Schistosomiasis Linked With HIV Infection

Jennifer A. Downs, MD, MSc

A recent study has shown that women with schistosomiasis are at greater risk for HIV infection.

Jennifer A. Downs, MD, MSc, Center for Global Health, Weill Cornell Medicine, New York, New York, and colleagues published the results of their study September 25, 2017, in PLoS Neglected Tropical Diseases. In an interview with Contagion^®, Dr. Downs, an infectious disease expert, emphasized that study’s findings “strongly suggest that controlling schistosomiasis may be a very effective way to decrease HIV transmissions in many regions of sub-Saharan Africa where schistosomiasis is endemic.”

Schistosomiasis is a parasitic infection caused by Schistosoma species of worms. It is acquired by contact with contaminated water and affects about 218 million people worldwide, mostly in Africa.

In regions of Tanzania in which S. mansoni is highly-endemic, the authors estimate that up to 50% of HIV-infected patients are also infected with S. mansoni.

Dr. Downs noted that this study was accomplished through long-term collaborations with colleagues in Tanzania at Weill Bugando Medical Centre and at the National Institute for Medical Research, as well as with colleagues at Leiden University Medical Center, the Netherlands.

“We had a strong team that worked together towards the common goal of understanding the relationship between schistosomiasis and HIV so that we could improve health for individuals in rural Tanzania.”

According to Dr. Downs, the rates of HIV acquisition are alarmingly high in rural adolescent girls and women. “I wanted to conduct this study because we hypothesized that schistosomiasis, which is a common parasitic infection acquired by contact with contaminated water, could be increasing the risk of HIV acquisition in these girls and women,” she said.

Because schistosomiasis can easily be treated with praziquantel, Dr. Downs explained that if schistosomiasis could be demonstrated as a risk factor for HIV acquisition, then this would provide new, strong evidence of the need to treat schistosomiasis—not only to decrease suffering caused by the parasitic infection itself, but also to decrease new HIV infections in communities where both schistosomiasis and HIV infections are common.

In their study, the researchers examined the prevalence of schistosomiasis in blood collected from adults from 7 villages in Tanzania who tested positive for HIV for the first time in 2007, 2010, and 2013. They then compared those samples with blood from adults who repeatedly tested negative for HIV.

The study showed 2 major effects of this parasitic infection on HIV.

“We found that women with schistosome infections had a 2.7-fold increased risk of becoming HIV-infected compared to women without schistosome infections,” said Dr. Downs.

“We also found that both women and men who had schistosome infections at the time they acquired HIV went on to develop higher HIV viral load levels than women and men who did not have schistosome infections.”

Schistosomiasis treatment efforts in much of sub-Saharan Africa focus primarily on school children, said Dr. Downs. “Our results now urge that clinicians and public health officials should expand treatment efforts for schistosomiasis to include adults as well,” she stressed. Not only would this diminish the morbidity of schistosome infections for adults with this infection, but additionally, this may be an effective means of decreasing HIV transmission and slowing HIV disease progression.

Dr. Downs and her team are also seeking to understand the changes induced by schistosome infections at the level of the mucosal tissue, and how they may increase a woman’s susceptibility to HIV.

“If we can understand what these changes are, then we will better understand how to treat schistosome infections, and we may be able to develop other strategies for HIV prevention as well,” she concluded.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.