Evaluation of Tetanus in Dogs

In the Literature

Dörfelt S, Mayer C, Wolf G, et al. Retrospective study of tetanus in 18 dogs-causes, management, complications, and immunological status. Front Vet Sci. 2023;10:1249833. doi:10.3389/fvets.2023.1249833

The Research …

Tetanus is a mammalian disease in which toxin from Clostridium tetani irreversibly binds to peripheral nerve endings, migrates retrograde to the CNS, and interferes with inhibitory interneurons, resulting in sustained skeletal muscle contraction and occasionally causing autonomic and other CNS signs (eg, rapid eye movement [REM] sleep behavior disorder, seizures). Treatment involves eliminating the infection, possible antitoxin therapy to neutralize unbound toxin, and supportive care until presynaptic components are regenerated. Reported mortality rates in dogs are variable and have been as high as 50%.^1,2

In this retrospective study, records of dogs (n = 18) treated for tetanus were evaluated regarding cause, course, treatment, complications, outcome, and antibody production after natural disease and subsequent vaccination. Nails, footpads, and digits were the most frequent sites of infection (14/18), and 6 of 12 dogs that underwent radiography had concurrent osteomyelitis. Median time from injury to first clinical sign was 6 days (range, 1-27 days). C tetani was successfully cultured in only 1 of 8 dogs and could not be ruled out in a second dog.

A majority of dogs were presented with tetanus grade II, which included miosis, strabismus, enophthalmos, risus sardonicus, erect ears, hypersensitivity to noise, dysphagia, and a stiff gait. In 10 dogs, clinical signs worsened within 5 days after presentation. Autonomic signs, including bradycardia, tachycardia, ventricular arrhythmia, and severe hypertension, developed in 6 dogs. In 13 dogs, REM sleep behavior disorder (abnormal movements and vocalization during sleep) was noted and took weeks to months to resolve.

Amputation of the affected digit was performed in 9 dogs. General nursing care of all affected dogs included limiting stimuli and providing bladder care. Medications included metronidazole with or without additional antibiotic therapy for complicating infections, methocarbamol, and sedatives as needed. Percutaneous endoscopic gastrotomy tubes were placed in 15 dogs due to dysphagia. Equine serum tetanus antitoxin was administered to 13 dogs following a test dose; no dogs had a hypersensitivity reaction. Two dogs that did not receive the antitoxin died; the remaining 16 dogs survived (survival rate, 88.9%).

Median hospitalization length of dogs that survived was 8 days (range, 0-26 days). Higher maximum tetanus grade was associated with significantly longer hospitalization. Respiratory complications did not affect outcome but necessitated more intensive care. Time to first sign of improvement ranged from 4 to 15 days.

… The Takeaways

Key pearls to put into practice:

• Infections resulting in clinical tetanus most commonly occur in the digits. Close examination and radiography should be performed in suspected cases.

• Although reported survival rates in dogs are variable, intensive supportive care can increase the likelihood of survival. Pet owners should be educated that clinical signs commonly worsen over the first 5 days after presentation and recommendations made as appropriate.

• Autonomic dysfunction associated with tetanus may be underreported in dogs due to inadequate monitoring. Continuous ECG and blood pressure monitoring are advised.

• REM sleep behavior disorder is common in dogs with tetanus and may persist for months following recovery. Although episodes appear similar to seizures, they can generally be interrupted by waking the patient. Variable success has been reported with potassium bromide, tricyclic antidepressants, and melatonin (anecdotal).³

• Vaccination can trigger an antibody response that may not occur following natural infection; however, generalized tetanus is rare, and recurrence has not been reported.