Prospective Study of Plasmodium vivax Malaria Recurrence after Radical Treatment with a Chloroquine-Primaquine Standard Regimen in Turbo, Colombia.

Plasmodium vivax recurrences help maintain malaria transmission. They are caused by recrudescence, reinfection, or relapse, which are not easily differentiated. A longitudinal observational study took place in Turbo municipality, Colombia. Participants with uncomplicated P. vivax infection received supervised treatment concomitantly with 25 mg/kg chloroquine and 0.25 mg/kg/day primaquine for 14 days. Incidence of recurrence was assessed over 180 days. Samples were genotyped, and origins of recurrences were established. A total of 134 participants were enrolled between February 2012 and July 2013, and 87 were followed for 180 days, during which 29 recurrences were detected. The cumulative incidence of first recurrence was 24.1% (21/87) (95% confidence interval [CI], 14.6 to 33.7%), and 86% (18/21) of these events occurred between days 51 and 110. High genetic diversity of P. vivax strains was found, and 12.5% (16/128) of the infections were polyclonal. Among detected recurrences, 93.1% (27/29) of strains were genotyped as genetically identical to the strain from the previous infection episode, and 65.5% (19/29) of infections were classified as relapses. Our results indicate that there is a high incidence of P. vivax malaria recurrence after treatment in Turbo municipality, Colombia, and that a large majority of these episodes are likely relapses from the previous infection. We attribute this to the primaquine regimen currently used in Colombia, which may be insufficient to eliminate hypnozoites

第958回千葉医学会例会・第13回磯野外科例会

<p>Prospective samples (collected between 2011 and 2012): Proportion of isolates with deletions of <i>pfhrp3</i> and its respective flanking genes, per site and total.</p

Genetic Characterisation of Plasmodium falciparum Isolates with Deletion of the pfhrp2 and/or pfhrp3 Genes in Colombia: The Amazon Region, a Challenge for Malaria Diagnosis and Control.

Most Plasmodium falciparum-detecting rapid diagnostic tests (RDTs) target histidine-rich protein 2 (PfHRP2). However, P. falciparum isolates with deletion of the pfhrp2 gene and its homolog gene, pfhrp3, have been detected. We carried out an extensive investigation on 365 P. falciparum dried blood samples collected from seven P. falciparum endemic sites in Colombia between 2003 and 2012 to genetically characterise and geographically map pfhrp2- and/or pfhrp3-negative P. falciparum parasites in the country. We found a high proportion of pfhrp2-negative parasites only in Amazonas (15/39; 38.5%), and these parasites were also pfhrp3-negative. These parasites were collected between 2008 and 2009 in Amazonas, while pfhrp3-negative parasites (157/365, 43%) were found in all the sites and from each of the sample collection years evaluated (2003 to 2012). We also found that all pfhrp2- and/or pfhrp3-negative parasites were also negative for one or both flanking genes. Six sub-population clusters were established with 93.3% (14/15) of the pfhrp2-negative parasites grouped in the same cluster and sharing the same haplotype. This haplotype corresponded with the genetic lineage BV1, a multidrug resistant strain that caused two outbreaks reported in Peru between 2010 and 2013. We found this BV1 lineage in the Colombian Amazon as early as 2006. Two new clonal lineages were identified in these parasites from Colombia: the genetic lineages EV1 and F. PfHRP2 sequence analysis revealed high genetic diversity at the amino acid level, with 17 unique sequences identified among 53 PfHRP2 sequences analysed. The use of PfHRP2-based RDTs is not recommended in Amazonas because of the high proportion of parasites with pfhrp2 deletion (38.5%), and implementation of new strategies for malaria diagnosis and control in Amazonas must be prioritised. Moreover, studies to monitor and genetically characterise pfhrp2-negative P. falciparum parasites in the Americas are warranted, given the extensive human migration occurring in the region

Number and type of repeats found in the PfHRP2 amino acid sequences.

<p>Number and type of repeats found in the PfHRP2 amino acid sequences.</p

Selection and spread of artemisinin-resistant alleles in Thailand prior to the global artemisinin resistance containment campaign.

The recent emergence of artemisinin resistance in the Greater Mekong Subregion poses a major threat to the global effort to control malaria. Tracking the spread and evolution of artemisinin-resistant parasites is critical in aiding efforts to contain the spread of resistance. A total of 417 patient samples from the year 2007, collected during malaria surveillance studies across ten provinces in Thailand, were genotyped for the candidate Plasmodium falciparum molecular marker of artemisinin resistance K13. Parasite genotypes were examined for K13 propeller mutations associated with artemisinin resistance, signatures of positive selection, and for evidence of whether artemisinin-resistant alleles arose independently across Thailand. A total of seven K13 mutant alleles were found (N458Y, R539T, E556D, P574L, R575K, C580Y, S621F). Notably, the R575K and S621F mutations have previously not been reported in Thailand. The most prevalent artemisinin resistance-associated K13 mutation, C580Y, carried two distinct haplotype profiles that were separated based on geography, along the Thai-Cambodia and Thai-Myanmar borders. It appears these two haplotypes may have independent evolutionary origins. In summary, parasites with K13 propeller mutations associated with artemisinin resistance were widely present along the Thai-Cambodia and Thai-Myanmar borders prior to the implementation of the artemisinin resistance containment project in the region

Sample collection sites in Colombia.

<p>On the map the sample collection sites are highlighted. The names in black indicate the seven Colombian Departments from which the isolates studied were collected: Antioquia (N = 42), Choco (N = 74), Valle (N = 27), Cauca (N = 44), Nariño (N = 122), Guaviare (N = 26) and Amazonas (N = 39). The study site highlighted in red, Amazonas, indicates the Department where <i>pfhrp2/pfhrp3</i> double negative isolates were found. Map source: DIVA-GIS, available in <a href="http://www.diva-gis.org/" target="_blank">http://www.diva-gis.org/</a>.</p

Clusters (C1—C6) defined by STRUCTURE v2.3.3. for the population of <i>pfhrp2-</i> and/or <i>pfhrp3</i>-negative parasites in Colombia (N = 132).

<p>Each isolate (<i>x</i>-axis) is represented by a single vertical bar, and this bar is broken down into various coloured segments whose length varies according to the membership fraction (<i>y-</i> axis) of each of the six inferred clusters (K = 6). Cluster 1 (red) contained 22.7% of the total isolates evaluated (30 isolates). These were mainly samples from the Pacific coast and northern Colombia. Cluster 2 (green) contained 14.4% of the samples evaluated (19 isolates). Ninety-five percent of the samples in Cluster 2 were from northern Colombia. Cluster 3 (blue) contained 25.8% of the samples evaluated (34 isolates), all of which were collected in in the Colombian Pacific coast. Cluster 4 (yellow) was the smallest cluster with 6.8% of the samples (9 isolates). These originated from Guaviare, Nariño and Choco. Cluster 5 (pink) contained 18.2% of the samples (24 isolates) and they were collected in southern and south-eastern Colombia. This cluster contained the <i>pfhrp2</i>/<i>pfhrp3</i> double negative samples. Cluster 6 (aqua) included 12.1% of the samples evaluated (16 isolates) and they originated from all the sites studied except Nariño.</p

Microsatellite profiles identified for <i>P</i>. <i>falciparum</i> isolates lacking <i>pfhrp2</i> and new <i>P</i>. <i>falciparum</i> genetic lineages identified in Colombia.

<p>Microsatellite profiles identified for <i>P</i>. <i>falciparum</i> isolates lacking <i>pfhrp2</i> and new <i>P</i>. <i>falciparum</i> genetic lineages identified in Colombia.</p