Molluscicidal and Antioxidant Activities of Silver Nanoparticles on the Snail Intermediate Hosts of Schistosomiasis

Abstract

Background: Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. This disease is the second important parasitic disease after malaria in terms of its burden of disease. Methods: One of control intervention for schistosomiasis control programme is to perform the mollusciciding to interrupt the transmission through snail intermediate host where the parasites developed from miracidia to cercaria that is the infective stage. Accordingly, it is possible to improve the molluscicding effects after adding nanoparticulate agents in molluscicides. Results: This research field has caused more attention, since silver nanoparticles (Ag-NPs) were characterized by the transmission electron micrographs (TEM) with X-Ray fluorescence (XRF), showed that it’s mostly spherical in shape with average particle size diameters 20nm with high purity of synthesized particles (99.99%) of element was Ag. The aim of the present study is to demonstrate the molluscicidal effects of Ag-NPs against the three species of snails, including two species of intermediate snail host of Schistosoma mansoni (Biomphalaria alexandarina and Biomphalria glabrata) and one species of intermediate snail host of S. japonicum (Oncomelania hupensis), and the cercaricidal effects of Ag-NPs against Schistosoma mansoni cercariae. At the same time, their effects on snail’s antioxidant enzymes, e.g. catalase (CAT), glutathione reduced (GSH), nitric oxide (NO) and total antioxidants capacity (TAC), and on freshwater cladoceran (crustacean) Daphnia magna that represent the potential toxicity to other aquatic organisms were observed as well. The results indicated that Ag-NPs had a molluscicidal effect on tested snails with the variation in lethal concentration dose. LC50 of Ag-NPs exposure for 24, 48, 72 hrs and 7 days to B. alexandrina snails was 7.91, 5.69, 3.83 and 1.91 ppm respectively, LC50 for 24, 48, 72 hrs and 7 days exposure to B. glabrata snails was 16.55, 10.44, 6.91 and 4.13 ppm respectively, while LC50 for 24, 48, 72 hrs and 7 days exposure to Oncomelania hupensis snails was 46.5, 29.85, 24.49 and 9.62 ppm respectively. While the cercaricidal effects on S. mansoni cercariae was fast, since the lethal time LT50 and LT90 exposed to Ag-NP with 80 ppm concentration was 27 min and 45 min, respectively; and its 100 ppm exposed was 15min and 41 min, respectively. Moreover, there is no mortality rate to Daphnia magna when exposed to more than double and half dose (50 ppm) of Ag-NPs for continuous 3 hs, of which LC90 to B. alexandarina snails was 18 ppm. Conclusions: The synergistic effect of synthesized Ag-NPs as molluscicidal and cercaricidal was clearly revealed that it’s promising to be effectively used against various intermediate host snails of intestinal schistosomes and reduced it’s a potential antioxidant activity.