Combined Effects of Parasitic Infection and Heavy Metal Exposure on Health and Profitability of Cultured African Catfish (Clarias gariepinus).

Abstract

Fish are essential for providing the world's nutritional requirements, as they account for 60% of the protein consumed worldwide and 30% of the protein consumed in developing nations. The African catfish is a valuable commercial fish due to its low prices and abundance as a source of omega fatty acids and protein. The health of these species can be affected by the quality of freshwater. So, this study elucidates the interaction between parasitic infection (severely and mildly infected) and heavy metals (HMs) as stressors in cultivated African Catfish (Clarias gariepinus). Results displayed high rates of parasitic infestation, 81.58% in the examined C. gariepinus, with an intensity range of 1-80 /fish. A total of 4 different types of endoparasites were recorded from all examined fish. These endoparasites are represented as two nematodes (Procamallanus sp and Paracamallanus sp), and two cestodes (Proteocephalus sp. and Polyonchobothrium clarias). Markedly, results displayed adverse effects of infection and heavy metal on the haemato-biochemical indices and oxidative stress in C. gariepinus. Also, the length-weight relationship, immune-related genes, and histopathological features in C. gariepinus were affected. Moreover, the HMs order in water and tissue is from the highest to the lowest: Fe&#x2009;>&#x2009;Zn&#x2009;>&#x2009;Cu&#x2009;>&#x2009;Mn&#x2009;<&#x2009;Pb&#x2009;>&#x2009;As&#x2009;>&#x2009;Cd, except Mn in fish tissue. Furthermore, HMs concentrations in C. gariepinus organs are arranged in descending order as follows: Liver&#x2009;>&#x2009;Gills&#x2009;>&#x2009;Kidney&#x2009;>&#x2009;Spleen&#x2009;>&#x2009;Intestine&#x2009;>&#x2009;Muscles. Concurrently, the (HMs) level was significantly reduced in severely and mildly infected fish than in uninfected fish. Also, there was a significant negative correlation between parasite prevalence and HMs. In contrast, Pb and Cd showed a positive correlation between water and fish organs. However, THQ and HI values were less than 1, suggesting that adults do not face significant non-carcinogenic health concerns. The data indicated that the combined stress of parasite infection and HMs reduces fish farming's profitability, including a total loss of 7.50&#x2009;&#xb1;&#x2009;0.89 tons/ feddan over the production season. Hence, this study shows that intestinal parasites modify heavy metal accumulation levels in C. gariepinus. Moreover, metal pollution and intestinal parasites cause significant economic losses in aquaculture through various adverse health effects. Also, monitoring heavy metals in fish tissues and water and using health risk assessment indices such as EDI, THQ, and HI are critical to protecting aquaculture management and public health.