Poverty diseases: the pains the world doesn’t see

Publicação: 2 de October de 2019

For researcher Andrea Lund, investing in environmental solutions may be the only way to reduce the risk of schistosomiasis in places where the incidence of the disease remains high

Researchers call for more attention to the role of socioeconomic and environmental systems and community involvement in the design of disease control programs

Considered the second most devastating socioeconomic parasitic disease in the world, schistosomiasis contributes to the maintenance of inequality and social exclusion. Present in countries where there are more people living in conditions of extreme poverty and vulnerability, living without access to sanitation facilities the disease plagues cities and keeps thousands of people in invisibility. It is a disease of poverty that the world does not see its pains.

To learn more about the relationship between social and environmental determinants of schistosomiasis transmission, a group of Stanford researchers conducted a research in four villages in northern Senegal. The author, Andrea Lund, explains that in each village people were recruited to participate in focus group discussions to tell about the water sources in their communities and how people dealt with it. Because water behaviors vary greatly depending on people’s age and gender, three discussions were held in each village: with men, with women and with young people.

The survey revealed three main findings. “First, we found that the people we talked to in these four villages were knowledgeable about the nature of schistosome infection risk. Then, with this knowledge, they have developed strategies to minimize their exposure to the parasite. But even with these strategies, resource-dependent livelihoods make it difficult to avoid exposure completely”, she reports. According to the author, these findings reinforce the multidimensionality of transmission and the risk of contracting the disease. “Environmental factors are an important determinant of risk, but so are the socio-economic norms and circumstances that lead to and perpetuate exposure. These complexities, while inconvenient, can’t be ignored when designing and implementing interventions to reduce the burden of schistosomiasis and curb the parasite’s transmission”, she says. The study (“Unavoidable Risks: Local Perspectives on Water Contact Behavior and Implications for Schistosomiasis Control in an Agricultural Region of Northern Senegal“) was published in the American Journal of Tropical Medicine and Hygiene.

The researchers concluded that involving communities in the design of disease control programs could help. According to Andrea Lund, interventions to control schistosomiasis are often of a top-down nature, coming in the form of drug distribution campaigns by governments or entities from outside the affected communities. “Our research showed not only that people in our study villages were aware and knowledgeable about schistosomiasis risk in their surroundings, […] and with this knowledge, they have developed strategies to minimize their exposure to the parasite”, she says. For her, this shows that schistosomiasis control programs can diversify their actions by involving communities in risk mitigation while distributing medicines. Community involvement can be a bottom-up complement to the prevailing top-down interventions.

Asked why medication administration failed in Senegal, the author emphasizes that it is difficult to know exactly why mass drug administration in the country has not reached significant levels of reduction. But this is not an isolated case. There are other places where disease prevalence and intensity have remained high despite several years of drug distribution. “The identification of these “persistent hot spots” is relatively recent and its hard to definitively determine what causes the persistence, but it’s likely a perfect storm of social and environmental conditions that put people in contact with parasite-laden water, leading to reinfection after treatment. Perhaps something about the ecology of the local snail population makes the risk in the environment particularly high. Perhaps people have few alternatives to being in contact with that water. Perhaps it is some combination of both conditions”, she weighs.

Inevitable risks and invisibility of these populations

The research team tries to understand the obstacles to prevention. However, in places where livelihoods are strongly linked to the environment and people have few alternatives other than being in contact with water, it is unreasonable to expect them to avoid such contact, because they will understandably always choose to meet the most urgent economic needs while accepting the associated health consequences inherent in this behavior, whose impacts gradually accumulate over time.

“When this is the case, it becomes even more important to think about how to reduce the risk of infection in the environment. Can we control snail populations in environmentally-friendly ways?”, asks Dr. Lund while acknowledging that in Senegal, schistosomiasis has become problematic due to environmental impacts from dam construction. To this end, her team looks at ways to mitigate these impacts that may help reducing the disease – recovering snail predators that were lost when dams were built and removing the invasive aquatic vegetation that provides a suitable habitat for them. A greater focus on the role of socioeconomic and environmental systems and community involvement in the design of disease control programs can contribute.

Regarding the cure, in the opinion of Andrea Lund, the biggest hurdle is because treatment resolves existing infections but does not protect against new ones. She is emphatic in pointing out that people will always be at risk of infection and reinfection as long as infected snails are in the environment. “In the persistent hot spots where treatment has not reduced the disease burden, we must embrace the inconvenient complexity of the social and environmental determinants of schistosomiasis risk and start thinking creatively about how to reduce risk in the environment while still allowing people to carry out their livelihoods”, she concludes.

The researcher admits that it is easy to not see a problem that does not affect us directly. According to her, it is also easy to gravitate toward an idea that simple solutions such as treatment campaigns will work everywhere. Treatment campaigns have reduced the burden of schistosomiasis in many places and this should not be overlooked. But, she said, in persistent hot-spot locations, campaigns have failed, and complementary strategies are needed, including controlling snail populations, changing behavior when possible, and community engagement.