Heavy metal concentrations in environmental samples and amphibian tissues in the Niger Delta, Nigeria: correlations with parasite species

Soil samples and amphibian host specimens were collected monthly from Agbada, an oil flow station in the Niger Delta region of Nigeria, for heavy metal analysis and also for the recovery of the helminth endo-parasites of the amphibians. Collection of samples was done monthly for a period of twelve months and heavy metal analysis was done by wet digestion of environmental and biological samples using atomic absorption spectrophotometer. Parasites were collected using standard protocols. Both environmental and biological samples accumulated varying concentrations of the heavy metals. All the concentrations of the metals in environmental samples were lower than the target values, whereas concentrations of all the metals in the biological samples exceeded the permissible limits. Seventeen parasite species were recovered from infected hosts and included nematodes, trematodes, cestodes, pentastomids, and acanthocephalan cysts. Pearson’s correlation coefficients  were computed for pairs of heavy metal concentrations in the environmental and biological samples with the parasite burdens and the results revealed among other findings that the lung trematodes, Haematoloechus exoterorchis and H. micrurus, correlated significantly positively with Cu in the soil samples and negatively with Pb and Cd in lungs and Cr in soil. This reflects the conditions that favor and hinder the ability of the parasites to establish infection in their host specimens.