Differential Prevalences of Pfmdr1 Polymorphisms in Symptomatic and Asymptomatic Plasmodium falciparum Infections in Lastoursville: A Rural Area in East-Central Gabon

PURPOSE: Plasmodium falciparum malaria remains a major public health challenge in sub-Saharan Africa. Plasmodium falciparum drug resistance mediated by polymorphisms in the Pfmdr1 gene contributes to the persistence of the disease on the African continent. This study investigated P. falciparum infection features and differences in the Pfmdr1 genotypes between symptomatic and asymptomatic malaria cases in a rural area in east-central Gabon. PATIENTS AND METHODS: A total of 875 children aged from 5 to 185 months were screened for P falciparum infection using Optima-IT(®) rapid diagnostic tests and standard microscopy. Pfmdr1 polymorphisms at codons 86, 184 and 1246 were investigated using PCR-RFLP. RESULTS: Among the 448 P. falciparum-infected children, 57.08% (n=250) were symptomatic and 42.92% (n=198) were asymptomatic (p < 0.0001). In a sub-set of 79 isolates, the Pfmdr1 wild-type N86 was more prevalent in symptomatic (100%) than in asymptomatic infections (70.7%) (p=0.007). The mutant 86Y and mixed 86N/Y genotypes were observed only in asymptomatic infections. The Y184 and 184F genotype prevalences (39.1% vs 19.4% and 60.9% vs 80.6%, respectively) were not significantly different between the two groups (p=0.097). The prevalence of the wild-type D1246 differed significantly between symptomatic (10.3%) and asymptomatic (100%) (p < 0.0001). The NFD and YFD haplotypes were more prevalent in asymptomatic than in symptomatic infections [(61.9% vs 31%; p=0.005) and (16.7% vs 0.0%; p=0.01)], whereas the NYD and YYD haplotypes were not significantly different between the two groups [(21.4% vs 14.3%, p=0.39) and (0.0% vs 7.1%, p=0.24)]. CONCLUSION: Our results confirm a high transmission of P. falciparum infection in rural Gabon, with a high prevalence of asymptomatic carriage. The higher prevalences of wild-type N86 in symptomatic infections and of D1246 in asymptomatic infections suggest a pathogenicity associated with polymorphisms in Pfmdr1. These results highlight the need to monitor the efficacy of artemisinin-based combination therapies in Gabon.