Snails and aquatic vegetation in Gezira irrigation canals
Hilali, A.M.; Desouqi, L.A.; Wassila, M.; Daffalla, A.A.; Fenwick, A.
Journal of Tropical Medicine and Hygiene 88(2): 75-81
1985
ISSN/ISBN: 0022-5304 PMID: 4032532 Document Number: 246532
All 38 canals in a limited area of the Gezira Irrigated Area, Sudan, were surveyed 4 times over a 2-year period to determine the aquatic and semi-aquatic vegetation types found and their distribution. A more detailed 2-year study of the correlation between snail density and aquatic vegetation was carried out in 18 of these canals. The schistosome vector snails Biomphalaria pfeifferi and Bulinus truncatus were found in conjuction with aquatic weeds and Biomphalaria pfeifferi in particular increased in numbers as weed growth continued. In the 2nd season of the study when mechanical weed clearing and regular focal mollusciciding was being carried out there was a noticeable reduction in weed density but repopulation was rapid. Snail numbers were reduced by mollusciciding and/or weed clearance in 4 canals, but outside the focal target canal stretches the weed clearance alone did not substantially reduce the snail populations.