Background: This study investigates the contamination of Polycyclic Aromatic Hydrocarbon residues in the environmental media, Malapterurus electricus, and the parasite, Electrotaenia malopteruri, in the Epe axis of the Lekki Lagoon. The paper also investigates the role of the intestinal parasite in the host-gut PAH accumulation and the effect on the gut lipid profile, anti-oxidants and histological alterations. Grab samples of surface water, sediment, fish liver, intestines and intestinal parasites were collected and analyzed for PAHresidues using gas chromatography. The intestines of infected and non-infested fish and the parasite were analyzed for pathological alterations, lipid profile and antioxidant enzymes. Results: The prevalence of the cestode parasite, Electrotaenia malopteruri was 37.21%, among these infected fishes, 14 (16.28%) were females while 18 (20.93%) were males. Among PAHs congeners with 2-3 and 4-6 aromatic cyclic rings, naphthalene had the highest bio-concentration in the fish organs from the environmental media. The fish intestine bioaccumulated naphthalene 181 times more than the surface water concentrations, and 48 times more than the sediment. Other congeners that bioaccumulated in the fish intestine were fluorine, pyrene, dibenz (a,h)anthracene, dibenzo(a,l)pyrene, and benzo(g,h,i)perylene. The parasite bioaccumulated benz (a)anthracene, chrysene, benzo(a)pyrene, and benzo (g,h, i)perylene 18, 23, 3 and 2 times more than the host intestine respectively. The cholesterone, triglycerides and low-density lipid levels in Electrotaenia malopteruri were higher than that in the intestines of the infected and non-infected individuals. The intestinal anti-oxidants induced in the infected and non-infected individuals and in the parasite, Electrotaenia malopteruri were SOD, CAT, MDA, GSH and GPx. The parasite had more SOD, CAT and GPx than the infected and non-infected individuals. The intestine of the infected individuals had more SOD, CAT, GSH and GPx than the intestine of non-infected individuals.
Conclusions: These infected individuals had a higher frequency of gut pathological alterations compared to the non-infected individuals. The parasites are capable of depurating Polycyclic Aromatic Hydrocarbons in the fish host and were also subjected to more stress than both the infected and non-infected hosts probably as a result of the bioaccumulated contaminants within its tissues.