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964 Tetanus

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the neuronal cell body in the spinal cord
BASIC INFORMATION
esophagus with or without aspiration pneu-
or brainstem. • Thoracic and abdominal imaging: mega-
Definition • Tetanospasmin blocks inhibitory monia possible; abdominal effusion possible
Tetanus is an infectious disease caused by a neurotransmitter release (glycine, gamma- if source of C. tetani is septic peritonitis
potent neurotoxin produced by the bacterium aminobutyric acid [GABA]), facilitating (metritis, enteritis, ruptured abscess)
Clostridium tetani, resulting in a sustained tonic muscle contraction. • Muscle biopsy: usually unremarkable
contraction of the muscles. • Tetanospasmin’s binding to presynaptic sites • Serum antibody titers to tetanus toxin may
of inhibitory neurons is irreversible; recovery support the diagnosis (compared with control
Synonym depends on sprouting of new axon terminals. animals).
Lockjaw • Signs occur within 5-10 days of injury but • Attempts at isolation of C. tetani from
can be delayed up to 3 weeks. wounds are unrewarding.
Epidemiology • Wounds close to the head are associated with
SPECIES, AGE, SEX a more rapid onset of signs than those in Advanced or Confirmatory Testing
All domestic animals are susceptible; cats are the extremities. No specific confirmatory test
more resistant than dogs.
DIAGNOSIS TREATMENT
RISK FACTORS
Open wounds; exposure to organism in feces Diagnostic Overview Treatment Overview
or in the environment Tetanus is diagnosed based on clinical signs and Treatment is mostly supportive and can be
history of a recent wound; there is no practi- protracted: resolution of clinical signs can take
GEOGRAPHY AND SEASONALITY cal clinical confirmatory test. The source of days to weeks, depending on form (generalized
Ubiquitous in the environment; no seasonality infection or wounds is not always immediately or localized) and individual response (see Video).
apparent.
Clinical Presentation Acute General Treatment
DISEASE FORMS/SUBTYPES Differential Diagnosis • As much as possible, keep the animal in
Focal versus generalized depends on inoculation Hypocalcemic tetany a quiet, soundproof area with minimal
site; the generalized form is more common. stimulation.
Initial Database • Wound debridement and resection of
HISTORY, CHIEF COMPLAINT The following test results can be seen, but none necrotic tissue; wounds are left open (avoid
• Cutaneous/soft-tissue wound: cut, puncture, is required for a diagnosis of tetanus: anaerobic conditions).
surgical (e.g., ovariohysterectomy) • CBC: leukocytosis (neutrophilia with left • Antitoxin: equine antitetanus serum (ATS)
• Progressively worsening gait stiffness shift) is given IM or IV or human tetanus
• Serum biochemistry profile: elevated serum immunoglobulin (TIG) given IM. Equine
PHYSICAL EXAM FINDINGS creatine phosphokinase (CPK) ATS:
• Extreme sensitivity to tactile and auditory • Cerebrospinal fluid (CSF) analysis: ○ Give the initial test dose 0.1-0.2 mL SQ or
stimulation: mildly to extremely exaggerated unremarkable ID 15-30 minutes before IV administra-
reaction to sound or touch • Electrocardiogram (ECG): tachyarrhythmias tion; monitor for anaphylaxis.
• Characteristic facial expression due to facial or bradyarrhythmias (atrioventricular [AV] ○ If no anaphylaxis, therapeutic dose is
muscle spasm: ears held erect, forehead block, sinus arrest) possible 2.5-25 IU/kg IV; continue to monitor
wrinkled, lips drawn back (risus sardonicus)
• Trismus (teeth clenching)
• Protrusion of third eyelids, enophthalmos,
strabismus, hypersalivation, laryngeal spasm,
dysphagia
• Mild hyperthermia due to excessive muscular
activity
• Dyspnea, coughing possible from aspiration
pneumonia
• Progression to periodic generalized tonic
muscle contraction possible
• Autonomic storms: cardiac arrhythmias,
hypotension or hypertension
• Death can result from respiratory
compromise.
Etiology and Pathophysiology
• C. tetani typically enters the body through
wounds.
• A potent neurotoxin (tetanospasmin) is
formed in the patient’s body during vegeta-
tive growth of C. tetani. TETANUS Dog with tetanus secondary to ovariohysterectomy. Note the highly characteristic facial expression
• Tetanospasmin enters the neuromuscular with pinnae drawn far toward the dorsal midline, upper eyelids drawn dorsomedially giving an anxious appearance,
endplate of motor nerves and migrates to and canthi of lips drawn caudally, producing the sardonic grin.

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