Peripheral blood and bone marrow leucocytes in Gambian children with malaria: numerical changes and evaluation of phagocytosis.

Neutrophilia, monocytosis, eosinopenia and reactive lymphocytes were found in the peripheral blood of infants and children with acute malaria at presentation. These changes were mostly reversed by days 3 and 7 after starting treatment. Mild rebound eosinophilia was seen in three cases after starting treatment. In patients with low grade malaria and anaemia, peripheral blood counts did not alter significantly after treatment. Two patients with mild eosinophilia at presentation were subsequently found to have strongyloidiasis and the eosinophil count rose markedly in one after treatment of malaria. Bone marrows were hypercellular in all cases. There was a low mean percentage of myeloid precursors in the marrow of all children as compared with the normal. This was due to increased lymphocyte percentage in those with acute malaria and to marked erythroid hyperplasia in those with low grade malaria. Phagocytosis of parasitized and non-parasitized red cells by bone marrow macrophages was seen most frequently in children with high parasitaemias, but erythroblast phagocytosis was more commonly seen in those with low grade malaria. There was no absolute correlation between the presence or absence of erythrophagocytosis in marrow macrophages and the presence or absence of a positive direct antiglobulin test (DAT) in children with malaria. This indicates that immunological mechanisms cannot be implicated as the sole cause of erythrophagocytosis in these bone marrows.