Chancroid

Chancroid is a sexually transmitted genital ulcer disease caused by Haemophilus ducreyi, a gram negative coccobacillus. It is far less common in high income settings than herpes or syphilis but remains endemic in parts of Africa, Asia, and the Caribbean, and is an important cofactor for HIV transmission given the mucosal breach it causes.

After an incubation period of 4 to 10 days, a tender papule develops that rapidly ulcerates. The resulting ulcer is classically painful, with a ragged, undermined, non-indurated border and a friable, purulent base ("soft chancre"), a key distinguishing feature from the painless, indurated chancre of primary syphilis. Ulcers are often multiple, from autoinoculation. Painful, unilateral inguinal lymphadenopathy develops in roughly 50% of cases, which can progress to a fluctuant bubo and spontaneous rupture if untreated.

Diagnosis is largely clinical in endemic settings given limited culture sensitivity and availability. Where facilities allow, culture on specialized media, PCR (most sensitive where available), or Gram stain of ulcer exudate (showing a "school of fish" pattern of gram negative coccobacilli) support confirmation. Given the difficulty of definitive laboratory confirmation, a probable diagnosis is often made clinically when a painful genital ulcer with typical features occurs alongside painful lymphadenopathy, and dark field microscopy or syphilis serology and HSV testing are negative. Co-testing for syphilis and HIV is essential given shared risk context and the frequency of dual infection.

• Azithromycin 1 g PO single dose, or ceftriaxone 250 mg IM single dose, are first line
• Alternatives: ciprofloxacin 500 mg PO bd for 3 days (avoided in pregnancy and breastfeeding), or erythromycin base 500 mg PO tds for 7 days
• Fluctuant buboes should be aspirated through healthy adjacent skin (incision and drainage is generally avoided given delayed healing) to reduce the risk of spontaneous rupture and sinus formation
• Sexual partners within the preceding 10 days should be examined and treated empirically regardless of symptoms
• Follow up at 3 to 7 days to confirm clinical improvement; ulcers should show symptomatic improvement within 3 days and objective improvement within 7 days, larger ulcers may take over 2 weeks to fully heal
• HIV positive patients may require a longer treatment course and closer follow up given a higher risk of treatment failure

Referral: sexual health services for full STI screening and partner notification; surgical input for large or complicated buboes.