Epidemiología de la malaria en Centroamérica

La malaria continúa siendo un problema de salud pública en la región de las Américas. Para conocer cuál es la magnitud del problema e identificar cuáles son los factores que vienen influyendo en el control de la malaria en los 8 países que conforman Centroamérica, se realizó un estudio descriptivo basado en la revisión de información disponible de los países de la subregión (México, Belice, El Salvador, Honduras, Guatemala, Nicaragua, Costa Rica y Panamá). Durante los últimos 10 años se viene apreciando una tendencia a la disminución de casos. Tres de los países (Guatemala, Honduras y Nicaragua) aportaron durante el año 2005 el 87.5% de los casos. Belice es el país que mayor éxito viene teniendo en el control de la enfermedad. Está caminando hacia la erradicación de esta enfermedad. México ha disminuido ostensiblemente el número. Preocupa la situación epidemiológica de Belice, quien a pesar de no aportar muchos casos, sus indicadores malariométricos están dentro de los más altos. Costa Rica está incrementando rápidamente la incidencia de casos. Revisar las estrategias de control y adaptarlas a los diferentes escenarios epidemiológicos es fundamental para controlar esta enfermedad. El abordaje ecosistémico y considerar la cosmovisión de la población afectada en la implementación de las estrategias de control deben ser consideradas. También es fundamental el trabajo coordinado entre los diferentes actores involucrados.Trabajo académic

Mefloquine pharmacokinetics and mefloquine-artesunate effectiveness in Peruvian patients with uncomplicated Plasmodium falciparum malaria

<p>Abstract</p> <p>Background</p> <p>Artemisinin-based combination therapy (ACT) is recommended as a means of prolonging the effectiveness of first-line malaria treatment regimens. Different brands of mefloquine (MQ) have been reported to be non-bioequivalent; this could result in sub-therapeutic levels of mefloquine with decreased efficacy. In 2002, mefloquine-artesunate (MQ-AS) combination therapy was adopted as the first-line treatment for uncomplicated <it>Plasmodium falciparum </it>malaria in the Amazon region of Peru. Although MQ resistance has yet to be reported from the Peruvian Amazon, it has been reported from other countries in the Amazon Region. Therefore, continuous monitoring is warranted to ensure that the first-line therapy remains efficacious. This study examines the <it>in vivo </it>efficacy and pharmacokinetic parameters through Day 56 of three commercial formulations of MQ (Lariam^®, Mephaquin^®, and Mefloquina-AC^®Farma) given in combination with artesunate.</p> <p>Methods</p> <p>Thirty-nine non-pregnant adults with <it>P. falciparum </it>mono-infection were randomly assigned to receive artesunate in combination with either (1) Lariam, (2) Mephaquin, or (3) Mefloquina AC. Patients were assessed on Day 0 (with blood samples for pharmacokinetics at 0, 2, 4, and 8 hours), 1, 2, 3, 7, and then weekly until day 56. Clinical and parasitological outcomes were based on the standardized WHO protocol.</p> <p>Whole blood mefloquine concentrations were determined by high-performance liquid chromatography and pharmacokinetic parameters were determined using non-compartmental analysis of concentration versus time data.</p> <p>Results</p> <p>By day 3, all patients had cleared parasitaemia except for one patient in the AC Farma arm; this patient cleared by day 4. No recurrences of parasitaemia were seen in any of the 34 patients. All three MQ formulations had a terminal half-life of 14–15 days and time to maximum plasma concentration of 45–52 hours. The maximal concentration (C_max) and interquartile range was 2,820 ng/ml (2,614–3,108) for Lariam, 2,500 ng/ml (2,363–2,713) for Mephaquin, and 2,750 ng/ml (2,550–3,000) for Mefloquina AC Farma. The pharmacokinetics of the three formulations were generally similar, with the exception of the C_maxof Mephaquin which was significantly different to that of Lariam (<it>p </it>= 0.04).</p> <p>Conclusion</p> <p>All three formulations had similar pharmacokinetics; in addition, the pharmacokinetics seen in this Peruvian population were similar to reports from other ethnic groups. All patients rapidly cleared their parasitaemia with no evidence of recrudescence by Day 56. Continued surveillance is needed to ensure that patients continue to receive optimal therapy.</p

South American Plasmodium falciparum after the Malaria Eradication Era: Clonal Population Expansion and Survival of the Fittest Hybrids

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

Schematic of Changes in Clonet Profiles between 1999 to 2007.

<p>Each circle represents a different clonet. After the removal of SP, the four clonets seen in Padre Cocha have been reduced in size in favor of a number of hybrids. The most common of these represent hybridizations of clonet B and C or C and D. Note, however, that the lack or low levels of other simple crosses of the various clonets, which suggests selection by drug pressure may have influenced surviving offspring.</p

Most common alleles in clonets.

<p>Values represent most common fragment sizes in nucleotides, followed by the percentage of isolates carrying them.</p><p>*Two apparently monomorphic markers were removed for analysis of clonet D due to poor amplification (<i>dhfr</i>: 0.52 kb and <i>dhps</i>: 9.0 kb).</p>1<p>The microsatellite loci name.</p>2<p>its chromosome,</p>3<p>the first value indicates the common allele size and the second is the percentage of isolates carrying it.</p>4<p>The column represents the number of monomorphic markers out of the total 66 markers examined in this study as a percentage, along with the number of samples used to calculate this value.</p

Drug resistance allele haplotypes seen in Iquitos in 2006–2007.

<p>The multiallelic linkage disequilibrium between drug-resistance alleles. It does not include neutral haplotypes because of the extent of chromosomal reassortment.</p>i<p>5/6 of these samples represented clonet B.</p>ii<p>16/17 of these samples appear to represent the same combination of clonet B and C.</p>iii<p>2/3 of these samples represented clonet C.</p>iv<p>7/12 of these samples represented the same combination of clonet C and D.</p>v<p>These samples represented a combination of clonet C and D.</p><p>*n denotes sample size. Haplotype group refers to a combination haplotype of the haplotypes seen around each of the four genes.</p

Network Analysis of Clonets in 1999 and Relatedness to Iquitos Clonets in 2006–2007.

<p>A network diagram of Iquitos in comparison to clonets calculated from neutral marker data from 1999–2000. This network diagram shows the genetic relationships between Iquitos and the previously reported clonets A, B, C, D, and E using the eleven neutral microsatellite markers described in the text. Small red circles represent hypothetical nodes that link haplotypes seen among our samples.</p

Pairwise F_ST by Collection Site or Clonet.

<p>Pairwise F_ST values calculated when comparing different collection sites or clonets using the 7 neutral markers described in the text. All values are significantly different from zero (p≤0.05).</p><p>*n denote sample size.</p

Hypothesized Spread of Clonets Across Peru.

<p>Clonet A: orange, B: green, C: purple, D: blue, E: brown. Our hypothesis of how these clonets may have spread through Peru is described in the text. In brief, we suggest that clonets A and B may have been recently introduced from the greater Amazon Basin, that clonet C may represent an older vestigial population, that clonet D may have been introduced during the 1980s from theAmazon interior of Ecuador, and that clonet E may represent a coastal lineage that has recently invaded the interior of Peru.</p

AMOVA Results.

<p>Locus by locus AMOVAs were used to create this table. N denotes sample size. Haplotype group refers to a combination haplotype of the haplotypes seen around each of the four genes. ** Two apparently monomorphic markers were removed from analysis (<i>dhfr</i>: 0.52 kb and <i>dhps</i>: 9.0 kb) due to poor amplification in clonet D.</p