Answer: Trichomonas vaginalis.
Step 1: The triad of a profuse, frothy, foul (offensive) vaginal discharge with intense itching plus a strawberry cervix is the classic picture of trichomoniasis caused by the protozoan Trichomonas vaginalis.
Step 2: The discharge is typically thin, greenish-yellow and frothy. Punctate haemorrhagic spots on the cervix and vaginal walls give the strawberry (colpitis macularis) appearance. There may be dysuria and a sexual mode of transmission.
Step 3: Bacterial vaginosis gives a thin, grey, fishy discharge but no frothiness, no strawberry cervix and little itching. Candidiasis gives a thick, white, curdy discharge with intense itching but no froth and no strawberry cervix.
Step 4: Frothy offensive discharge plus a strawberry cervix is diagnostic of Trichomonas vaginalis. Treatment is metronidazole, including the partner. Ref: Dutta Gynaecology, 6e, p.163-164.