Schistosomiasis: how a theory brings HIV, a parasite, the price of pills and the demand for evidence together

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The possibility that a parasitic worm could be contributing to HIV’s disproportionate impact on women in Africa has been considered long enough, and taken seriously enough to inspire the optimistic title of this 2009  editorial, “Africa’s 32 Cents Solution for HIV/AIDS.” The idea that schistosomiasis, often picked up during childhood through a freshwater-borne parasite prevalent in some regions of Africa, can cause vaginal sores that could increase the likelihood of HIV exposure through sex also has inspired a series of epidemiological studies. In 2006, for example, a study in a rural Zimbabwean community found women showed three times the risk of having HIV if they had genital schistosomiasis. Three years ago, a literature review looking at studies involving more than 1,000 women found a link between nearly three to four times greater odds of those with schistosomiasis having HIV. And an analysis last year, examining the “Potential Cost-Effectiveness of Schistosomiasis Treatment for Reducing HIV Transmission in Africa,” concluded that mass treatment of the parasitic infection would be cheaper per case of HIV infection averted than other interventions currently underway.

With all that attention, it may be surprising that schistosomiasis remains an “NTD” — a neglected tropical disease, second only to malaria as the most common parasitic disease and, according to the United States Centers for Disease Control and Prevention, the deadliest, accounting for an estimated 280,000 deaths in Africa alone. The consequences for children, USAID notes, are the most severe, including setbacks to physical and cognitive development, malnutrition and school absenteeism. USAID also notes that “the disease can be prevented and transmission controlled with a single annual dose of praziquantal.” But, according to World Health Organization data cited by USAID, in 2008, only 8 percent of people with schistosomiasis had access to the medicine.

A series of experts, including the last two heads of the U.S. President’s Emergency Plan For AIDS Relief, according to a recent New York Times article, as well as present U.S. Global AIDS Coordinator Ambassador Deborah Birx have expressed doubts that a sufficient connection between schistosomiasis and HIV exists, and point to the challenge of diverting resources from interventions that have been tested and proven effective, including antiretroviral treatment, which saves lives and prevents transmission.

Still, efforts to prevent HIV have not always provided proof. As noted here, the most recent Conference on Retroviruses and Opportunistic Infections saw some widely used strategies debunked, with research indicating that campaigns targeting “sugar daddies” and “multiple concurrent partnerships” missing their targets of preventing HIV transmission. Steve Bellan, the author of “Transmission Rates and Not Sexual Contact Patterns Drive HIV Epidemic Intensity in Africa,” showing transmission rates had no correlation to rates of “multiple concurrent partnerships,” suggested that the answer to why rates of HIV differ by region is more likely to be found in biomedical factors, including the presence of other infections.

One reason a definitive answer, or effort to delineate and respond to the potential link between HIV and this parasitic infection, though, also is highlighted in the New York Times article, which focused on the KwaZulu Natal province, and noted that while generic versions of the drug to fight schistosomiasis can be had for eight cents a pill, South Africa’s patent laws require using the branded Bayer version at $4 dollars a pill. This at least supports one link — that between patent reform and public health.

One thought on “Schistosomiasis: how a theory brings HIV, a parasite, the price of pills and the demand for evidence together

  1. Pingback: A simple theory, and a proposal, on HIV in Africa | Herpes Survival Kit

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