Following the positive results obtained regarding the molluscicidal
properties of the latex of Euphorbia splendens that were corroborated in
laboratory and field tests under restricted conditions, a field study was
conducted in experimental streams located in an endemic area. After
recording the average annual fluctuations of vectors in three streams, a
solution of E. splendens latex at 12 ppm was applied in stream A, a
solution of niclosamide at 3 ppm that was applied in stream B and a third
stream (C) remained untreated for negative control. Applications of E.
splendens and niclosamide resulted in a mortality of 100% among the snails
collected in the streams A and B. No dead snails were found in the negative
control stream. A monthly follow-up survey conducted during three
consecutive months confirmed the return of vectors to both experimental
streams treated with latex and niclosamide. This fact has called for a need
to repeat application in order to reach the snails that remained buried in
the mud substrate or escaped to the water edge, as well as, newly hatched
snails that did not respond to the concentration of these molluscicides.
Adults snails collected a month following treatment led us to believe that
they had migrate from untreated areas of the streams to those previously
treated.
