Schistosomiasis host snail control in irrigation night storgage reservoirs
The control of the host snails of schistosomiasis in irrigation schemes, particularly in night storage reservoirs, is important if the users of irrigation water and the occupants of the villages served by the irrigation scheme are to be protected from transmission of the disease. The report describes two biological methods of snail control which have been evaluated under laboratory and controlled field conditions.
Background
The construction of dams and establishment of new irrigation systems can create habitats suitable for aquatic snails, such as the host snails of schistosomiasis. It is important that methods are found which can safely control the host snails of schistosomiasis in irrigation schemes, but which do not interfere with the normal operation of the scheme.

Potential transmission sites in irrigation schemes include:
- Long main canals
- Night storage reservoirs
- Pools in natural streams

This research output focused on the control of snails in night storage reservoirs.

The report
The report describes two biological methods of snail control which have been evaluated under laboratory and controlled field conditions:

  • The introduction of competitor snails
  • The introduction of two species of fish, one to reduce aquatic vegetation and the other to predate snails.
At the time of completing the study the methods had not evaluated on a wider field scale

What it Covers
The report provides an introduction to schistosomiasis and explains how irrigation schemes can create habitats suitable for aquatic snails. In addition to the evaluation of biological control, summary information is included on the control of schistosomiasis through environmental control of snails.

   This includes design of channels to maintain high flow velocities, operation of channels and reservoirs to ensure fluctuation of the water level and periods of desiccation.

The conclusions of the preliminary trials of the biological control methods - snail competition and the use of selected fish species - indicate that the methods may be complimentary and further investigation is justified. However, both methods would require some modification to the routine operation and management of a scheme to maximise their effectiveness.

Contributors
HR Wallingford Ltd, UK; Blair Research Institute, Zimbabwe; Danish Bilharziasis Laboratory.

Intended Users
The report presents preliminary findings and is aimed at researchers.

HR Wallingford, 1997. Schistosomiasis host snail control in irrigation night storage reservoirs. HR Wallingford, UK. Report no. OD/TN 83.

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For a CD ROM or a hard copy contact:
International Development Group, HR Wallingford Ltd, Howbery Park, Oxon, OX10 8BA, UK
Tel: +44 (0) 1491 835381, Fax: +44 (0) 1491 826352, E-mail: w5outputs@hrwallingford.co.uk