Sapphire is a 6 year old mare and one morning her owner noticed that she could not reach the ground with her head and was forced to bend her knees in order to graze. At first it was thought that she may have injured her neck, as it felt very rigid to the touch. After a few hours, she also started struggling to chew hay and feed and the third eyelid was very prominent in the corner of both eyes.
When walked, she had an odd, stiff gait and seemed to be “on tiptoes”. Her shoulder muscles were trembling and her tail was held in a noticeably raised position. Her nostrils were flared and her face had a taut expression.
When the vet tried to examine her mouth, the jaws were so tightly locked that it was impossible to force them open. Trying to open the mouth made Sapphire very agitated and the third eyelids would completely cover the eyes as a result of the eyeball being pulled back into the eye socket.
Protrusion of the third eyelid (arrow)
stiff neck and head muscles
Based on these symptoms a diagnosis of tetanus was made. Sapphire had never been vaccinated against tetanus.
Tetanus is caused by an organism called Clostridium tetani that is commonly present in the soil. In most cases, it is introduced into the tissues through wounds, particularly deep puncture wounds as they provide an ideal site for infection as the bacteria thrive in anaerobic (low oxygen) environments. Sometimes (as in Sapphire`s case), the point of entry cannot be found because the wound itself is difficult to detect.
Once introduced into the body, the bacteria produce a potent toxin that is then absorbed by the motor nerves in the area and travels up the nerve tract to the spinal cord. The toxin causes contractions of the muscles by interfering with the nerve endings. If more toxin is released at the site of the infection that then can’t be dealt with, the excess is carried off by the lymph to the bloodstream and distributed to other locations in the body, thereby spreading the disease.
The incubation period (between occurrence of wound and clinical signs) varies from one to several weeks but usually averages 10–14 days.
Horses are considered the most susceptible to Tetanus of all domestic animals.
If the disease progresses, animals can become recumbent due to extreme stiffness of the limb muscles and convulsions can occur (especially as a result of external stimuli such as noise, bright light or touch). Death occurs from complications of exhaustion; inability to eat, drink, pass droppings or urine; respiratory failure from respiratory muscle involvement or from musculoskeletal injuries (fractures while trying to get up).
Mortality rate is very high (50-75%) and treatment is only possible in early / mild cases but is prolonged, expensive and requires a lot of supportive care. Advanced cases require euthanasia to prevent a very painful death.
Sapphire`s owners were prepared to provide all the necessary supportive care and her welfare was not sufficiently compromised to necessitate immediate euthanasia. It was decided that it was preferable not to move Sapphire to a hospital facility in order to minimise the adverse effects of transport stress and unfamiliar surroundings on the condition. Intensive treatment was started at home straight away.
Sapphire received a high dose of tetanus antitoxin intravenously in order to neutralise any toxin still in the bloodstream and to halt progression of the disease. The antitoxin does not have any effect on the nerve terminals that are already affected by the tetanus toxin and growth of new nerve terminals is required for recovery, a process that may take weeks running into months.
She also received antibiotics (penicillin) twice daily to kill any tetanus bacteria that may still be present in the body, painkillers to relieve pain caused by constant muscle contractions and Acepromazine (Sedalin) to produce muscle relaxation and mild sedation.
It was important to keep Sapphire as quiet as possible, as she was over sensitive to noises and light and any stimulus could have triggered muscle spasms. The routine of her “yard companions” was changed so that she would have a friend staying with her at all times, she wore a fly mask if the days were too bright and care was taken to avoid unnecessary loud noises.
At the beginning of treatment, Sapphire`s jaw muscles were so contracted that she was unable to open her mouth to eat or drink anything, so her owners were instructed on how to administer rectal fluids every two hours.
Gradually, Sapphire`s muscles started relaxing and she became able to eat sloppy food (she particularly liked Veteran Vitality and Fast fibre!).
As she was still unable to reach the ground due to the stiffness of her neck and back muscles, her feed bowls were elevated so she could reach them comfortably.
After a few days, it was noticed that she would drink warm water, especially if mixed with small amounts of her soakable feed. The rectal fluids were gradually reduced over 2 weeks until she was able to drink normal amounts of water on her own.
After a week Sapphire became able to eat small amounts of wet hay (put in a small holed net to prevent choking). As the condition improved over the next 3 weeks, hay quantity was increased to a normal ratio and sloppy feeds correspondently reduced.
Sapphire was also sweating profusely (which is a feature of the disease), so electrolytes were added to her diet. The tendency to sweat carried on for about 2 weeks.
Gradually all of her muscles relaxed (the last ones to do so were her back muscles) and by week 4 of treatment she was completely normal and ready to go back out in the paddock!
At the time of writing (5 weeks since onset), Sapphire is doing very well and enjoying a few hours in the field. She is recovering from a skin infection caused by the sweating during her illness and is receiving Milk Thistle to help support her liver. Her liver enzymes were found to be mildly elevated on a blood test. Liver damage can be a side effect of treatment with high doses of antitoxin and she will need further monitoring over the next few months.
During treatment, Sapphire received a course of tetanus immunisation (2 injections 3 weeks apart), as natural infection does not provide effective immunity.
Sapphire on her first outing after tetanus
While tetanus is such a serious disease, it is also highly preventable because of the availability of efficacious vaccines.
All horses should receive a primary course (2 injections 21-92 days apart) from 5-6 months of age. The first booster should be given within 18 months and every two years thereafter.
Onset of immunity is 2 weeks after the completion of the primary course, so it is important to remember that if a horse sustains an injury before the primary course is completed, administration of tetanus antitoxin will be necessary.
All pregnant mares should receive a booster vaccination against tetanus in the last 2 months of pregnancy, to ensure adequate protection is passed to the foal via the colostrum.