Schistosomiasis control measures for small irrigation schemes in Zimbabwe : results from three years of monitoring at Mushandike Irrigation Scheme

ABSTRACT

A pilot study was initiated in 1984 on the 600 ha Mushandike Irrigation Project near Masvingo; Zimbabwe; with the objective of developing and field-testing practical guidelines to reduce the risk of schistosomiasis transmission for use by those involved in planning; designing; constructing and operating small-holder irrigation projects in Zimbabwe. Schistosomisasis is a parasitic disease which is particularly pravalent on irrigation land because of high levels of human contact with water and because colonisation by the aquatic snails; which act as its intermediate hosts; is generally favoured by the equatic enviornments created within irrigation and drainage systems. A number of important phases of the project are complete. These include formulating criteria for schistosomiasis control; implementing these criteria with the design and construction processes; establishing regular monitoring of the human and snail populations and introducing micro-computer assisted irrigation scheduling to reduce the likelihood of smail colonisation in parts of the system. Interim results form the monitoring exercise are now available which enable comparisons to be drawn between different zones of the project and with irrigated land nearby on which control measures have not been introduced. These results indicate that a combination of concrete lining; irrigation scheduling and using innovative control structures on the infield works has had a major impact on the snail hosts. Some disease transmission is; however; occuring in the pilot areas. This is apparently associated with some unsuitable village lacations; inadequate access to safe domestic water supplies and enhanced flows in some natural drainage channels; This report reviews the monitoring to date and discusses what further studies are needed to establish the effectiveness of the control measures: