A thirteen-year analysis of Plasmodium falciparum populations reveals high conservation of the mutant pfcrt haplotype despite the withdrawal of chloroquine from national treatment guidelines in Gabon

<p>Abstract</p> <p>Background</p> <p>Chloroquine resistance (CR) decreased after the removal of chloroquine from national treatment guidelines in Malawi, Kenia and Tanzania. In this investigation the prevalence of the chloroquine resistance (CQR) conferring mutant <it>pfcrt </it>allele and its associated chromosomal haplotype were determined before and after the change in Gabonese national treatment guidelines from chloroquine (CQ) to artesunate plus amodiaquine (AQ) in 2003.</p> <p>Methods</p> <p>The prevalence of the wild type <it>pfcrt </it>allele was assessed in 144 isolates from the years 2005 - 07 by PCR fragment restriction digest and direct sequencing. For haplotype analysis of the chromosomal regions flanking the <it>pfcrt </it>locus, microsatellite analysis was done on a total of 145 isolates obtained in 1995/96 (43 isolates), 2002 (47 isolates) and 2005 - 07 (55 isolates).</p> <p>Results</p> <p>The prevalence of the mutant <it>pfcrt </it>allele decreased from 100% in the years 1995/96 and 2002 to 97% in 2005 - 07. Haplotype analysis showed that in 1995/96 79% of the isolates carried the same microsatellite alleles in a chromosomal fragment spanning 39 kb surrounding the <it>pfcrt </it>locus. In 2002 and 2005 - 07 the prevalence of this haplotype was 62% and 58%, respectively. <it>Pfcrt </it>haplotype analysis showed that all wild type alleles were CVMNK.</p> <p>Conclusion</p> <p>Four years after the withdrawal of CQ from national treatment guidelines the prevalence of the mutant <it>pfcrt </it>allele remains at 97%. The data suggest that the combination of artesunate plus AQ may result in continued selection for the mutant <it>pfcrt </it>haplotype even after discontinuance of CQ usage.</p