The other day at work I had a revelation. Either I had never sold tetanus antitoxin or I had never really put two and two together until taking this course. The idea that we actually become ill, not from the bacteria itself, but from the toxins they produce, has stuck in my mind ever since the famous “egg salad sandwich” class. So, when I dispensed tetanus antitoxin for a horse that had been castrated the previous day, it got me thinking….
Tetanus is a disease caused by the bacteria Clostridium tetani, which can be found in hospitals, dust, the feces and intestinal tract of horses and humans, and consequently found in the soil. It can contaminate many kinds of wounds, including the umbilici of foals and surgical incisions (Ah ha!).
An often fatal disease, tetanus is one of those illnesses that horses are most susceptible to and should be vaccinated for annually. The vaccine, called tetanus toxoid, is very safe and induces long-lasting immunity. Vaccination is the only proven method of prevention against diseases like tetanus, where there is no known cure and where treatment is usually unsuccessful. Side effects from the tetanus toxoid vaccine are very rare and should be outweighed by the benefits of vaccinating.
Clostridium tetani enters the body via a variety of different types of wounds, surgical incisions, and natural means including foal umbilici and retained placenta. After entrance, the bacteria emit powerful toxins that affect the central nervous system by blocking neurotransmission, and thus inducing involuntary muscle contractions and spasms. The first symptoms to occur include paralysis of the jaw muscles and the muscles around the wound, body spasms or convulsions, stiff legged movement and pricked ears, progressing on to muscles so rigid that the horse often falls and is not able to get up again. Death results from dehydration and starvation due to paralysis and/or from respiratory muscle paralysis. On average, the incubation period for tetanus is 8 days. However, bacterial spores can remain dormant in muscle tissue until trauma produces the much desired low oxygen environment.
If a horse has never been vaccinated against tetanus and there is a possibility for Clostridium tetani to enter the body (like the horse that had just been castrated), tetanus antitoxin should be administered along with the tetanus toxoid to prevent infection at a later date. The antitoxin is an antibody capable of neutralizing a toxin (Clostridium tetani toxin). It induces short-lived (about 2-3 weeks) but immediate protection against tetanus. Made from the blood of horses that have been repeatedly injected with large amounts of Clostridium tetani toxin, the antitoxin is considered a treatment, not a vaccine as it does not provide any long term protection. Therefore, when an unvaccinated animal sustains a wound, the antitoxin should be administered as protection for the first few weeks while the tetanus toxoid takes time to stimulate long term immunity (approximately 3-4 weeks).
Vaccine protocols should also be followed for humans, especially when working closely with horses. It is recommended that the human tetanus vaccine be updated every 10 years. However, even with antitoxin, there is still no 100% guarantee and proper, preventive care should still be taken when treating open wounds, both human and horse.