Tetanus is caused by the bacteria called Clostridium tetani. Outside of the body the spores of the bacteria live in any type of soil, dust or manure. The bacteria from the dirt or manure can enter the body through any wound such as a cut, open burn, surgical incision or puncture in the skin as well as punctures in the soles of the hoof. Even a small innocuous wound may be an entry point for the Clostridium bacteria. Foals whose dams have not been vaccinated for tetanus can develop tetanus through an infected naval. Puncture wounds are particularly worrisome as they are difficult to clean and provide the perfect anaerobic conditions for the bacteria to thrive.
The bacteria enter the wound and there begin to multiply. The powerful toxin (a neurotoxin) that the bacteria produce as they multiply blocks the nerves’ messages to the muscles causing the muscles to tense up.
It may take ten days to two weeks for the symptoms of tetanus to appear. There will be stiffness and the head and neck area, hind quarters and area of the wound may be affected first. The nostrils may be unusually flared. The animal will become progressively stiffer, taking on a ‘saw horse’ stance with head and tail up and will not be able to eat or drink.
The mortality rate for horses with tetanus is unfortunately high and treatment is usually difficult.
Tetanus is easily prevented in horses. Your horse should be vaccinated against tetanus at least every two years although as part of the core vaccinations, most people will vaccinate yearly. Foals need to be vaccinated after about four months. If the mare is vaccinated, the foal will receive some protection from the colostrum. Because you work around dirt and manure when you’re with your horse, be sure your tetanus shot is up-to-date as well.