Most individuals diagnosed with chancroid have visited countries or areas where the disease is known to occur frequently, although outbreaks have been observed in association with crack cocaine use and prostitution.Chancroid is a risk factor for contracting HIV, due to their ecological association or shared risk of exposure, and biologically facilitated transmission of one infection by the other. Approximately 10% of people with chancroid will have a co-infection with syphilis and/or HIV. Pathogenesis
H. ducreyi enters skin through microabrasions incurred during sexual intercourse. The incubation period of H. ducreyi infection is 10 to 14 days after which there is progression of the disease. A local tissue reaction leads to development of erythomatous papule, which progresses to pustule in 4–7 days. It then undergoes central necrosis to ulcerate. Diagnosis
Variants
Some of clinical variants are as follows. Laboratory findings
From bubo pus or ulcer secretions, H. ducreyi can be identified using special culture media; however, there is a <80% sensitivity. PCR-based identification of the organisms is available, but none in the United States are FDA-cleared. Simple, rapid, sensitive and inexpensive antigen detection methods for H. ducreyi identification are also popular. Serologic detection of H. ducreyi uses outer membrane protein and lipooligosaccharide. Most of the time, the diagnosis is based on presumptive approach using the symptomatology which in this case includes multiple painful genital ulcers.
Differential diagnosis
Despite many distinguishing features, the clinical spectrums of following diseases may overlap with chancroid:
Primary syphilis
Genital herpesPractical clinical approach for this STI as Genital Ulcer Disease is to rule out top differential diagnosis of Syphilis and Herpes and consider empirical treatment for Chancroid as testing is not commonly done for the latter. Comparison with syphilis
There are many differences and similarities between the conditions syphilitic chancre and chancroid:
SimilaritiesBoth originate as pustules at the site of inoculation, and progress to ulcerated lesions
Both lesions are typically 1–2 cm in diameter
Both lesions are caused by sexually transmissible organisms
Both lesions typically appear on the genitals of infected individuals
Both lesions can be present at multiple sites and with multiple lesionsDifferencesChancre is a lesion typical of infection with the bacterium that causes syphilis, Treponema pallidum
Chancroid is a lesion typical of infection with the bacterium Haemophilus ducreyi
Chancres are typically painless, whereas chancroid are typically painful
Chancres are typically non-exudative, whereas chancroid typically have a grey or yellow purulent exudate
Chancres have a hard (indurated) edge, whereas chancroid have a soft edge
Chancres heal spontaneously within three to six weeks, even in the absence of treatment
Chancres can occur in the pharynx as well as on the genitals

Prevention
Chancroid spreads in populations with high sexual activity, such as prostitutes. Use of condom, prophylaxis by azithromycin, syndromic management of genital ulcers, treating patients with reactive syphilis serology are some of the strategies successfully tried in Thailand.