The Effect of Sublethal Concentrations of the Molluscicide Triphenyl Lead Acetate on Biomphalaria glabrata (Say) and on the Development of Schistosoma mansoni in the Snail

Abstract

1. B. glabrata exposed to the sublethal concentrations (0·04 ppm, 0·03 ppm and 0·02 ppm) of TPLA died from the effects of the molluscicide over a period of time. Most of the deaths occurred between the 10th and 35th days after treatment, showing that although TPLA is slow acting, its effect is not continuous but restricted to a limited period of time.2. 0·01 ppm of TPLA was chosen as a sublethal concentration to study the effect of the molluscicide on the development of S. mansoni in B. glabrata.3. 240 B. glabrata were infected with S. mansoni, and 40 of these were treated with 0·01 ppm of TPLA 4 days before infection. The remaining 200 were divided into 5 groups of 40 each, one group being maintained as a control and the other four treated 2, 10,15 and 20 days postinfection respectively. Other suitable controls for comparison were also maintained.4. The infection rate in all groups was high, and comparison with the control showed that there was no significant difference in infection rate between the treated groups and the control group at the 5% level. However, the infection rate in the preinfection treated group was lower than in the control group and significant at the 10% level.