Option 1: Kala Azar is a disease caused by the bite of infected sandflies and is not related to wounds or surgical instruments.

Option 2: Chancroid is a sexually transmitted infection caused by the bacterium Haemophilus ducreyi and is also unrelated to wounds or surgical instruments.

Option 3: Diphtheria is an infectious disease caused by the bacteria Corynebacterium diphtheriae, usually spread through respiratory droplets and not through wounds or surgical instruments.

Option 4: Tetanus, the correct answer, is caused by the bacteria Clostridium tetani, which can enter the body through wounds or injuries, especially if they are not properly cleaned or treated. The bacteria produce toxins that affect the nervous system, causing muscle stiffness and spasms.

Therefore, the correct answer is option 4, Tetanus, as it is the only disease in the list that can be caused through wounds or unsterilized surgical instruments.