HIV infection may increase the risk of sexually transmitted diseases (STDs)

Data from a prospective study of female sex workers in Mombasa, Kenya show that HIV-infection increases the risk of acquiring certain sexually transmitted diseases and other genitourinary tract infections.

The ten-year study, published in the February 1^st issue of The Journal of Infectious Diseases, found a significantly higher incidence of GUD, gonorrhoea, and vulvovaginal candidiasis, and a trend towards increased incidence of trichomoniasis among HIV-positive patients. Multivariate analyses showed that the increased risk of STDs was not due to differences in reported sexual behavior/condom use or others factors.

Interaction of HIV and STDs

Epidemiologists have long postulated that a “synergy” between HIV and STDs is partly to blame for the rapid spread of HIV in parts of the world. Numerous studies have shown that conditions such as genital ulcer disease (GUD), nonulcerative STDs (e.g., Neisseria gonorrhoeae and Chlamydia trachomatis infection), and vaginal conditions such as vulvovaginal candidiasis and bacterial vaginosis, can significantly increase susceptibility to HIV infection.

However, few prospective studies have examined whether the effect is reciprocal — whether HIV increases susceptibility to STDs and genital-tract conditions. If it does, it could have a substantial impact on global HIV transmission, since genital-tract infections can increase the infectiousness of HIV-positive individuals.

The study

To determine the effect of HIV on the incidence of STDs and other genital-tract infections, 1215 HIV negative women were enrolled into the trial. Participants underwent monthly HIV and STD screening and 238 tested positive for HIV during the trial.

During follow-up, there was a high incidence of STDs and other genital-tract conditions. In the multivariate analyses, HIV-positive women had significantly higher rates of GUD (hazard ratio [HR], 2.8; 95% confidence interval [CI], 2.0–3.9), gonorrhoea (HR, 1.6; 95% CI, 1.1–2.2), and vulvovaginal candidiasis (HR, 1.5; 95% CI, 1.3–1.8), compared to HIV-negative women. There was also a trend for more frequent detection of trichomoniasis (HR, 1.3; 95% CI, 1.0–1.7).

However, HIV status did not seem to significant affect rates of syphilis, chlamydia, cervical mucopus, cervicitis, bacterial vaginosis, and abnormal vaginal discharge.

The researchers then examined whether the conditions seen more frequently in those with HIV became even more common as CD4 cell counts fell. The risk of GUD and vulvovaginal candidiasis was found to increase in a stepwise fashion in HIV-positive women with decreasing CD4 cell counts. But declining CD4 cell counts were not associated with increased risk of gonorrhoea or trichomoniasis, which unlike GUD and vulvovaginal candidiasis, require reexposure for new episodes to occur.

Explanations

The study authors note the possibility that HIV-positive women under-reported risky sexual behaviour. However, the fact that only certain (not all) of the STDs were more common argues against this conclusion.

The researchers propose several possible explanations for their findings.

• HIV may influence the susceptibility to genital-tract infections or the duration, response to treatment, recurrence rate, or severity of genital-tract infections.
• HIV-mediated CD4 cell depletion promotes HSV reactivation, which could explain an increase in the incidence of GUD.
• In HIV-1–seropositive women, an increased incidence of mucosal candidiasis may be related to multiple factors, including immunosuppression and direct effects from higher levels of HIV-1 viraemia.

Implications

The study researchers fear that a synergistic effect between HIV and the STDs could have an effect on HIV-1 pathogenesis by increasing plasma HIV-1 load that then could lead to accelerated disease progression. However, they postulate that programs directed at HIV-positive individuals with STDs may have a substantial impact on the spread of HIV-1.

“The high incidence of GUD and cervical and vaginal infections associated with HIV-1 indicates the need for more intensive treatment and prevention of these conditions as a means of decreasing HIV-1 infectivity. The findings… highlight the need for both research and program support to implement targeted screening and treatment for genital-tract infections in HIV-1–seropositive individuals, as an HIV-1 prevention strategy.”