Tropical Medicine and International Health volume 4 no 12 pp 872–874 december 1999 © 1999 Blackwell Science Ltd 872 Short communication: Plasmodium falciparum and P. malariae infections in isolates from sickle cell gene carriers living in a hyperendemic area of Gabon Georgette Blampain-Azzibrouck 1 , Faustin Lekoulou 1 , Georges Snounou 2 , Jean-Claude Ravollet 3 and Francine Ntoumi 1 1 Centre International de Recherches Médicales, Franceville, Gabon 2 Department of Infection and Tropical Medicine, Imperial College School of Medicine, Lister Unit, Northwick Park Hospital, Harrow, United Kingdom 3 Hôpital de la COMUF, Mounana, Gabon keywords malaria, Plasmodium falciparum, Plasmodium malariae, PCR, sickle-cell trait, Gabon correspondence Francine Ntoumi, Centre International de Recherches Médicales (CIRMF), B.P. 769, Franceville, Gabon. e-mail : fntoumi@cirmf.sci.ga Introduction Plasmodium falciparum is one of the major causes of child- hood mortality in sub-Saharan Africa. In hyperendemic areas of Africa two to four species of the parasite coexist and people may be simultaneously infected with more than one. Preliminary analysis of the distribution of P. falciparum- infected children in Côte d’Ivoire revealed that concurrent P. malariae infections were more frequent in asymptomatic than in symptomatic children (Black et al. 1994). Recently in a study of malaria in Vanuatu, it was observed that the clini- cal incidence of P. vivax differed significantly between homozygous +–thalassaemic and normal/heterozygous young children, and it was speculated that this might play a part in the protective effect of +-thalassaemia (Maitland et al. 1996, 1997; Williams et al. 1996). In previous studies of malaria parasites circulating in Gabonese villagers (Ntoumi et al. 1997), it was shown that P. falciparum populations were more complex (multiple lines) in sickle-cell trait carriers than in hosts with normal haemo- globin. The aim of this study was to examine the complexity of malaria species infections according to haemoglobin car- riage ascertain whether in vivo haemoglobin S carriers differ in their susceptibility to different malaria species. The preva- lence of Plasmodium was evaluated using a sensitive PCR parasite-detection protocol (Snounou et al. 1993b). Methods Blood samples were collected from residents of Mounana, a mining region located in south-eastern Gabon, during the rainy season (February to May) 1996. This region is hyper- endemic for malaria. The persons sampled had no history of fever and no malaria symptoms, and were recruited in the study when they attended the hospital of Mounana for a check-up. The subjects were grouped according to their haemoglobin phenotype (50 with haemoglobin AA and 64 with haemoglobin S). Their age ranged from 1 to 76 years. Urine samples were also collected and used to test for the presence of antimalarial drugs (Saker & Solomons 1987). The haemoglobin genotype was determined using acetate electrophoresis. Parasitaemias were enumerated by examin- ation of 200 microscopic fields of Giemsa-stained thick and thin blood smears. This study was approved by the ethical committee of the International Centre for Medical Research of Franceville, Gabon. Red blood cell pellets were prepared from venous blood samples as described by Ntoumi et al. (1995) and frozen in liquid nitrogen. Parasite DNA was extracted from 100 l of whole blood by phenol-chloroform procedure described by Robert et al. (1996) and resuspended into 20 l of sterile water. Parasites were detected and speciated using a nested PCR assay in which the small subunit ribosomal RNA genes TMIH500