Transmission Electron Microscopy–Based Analysis of Silver Nanoparticle–Induced Ultrastructural Damage and Bioaccumulation in Heterakis dispar (Nematoda: Heterakidae) Under In vitro Conditions

Helminths cause a wide range of diseases in different components of ecosystems and may induce serious pathological conditions in the host organisms. In recent years, nanoparticles have been increasingly used in ecology, veterinary medicine, and biology. In this study, the effect of silver (Ag) nanoparticles on the waterfowl parasite Heterakis dispar (Schrank, 1790), isolated from domestic geese (Anser anser domesticus L., 1758), was investigated under in vitro conditions, with particular emphasis on nanoparticle accumulation patterns and associated ultrastructural changes, studied at the ultrastructural level. In the experiments, H. dispar nematodes collected from the hosts were exposed in vitro to Ag nanoparticles at concentrations of 10, 50, and 100 μg/mL. Control and experimental groups of nematodes were examined using light and transmission electron microscopes. The sizes of Ag nanoparticles in a free state were 9.03-23.82 nm, and particles detected within the helminth organism were approximately 11-17 nm. It was visually observed that the particles were present in multiple layers of the body wall, in the digestive and reproductive organs of the parasitic worm. Silver nanoparticles enter the helminth through the body wall (from cuticle to the hypodermis, muscular layer, and organs located in the pseudocoelomic or body cavity) and the digestive organs (through the intestinal microvilli). At the ultrastructural level, notable alterations were observed in treated specimens. The results prove that Ag nanoparticles have anthelmintic activity.