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High Prevalence of Haemophilus ducreyi Among Patients With Suspected Primary syphilis in Malawi, 2019-2022
Mitch M Matoga1, Jane S Chen2, Arlene C Seña2
1Reproductive and Sexual Health Clinic, University of North Carolina Project Malawi, Lilongwe, Malawi.
Insights
Syphilis and chancroid are common causes of genital ulcer disease (GUD) in Malawi. Molecular diagnostics are crucial for accurately identifying GUD etiologies in STI clinics.
Area of Science:
- Infectious Diseases
- Microbiology
- Public Health
Background:
- Global syphilis rates are rising, while chancroid incidence has decreased.
- Genital ulcer disease (GUD) remains a significant public health concern.
Purpose of the Study:
- To determine the etiologies of GUD in Lilongwe, Malawi.
- To evaluate diagnostic methods for GUD pathogens.
Main Methods:
- Recruited 568 patients with GUD from an STI clinic in Malawi.
- Utilized darkfield microscopy (DFM) and PCR for Treponema pallidum (TP), Haemophilus ducreyi (HD), HSV, and CT.
- Assessed DFM sensitivity/specificity vs. TP PCR and HD PCR performance.
Main Results:
- Syphilis (TP) was identified in 65% of participants by PCR.
- Chancroid (HD) was found in 23% of participants.
- Herpes simplex virus (HSV) was present in 17%, and Chlamydia trachomatis (CT) in 6%.
Conclusions:
- Syphilis and chancroid are prevalent causes of GUD in Malawi.
- Sensitive molecular diagnostics are essential for managing GUD in syndromic management settings.
- Regular assessment of GUD etiologies is vital for effective public health strategies.
Background:
As syphilis rates have increased globally, chancroid has dramatically declined as a cause of genital ulcer disease (GUD).
Methods:
We recruited patients aged ≥18 years presenting to a sexually transmitted infection clinic with GUD from Lilongwe, Malawi, from November 2019 through April 2022. Lesion exudates were tested by darkfield microscopy (DFM) and polymerase chain reaction (PCR) for Treponema pallidum (TP) and by PCR for Haemophilus ducreyi (HD), herpes simplex virus, and Chlamydia trachomatis. We evaluated the sensitivity and specificity of DFM relative to TP PCR, the distribution of GUD etiologies by PCR, and the performance of our HD PCR relative to Allplex Genital Ulcer assay (Seegene Inc) using the Cohen's kappa statistic.
Results:
We enrolled 568 participants; the median age was 27 years (interquartile range: 23, 34), 61% (345/564) were men, and 13% (60/464) had human immunodeficiency virus (HIV) or were newly diagnosed with HIV. DFM identified TP in 55 (10%) participants, with a sensitivity and specificity of 12% and 94%, respectively. PCR identified TP in 367 (65%), HD in 128 (23%), herpes simplex virus in 98 (17%), and Chlamydia trachomatis in 36 (6%) of participants with only 1/36 (2.8%) with serovar L1, L2, or L3 consistent with lymphogranuloma venereum; no etiology was identified in 48 (8%). External validation confirmed the high HD prevalence (Cohen's kappa 0.78, 89% agreement).
Conclusions:
Syphilis and chancroid are common etiologies of GUD in Malawi. Our findings underscore the value of highly sensitive molecular diagnostic methods to periodically assess GUD causes among patients with sexually transmitted infections in countries using syndromic management.
