The aim of this study was to determine the toxicity of niclosamide
(Bayluscide ®) on
Melanoides tuberculata
and
Biomphalaria glabrata
under laboratory conditions. The latter species is the intermediate host
of
Schistosoma mansoni
(Sambon 1917).
M. tuberculata
was successfully used as competitor of B. glabrata in biological control
programs in French West Indies. Both molluscicide and biological control
using
M. tuberculata
have proved to be successful in reducing the population density of
B. glabrata
. The associated use of molluscicide in this area would be an effective
measure if
M. tuberculata
were less susceptibility to the molluscicide than
B. glabrata
. Three hundreds individuals each of
B. glabrata
and of
M. tuberculata
, collected in Sumidouro, State of Rio de Janeiro, were used in the experiment.
The molluscs were exposed to 14 different concentrations of niclosamide
as recommended by the World Health Organization. Probit analysis was used
to determine the LC 50 and LC 90. The LC 50 and LC 90 values for
B. glabrata
were 0.077 mg/l and 0.175 mg/l, respectively and the LC 50 and LC 90 values
for
M. tuberculata
were 0.082 mg/l and 0.221 mg/l respectively. As the lethal concentrations
of niclosamide were approximately the same to both species, this could be
a disadvantage when controlling
B. glabrata
with niclosamide in an area of
M. tuberculata
occurrence. It migth therefore be preferable to utilize the latex extracted
from the Euphorbia splendens, which presented a much higher efficiency for
B. glabrata
than to
M. tuberculata
.
