Dr Joseph Nelson Siewe Fodjo

Onchocerciasis (river blindness) is a neglected tropical disease manifesting clinically as skin and eye problems. It is caused by the parasite Onchocerca volvulus, transmitted by the blackfly insect. It is the world’s second-leading cause of preventable blindness, with 99% of the almost 21 million infected people living on the African continent.

Epidemiological evidence suggests that infection with this parasite can also induce neurological conditions such as epilepsy and neurocognitive decline; furthermore, the painful bites of blackflies are a source of nuisance and psychological distress among affected communities. Blackflies breed best in fast-flowing fresh waters. It is a pest in several countries, including Cameroon, where the construction of dams has created conducive circumstances for the blackfly vector to thrive.

Thus far, attempts to control these insects have involved the use of chemicals to kill the developing larvae in rivers, often resulting in adverse repercussions for the environment and the emergence of resistance against the larvicides used. This option is also expensive and requires advanced technical skills for implementation. As a result, the approach was abandoned, leaving several communities helpless in the face of blackfly nuisance and onchocerciasis-associated morbidity.

During his PhD, Dr Joseph Nelson Siewe Fodjo tested a greener, more sustainable solution to this problem around the Maridi dam in South Sudan. He is extending the scope of his work with his Future Africa Research Leader Fellowship (FAR-LeaF) project, titled ‘Eco-friendly approach to reduce onchocerciasis transmission around the Edea dam in Cameroon’.

His team’s novel “slash and clear” technique will reduce the blackfly population around the dam. With the use of machetes, they will cut down trailing vegetation and other breeding substrates on the fast-flowing downstream section of the dam. In South Sudan, they found that a single “slash and clear” intervention was enough to drastically decrease the blackfly population in the surrounding villages for months. Mathematical models suggest the process can significantly accelerate onchocerciasis elimination prospects in endemic sites.

The technique has the advantage of being less dangerous for the aquatic environment as larvicidal chemicals are not being poured into rivers. Trained local villagers can perform the technique making it a sustainable option and one that can be a source of income in the long term. This is important because several dams are being constructed across the Sanaga River of Cameroon for hydroelectricity generation, and many villages and communities nearby have experienced a surge in blackfly bites, rekindling onchocerciasis transmissions.

The research will investigate whether or not the new technique will derange the ecological balance around the rivers during the months following its implementation. The project will be piloted around the Edea dam, where necessary blackfly nuisance and high burdens for both onchocerciasis and epilepsy have been documented. If proven to be more beneficial than harmful, the technique could be replicated at other dam sites, thus improving the health and well-being of communities.

Dr Siewe Fodjo will measure blackfly biting rates before and after the intervention using specially designed blackfly traps, and will interview indigenous people about notable changes regarding blackfly nuisance and diseases in their community. The reduction of blackflies in the area is expected to last many months, and local volunteers will be taught to repeat the intervention without supervision.