Background

Tetanus is a neurological disease characterized by spastic paralysis, caused by tetanospasmin, a neurotoxin of the anaerobic spore-forming bacillus Clostridium tetani. Tetanus rarely occurs in cats, especially in the generalized form, due to their innate resistance.

Case Presentation

A four-year-old, male, neutered, domestic short-haired cat with outdoor access was presented with an abdominal injury and a progressive walking difficulty due to a severe extensor rigidity of all limbs. The cat was diagnosed with tetanus and was administered antibiotic (metronidazole 10 mg/kg every 8 hours intravenously), antiemetics (maropitant 1 mg/kg, metoclopramide 0.04 mg/kg/h intravenously) and analgesic (methadone 0.2 mg/kg every four hours intramuscularly). To provide sedation and muscle relaxation, midazolam was intravenously infused at 0.2±0.1 mg/kg/h, together with magnesium sulphate that was intravenously administered by initial bolus of 70 mg/kg over 30 minutes, followed by constant rate infusion at 10 mg/kg/h. Blood tests were repeated every 12 hours to measure serum magnesium (target range of 2–4 mmol/L) and calcium concentrations to check for development of hypocalcemia in response to hypermagnesemia. During hospitalization symptoms worsened: the cat had hypersensitivity to noise stimuli accompanied with tetanic seizures, hyperthermia and autonomic dysfunction presenting as severe hypertension, sinus tachycardia and, occasionally, ventricular tachycardia. Phenobarbital was added to therapy (2 mg/kg every 12 hours), but it was discontinued due to the development of immune-mediated hemolytic anemia. A dexmedetomidine infusion (1±0.5 µg/kg/h) was started and the dose was adjusted according to the patient’s response. Dexmedetomidine improved hemodynamic stability without adverse reactions and its administration was stopped after 96 hours. Magnesium infusion was continued for six more days and no side-effects were observed. The cat gradually improved and it was discharged on day 28.

New/Unique Information

This case illustrates, for the first time, the successful treatment of generalized tetanus in a cat by ancillary use of supraphysiologic doses of magnesium and dexmedetomidine. Infusion of dexmedetomidine provided anxiolysis, myorelaxation and control of autonomic dysfunction.

E-mail: marzia.moretti@sanmarcovet.it