The Fight Against Schisto, the Snail-Borne Spreader
New USAID-supported research is revolutionizing schistosomiasis treatment strategies
Among neglected tropical diseases (NTDs), schistosomiasis (schisto) impacts a staggering 240 million people. Also referred to as bilharzia or snail fever, schisto is caused by parasites carried in water by freshwater snails.
It is a devastating parasitic disease because it can cause a myriad of health problems. It can stunt a child’s growth, cause liver or bladder diseases, and even lead to infertility.
However, the disease is preventable with safe, effective medicines and treatable when detected early.
A Complex Problem & Public Health Solution
Despite available treatment options, such as the drug Praziquantel, efforts to control the spread of the disease have stalled in some places. The reasons are complex but include lack of drug availability and difficulty delivering treatments to very remote communities. Adding to the complexity, some affected people are asymptomatic, which contributes to the disease’s silent spread.
Enter mass drug administration (MDA), a comprehensive approach endorsed by the World Health Organization (WHO) to provide treatment for NTDs to communities where disease risk is high. Pharmaceutical manufacturers have generously donated NTD treatments, making this approach possible.
Treatment for schisto has typically focused on school children since they also receive treatment for intestinal worms through existing programs. Schisto treatment has been very successful in bringing the disease more under control globally.
But as the prevalence of the disease has diminished, it is important to refocus the MDA to use the finite supply of treatments — and resources to deliver them — where they are needed most. New diagnostic tests are also needed to find remaining pockets of disease and accurately measure the impact of treatment, especially now that WHO has proposed that all ages (including adults) be treated in an effort to eliminate the disease.
Precision Public Health
Recognizing these issues, USAID and the Bill & Melinda Gates Foundation, through the Coalition for Operational Research on NTDs (COR-NTD) grant, are supporting continued research looking at ways to defeat schisto. The hope is that decision makers will be better able to determine the optimal areas to treat, reducing over-treatment in regions where the disease is less prevalent, maximizing resources, and ultimately delivering greater impact where it is needed most.
COR-NTD and its partners have embarked on the study across multiple countries — Ghana, Mali, Togo, and Cote d’Ivoire — to identify cost-effective and feasible methods to target treatment at the sub-district level. Partners of this collaborative study overcame barriers from COVID-19, geographical challenges, and logistical hurdles to collect data from over 30,000 individuals.
What We’re Learning
While the study is ongoing, three insights have risen to the top.
1. For years, stakeholders have expected that treatment will lead to a uniform reduction in schisto in treated areas. The study has revealed a more complex picture. People continue to encounter infected water and they continuously contaminate water sources which contributes to ongoing transmission of schisto even after treatment. This finding re-emphasizes the need for improved sanitation and education about water contact.
2. A simple dipstick test for hematuria, or blood in the urine, plays a pivotal role in identifying children with high levels of the urinary form of schisto. Previously, urine samples taken in the community were sent to a lab, delaying results. However, the study showed that the available dipstick is effective at diagnosing the individual in the community, accelerating diagnosis and saving both time and money.
3. Preliminary study results were reviewed by principal investigators and ministry of health representatives who used the data to identify a new and improved approach for making accurate treatment decisions. Country partners across Africa are presently piloting this new approach.
Next Steps
As the study progresses, modelers and statisticians will continue to review data to learn more about the best ways to target populations for treatment. An important aspect of the work is to ensure that the resulting recommendations are applicable to all parts of Africa where schisto is found.
Dr. Yaya Coulibaly, one of the co-investigators from the Mali site noted that, “the most appreciated aspect of this multi-country study is the fact that it takes into account several archetypes and cultural settings, increasing the likelihood of the results suitability to these different settings.”
Dr. Kofi Asemanyi-Mensah, the former NTD Program Manager in Ghana, expressed that the insights gained from the study have already helped shape the nation’s schisto treatment plan.
As the study unfolds, the hope is to combat schisto more effectively and pave the way for targeted, impactful interventions against a range of NTDs.
About the Author
The Neglected Tropical Disease Support Center is the Secretariat for the Coalition for Operational Research on Neglected Tropical Diseases and supported by USAID.
