Reinforcing snail control activities for schistosomiasis

The transmission of schistosomiasis involves infected hosts excreting eggs that pass through a fresh-water-intermediated host snail living in marshlands, ponds, rivers or irrigation canals that will produce larvae that will infect humans.

WHO recommends a comprehensive strategy including preventive chemotherapy, snail control, provision of safe drinking-water, sanitation, health education for behavioural change and environmental management to control and eliminate schistosomiasis.

Snail control aims at removing the intermediate host snails to interrupt the transmission chain. It can be done through a variety of methods: environmental control, biological control, chemical control etc. Snail control was for many years the only strategy for the prevention of schistosomiasis prior to the advent of preventive chemotherapy.

Community capacity in malacology and snail control has declined in endemic countries due to the low interest of the programmes for the implementation the vector control interventions.

Over the past few years, WHO has made efforts to fill this gap by formulating updated guidance on public health use of molluscicides and on monitoring and evaluation of programmes relying in this intervention. Two documents have been published recently by  WHO:  i. a manual on field application of  molluscicide and ii. Guidelines on the evaluation of molluscicides. By publishing these guidelines, WHO encourages producers to develop new molluscides.

WHO supports Member States in strengthening their capacity to implement snail control activities. Several training workshops on malacology and snail control were organized in Cameroon, Tanzania (Zanzibar) and Burkina Faso from 2016 to 2018.