Initially, the owner may notice some increased muscle stiffness followed by muscle tremors. This stiffness may be noted when the horse is walking or trotting, and the tail may be held out stiffly. Following these classic tetanus signs, the horse will appear anxious, with ears pricked forward and nostrils flared. As the disease progresses, chewing becomes more difficult and drooling is evident. Some horses will fall and their legs will remain rigid and extended.
Horses generally die from asphyxiation, which results from paralysis of respiratory muscles.
The typical course of the disease is five to 10 days from the onset of clinical signs, although some horses may appear only mildly affected and signs will persist for weeks. The prognosis for horses with tetanus is always guarded, and, if untreated, the prognosis is grave. Prevention is the key to tetanus control. Tetanus vaccine is one of the most effective and inexpensive equine vaccines available, and owners are strongly encouraged to vaccinate all of their horses. Mares should receive a tetanus toxoid booster one month prior to foaling to ensure good quality colostrum for the newborn foal.