In the latest Vaccine Smarts column by UTMB’s Dr. Richard Rupp and Bridget Hawkins: Contrary to common belief, rust does not cause tetanus. Tetanus is caused by a bacterium that is in the feces of many animals such as birds, dogs, cats, rats and cattle. Feces frequently contaminate the soil and other things that are outdoors. Rust is just a marker that something has been outdoors and has a good chance of being contaminated. Tetanus rarely develops with superficial scrapes because the wound is open to the air and this high oxygen environment makes it difficult for the bacterium to grow. Nails are the perfect way to introduce tetanus because the nail puncture places the bacterium deep into the body, away from open air.