Abstract
The objective of this article is to report seroprevalences on HIV and herpes simplex virus 2 (HSV-2) in female sex workers (FSW) and in two sentinel populations of pregnant women living in Senegal. Serosurveys of HIV and HSV-2 were conducted in two unselected sentinel populations from Dakar, Senegal, and its provinces, including in 2003 only pregnant women and 2006 pregnant women and FSW. The population study involved 888 pregnant women and 604 FSW.
In pregnant women, HIV and HSV-2 seroprevalences were, respectively, 1.01% and 15.65%. There was no association between HSV-2 and HIV infection, whatever the age. In contrast, the seroprevalence of HIV infection in the group of FSW was high, reaching 22.9% in women over 30 years old. FSW above 20 years of age harboured much higher HSV-2 seroprevalences that those found in pregnant women of similar age groups. In FSW, strong associations between HSV-2 and age, and among HSV-2 and HIV-1 as well HIV-2, were evidenced. In conclusion, HIV epidemic remains concentrated in high-risk groups of the Senegalese population, such as the FSW population in which the seroprevalence of HSV-2 infection is very high. Intervention against STI including HSV-2 is urgently needed to prevent the spreading of HIV epidemic.
INTRODUCTION
Genital herpes simplex virus (HSV) infection is considered as a potent co-factor of HIV-1 heterosexual bidirectional transmission in sub-Saharan Africa, according to both biological plausibility and epidemiological evidence. 1 The recent fall in HIV prevention by suppressive treatments in Africa 2,3 does not argue against the role of HSV as a co-factor of heterosexual transmission of HIV, but rather suggests more complex relationship between replication of both viruses at genital levels.
The current situation of HIV epidemic in Senegal highly differs from HIV epidemics generally encountered in many other African countries. Thus, the prevalence of HIV-1 among sex workers in Dakar increased quickly, passing from 0.1% in 1986 to more than 10% in 1994 and 19% in 1997. By contrast, the HIV-1 seroprevalence remained low among pregnant women with respective rates of 1.5% in 2004 and 0.7% in 2006. 4 Therefore, the HIV epidemic in Senegal is clearly of a concentrated type with a low and stable prevalence in the general population and raised in the groups at high risk. 5
Among various factors possibly involved in the low prevalence of HIV-1 in Senegal, the low prevalence of HSV type 2 (HSV-2) has been recently hypothetized. 6 Indeed, the HSV-2 seroprevalence was relatively low among pregnant women from Dakar and in the Kaolack region it was 20% in 2004. 6 Moreover, an HSV-2 seroprevalence of 22.3% was reported in 2005 in men having sex with men and living in the urban areas of Senegal. 7 Put together, these observations suggest the possibility of HSV-2 infection being a co-factor of HIV transmission in certain Senegalese populations, rendering it necessary to survey both HIV and HSV-2 epidemics in a public health perspective. 6,7 The current study is reporting on HIV and HSV-2 seroprevalences in female sex workers (FSW) and in two sentinel populations of pregnant women living in Senegal.
MATERIALS AND METHODS
Populations
Pregnant women (n = 888) were included during the year 2003 in the antenatenal care centres in the province of Kaolack and in the centre ‘Roi Baudouin’ which is a district hospital located in the suburban area of the capital city Dakar (total = 260), and within 2006 in several antenatal care centres during the national HIV serosurvey (total = 628). A total of 604 FSW was enrolled only in 2006 throughout Senegal. All women were recruited after informed written or verbal consent. All women were interviewed by a health-care worker for sociodemographic characteristics and sexual behaviour, and they received clinical examination. Testing for HIV and seeking for other common agents responsible for sexually transmitted diseases were systematically proposed. A blood sample was obtained after oral consent to carry out HIV and HSV-2 screening.
Although the study populations of pregnant women and FSW were not randomized, their great sample sizes and their inclusions without selection minimized possible bias.
Laboratory procedures
Testing for HIV was performed as recommended by the national guidelines for HIV screening by enzyme-linked immunosorbent assay (ELISA) (Abbott Murex HIV antigen/antibody combination enzyme immunoassay, Chicago, USA); all positive sera were confirmed by Bispot HIV1/HIV2 (PBS Orgenics, Yavne, Israel); finally, Western blot confirmatory analysis was performed only in case of discrepancies. The presence of circulating HSV-2 antibodies was detected using a specific IgG2 ELISA test (Kalon Biologicals Ltd, Aldershot, UK), a convenient assay for African samples. 8
Data analysis
Data were entered into Epi-info Version 6.04d (CDC, Atlanta, GA, USA, 2001). Frequency of distributions, percentages and mean median were used to describe variables. Odds ratios (with 95% confidence intervals (CI)) were used to measure the magnitude of the association between HIV and HSV-2 antibodies, as well as age groups and sexual behaviours. Variables with a P value <0.05 were included in the final model to determine the relationship between having HSV-2 antibodies and selected variables of interest using Stata version 6.0 (Stata Corporation, TX, USA, 1999). The study protocol and the questionnaire were reviewed and approved by the AIDS Division and the Ethical Committee of the Ministry of Health. All positive person were referred to different health-care centres throughout the country for clinical and psychosocial care, if needed.
