Tetanus

From Dog
A 10-week-old, intact female, yellow Labrador retriever with generalized tetanus exhibiting extended limbs, a swollen face, and a wrinkled forehead[1]

Tetanus is a neurotoxic state caused by Clostridium tetani bacterial septicemia and occurs in dogs worldwide.

This disease is caused by the action of the neurotoxin tetanospasmin, produced during the vegetative growth phase of Clostridium tetani. Other toxins, like tetanolepsin, are also produced, but are clinically insignificant[2].

Tetanus in dogs is reported with a greater frequency than that observed with cats (factor of 10) but less than horses (factor of 600)[3]. Exotoxins are produced locally at the site of the wound and disseminate systemically over time.

Tetanus is usually initiated by a deep penetrating bite or stab wounds which facilitate anaerobic growth of this bacteria, but has been reported from dogs with penetrating oral wounds from eating sharp objects such as bones or wood, surgical sites, puncture wounds, tick bites, and teething[4].

Clinically affected dogs present 3 - 7 days post infection with initial signs referable to neurotoxicity[5], such as ocular or facial abnormalities.

Young, large-breed dogs are more commonly affected[6] and present with localized stiffness, often involving the masseter muscles and muscles of the neck resulting in the pathognomonic 'sardonic smile' and locked jaw syndrome[7] which are characteristic of the disease. Hyperesthesia and seizures are observed in advanced cases, and death is by asphyxiation due to respiratory paralysis[8].

Complications are common and include pressure sores, hyperthermia, and dysuria. Less common complications include transient megaesophagus and hiatal hernia associated with gastroesophageal reflux, aspiration pneumonia, fractures, and laryngeal spasm[9]. A significant inverse relationship exists between development of severe clinical signs and survival, with dogs that show only minor initial signs such as cardiac abnormalities on ECG or hypertension often resulting in euthanasia due to complications[10].

Diagnosis is based on presenting clinical signs of muscle tremors and rigidity, bacterial culture from wounds and isolation of tetanus toxoid in serum samples.

Treatment usually consists of wound debridement and treatment with metronidazole, sodium ampicillin (25 mg/kg IV every 8 hours), diazepam (0.5 mg/kg IV as needed) and tetanus immunoglobulin (300,000 IU tetanus antitoxin IV, bid).

A combination of chlorpromazine and phenobarbital or diazepam may be used to reduce hyperesthetic reactions, convulsions and aspiration pneumonia[11].

Intravenous fluid therapy, airway management via tracheostomy (if required), and nursing care are important for recovery. Hyperthermia due to convulsions is common and must be addressed to prevent shock[12].

Most patients recover within 4 weeks if treated aggressively.

Preventative measures are difficult, but tetanus toxoid, given yearly, especially in working dogs, may limit outbreaks.

References

  1. Sprott KR (2008) Generalized tetanus in a Labrador retriever. Can Vet J 49(12):1221-1223
  2. DeRisio L et al (2006) Focal canine tetanus: Diagnostic value of electromyography. J Small Anim Pract 47:278–280
  3. Acke E et al (2004) Tetanus in the dog: Review and a case-report of concurrent tetanus with hiatal hernia. Irish Vet J 57:593–597
  4. Greene CE (2006) Tetanus. In: Greene CE, editor. Infectious Diseases of the Dog and Cat. 3. St. Louis, Missouri: Saunders Elsevier. pp:395–402
  5. Burkitt JM et al (2007) Risk factors associated with outcome in dogs with tetanus: 38 cases (1987–2005). J Am Vet Med Assoc 230:76–83
  6. Bandt C et al (2007) Retrospective study of tetanus in 20 dogs: 1988-2004. J Am Anim Hosp Assoc 43(3):143-148
  7. Gatineau M et al (2008) Locked jaw syndrome in dogs and cats: 37 cases (1998-2005). J Vet Dent 25(1):16-22
  8. de Vries BR (1990) A case of tetanus in a dog. Tijdschr Diergeneeskd 115(15-16):749
  9. Dieringer TM & Wolf AM (1991) Esophageal hiatal hernia and megaesophagus complicating tetanus in two dogs. J Am Vet Med Assoc 199(1):87-89
  10. Burkitt JM et al (2007) Risk factors associated with outcome in dogs with tetanus: 38 cases (1987-2005). J Am Vet Med Assoc 230(1):76-83
  11. Adamantos S & Boag A (2007) Thirteen cases of tetanus in dogs. Vet Rec 161(9):298-302
  12. Simmonds EE et al (2011) Magnesium sulfate as an adjunct therapy in the management of severe generalized tetanus in a dog. J Vet Emerg Crit Care (San Antonio) 21(5):542-546