The possible role of soil particles in the aetiology of non-filarial (endemic) elephantiasis: a macrophage cytotoxicity assay.

A link between the incidence of non-filarial elephantiasis and tropical red clay soil has been suggested after epidemiological surveys in Ethiopia and other African countries, although the mode of action of these soils in disease induction is unknown. We have thus investigated the physical composition of soils from both endemic and non-endemic areas of Ethiopia and their effect on the viability of macrophages using in vitro systems. Endemic and non-endemic soils were avidly phagocytosed by the macrophages. Cell shape was seen to change over a 144-hour period, the cells changing from approximately circular to spindle or stellate shape. Both groups of soils were cytotoxic towards the macrophages. Greatest cell death occurred during the first 48-hour period although some cells were viable after 96 hours. The soil groups could be divided by assessing their contents of silicon and aluminium, as well as observing the number of sub-2 micron particles they contained. The present study gives support to the epidemiological studies implicating soils as the cause of non-filarial elephantiasis.