I used to believe rusted nails could cause tetanus because my mum told me so. She also said horse shit caused this.
In reality it’s a bacterium that can possibly be in horse manure but not necessarily and a nail, not necessarily rusted, could be contaminated with it. Rust causes it to be more porous so bacteria could nest inside of cavities. You would need the combination of a contaminated object penetrating deep inside your bloodstream to catch it. Accidentally touching horse shit or being stung by a rusted nail somewhere in the sea as I once was won’t cause anything bad. Yeah I was swimming in the sea and got injured by a rusted iron object and I thought my end was near and didn’t tell mum. I’m still alive with better education.