Study to Understand Resistance to Malaria in Nigeria

As a pilot study, the University of Ibadan in Nigeria has contributed a small number of severe malaria cases and healthy controls to Consortial Project 1. Malaria is endemic in Nigeria with seasonal transmission patterns, the peak transmission season being during the rainy season (Apr-Oct) followed by the dry season (Nov-Mar). Ibadan is a city located in the Southwest of Nigeria in the rain forest belt with 80 inches of rain or more per year and a relative humidity typically above 80 percent during the wet season. The predominant species of malaria parasite is Plasmodium falciparum accounting for about 96% of malaria infections. Two main species predominate as vectors in Nigeria, Anopheles gambiae and A. funestus.

Description of study population - Cases

Cases consist of children (aged 4-126 months) presenting with severe malaria, cerebral malaria and severe malaria anaemia. The children were recruited from three hospitals in the city of Ibadan: one tertiary hospital and two secondary level hospitals during the May-September transmission season of 2007. The inclusion criteria for recruitment were according to the World health Organization definitions. Severe malaria was defined by the presence of P. falciparum in the thick blood film with at least one of the following conditions: unrousable coma, with coma score, clear cerebro-spinal fluid from lumbar puncture, extreme weakness/prostration (inability to sit or stand without support), convulsions (more than one episode within 24 hours), severe anemia (Haematocrit <15% or Hb <5 g/dl). Children with co-existing bacterial meningitis and other encephalitis (especially the locally prevalent viral encephalitides) were excluded from the study.

Description of study population - Controls

Controls comprised of children (aged 6-112 months) recruited during a cross-sectional survey in September 2007 from communities in the areas surrounding the three hospitals from which cases were recruited. Clinically well children who had not been ill two weeks preceding recruitment, were recruited into the study.