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Efforts to control malaria may affect malaria parasite genetic variability and drug resistance, the latter of which is associated with genetic events that promote mechanisms to escape drug action. The worldwide spread of drug resistance has been a major obstacle to controlling Plasmodium falciparum malaria, and thus the study of the origin and spread of associated mutations may provide some insights into the prevention of its emergence. This study reports an analysis of P. falciparum genetic diversity, focusing on antimalarial resistance-associated molecular markers in two socioeconomically different villages in mainland Equatorial Guinea. The present study took place 8 years after a previous one, allowing the analysis of results before and after the introduction of an artemisinin-based combination therapy (ACT), i.e., artesunate plus amodiaquine. Genetic diversity was assessed by analysis of the Pfmsp2 gene and neutral microsatellite loci. Pfdhps and Pfdhfr alleles associated with sulfadoxine-pyrimethamine (SP) resistance and flanking microsatellite loci were investigated, and the prevalences of drug resistance-associated point mutations of the Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps genes were estimated. Further, to monitor the use of ACT, we provide the baseline prevalences of K13 propeller mutations and Pfmdr1 copy numbers. After 8 years, noticeable differences occurred in the distribution of genotypes conferring resistance to chloroquine and SP, and the spread of mutated genotypes differed according to the setting. Regarding artemisinin resistance, although mutations reported as being linked to artemisinin resistance were not present at the time, several single nucleotide polymorphisms (SNPs) were observed in the K13 gene, suggesting that closer monitoring should be maintained to prevent the possible spread of artemisinin resistance in Africa., (Copyright © 2016 American Society for Microbiology.)

Background: Mozambique implemented artemisinin-based combinations therapy (ACT) using artemether-lumefantrine (AL) as the first-line treatment for uncomplicated malaria in 2009. AL remains highly efficacious, but widespread use may soon facilitate emergence of artemisinin tolerance/resistance. The prevalence of pfmdr1 different alleles in Maputo and Mozambique is not known, either after or before the introduction of ACT. Pfmdr1 molecular markers related to Plasmodium falciparum susceptibility were analysed before and after transition to ACT., Methods: A first group of samples was collected between June 2003 and June 2005 and a second group in the period between March 2010 and March 2012. Three alleles were analysed by PCR-RFLP: N86Y, Y184F and D1246Y, in the pfmdr1 gene., Results: Alleles N86, 184F and D1246 increased from 19.5, 19.6 and 74.4% in 2003-2005 to 73.2, 22.7 and 96.7% in 2010-2012, respectively. After implementation of ACT (2010-2012), pfmdr1 haplotypes, either two- and three-codon basis, were generally less diverse than before the implementation of ACT (2003-2005). The prevalence of haplotypes N86-184Y, N86-D1246 and 184Y-D1246 increased from 12,2, 27.3 and 71.7% in 2003-2005 to 59.4, 84.3 and 78.6% in 2010-2012. The three-codon basis haplotypes NFD and NYD also increased significantly during the same period., Conclusion: The alleles N86 and 184 F and the triple haplotype N86-184 F-D1246 showed a significantly increased prevalence after introduction of ACT.

Background: In Plasmodium, the high level of genetic diversity and the interactions established by co-infecting parasite populations within the same host may be a source of selection on pathogen virulence and drug resistance. As different patterns have already been described in humans and mosquitoes, parasite diversity and population structure should be studied in both hosts to properly assess their effects on infection and transmission dynamics. This study aimed to characterize the circulating populations of Plasmodium spp and Plasmodium falciparum from a combined set of human blood and mosquito samples gathered in mainland Equatorial Guinea. Further, the origin and evolution of anti-malarial resistance in this area, where malaria remains a major public health problem were traced. Methods: Plasmodium species infecting humans and mosquitoes were identified by nested-PCR of chelex-extracted DNA from dried blood spot samples and mosquitoes. Analysis of Pfmsp2 gene, anti-malarial-resistance associated genes, Pfdhps, Pfdhfr, Pfcrt and Pfmdr1, neutral microsatellites (STR) loci and Pfdhfr and Pfdhps flanking STR was undertaken to evaluate P. falciparum diversity. Results: Prevalence of infection remains high in mainland Equatorial Guinea. No differences in parasite formula or significant genetic differentiation were seen in the parasite populations in both human and mosquito samples. Point mutations in all genes associated with anti-malarial resistance were highly prevalent. A high prevalence was observed for the Pfdhfr triple mutant in particular, associated with pyrimethamine resistance. Analysis of Pfdhps and Pfdhfr flanking STR revealed a decrease in the genetic diversity. This finding along with multiple independent introductions of Pfdhps mutant haplotypes suggest a soft selective sweep and an increased differentiation at Pfdhfr flanking microsatellites hints a model of positive directional selection for this gene. Conclusions: Chloroquine is no longer recommended for malaria treatment in Equatorial Guinea but sulphadoxine- pyrimethamine (SP) remains in use in combination with artesunate and is the only drug recommended in preventive chemotherapy in pregnancy. The high prevalence of point mutations in Pfdhfr and Pfdhps points to the danger of an eventual reduction in the efficacy of SP combined therapy in P. falciparum populations in Equatorial Guinea and to the essential continuous monitoring of these two genes. [ABSTRACT FROM AUTHOR]

