In both syphilis and gonorrhoea, the infections are usually found...

Syphilis and gonorrhoea are sexually transmitted infections that share several common primary sites of infection due to the modes of transmission.

The bacteria causing these infections (Treponema pallidum for syphilis and Neisseria gonorrhoeae for gonorrhoea) typically enter the body through mucous membranes during sexual contact. Therefore, the genital tract, rectum, and oral region are common primary infection sites for both diseases.

However, Neisseria gonorrhoeae can also cause a primary infection in the eye, known as gonococcal conjunctivitis. This can occur in adults through autoinoculation (transferring the bacteria from the genitals to the eyes via hands) or in newborns during passage through an infected birth canal (ophthalmia neonatorum).

In contrast, syphilis does not typically present with the eye as a primary infection site (where the initial chancre forms). While ocular syphilis can occur, it is generally a complication of secondary or tertiary syphilis rather than a primary site of entry.

Therefore, the eye is a characteristic primary infection site for gonorrhoea but not for syphilis.

Answer: eye