Impact of subpatent multi-species and multi-clonal plasmodial infections on anaemia in children from Nigeria

Childhood anaemia in sub-Saharan Africa is often caused by Plasmodium falci parum malaria. The influence of subpatent, multi-species and polyclonal inf ections with malaria parasites on haematological parameters was assessed in 1996/97 in clinically healthy children in Nigeria. Of the 228 children stu died, 64% were anaemic by the WHO age-dependent criteria. A univariate anal ysis of risk factors indicated that the prevalence of anaemia was dependent on the number of Plasmodium species detected by species-specific PCR (P < 0.0001). Furthermore, the prevalence of anaemia increased gradually with th e complexity (P < 0.003) as well as with the extent of P. falciparum parasi taemia (P < 0.0001). A logistic regression analysis revealed that individua ls with an enlarged spleen tended to be anaemic. The number of Plasmodium s pecies by which an individual was infected was independently associated wit h anaemia (P < 0.03). ANOVA revealed that the age-corrected values for haem oglobin (Hb) and red blood cells (RBCs) were mainly influenced by the occur rence of mixed infections. Haematological parameters were also influenced b y the number of different P. falciparum clones by which an individual was i nfected. Hb levels and RBC counts were further diminished by additional inf ections with P. malariae and/or P. ovale. However, the effect of multi-spec ies infections on haematological parameters exceeded that of multi-clonal i nfections.