Chancroid is a sexually transmitted infection caused by the bacteria Haemophilus ducreyi, which is rare in developed countries, and more common in the tropics and Asia.
Three to five days after sexual contact with a carrier, a sore develops on the penis or vulva, which rapidly breaks down to form a painful ulcer. Several sores and ulcers may be present at the same time. Lymph nodes in the groin then swell up into hard, painful lumps, that may degenerate into an abscess and discharge pus. The patient is feverish and feels ill.
Some patients develop a mild form with minimal symptoms, but they can transmit the disease. This is particularly common in women, where the sores may be hidden internally in the vagina. The condition is diagnosed by taking swabs from the sores and identifying the bacteria present in the pus, or skin tests that often remain positive for life.