Infection generally occurs through wound contamination, and often involves a cut or deep puncture wound. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the anaerobic bacterium "Clostridium tetani". As the infection goes on, muscle spasms develop in the jaw. This led to the common name of the condition, lockjaw. This is usually followed by difficulties with swallowing. The condition leads to general muscle stiffness and spasms in other parts of the body. Infection can be prevented by proper immunization and by post-exposure prophylaxis.