Acaricidal, pediculocidal and larvicidal activity of synthesized ZnO nanoparticles using wet chemical route against blood feeding parasites.

The present study was based on assessments of the anti-parasitic activities to determine the efficacies of synthesized zinc oxide nanoparticles (ZnO NPs) prepared by wet chemical method using zinc nitrate and sodium hydroxide as precursors and soluble starch as stabilizing agent against the larvae of cattle tick Rhipicephalus (Boophilus) microplus, Canestrini (Acari: Ixodidae); head louse Pediculus humanus capitis, De Geer (Phthiraptera: Pediculidae); larvae of malaria vector, Anopheles subpictus, Grassi; and filariasis vector, Culex quinquefasciatus, Say (Diptera: Culicidae). R. microplus larvae were exposed to filter paper envelopes impregnated with different ZnO NP concentrations. Direct contact method was conducted to determine the potential of pediculocidal activity. Parasite larvae were exposed to varying concentrations of synthesized ZnO NPs for 24 h. The results suggested that the mortality effects of synthesized ZnO NPs were 43% at 1 h, 64% at 3 h, 78% at 6 h, and 100% after 12 h against R. microplus activity. In pediculocidal activity, the results showed that the optimal times for measuring mortality effects of synthesized ZnO NPs were 38% at 10 min, 71% at 30 min, 83% at 1 h, and 100% after 6 h against P. humanus capitis. One hundred percent lice mortality was observed at 10 mg/L treated for 6 h. The mortality was confirmed after 24 h of observation period. The larval mortality effects of synthesized ZnO NPs were 37%, 72%, 100% and 43%, 78% and 100% at 6, 12, and 24 h against A. subpictus and C. quinquefasciatus, respectively. It is apparent that the small size and corresponding large specific surface area of small nanometer-scale ZnO particles impose several effects that govern its parasitic action, which are size dependent. ZnO NPs were synthesized by wet chemical process, and it was characterized with the UV showing peak at 361 nm. X-ray diffraction (XRD) spectra clearly shows that the diffraction peaks in the pattern indexed as the zinc oxide with lattice constants a = 3.249 and c = 5.206 Å. The FTIR spectrum showed the range of 400-4,000 cm(-1). The band at 899.56 cm(-1); 1,151.87 cm(-1); 1,396 cm(-1); and these bands showed the complete composition of ZnO NPs. SEM micrograph showed 60-120-nm size and aggregates of spherical shape nanoparticles. EDX showed the complete chemical composition of the synthesized nanoparticles of zinc oxide. The maximum efficacy was observed in zinc oxide against the R. microplus, P. humanus capitis, and the larvae of A. subpictus, C. quinquefasciatus with LC(50) values of 29.14, 11.80, 11.14, and 12.39 mg/L; r (2) = 0.805, 0.876, 0.894, and 0.904, respectively. The synthesized ZnO NPs showed the LC(50) and r (2) values against the R. microplus (13.41 mg/L; 0.982), P. humanus capitis (11.80 mg/L; 0.966), and the larvae of A. subpictus (3.19; 0.945 mg/L), against C. quinquefasciatus (4.87 mg/L; 0.970), respectively. The control (distilled water) showed nil mortality in the concurrent assay. This is the first report on anti-parasitic activity of the synthesized ZnO NPs.