Limiting Schistosomiasis May Reduce HIV Transmission Rates

Kristin Wall, PhD

New research suggests that treating a common parasitic infection might help control the spread of HIV.

Both HIV and schistosomiasis—an infection caused by drinking water containing schistosome parasites—are common in Africa. The majority of the world’s 35 million HIV-positive people and 200 million people with schistosomiasis live on the continent, according to researchers from Emory University.

Given their prevalence and the similarity of their geographic footprints, lead researcher Kristin Wall, PhD, and colleagues wanted to explore what, if any, relationship there was between the 2 infections.

The team tested sera from 2145 patients in Zambia who had been enrolled in a study of HIV-discordant heterosexual couples in the late 1990s through 2012. Samples were tested for schistosomiasis-related antibodies. Those data were then cross-referenced with other health data, such as HIV status and death.

A majority—59%—of the patients tested had schistosomiasis-specific antibodies. They found that when the HIV-positive partner had schistosomiasis antibodies (regardless of gender), their partner had a greater chance of becoming infected with HIV (adjusted hazard ratio 1.8 for women; 1.4 for men). There were also other correlations, wrote Wall, an assistant professor of epidemiology at Emory.

“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,” she wrote.

The new study aligns with other research that found people with schistosomiasis had a higher risk of HIV or HIV-related complications.

A 2006 study in Zimbabwe found 41% of women with laboratory proven genital schistosomiasis also tested positive for HIV. Meanwhile, just 26% of women in the study without schistosomiasis tested positive for HIV.

Another study, in 2011, found similar results, suggesting that urogenital schistosomiasis causes broad immunological effects and local genital tract effects that heighten HIV risk.

“In those who become HIV-infected, schistosomal co-infection may accelerate HIV disease progression and facilitate viral transmission to sexual partners,” wrote senior author Jennifer A. Downs, MD, MSc, PhD, of Weill Cornell Medical College, at the time.

In the new study, Wall and colleagues argued the apparent connection between schistosomiasis and HIV suggests an opportunity to reduce HIV infections.

"Since treatment of schistosome infections with praziquantel is inexpensive, effective, and safe, schistosomiasis prevention and treatment strategies may be a cost-effective way to reduce not only the symptoms associated with the infection, but also new cases of HIV and death among HIV+ persons," Wall and colleagues wrote.

Another important finding, Wall said, is that schistosomiasis is a problem in urban, as well as rural areas. The 2006 study, for instance, focused on the rural poor in Zimbabwe. However, the new study is based on data from patients in Lusaka, Zambia, a city of 1.7 million people.

“Though often viewed as an infection of predominantly rural areas and children, this study highlights that schistosomiasis prevention and treatment efforts are also needed in urban areas and among adults,” the authors noted.

The study, “Schistosomiasis is associated with incident HIV transmission and death in Zambia,” was published online in PLOS Neglected Tropical Diseases.