In line with previous studies [[3], [4], [5], [6], [7], [8], [9],11,12], we found decreases in Hb and MCV that were significant in the analysis of individuals older than 16 years as well as in the sub-analyses of urogenital and intestinal schistosomiasis, whilst differences in haematocrit were not significant. The gene discussed is GSTM1; the disease is intestinal schistosomiasis.