Molecular Characterization and Immunological Approaches Associated with Yellow Grub Trematode (Clinostomid) Infecting Nile Tilapia

Abstract

Yellow grub disease is caused by clinostomid metacercariae (CM) infecting freshwater fish and has a potential impact on human health by causing Halzoun disease. This study aimed to combine both molecular and immunological approaches to characterize CM naturally infecting Nile tilapia. Two hundred and fifty Nile tilapia, Oreochromis niloticus, were collected from Giza Governorate and screened for the presence of CM. Samples were collected from buccal cavities and blood of 20 highly infected fish (≥10 cysts/fish) under aseptic conditions. Partial sequencing of the ITS rRNA region was performed to identify and distinguish the causative agents from closely related species. The cellular immune response between infected and noninfected O. niloticus was investigated by quantitative real-time-PCR targeting tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Results showed significant increases in the levels of both TNF-α and IL-1β ( p < 0.01 ) in fish infected with Clinostomum phalacrocoracis when compared to those infected with Clinstomum complanatum and negative controls (3.6 ± 0.2). Furthermore, the assessment of the levels of lysozyme activity in infected fish sera showed high levels versus noninfected ones.