Puncture from rusty nails and the traditional dirty wounds are not the only portals for tetanus.
A suppurative ear infection, a poorly treated ear infection, a botched abortion done with dirty instruments, can all lead to tetanus.
So could dressing of the umbilical stump of newborns with cow dung, or any wound [including circumcision wounds, or even piercings for ear rings] with herbal concoctions.
All the deadly organism needs is a contaminated wound, a suppurative infection, a devitalised area of tissue, or just an anaerobic environment!
The key to prevention thus is keeping of wounds clean and prompt treatment of suppurative infections. Also timely immunisation against tetanus, and prompt reinforcements with booster doses.