EQUINE | CPD Article
tetracycline,
macrolides
and
metronidazole 8 .
Procaine penicillin is the drug of choice and should
be administered at 22 000 – 44 000 IU/kg IM q 12
hr for 7 -10 days 9 with the addition of metronidazole
indicated for deep and contaminated wounds 8 . Local
infiltration of penicillin, with the optional addition of
3000 – 9000 IU tetanus antitoxin, into the wound may
further neutralize unbound toxin at the site 5 .
Appropriate wound care is very important. Aggressive
debriding, copious flushing and aerating the wound
will further reduce toxin production 10 and thus assist
in limiting the severity of clinical signs 4 . Hoof abscess
should be opened and poulticed daily.
Acetyl promazine is to be administered at 0.01 mg/
kg IM q 8 -12hr as a muscle relaxant and sedative.
Sedation should help reduce the intense reflex
response to sudden movement and noise 12 that often
results in violent spasms. Phenobarbital administered
initially at 6-12 mg/kg slow IV followed by 6-12mg/kg
PO q12h alone or in combination with acepromazine
can also be used 5 in more severely affected horses.
Haloperidol 0.01mg/kg IM every 7 days can be used
as a longer acting sedative 5 .
Intravenous fluids will be required for horses that have
lockjaw and are unable to eat or drink. Excellent
supportive nursing 9 is very important during the acute
period of spasms and the horse should be placed in a
deep bedded, dark stable with water and food points
high enough for the horse to access without lowering
its head 12 if the horse has not developed lockjaw. Ear
plugs will assist in minimising any auditory stimulus 5 .
Nursing care will need to be adjusted to each
individual case as affected animals often develop
different complications depending on the severity of
the disease and therefore urinary catheterization, daily
manual rectal evacuation, slinging of horses that have
difficulty in standing or frequent turning of recumbent
38
horses may be needed 12 . The placement of an in-
dwelling nasogastric tube for horses with dysphagia 1,5
can be considered as this will allow for feeding and
on-going fluid administration.
Treatment is challenging as clinical signs may persist
for weeks with many affected horses only showing
improvement after 2 weeks of on-going treatment 5 and
care. The cost and duration of this intensive supportive
care, treatment and the availability of appropriate
treatment must also be carefully considered 4 as
recovery is generally only 6 – 8 weeks after the onset
of clinical signs.
The initial clinical examination will allow for the
identification of the prognostic indicators4; the
presence of dysphagia, a recumbent patient and the
rapid progression of clinical signs over 24 hours are
all grave signs 9 . The horse’s immunity, vaccination
status and the Clostridial dose will also impact on
the prognosis 4 . The mortality rate is high 50 – 80% 9
and most complications are so severe that they often
result in humane euthanasia. Hoof sole punctures may
have the poorest outcome 9 although this is debated as
some studies have shown that the wound’s location
does not affect the survival rate 4 . Clients must be made
aware of the poor prognosis and high costs involved in
attempting treatment of an affected horse.
There is wide debate regarding the use of Tetanus
Anti-Toxin (TAT). The dose and administration ranges
from 5 000 – 200 000 IU and can be administered
IV, IM, SC or intrathecally 4,6,7,9 . TAT neutralizes the
circulating toxin 7 outside of the Central Nervous
System as it does not cross the Blood Brain Barrier 6 .
Intrathecal administration in humans is recommended
as it concentrates TAT in the CSF at the nerve roots 3 .
However, equine intrathecal administration is poorly
investigated and the dosage, administration site,
possible concurrent corticosteroid use and possible
• Equine Health Update •