Polymeric controlled release formulations of niclosamide for control of Biomphalaria alexandrina, the vector snail of schistosomiasis

Schistosomiasis is one of the most important public health problems in many developing countries. The present study was conducted to investigate the effect of the polymeric niclosamide formulations against Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni in Egypt. Three new polymeric formulations were prepared for the molluscicide niclosamide. The formulations were prepared either by the chemical modifications of poly(glycidyl methacrylate) or by physical entrapment of the niclosamide in calcium alginate beads. The release of the niclosamide from the polymeric formulations was investigated. The activity of the prepared formulations against Biomphalaria alexandrina was investigated. The results obtained revealed higher potency for polymerized niclosamide B3 than B1; the lowest potency was revealed for B2. After an exposure period of 24 hours, LC50 values were 0.073, 0.098 and 1.09 ppm for B3, B1 and B2, respectively. In addition, the molluscicidal potency of the test polymeric niclosamide was age dependent, where old snails were more tolerant to the test solutions than young and newly hatched snails. The results also indicated that the molluscicidal activity of B3 was extended for 21 days and 17 days for B1, compared with 5 days for free niclosamide. However, the molluscicidal potency of the polymerized niclosamide was increased after boiling for one hour, and was increased with increasing the pH of the medium to pH 9. In addition, their potency was increased with decreasing the water hardness concentrations (CaCO3).