Background: Plasmodium falciparum is the major cause of malaria infection in the island of São Tomé, in the Republic of São Tomé and Príncipe (STP), with an incidence of 40 - 50% before 2004. Since 2004, through the coordination of the Ministry of Health of STP and their Centro Nacional de Endemias (CNE), an integrated malaria control programme has been intensively deployed on the island of São Tomé. Malaria morbidity and mortality decreased by 95% after three years of effective intervention. In the low transmission settings, however, malaria seasonal fluctuation can be a potential problem directly related to epidemics if ongoing control measures are interrupted. Studies on a number of associated factors with malaria epidemics and the measures taken to respond to outbreaks are presented. Methods: The integrated malaria control programme included indoor residual spraying (IRS), long-lasting insecticidal nets (LLINs), intermittent preventive therapy for pregnant women, as well as early diagnosis and prompt treatment with artemisinin-based combination therapy (ACT). Regular implementation of an island-wide IRS programme was carried out yearly in 2004-2007, and enhanced throughout the island in 2009. Malaria incidence and prevalence were estimated based on passive case detection and mass screening, respectively. Slide positivity rates were used for monitoring the beginning of a malaria epidemic or a seasonal peak. Results: A steep decline of ca. 95% of malaria morbidity and mortality was observed between 2004 and 2008 with use of the combined control methods. Malaria incidence was 2.0%, 1.5%, and 3.0% for 2007, 2008, and 2009, respectively. In April 2008, a cross-sectional country-wide surveillance showed malaria prevalence of 3.5%, of which 95% cases were asymptomatic carriers. Only 50% of asymptomatic carriers were cured with ACT treatment, while 90% of the symptomatic patients were cured by ACT treatment as confirmed with a follow up study. Malaria morbidity increased by three-fold during the first half of 2009 as compared to the same period in 2008. Over this period of six months, severe malaria was also noted in all age groups and malaria mortality increased by two-fold in children less than five years old. After an emergency IRS was deployed, with increased use of LLINs, and an active search of asymptomatic carriers was followed and given complete ACT treatment, malaria incidence decreased to less than 1% in the second half of 2009. Conclusion: At the initial stage of the integrated malaria control programme, IRS contributed to the visible effect on the rapid reduction of malaria morbidity and mortality, while this programme highlights an urgent demand for the improvement of other measures, particularly promotion of LLINs usage, with close monitoring of asymptomatic carriers and with ACT treatment in malaria transmission hotspots. In addition, both daily reports and a regular active surveillance to prevent malaria outbreaks should be established permanently, so that a fast response to epidemics can be effectively made when necessary. [ABSTRACT FROM AUTHOR]

Background: After the introduction of an artemisinin-based combination therapy, the reduction of prevalence of malaria infections has shown a remarkable progress during the last decade. However due to the lack of a consistent malaria control programme and socioeconomic inequalities, Plasmodium infection is still one of the major cause of disease in Equatorial Guinea, namely in the rural communities. This study explored the associated risk factors of malaria transmission at the microeconomic level (households) in two rural villages of mainland Equatorial Guinea. Methods: This survey involved 232 individuals living in 69 households located in two rural villages, Ngonamanga and Miyobo, of coastal and interior of Equatorial Guinea, respectively. Malaria prevalence was measured by PCR and parasitaemia level by optical microscopy; household socioeconomic status (SES) was measured based on house characteristics using a 2-step cluster analysis. Logistic regression analysis was performed to investigate the relationship of a diverse set of independent variables on being diagnosed with malaria and on showing high levels of parasitaemia. Results: The prevalence of Plasmodium spp. infection was 69%, with 80% of households having at least one parasitaemic member. The majority of houses have eaves (80%), walls of clay/wood (90%) and zinc roof (99%) and only 10% of them have basic sanitation facilities. The studied areas showed reduced rates of indoor residual spraying coverage (9%), and long-lasting insecticide-treated net ownership (35%), with none of these preventive tools showing any significant effects on malaria risk in these areas. Neither the risk of malaria infection (PCR positive result) or the development of high parasitaemia did show association with SES. Conclusions: This study has contributed to reinforce the importance of living conditions associated to a high risk of malaria infection and vulnerability to develop high parasitaemia. This study also contributes to future malaria control interventions to be implemented in mainland Equatorial Guinea or in other countries with similar environmental conditions. [ABSTRACT FROM AUTHOR]