Tissue and parasite accumulation of heavy metals in the giant rat (<i>Cricetomys gambianus</i>) as bioindicators of heavy metal pollution

Abstract

Heavy metal concentrations in tissues and cestode parasite of the African giant rat collected from staff quarters of the University of Benin, Benin City, Nigeria were determined using Atomic Absorption Spectrophotometry (AAS). Possible human health risk associated with consumption of contaminated rats was also determined using appropriate human intake models. The cestode isolated from the rat was identified as Inermicapsifer guineensis with total infection rate of 100%. The mean concentrations of heavy metals (mg/kg) in liver tissues of the giant rat ranged from 1.82 to 3.98 (Pb), 0.22 to 0.54 (Cd), 22.14 to 45.53 (Zn), 1.87 to 3.37 (Cu) and 1.25 to 3.15 (Co); in heart tissues ranged from 1.39 to 2.01 (Pb), 0.27 to 0.32 (Cd), 23.93 to 53.97 (Zn), 2.17 to 4.66 (Cu) and 1.45 to 2.27 (Co); in kidney tissues ranged from 0.75 to 1.67 (Pb), 0.41 to 0.93 (Cd), 22.77 to 42.14 (Zn), 1.82 to 1.90 (Cu) and 2.05 to 3.08 (Co); in muscle tissues ranged from 1.02 to 1.77 (Pb), 0.24 to 0.31 (Cd), 22.60 to 45.52 (Zn), 1.73 to 2.13 (Cu) and 1.04 to 1.82 (Co) and in parasite tissues ranged from 0.002 to 0.005 (Pb), 0 to 0.001(Cd), 1.19 to 2.63 (Cu) and 0.001 to 0.003 (Co). Mean total concentrations of individual heavy metals in the tissues and parasite of the rat decreased in the order zinc > copper > cobalt > lead > cadmium. Considering the mean concentrations of accumulated heavy metals, the heart and liver were found to be key target organs for heavy metal accumulation. Highly significant positive correlations was observed between heavy metal concentrations in tissues and the parasite (p<0.05, r=0.998), however, bioaccumulation values indicated much higher concentrating
capacity of heavy metals in the rat organs than the cestode parasite. Heavy metals are potential risk sources of contamination in the African giant rat (Cricetomys gambianus) and should therefore be priority for management in order to control human health risk through ingestion pathway exposures.

Keywords: Heavy metals, African giant rat, Parasite, Organs, Risk