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General Considerations
Chancroid is a sexually transmitted genital ulcer disease caused by Haemophilus ducreyi, a small, fastidious, gram-negative rod. Worldwide, chancroid incidence exceeds that of syphilis in many developing countries. In 1997, the World Health Organization estimated that there were six million new cases of chancroid. Based on polymerase chain reaction (PCR) assays, chancroid prevalence has been shown to range from 23% to 56% in endemic areas (Africa, Asia, and the Caribbean). In the United States and western Europe outbreaks are episodic. The infection is also up to 25 times more prevalent in men than in women, a difference recognized in both naturally occurring and experimental disease in humans and macaques. In fact, although controversial, it has been suggested that women may be asymptomatic carriers or reservoirs of the infection.

Although chancroid is uncommon in North America, outbreaks occur in the inner cities of the United States. The most recent of these began in the late 1980s in an outbreak attributed to sexual behavior associated with crack cocaine use and sex in exchange for drugs or money. The number of cases peaked in 1988, when 5001 cases were reported. Since then, the number of cases has sharply declined to an all-time low of 30 cases reported in 2004. Currently chancroid is rare in the United States and Canada.

The reasons for the decline in reported chancroid cases are multifactorial and not completely understood. There did not appear to have been a decline in sexual risk behavior or crack cocaine use in the at-risk populations. Improved provider education and awareness, condom promotion, partner notification and treatment programs, and the addition of chancroid treatment to the syndromic management of genital ulcers all may have played a role. Previous localized chancroid outbreaks appear to have been controlled by identifying and treating reservoir core groups such as commercial sex workers.

A major constraint to understanding chancroid epidemiology has been the lack of sensitive and specific diagnostic tests. The organism is fastidious and difficult to culture. When diagnosis is based on clinical criteria alone, the infection is likely to be grossly over-reported in some circumstances and under-reported in others. The development of sensitive and specific PCR assays for H ducreyi, it is hoped, will correct the problem of misdiagnosis in the future.

Chancroid has been shown to facilitate HIV transmission by providing both a portal of entry and an exit for the virus. In other words, chancroid increases both the transmissibility and the susceptibility of HIV and may do so by two mechanisms. First, increased viral shedding occurs in the ulcer exudates in HIV-infected patients with chancroid, thus making the virus available for transmission during sexual intercourse. Studies have shown that the mere presence of lesions does not always prevent chancroid patients from having sex. Second, recruitment of CD4 cells, the primary targets of the virus, to chancroidal ulcers serves to increase susceptibility of HIV-infected individuals to HIV acquisition. Finally, there are challenges in chancroid treatment among HIV coinfected patients as prolonged duration of ulceration and more frequent treatment failures have been reported.

Any sexually active person can be infected with chancroid. Chancroid is very common in Africa and is becoming more common in the United States. Chancroid may be successfully treated with certain antibiotics.