Epidemiology of metal accumulation through the coupled life cycles of copepods, tape worms, cyprinid fish and humans in the coastal zone of Lake Victoria, Kenya.

The cyprinid fish Rastrineobola argentea is one of three economically most important fishes of Lake Victoria despite the very large changes in the trophic structure of the lake caused by the invasion the water hyacinth and the introduction of the Nile perch. The current foodchain microalgae-copepods-fish-humans/birds is compromised by a very high degree of infestation with the tapeworm Ligula intestinalis. At the same time the increased run-off and pollution from the catchment has intensified the cycles of metals and metalloids in the coastal zone. Preliminary observations indicate that both the transfer of food and the associated metals/metalloids from copepods into fish is confounded by the infestation with the parasites. Yet, it is unknown whether an increased metal concentration in the flesh of the R. argentea would be a consequence or a cause of infestation with the tapeworms. This research aims to establish the distribution of metals (Hg and Pb) and metalloids (As and Se) in the water, sediment and biota of Lake Victoria; to establish the feedback of infestation of R argentea with L. intestinalis and to establish the relationship of the metal/metalloids accumulation in landed R. argentea and body burdens of young children having a large share of the fish in their diet. It is hypothesized that metals and metalloids from water and sediment from L. Victoria accumulate in the local food chain via specific bio-concentration mechanisms that ultimately affect the health of exposed children. The biological and environmental samples collected from the lake will be analysed for metal/metalloids using Atomic Absorption Spectrophotometry and Gas Chromatographic Mass Spectrometry to discriminate alkylated and inorganic forms of Hg, Pb, As, and Se. An experimental verification will be conducted using consortia of copepods-fish-tape worms exposed to manipulated regimes of metals/metalloids. Hair samples will be collected from children in lakeshore families exposed and unexposed to R. argentea via their diet. Data from three test sites in the Kenyan part of the lake will be statistically evaluated and thereby the epidemiology of metal/metalloid associated health effects in the lake will be analysed.