Molluscicidal and antioxidant activities of silver nanoparticles on the multi-species of snail intermediate hosts of schistosomiasis

PLoS Negl Trop Dis. 2022 Oct 10;16(10):e0010667. doi: 10.1371/journal.pntd.0010667. eCollection 2022 Oct.

Abstract

Background: Schistosomiasis, also known as bilharzia, is the second important parasitic disease after malaria. The present study aimed to evaluate the molluscicidal effects of silver nanoparticles on Biomphalaria alexandrina, B. glabrata, Oncomelania hupensis, snail intermediate hosts of intestinal schistosomes (i.e. Schistosoma mansoni and S. japonicum), along with the changes their antioxidant enzymes.

Methods: Silver (Ag) nano powder (Ag-NPs) was selected to test the molluscicidal effects on three species of freshwater snails. Exposure to Ag-NPs induced snail mortality and the LC50 and LC90 values of Ag-NPs for each snail species were calculated by probit analysis. Control snails were maintained under the same experimental conditions in dechlorinated water. Snail hemolymph was collected to measure the levels of antioxidant enzymes, such as total antioxidants capacity (TCA), glutathione (GSH), catalase (CAT) and nitric oxide (NO). In addition, the non-target organism, Daphnia magna, was exposed to a series of Ag-NPs concentration, similar to the group of experimental snails, in order to evaluate the LC50 and LC90 and compare these values to those obtained for the targeted snails.

Results: The results indicated that Ag-NPs had a molluscicidal effect on tested snails with the variation in lethal concentration. The LC50 values of Ag-NPs for B. alexandrina snails exposed for 24, 48, 72 hrs and 7 days were 7.91, 5.69, 3.83 and 1.91 parts per million (ppm), respectively. The LC50 values for B. glabrata snails exposed for 24, 48, 72 hrs and 7 days were 16.55, 10.44, 6.91 and 4.13 ppm, respectively, while the LC50 values for O. hupensis snails exposed for 24, 48, 72 hrs and 7 days were 46.5, 29.85, 24.49 and 9.62 ppm, respectively. Moreover, there is no mortality detected on D. magna when exposed to more than double and half concentration (50 ppm) of Ag-NPs during a continuous period of 3 hrs, whereas the LC90 value for B. alexandrina snails was 18 ppm. The molluscicidal effect of the synthesized Ag-NPs seems to be linked to a potential reduction of the antioxidant activity in the snail's hemolymph.

Conclusions: Synthesized Ag-NPs have a clear molluscicidal effect against various snail intermediate hosts of intestinal schistosome parasites and could potentially serve as next generation molluscicides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / pharmacology
  • Biomphalaria*
  • Catalase
  • Glutathione / pharmacology
  • Metal Nanoparticles*
  • Molluscacides* / pharmacology
  • Nitric Oxide
  • Schistosoma mansoni
  • Schistosomiasis* / prevention & control
  • Silver / pharmacology
  • Water

Substances

  • Antioxidants
  • Molluscacides
  • Water
  • Nitric Oxide
  • Silver
  • Catalase
  • Glutathione

Grants and funding

This project was supported by Research Fund for the Technical Reserves from National Institute of Parasitic Diseases at Chinese CDC (No. CB-1603 to YHG), and by Young excellent scientists program of Ministry of Science and Technology of the People’s Republic of China (to KMZ). It is also supported by the Regular Assistance Project of International Department of the Ministry of Science and Technology of China (Grant No. KY201904013 to XNZ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.