Disease control
Collection of shells of snail species (Bulinus sp. and Biomphalaria sp.) that are intermediate hosts for Schistosoma blood flukes
Biomphalaria choanomphala is very abundant within its distribution range. Pick up almost any water hyacinth leaf in Lake Victoria (with gloves on - you wouldn't want to catch schistosomiasis) and you're likely to see one clinging to the underside of the floating leaf.
However, because of their role in transmitting schistosomiasis, in the 1980s there was an attempt to control the disease by killing all the host snails through widespread use of molluscicides.
This approach was too broad-brush, and highly ineffective:
- it killed lots of non-target (and non-dangerous) snails and other aquatic life
- it didn't really seem to affect the number of Biomphalaria snails in any significant way
Maintaining mollusc diversity in the face of disease control
Nowadays, we appreciate that this might have been the wrong way to tackle the problem: despite its role as a disease host, B. choanomphala is still part of nature and a building block of the biodiversity of Lake Victoria.
It may be more appropriate to manage the snails more sensitively and locally, for example by:
- filling up unused irrigation ditches and ponds (which also harbour malaria-carrying mosquito larvae).
- restoring some of the original fish biodiversity to the very over-fished Lake Victoria. This may act as a natural way of controlling B. choanomphala without eliminating it completely.