RESUMO
Chloroquine (CQ) is used as a first-line therapy for the treatment of Plasmodium falciparum malaria in Nicaragua. We investigated the prevalence of molecular markers associated with CQ and sulfadoxine-pyrimethamine (SP) resistance in P. falciparum isolates obtained from the North Atlantic Autonomous Region of Nicaragua. Blood spots for this study were made available from a CQ and SP drug efficacy trial conducted in 2005 and also from a surveillance study performed in 2011. Polymorphisms in P. falciparum CQ resistance transporter, dihydrofolate reductase, and dihydropteroate synthase gene loci that are associated with resistance to CQ, pyrimethamine, and sulfadoxine, respectively, were detected by DNA sequencing. In the 2005 dataset, only 2 of 53 isolates had a CQ resistance allele (CVIET), 2 of 52 had a pyrimethamine resistance allele, and 1 of 49 had a sulfadoxine resistance allele. In the 2011 dataset, none of 45 isolates analyzed had CQ or SP resistance alleles.
Assuntos
Cloroquina/farmacologia , Resistência a Medicamentos/genética , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Pirimetamina/farmacologia , Sulfadoxina/farmacologia , Alelos , Antimaláricos/farmacologia , DNA de Protozoário/genética , Di-Hidropteroato Sintase/genética , Combinação de Medicamentos , Humanos , Malária Falciparum/tratamento farmacológico , Proteínas de Membrana Transportadoras/genética , Nicarágua , Plasmodium falciparum/isolamento & purificação , Polimorfismo Genético , Análise de Sequência de DNA , Tetra-Hidrofolato Desidrogenase/genéticaRESUMO
Previous work suggests that Brazilian Plasmodium falciparum has limited genetic diversity and a history of bottlenecks, multiple reintroductions due to human migration, and clonal expansions. We hypothesized that Brazilian P. falciparum would exhibit clonal structure. We examined isolates collected across two decades from Amapá, Rondônia, and Pará state (nâ=â190). By examining more microsatellites markers on more chromosomes than previous studies, we hoped to define the extent of low diversity, linkage disequilibrium, bottlenecks, population structure, and parasite migration within Brazil. We used retrospective genotyping of samples from the 1980s and 1990s to explore the population genetics of SP resistant dhfr and dhps alleles. We tested an existing hypothesis that the triple mutant dhfr mutations 50R/51I/108N and 51I/108N/164L developed in southern Amazon from a single origin of common or similar parasites. We found that Brazilian P. falciparum had limited genetic diversity and isolation by distance was rejected, which suggests it underwent bottlenecks followed by migration between sites. Unlike Peru, there appeared to be gene flow across the Brazilian Amazon basin. We were unable to divide parasite populations by clonal lineages and pairwise FST were common. Most parasite diversity was found within sites in the Brazilian Amazon, according to AMOVA. Our results challenge the hypothesis that triple mutant alleles arose from a single lineage in the Southern Amazon. SP resistance, at both the double and triple mutant stages, developed twice and potentially in different regions of the Brazilian Amazon. We would have required samples from before the 1980s to describe how SP resistance spread across the basin or describe the complex internal migration of Brazilian parasites after the colonization efforts of past decades. The Brazilian Amazon basin may have sufficient internal migration for drug resistance reported in any particular region to rapidly spread to other parts of basin under similar drug pressure.
Assuntos
Alelos , Resistência a Medicamentos/genética , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Proteínas de Protozoários/genética , Evolução Biológica , Brasil , Variação Genética , Genótipo , Geografia , Humanos , Repetições de Microssatélites , Mutação , Tetra-Hidrofolato Desidrogenase/genéticaRESUMO
Malaria has reemerged in many regions where once it was nearly eliminated. Yet the source of these parasites, the process of repopulation, their population structure, and dynamics are ill defined. Peru was one of malaria eradication's successes, where Plasmodium falciparum was nearly eliminated for two decades. It reemerged in the 1990s. In the new era of malaria elimination, Peruvian P. falciparum is a model of malaria reinvasion. We investigated its population structure and drug resistance profiles. We hypothesized that only populations adapted to local ecological niches could expand and repopulate and originated as vestigial populations or recent introductions. We investigated the genetic structure (using microsatellites) and drug resistant genotypes of 220 parasites collected from patients immediately after peak epidemic expansion (1999-2000) from seven sites across the country. The majority of parasites could be grouped into five clonal lineages by networks and AMOVA. The distribution of clonal lineages and their drug sensitivity profiles suggested geographic structure. In 2001, artesunate combination therapy was introduced in Peru. We tested 62 parasites collected in 2006-2007 for changes in genetic structure. Clonal lineages had recombined under selection for the fittest parasites. Our findings illustrate that local adaptations in the post-eradication era have contributed to clonal lineage expansion. Within the shifting confluence of drug policy and malaria incidence, populations continue to evolve through genetic outcrossing influenced by antimalarial selection pressure. Understanding the population substructure of P. falciparum has implications for vaccine, drug, and epidemiologic studies, including monitoring malaria during and after the elimination phase.
Assuntos
Resistência a Medicamentos/genética , Malária Falciparum/parasitologia , Plasmodium falciparum/classificação , Plasmodium falciparum/genética , Antimaláricos/farmacologia , Antimaláricos/uso terapêutico , Di-Hidropteroato Sintase/genética , Epidemias/prevenção & controle , Frequência do Gene , Genótipo , Geografia , Haplótipos , Humanos , Desequilíbrio de Ligação , Malária Falciparum/epidemiologia , Malária Falciparum/prevenção & controle , Proteínas de Membrana Transportadoras/genética , Repetições de Microssatélites/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , Peru/epidemiologia , Filogenia , Plasmodium falciparum/efeitos dos fármacos , Crescimento Demográfico , Proteínas de Protozoários/genética , Tetra-Hidrofolato Desidrogenase/genéticaRESUMO
Molecular tools are valuable for determining evolutionary history and the prevalence of drug-resistant malaria parasites. These tools have helped to predict decreased sensitivity to antimalarials and fixation of multidrug resistance genotypes in some regions. In order to assess how historical drug policies impacted Plasmodium falciparum in Venezuela, we examined molecular changes in genes associated with drug resistance. We examined pfmdr1 and pfcrt in samples from Sifontes, Venezuela, and integrated our findings with earlier work describing dhfr and dhps in these samples. We characterized pfmdr1 genotypes and copy number variation, pfcrt genotypes, and proximal microsatellites in 93 samples originating from surveillance from 2003 to 2004. Multicopy pfmdr1 was found in 12% of the samples. Two pfmdr1 alleles, Y184F/N1042D/D1246Y (37%) and Y184F/S1034C/N1042D/D1246Y (63%), were found. These alleles share ancestry, and no evidence of strong selective pressure on mutations was found. pfcrt chloroquine resistance alleles are fixed with two alleles: S(tct)VMNT (91%) and S(agt)VMNT (9%). These alleles are associated with strong selection. There was also an association between pfcrt, pfmdr1, dhfr, and dhps genotypes/haplotypes. Duplication of pfmdr1 suggests a potential shift in mefloquine sensitivity in this region, which warrants further study. A bottleneck occurred in P. falciparum in Sifontes, Venezuela, and multidrug resistance genotypes are present. This population could be targeted for malaria elimination programs to prevent the possible spread of multidrug-resistant parasites.