Page 1102 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1077

VetBooks.ir Management might induce a more robust antibody response than
provoked by the natural challenge or provided by
The aims of treatment are to: inhibit TeNT produc-
tion; neutralise unbound TeNT; establish immunity;
publication of a large number of tetanus cases, 43%
provide supportive care; and aid muscular relaxation. administration of tetanus antiserum. In a recent
of clinical cases that were vaccinated with tetanus
Inhibition of TeNT production toxoid at admission survived versus 12% of those
Local and parenteral antimicrobial therapy should that were not given tetanus toxoid (p = 0.08). Even
be initiated rapidly, to prevent further production among the non-survivors, those that were vaccinated
of TeNT by eradicating bacteria at the site of infec- at admission lived longer than those that were not
tion. Tetanus patients should be checked thoroughly vaccinated (p = 0.028). The authors of this study sug-
for wounds, which should be debrided and lavaged if gest that administration of tetanus toxoid to clini-
identified. There is some debate about the most appro- cal cases (a relatively cheap therapeutic option) may
priate antimicrobials to be administered to a tetanus have a positive impact on outcome.
patient. Historically, penicillin has been the drug of
choice for eliminating the vegetative form of C. tetani. Supportive care
However, studies have demonstrated that penicillin Clinical signs of tetanus are exacerbated by any
inhibits binding of the inhibitory neurotransmitter external stimuli, such as noise and bright lights.
GABA to the GABA receptor on inhibitory interneu- Therefore, a crucial aspect of the care of tetanus
rons, which may potentiate the anti-inhibitory effects patients is to ensure a quiet and darkened environ-
of TeNT on the motor neuron. Therefore, penicil- ment. Good footing, such as rubber matting and
lin is no longer the antimicrobial of choice for tetanus shavings, may help the horse to remain ambulatory.
in humans. Antimicrobials such as tetracyclines and The bedding should be deep and kept scrupulously
metronidazole are suitable alternatives as they inhibit clean and dry, to reduce the development of decubi-
protein synthesis and may, therefore, reduce TeNT tal ulcers if patients become recumbent. Hydration
production by C. tetani. status should be monitored and intravenous fluid
and electrolyte supplementation administered as
Passive immunisation required. Nutritional support should be considered
In theory, inactivating TeNT that has not bound for dysphagic horses, and parenteral administration
to the neuron should be a priority in tetanus cases. should be considered, because tetanus patients may
However, the effectiveness of administration of not tolerate nasogastric intubation.
tetanus antiserum (passive immunisation) in clini-
cal tetanus cases has been debated for many years. Muscular relaxation
Recent studies have reported: (1) no significant dif- A quiet environment will also promote muscular
ference when survival was compared between those relaxation. Drugs such as acepromazine, barbituates,
cases receiving tetanus antiserum and those that did alpha-2 agonists and benzodiazepines may also help to
not and (2) no clear survival advantage in patients relax the patient. A failure to respond to muscle relax-
that had received tetanus antiserum. Additionally, ants may indicate a poorer prognosis. The use of con-
intrathecal administration of tetanus antiserum has stant rate infusions of magnesium sulphate reduces
been described, but a clear advantage of this route the requirement for sedatives and muscular relaxants
of administration over subcutaneous or intravenous in human tetanus patients, but their value in horses
routes has not been demonstrated in horses. with tetanus has not been established at this time.

Active immunisation Prognosis
The concentration of TeNT required to induce neu- Binding of TeNT to neurons is irreversible, so
rological disease may be lower than that required to recovery depends on the production of new nerve
evoke a protective immune response. Vaccination terminals. The survival rate of clinical cases of teta-
with tetanus toxoid in the face of clinical disease nus vary from 25% to 41% as reported in recent