Control of Schistosomiasis
A Practical Guide for Irrigation Development
Schistosomiasis is a major health problem in parts of Africa, South America and Asia where it is endemic in many countries. Freshwater is required for several parts of the lifecycle of the schistome parasite and, as a consequence, this disease can be a major problem where freshwater resources are being developed. In particular, there is concern over the increased transmission of Schistosomiasis linked to irrigation projects. This practical guide sets out the lifecycle of the parasite and describes practical interventions to reduce levels of infection on irrigation schemes.
Background
In a research project at Mushandike irrigation scheme in Zimbabwe, an assessment was made of the extent to which engineers and planners, in co-operation with health professionals, could control the transmission of schistosomiasis through careful design and operation of the irrigation works and domestic facilities.
With an understanding of the schistome life cycle, all those involved in the planning and design of water resources projects, can incorporate measures into the basic scheme design which can have a significant effect on reducing levels of schistosomiasis infection. The Guide aims to provide that understanding.

The Guide
The Guide illustrates and describes each stage of the Schistome life cycle and explains the available control measures which can be targeted at that stage.
The control measures which design engineers and planners can incorporate into the basic design and operation of the irrigation system are also described in some detail.

What it covers
The control measures discussed in the guide include:

  • Chemotherapy of schistosomiasis
  • Eggs and sanitation
  • Control measures aimed at eliminating snails
         - Chemical
         - Engineering/Environmental
         - Biological
  • Reducing contact with cerariae infested water.
    Experience from a number of countries shows that the long term control of Schistosomiasis is most effective when carried out within the primary health care system.

    This report will therefore be useful to health professionals to raise their awareness that methods do exist by which design engineers can use preventative measures,such as:

  • Designing and building irrigation networks to avoid areas of ponding
  •  
  • Lining secondary and tertiary canals with concrete
  • Introducing fast flowing canals
  • Introducing water scheduling which permits each section of the canal network to periodically dry out

    Decisions made at the early planning phase can also have long-lasting implications for the health of the population. Potential transmission sites include:
    - Long main canals
    - Night storage ponds
    - Pools in natural streams

    Distance from potentially infected water bodies should, therefore, be an important consideration in the selection of sites for locating villages.

    The provision of safe water supplies and adequate sanitation will also contribute significantly to reducing infection levels and preventing contamination of water bodies with schistome eggs.

    Contributors
    HR Wallingford Ltd, UK; Blair Research Institute, Zimbabwe; AGRITEX, Zimbabwe.

    Intended users
    The report provides guidance and recommendations for planners, design engineers and other decision-makers involved in irrigation projects on how they can contribute to controlling schistosomiasis.
    It will also be of use to health professionals.

    Thomson, AJ; Chimbari, M; Chandiwana, SK; Ndlela, B and Chitsiko, RJ, 1996. Control of Scistosomiasis: A Practical Guide for Irrigation Development. HR Wallingford, UK. Report no. OD/TN 78.

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