Schistosomiasis is associated with incident HIV transmission and death in Zambia

Abstract

Background: We examined relationships between schistosome infection, HIV transmission or acquisition, and all-cause death.

Methods: We retrospectively tested baseline sera from a heterosexual HIV-discordant couple cohort in Lusaka, Zambia with follow-up from 1994-2012 in a nested case-control design. Schistosome-specific antibody levels were measured by ELISA. Associations between baseline antibody response to schistosome antigens and incident HIV transmission, acquisition, and all-cause death stratified by gender and HIV status were assessed. In a subset of HIV- women and HIV+ men, we performed immunoblots to evaluate associations between Schistosoma haematobium or Schistosoma mansoni infection history and HIV incidence.

Results: Of 2,145 individuals, 59% had positive baseline schistosome-specific antibody responses. In HIV+ women and men, baseline schistosome-specific antibodies were associated with HIV transmission to partners (adjusted hazard ratio [aHR] = 1.8, p<0.005 and aHR = 1.4, p<0.05, respectively) and death in HIV+ women (aHR = 2.2, p<0.001). In 250 HIV- women, presence of S. haematobium-specific antibodies was associated with increased risk of HIV acquisition (aHR = 1.4, p<0.05).

Conclusion: Schistosome infections were associated with increased transmission of HIV from both sexes, acquisition of HIV in women, and increased progression to death in HIV+ women. Establishing effective prevention and treatment strategies for schistosomiasis, including in urban adults, may reduce HIV incidence and death in HIV+ persons living in endemic areas.

Fig 1. Adjusted associations between women's and men's baseline schistosome-specific antibody status and HIV transmission and acquisition.

CI: confidence interval; aHR: adjusted hazard ratio *Controlling for factors associated with both the exposure and outcome of interest: Genital conditions (non-ulcerative) of woman, genital ulcer of woman **Controlling for factors associated with both the exposure and outcome of interest: Male partner's baseline schistosome-specific antibody status ***Controlling for factors associated with both the exposure and outcome of interest: Viral load of man ****Controlling for factors associated with both the exposure and outcome of interest: Female partner's baseline schistosome-specific antibody status.

Fig 2. Adjusted associations between women's and men's baseline schistosome-specific antibody status and death.

CI: confidence interval; aHR: adjusted hazard ratio *Controlling for factors associated with both the exposure and outcome of interest: HIV stage of woman **Unadjusted model ***Controlling for factors associated with both the exposure and outcome of interest: Viral load of man ****Controlling for factors associated with both the exposure and outcome of interest: Female partner's baseline schistosome-specific antibody status.