With sparkling eyes and a smile on his lips, Moussa Ndiaye, an octogenarian rice farmer, contemplates with satisfaction his harvest in his rice paddy in northern Senegal: the yield is good, but not only in terms of rice grains...

His field is part of a pilot study with promising results. It aims to combat bilharzia, one of the world's major parasitic diseases, while increasing rice yields, thanks to the surprising introduction of fish into the rice paddies, which are then caught and sold: a rare opportunity for local farmers.

More than 40 farmers from different villages are involved in this research project. These ecosystem-based solutions represent a growing trend in science.

The village of Moussa Ndiaye, Lampsar, is located in the lower valley of the Senegal River, near the border with Mauritania, a region where the inhabitants have long lived from river-related activities, but where fish are not usually caught in the rice paddies.

"Since our youth, since our grandparents, we have practiced fishing. We are +Waalo-Waalo+", Mr. Ndiaye, 80, told AFP, referring to an ancient kingdom in northern Senegal.

However, in addition to fish, the region is unfortunately known for the presence of bilharzia (or schistosomiasis), an acute and chronic parasitic disease caused by worms, schistosomes.

This disease, whose transmission has been recorded in 79 countries, mainly in tropical and subtropical regions according to the WHO, spreads through contact with fresh water contaminated by these parasites, which are hosted by infected freshwater snails.

- Increased yield -

The World Health Organization (WHO) estimated in 2024 that at least 253.7 million people needed preventive treatment for schistosomiasis. The WHO estimates that at least 93.6% of those who need such treatment currently live in Africa.

The presence of these infected freshwater snails is common in rice paddies. Moussa has already contracted bilharzia three times in his life, and his sons have also suffered from it.

This disease is easily treated, but the infection often goes unnoticed at first, and intestinal or urogenital complications often only manifest themselves several years later, leading to damage to certain organs, or even, in some cases, to death.

Children – particularly vulnerable to infection – who become infected may frequently miss school, or adults may find themselves unable to work for long periods, exacerbating the cycle of poverty.

Scientists have therefore decided to experiment with the introduction into rice paddies of Nile tilapia, which fertilizes rice with its excrement, and another fish called "ndiéguel" in Wolof (Heterotis niloticus), which eats the snails responsible for bilharzia.

"We are really tackling a lot of challenges," Emily Selland, from the University of Notre Dame in the United States, lead author of an article on this pilot study published this year in Nature Sustainability, told AFP.

"We initially approached the situation from the point of view of the disease," she explains, "but there was also the nutritional, economic, and ecological aspect."

His study revealed that the introduction of fish increased crop yields by 25%, resulting in a net benefit for each household of at least $380 per year.

The presence of predatory fish in the rice paddies has also reduced the number of snails.

Gathered in a house in Lampsar on a sweltering afternoon, several rice farmers share their experiences.

"I've noticed that fields with fish are always greener than those without, thanks to the fish excrement," 62-year-old Abdoulaye Diop told AFP. "The fish waste serves as organic fertilizer and increases rice yields," he added happily.

He explains that since his first harvest he has been able to invest in sheep and poultry farming.

Earlier that day, when interviewed in his green rice paddy, Mr. Ndiaye, the research project coordinator for the Lampsar community, added: "It really is profitable! People are interested in it."

- To other African countries -

On the day the AFP team met him, he had collected 20 bags of

rice weighing 80 kilos each, and a few days later, more than 350 Nile tilapia, on his farm.

Maï Diop, from a family of rice farmers spanning several generations, states unequivocally that her goal in participating in this project is to "have much more income" which will allow her to support her family.

"At home, we eat rice at least one out of every three meals. Thieboudienne is my favorite dish!", she says, referring to this traditional dish made with rice and fish, an emblem of Senegalese cuisine.

In an aquaculture facility located within the Gaston Berger University in the city of Saint-Louis, not far from Lampsar, Nile tilapia and snails are waiting to be transferred to experimental rice paddies belonging to "AfricaRice", a pan-African rice research center.

The objective is to conduct the same research, but in a controlled environment, and where appropriate to develop the project in other African countries.

"The idea is not to simply stay in Senegal, it is that once we have the expected results, this will be implemented in many African countries," hopes Ali Ibrahim, representative of the AfricaRice Regional Station for the Sahel.