Parasitic Infections by Encysted Metacercariae and Henneguya sp. Affected by Heavy Metals on Wild African Catfish (Clarias gariepinus)

Abstract

Aquaculture has become a vital source of protein to meet the global demand for food. The African catfish (Clarias gariepinus), a widely distributed and cultured freshwater species, is a significant component of this industry. This year-long study investigated the impact of Encysted Metacercariae (EMC) and Henneguya (HNG) parasites on the gills of wild African catfish in Burullus Lake, Egypt. 360 catfish were collected monthly over the course of a year to undergo clinical and parasitological examinations. While no overt clinical signs of illness were observed in the collected fish, parasitological analysis of internal organs, including gills, revealed the presence of EMC throughout the year. Microscopic examination confirmed the presence of cysts in some individuals. Infection rates were determined to be 5.72% for EMC and 41.88% for HNG. Importantly, the physicochemical parameters and heavy metal concentrations in Burullus Lake water remained within acceptable limits during the study period. Statistical analysis revealed significant seasonal variations in infection rates (p < 0.05), with the highest levels occurring during winter (62.61% for EMC and 78.88% for HNG). Additionally, infected catfish exhibited significantly elevated levels of both essential (Zn, Cu, Fe) and non-essential (Cd, As, Pb) heavy metals in their gill tissues during the winter compared to other seasons (p < 0.05). This study aimed to assess the prevalence and distribution of these two zoonotic parasites (EMC and HNG) in the African catfish population inhabiting Burullus Lake during the year 2023.