Horse Side Vet Guide ®

Equine Health Resource


Synonyms: Lockjaw

Tetanus is caused by Clostridium tetani, a bacterium that resides in the soil. The organism lives in anaerobic environments (environments with no oxygen). It gains access to the horse’s system by colonizing an infected wound, especially deep and infected puncture wounds. There it produces an extremely potent toxin which affects specific (inhibitory) nerve endings in the spinal cord, causing constant muscle contraction of the main muscle groups.

Affected horses generally (not always) have a history of a wound. Their limbs appear stiff, their third eyelids cover their eyes. Their ears are typically erect, tails raised and nostrils flared. They rapidly reach a point where they cannot rise, and they lie on their side, with their limbs rigid.

Tetanus is well known for causing what appear to be seizures, brought on by loud noises. Beyond this classic appearance of affected horses, there are no diagnostic tests to confirm a diagnosis.

Vets “back into a diagnosis” of tetanus by ruling out other causes and by knowing that the horse has not been vaccinated for it. Horses with the third eyelid covering the eyes are tetanus cases until proven otherwise.

Treatment involves supportive nursing care, antibiotics, local wound care, and tetanus antitoxin. In some cases, vaccination may also be performed in the face of disease, but this is case dependent and depends on vaccination status.

I Might ObserveRelated Observations

Rigid, Stiff Limbs or Legs
Sick Horse Hyper-Reactive to Loud Sound or Sudden Movement
Cannot Chew, Chewing Abnormally
Puncture Wound, Anywhere on Body
Pink Membrane of Third Eyelid is Covering Eye(s)
Rigid, Stiff Limbs or Legs
Cannot Swallow, Difficulty Swallowing
Not Eating, Loss of Appetite, Not Hungry
Stiff Neck or Back, Resists Lateral Bending
Slobbering, Drooling or Salivating
Difficulty Breathing, Struggles for Breath
Agitated, Anxious, Nervous or Stressed
Wound to Lower Neck
Lying Down & Paddling
Gunshot Wound Suspected
Penetrating Nail or other Object in Sole, Hoof or Frog
Wound to Upper Limb or Leg, Generally
Saw-Horse Stance, Hind Limbs Under & Front Limbs Forward
Fever, Rectal Temperature Greater than 101.5 (in Adult)
Wound to Head or Face
Wound to Cheek with Drainage or Swelling & Odor
Hypersensitive to Touch, Generally
Wound, Open Sore Caused by Pressure from Bandage or Cast
Sweating Excessively
Wound to Muzzle, Nose or Nostril
Wound to Ear
Wound to Chest
Wound to Face or Head with Obvious Broken Bone, Fracture Involved
Wound to Body, Neck or Back
Wound to Front of Lower Limb or Leg
Wound is Growing, Getting Larger
Wound to Limb near Joint or Tendon Sheath
Wound to Back of Lower Limb or Leg
Wound to Lower Limb or Leg, Generally
Wound to Back
Wound to Armpit or Groin
Wound or Puncture Smells
Wound is Very Slow Healing or Not Healing
Wound to Coronary Band, Hairline of Hoof
Snakebite, Witnessed or Presumed
Wound to Lip or Mouth
Wound to Hoof Wall, Piece is Pulled or Torn Off
Dropping Chewed Feed or Hay Balls, Quidding
Abrasion or Scrape on Upper Limb or Leg
Abrasion or Scrape on Lower Limb or Leg
Wound or Cut to Tongue
Abrasion or Scrape on Head or Face
Wound at or near Hock
Irritability, Moodiness, or Aggression Toward People
Eye is Making Abnormal Rapid & Jerky Movements
Wound at or near Carpus (Knee)
Eye Appears Wounded or Cut
Eyelid is Wounded or Cut
Intestine Hanging Out through Wound or Incision
Eye has Splinter or Stick Near or Penetrating Eye Itself


  • What vaccination program should my remaining horses be on?

    Vaccination is the single step that is necessary for protection. It is simple and effective. Vaccination should be performed annually, although protection MAY last longer. Tetanus vaccine is recommended as one of the "core" vaccines by the American Association of Equine Practitioners (AAEP).

    If a wound occurs, be sure to discuss with your vet, especially if your horse has not been vaccinated. Deep wounds and those on the lower limbs are more likely to become infected. When in doubt, talk to your vet about any puncture wound sustained by your horse.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Helpful Outside ResourcesCredible Equine Health Information on the Internet

    Author: Doug Thal DVM Dipl. ABVP


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