Prawns vs Snails: Scientists Launch Biocontrol Project in Mwea to Fight Bilharzia and Save Kenya’s Rice

By Gladys Mathenge

In a pioneering effort to tackle both agricultural pests and public health threats, the Institute in partnership with Israel’s Ministry of Agriculture and Ben Gurion University, has launched a pilot project introducing freshwater prawns into water bodies in Central, Coastal and Western regions of the country.

On Monday, 15th September 2025, the research teams accompanied by a battery of journalists visited the rice paddies at the Mwea Irrigation Scheme to witness the first hand release of prawns aimed at controlling the invasive golden apple snails while reducing the spread of bilharzia (schistosomiasis).

The idea is to use monosex freshwater prawns scientifically known as Macrobrachium spp. as natural predators of the destructive apple snails, which have been ravaging Kenya’s largest rice-growing region. The same snails also act as hosts for parasites that transmit bilharzia, a disease that continues to affect millions across Africa. By combining food production with disease control, the project seeks to deliver a sustainable, environmentally friendly, and economically viable solution.

“During peak season in Mwea, in a one-meter square of field you can find about 200 snails. They cause up to 16 percent losses in rice yield and pose a serious public health threat,” said Mr. Geoffrey Maina, KEMRI principal laboratory analyst. “They thrive along the canals during the rainy season, especially when rice is at the seedling stage.”

Prof. Amir Sagi of Ben Gurion University explained the dual benefits: “The idea is to establish prawn production so farmers will harvest both rice and prawns. The prawns feed on the snails, and at the end of the season, farmers have two products. This prawn species is grown as monosex, so it cannot reproduce or become invasive.”

KEMRI’s Co-Principal Investigator, Mr. Ibrahim Mwangi, emphasized the public health angle. “Even though praziquantel is available for bilharzia treatment, re-infection rates are high due to continued exposure to contaminated waters. Using prawns alongside treatment will complement control efforts. We are also seeking collaboration with local aquaculture farmers to rear these prawns here in Kenya.”

Israel’s Ministry of Agriculture Project Manager, Dr. Amit Savaya, underscored the potential of the approach for the wider region. “These prawns can eat dozens of snails within minutes. Since apple snails are already spreading across East Africa, starting with Kenya gives us a chance to scale this model to other countries, where it could strengthen food security and provide a protein source.”

 At the launch event, journalists and stakeholders observed live demonstrations in Mwea’s rice paddies and engaged with experts on how the approach can be adapted nationally. Beyond health and agriculture, the project also seeks to create new livelihood opportunities through aquaculture, enabling farmers to diversify income while cutting back on chemical use.

As invasive snails continue to spread across East Africa, the Mwea pilot could become a blueprint for how science-driven innovation integrates agriculture, health, and sustainability to protect food systems and improve community well-being.