RESULTS
Results of HIV and HSV-2 seroprevalences among the study pregnant women and FSW are depicted in Table 1.
HIV and HSV-2 seroprevalences by age and year of sampling, among 888 unselected pregnant women included in 2003 and 2006, and among 604 unselected female sex workers included in 2006, living throughout Senegal
Pregnant women
In 2003, HIV seroprevalence among pregnant women was low with 1.53%. There was a trend of HIV prevalences decreasing between 2003 and 2006, although it was not statistically significant. HSV-2 seroprevalences were between 7.7% and 27.1% depending on age and year of sampling. Overall, among all unselected included pregnant women, the HIV seroprevalence was 1.01%, and the HSV-2 seroprevalence was 15.65%. There was no association between HSV-2 and HIV infection, whatever the age, as depicted in Table 2.
Associations between HIV and HSV-2 serostatus, according to age, among 888 unselected pregnant women included in 2003 and 2006, and among 604 unselected female sex workers included in 2006, living throughout Senegal
*Odds ratios with 95% confidence intervals [CI]
†Number of HIV-seropositive (percentage in brackets)
‡Number of HIV-seronegative (percentage in brackets)
S = significant; NS = not significant
Female sex workers
The seroprevalence of HIV in the group of FSW was high, reaching 22.9% in women over 30 years old. The overall HIV seroprevalence in FSW (20.1%) was significantly higher than that in the whole study populations of pregnant women (1.0%) (P < 0.01). The HSV-2 seroprevalence among FSW less than 20 years old was similar to those found in pregnant women of the same age group. In contrast, FSW above 20 years old harboured much higher HSV-2 seroprevalences than those found in pregnant women of similar age groups. In FSW, a strong association between HSV-2 and age could be evidenced (P < 0.05; Table 2). Among the 115 FSW co-infected by HIV and HSV-2, 78 were infected by HIV-1, 34 by HIV-2 and three presented a dual HIV-1/HIV-2 positivity. There was also a strong association between HSV-2 and HIV seropositivities (P = 0.02; Table 2). In addition, the association between HSV-2 and HIV was maintained according to the type of HIV infection (HSV-2 and HIV-1: P < 0.00; HSV-2 and HIV-2: P < 0.05).
DISCUSSION
The present study confirms and extends our previously serosurvey findings from pregnant women living in Dakar or Koalack, enrolled as sentinel population in 2003, and showing a likely low seroprevalence of HSV-2 infection in Senegal, comparable with those usually reported in Western countries, in conjunction of a low prevalence of HIV infection. We herein confirm the low prevalence of HIV infection in pregnant women from Senegal, from urban as well as rural areas, with a trend of decreasing between 2003 and 2006, and the lack of association between HIV and HSV-2 infections among pregnant women.
On the contrary, the serological data from the study FSW population evidenced for the first time in Senegal, a high prevalence of HSV-2 infection and a strong association between HIV and HSV-2 infections. The observed relationship between the HSV-2 seroprevalence and age in the FSW population was previously reported, as a marker of high-risk sexual behaviour in sub-Saharan Africa. 9 Our findings, furthermore, demonstrate that the association between HSV-2 and HIV infection may be observed not only for HIV-1 but also for HIV-2, suggesting that HSV-2 genital infection may constitute a co-factor of heterosexual transmission of HIV infection of both types.
Put together, our epidemiological surveys confirm that the HIV epidemic remains concentrated in the Senegalese population, and show that the HSV-2 epidemic has not spread thorough the whole Senegalese population, remaining concentrated in the high-risk group of FSW, similarly to HIV epidemic. Thus, the FSW population constitutes clearly one of the high-risk groups for HIV transmission in Senegal. Within that group, the strong association between HSV-2 and HIV infection highly suggests that HSV-2 infection may constitute a co-factor of HIV heterosexual transmission, as previously reported in FSW as well as in the general population living in the context of generalized HIV epidemics in sub-Saharan Africa. 9,10 Footbridge groups co-existing around the FSW population could now play a role in the passage of HIV from the high-risk FSW group towards the general population.
On a public health perspective, our observations recommend the survey of HSV-2 progression in the high risk HIV-1 population from Senegal, and propose convenient interventions against HSV-2 to try to prevent the progression of HIV infection via heterosexual intercourse. Public health stakeholders should take into account the current opportunity that HSV-2 infection appears as HIV infection and is limited to high-risk groups, and probably surrounding footbridge populations. This will allow more easily multidimensional interventions against sexually transmitted infections, including HSV-2, and comprising legal information and specific medical follow-up based on education, condom promotion and management.
Footnotes
ACKNOWLEDGEMENTS
Financial support was provided through MoH, NAC, FHI/USAID and Global Funds. OD is the statistician in the reference laboratory who performed all the statistical analysis.