Project properties
Title Swimmers itch (zwemmersjeuk)
Group Aquatic Ecology and Water Quality Management Group
Project type thesis
Credits 36
Supervisor(s) Edwin Peeters (edwin.peeters@wur.nl)
Examiner(s) Edwin Peeters
Contact info More information with Marieke de Lange, marieke.delange@wur.nl, 0317-485784
Begin date 2016/02/29
End date 2016/10/31
Description The water board Rivierenland has asked Alterra to set up an investigation into an effective approach to swimmer's itch in recreational lakes. Swimmer's itch is an inflammatory reaction in the skin where larvae of the worm Trichobilharzia ocellata have penetrated, during or after bathing in natural freshwater. The larvae cannot penetrate human skin but die in the skin. This causes itching, which can sometimes last for days. In the Annex, background information on the lifecycle of Trichobilharzia, and possible measures to reduce or prevent nuisance are given.

Currently Alterra and Koeman & Bijkerk are making an inventory of partners (other water boards, recreation entrepreneurs, provinces) and locations to conduct fieldwork. The complete scope of the analysis has not yet been fixed pending this inventory.

However, it is clear that there are several aspects that need to be investigated, preferably under controlled laboratory conditions. This lends itself well as a thesis research projects.

1) The effectiveness of a cercariae trap.
Cercariae are positive phototactic and possibly also chemotactic. The latter could be used to develop a cercariae trap. A possible active substance is linoleic acid, which can be applied on buoys which are placed around 'hot spots'. To test the efficiency of such traps, experiments are needed in the laboratory, possibly combined with larger-scale experiments in the field.

2) The effectiveness of a cercariae barrier
After leaving the snail cercariae swim to the surface in search of a duck or other waterfowl. Snails that are infected with Trichobilharzia are located in the vegetated riparian zone of the lake. When these hot spots can be identified, a barrier can be constructed to prevent cercariae reaching the bathing area. Such a barrier may consist of a curtain suspended from a buoy line and up to approximately a half meter depth in the water. To test the efficiency of such a barrier, experiments are needed in the laboratory, possibly combined with larger-scale experiments in the field.

3) Testing of a relatively simple method to measure the density of cercariae in the field.
There is a scientific article available that describes a method to 'lure' cercariae on a microscope slide with linoleic acid, and then counting them using a light microscope. This is potentially a simple method to be used by the local water manager. This should be further tested in the lab and the field. Possibly combined with the effectiveness of the cercariae trap and barrier.


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