergic reaction. However these
same horses seemed to have an increased
resistance to worms, in that they shed
far fewer worm eggs in their droppings
compared with unrelated horses on the
same pasture.
Is RAO inherited?
Figure 3
- Improving ventilation is key to the
management of stabled RAO sufferers
AUTUMN 2012 ISSUE
EQUINE MATTERS
18