Sexual transmission of hepatitis B in Mwanza, Tanzania.

Abstract

Hepatitis B virus (HBV) is endemic and poses a grave public health problem in Africa where it is mainly transmitted from mother to baby or during childhood. Sexual transmission has also been suggested to play a role in East Africa, but this has never been properly demonstrated. Additional preventive strategies may be proposed if sexual transmission of HBV occurred in this region where HIV and other STDs are highly prevalent. To determine the prevalence of markers for hepatitis B virus (HBV)and other sexually transmitted diseases (STD) in routine blood samples taken from three populations in Mwanza, Tanzania, and to use the data collected to look at the association between hepatitis B and other STDs, including human immunodeficiency virus (HIV). Routine blood samples were collected from 1,025 patients attending a clinic for STDs, 253 voluntary blood donors from secondary schools, and 952 blood donors who gave blood in a hospital specifically for a relative who needed a blood transfusion. All samples were tested for HIV by double enzyme-linked immunosorbent assay (ELISA), and for syphilis using the Treponema pallidum hemagglutination (TPHA) and rapid plasma reagin (RPR) tests. Two markers for HBV were examined by the double ELISA method, the presence of the anti-hepatitis B core antigen (anti-HBc) and the hepatitis B surface antigen (HBsAg). There were high prevalences of HBV, syphilis, and HIV in relative donors and STD patients. Although HBV markers were more prevalent in men of increasing ages, syphilis and HIV markers were more prevalent in young women. Evidence of past infection with HBV (presence of anti-HBc) was associated with serologic markers of recent treponemal infection (both TPHA and RPR positive) in both sexes (men odds ratio [OR] = 1.91, P < 0.011; women OR = 2.34, P < 0.02) and with HIV in men (OR = 1.93, P < 0.003). Current infection with HBV (presence of HBsAg) was associated with recent syphilis in men (OR = 2.13, P < 0.006). In STD patients, current infection with HBV was associated with Trichomonas vaginalis in women (OR = 3.57, P < 0.002) and recent syphilis in men (OR = 3.46, P < 0.001). There was no further association between HBV markers and any other STD pathogen or any particular STD syndrome, nor was there any association between current HBV infection and HIV in both sexes. The population attributable fraction for sexual acquisition of hepatitis B is estimated at 7.2% in men and 3.0% in women, based on the association between hepatitis B and syphilis. These findings suggest that sexual acquisition of hepatitis B occurs at low levels in Mwanza, and that HBV can be prevented through enhancement of the current HIV/STD control activities, in addition to improved vaccination strategies.