The toxic and behavioural effects of niclosamide (Bayluscide WP 70^R) on
Biomphalaria straminea from a highly endemic area of schistosomiasis in
northeastern Brazil were investigated through laboratory bioassays. The
LD50 and LD90 were 0.114 mg/l and 0.212 mg/l, respectively. Water-leaving
behaviour occurred among 14% to 30% of the snails in the presence of
sublethal doses of niclosamide and among 16% of the controls. It was
concluded that both the relatively low susceptibility to niclosamide and
water-leaving behaviour of local B. straminea may be responsible for
the recolonization of transmission foci after mollusciciding. It was
suggested that recently improved measures of snail control, such as
controlled-release formulations of niclosamide and plant molluscicides
should be considered in areas where snail control is recommended.
