Tetanus

From Cat
Young adult Domestic shorthair cat with tetanus following a puncture wound penetrating the skull. The cat made a full recovery after treatment
Localised tetanus that affects the left thoracic limb. Note the elbow is extended rigidly, whereas the carpus is flexed
Localised tetanus involving the pelvic limb. The toes are extended such that the cat cannot place the palmar surface of its paw on the benchtop

Clostridium spp infection in cats are relatively rare.

Clostridium tetani is the causative agent of tetanus. The organism is found in soil, especially heavily-manured soils, and in the intestinal tracts and feces of various animals. Carrier rates in humans vary from 0 to 25%, and the organism is thought to be a transient member of the flora whose presence depends upon ingestion. The organism produces terminal spores within a swollen sporangium giving it a distinctive drumstick appearance. Although the bacterium has a typical Gram-positive cell wall, it may stain Gram-negative or Gram-variable, especially in older cells.

Tetanus is a common disease of humans and dogs but rare in cats, due to their innate resistance to the clostridium toxin. Mortality rates in humans reported vary from 40% to 78%. The disease stems not from invasive infection but from a potent neurotoxin (tetanus toxin or tetanospasmin) produced when spores germinate and vegetative cells grow after gaining access to wounds. The organism multiplies locally and symptoms appear remote from the infection site[1].

Most cases of tetanus result from small puncture wounds or lacerations which become contaminated with C. tetani spores that germinate and produce toxin. The infection remains localized, often with only minimal inflammatory damage. The toxin is produced during cell growth, sporulation and lysis. It migrates along neural paths from a local wound to sites of action in the central nervous system.

Clinical signs

Clinical diagnosis may not be obvious in the early stages of the disease when characteristic signs of generalised tetanus are absent. However, the history of a penetrating/neglected wound and the presence of persistent involuntary muscle rigidity in a mentally alert animal should always lead to the suspicion of tetanus. Prompt diagnosis and treatment are the keys to a successful outcome[2]. See video of clinical case

Clinical signs may be seen between two days and three weeks after injury[3]. The bacteriologic examination of serous fluid from the site of injury usually reveals an infection with Clostridium. EMG in one cat during anaesthesia showed motor united potentials (MUPs) on the spastic leg. All patients received antibiotics (Penicillin, Amoxicillin/Clavulanic acid and Metronidazole). Supportive aid were initially sedation, wound revision and in one cat nutrition through oesophageal sonde. In a second phase physiotherapy was performed. All three animals were significantly better after a couple of weeks, two cats were without symptoms after eight and five weeks respectively[4].

The clinical pattern of generalized tetanus consists of severe painful spasms and rigidity of the voluntary muscles. The characteristic symptom of "lockjaw" involves spasms of the masseter muscle. It is an early symptom which is followed by progressive rigidity and violent spasms of the trunk and limb muscles. Myopathy is a common presentation. Spasms of the pharyngeal muscles cause difficulty in swallowing. Death usually results from interference with the mechanics of respiration. Wrinkling of the forehead and mild trismus (inability to open the mouth) were also seen. The routine diagnostic workup (CBC, survey radiographs of the spine, CSF analysis) did not reveal any abnormalities in both cats. EMG testing on the affected muscles often shows persistent spontaneous motor unit potentials, strongly indicating tetanus.

Diagnosis

In most cases, a strong tentative diagnosis can be made from clinical signs and history.. Extreme spasticity localised to one limb subsequent to penetrating trauma is sufficiently distinctive to diagnose localised tetanus confidently. Most cases of tetanus are recognised after initial localised tetany, whereas the clinical stigmata of trismus (lockjaw), risus sardonicus (facial spasm) and nictitans prolapse are typical of this condition.

Definitive diagnosis can be made by isolating C. tetani from an infected focus, although neurological signs may not occur until after the initiating wounds have healed[5].

Treatment

The prognosis for localised tetanus is uniformly good, and approximately two-thirds of cats reported with generalised tetanus have survived. Clinical signs typical resolve within 2-3 months[6].

Treatment is usually symptomatic, with muscle relaxants (diazepam) and broad-spectrum antimicrobials (penicillin-based drugs plus metronidazole) and supportive (physical therapy, assist feeding and intravenous fluid therapy[7]. The judicious use of tetanus antitoxin is also a consideration in early cases, as the antitoxin is ineffective when the tetanus toxin has already enetered the nervous system. Many cats survive without receiving antitoxin supplements[8].

References

  1. Textbook of Bacteriology
  2. De Risio L, Gelati A (2003) Tetanus in the cat - an unusual presentation. J Feline Med Surg 5(4):237-40
  3. Mansfield, P, Wilt, G & Powers, R (1984) Clostridial myositis associated with an intrathoracic abscess in a cat. J Am Vet Med Assoc 184:1150
  4. Tomek A, Kathmann I, Faissler D, Cizinauskas S, Timmann D, Reimer Y, Moser J, Jaggy A. (2004) Tetanus in cats: 3 case descriptions. Schweiz Arch Tierheilkd 146(6):295-302
  5. August, JR (2006) Consultations in feline internal medicine. Vol 5. Elsevier Saunders
  6. Killingworth, C et al (1977) Feline tetanus. J Am Anim Hosp Assoc 13:209
  7. Polizopoulou ZS, Kazakos G, Georgiadis G, Soubasis N, Koutinas Ch, Koutinas AF. (2002) Presumed localized tetanus in two cats. J Feline Med Surg 4(4):209-12
  8. Lee, EA & Jones, BR (1996) Localised tetanus in two cats after ovariohysterectomy. N Z Vet J 44:105