Heritability of P. falciparum and P. vivax Malaria in a Karen Population in Thailand

The majority of studies concerning malaria host genetics have focused on individual genes that confer protection against rather than susceptibility to malaria. Establishing the relative impact of genetic versus non-genetic factors on malaria infection and disease is essential to focus effort on key determinant factors. This relative contribution has rarely been evaluated for Plasmodium falciparum and almost never for Plasmodium vivax. We conducted a longitudinal cohort study in a Karen population of 3,484 individuals in a region of mesoendemic malaria, Thailand from 1998 to 2005. The number of P. falciparum and P. vivax clinical cases and the parasite density per person were determined. Statistical analyses were performed to account for the influence of environmental factors and the genetic heritability of the phenotypes was calculated using the pedigree-based variance components model. The genetic contribution to the number of clinical episodes resulting from P. falciparum and P. vivax were 10% and 19% respectively. There was also moderate genetic contribution to the maximum and overall parasite trophozoite density phenotypes for both P. falciparum (16%&16%) and P. vivax (15%&13%). These values, for P. falciparum, were similar to those previously observed in a region of much higher transmission intensity in Senegal, West Africa. Although environmental factors play an important role in acquiring an infection, genetics plays a determinant role in the outcome of an infection with either malaria parasite species prior to the development of immunity

Longitudinal study of Plasmodium falciparum and Plasmodium vivax in a Karen population in Thailand

<p>Abstract</p> <p>Background</p> <p>Clinical case treatment of malaria infections where <it>Plasmodium falciparum </it>and <it>Plasmodium vivax </it>are sympatric has achieved effective reductions in <it>P. falciparum </it>prevalence and incidence rates, but has been less successful for <it>P. vivax</it>. The high transmissibility of <it>P. vivax </it>and its capacity to relapse have been suggested to make it a harder parasite species to control.</p> <p>Methods</p> <p>A clinical malaria case treatment programme was carried out over a decade in a Karen community composed of seven hamlets on the Thai-Myanmar border.</p> <p>Results</p> <p>From 1994 to 2004, prevalence rates of both <it>P. falciparum </it>and <it>P. vivax </it>decreased by 70–90% in six of the seven study hamlets, but were unchanged in one hamlet. Overall, incidence rates decreased by 72% and 76% for <it>P. falciparum </it>and <it>P. vivax </it>respectively over the period 1999–2004. The age-incidence and prevalence curves suggested that <it>P. vivax </it>was more transmissible than <it>P. falciparum </it>despite a greater overall burden of infection with <it>P. falciparum</it>. Male gender was associated with increased risk of clinical presentation with either parasite species. Children (< 15 years old) had an increased risk of presenting with <it>P. vivax </it>but not <it>P. falciparum</it>.</p> <p>Conclusion</p> <p>There was a considerable reduction in incidence rates of both <it>P. vivax </it>and <it>P. falciparum </it>over a decade following implementation of a case treatment programme. The concern that intervention methods would inadvertently favour one species over another, or even lead to an increase in one parasite species, does not appear to be fulfilled in this case.</p

Hydrogen recycling during RF plasma heating in the U-3M torsatron

The hydrogen recycling behavior has been studied during the plasma experiments in torsatron U-3M. For this purpose, the time dependence of the molecular hydrogen pressure in the U-3M torsatron vacuum chamber in the modes of RF wall conditioning and RF plasma heating has been measured. The experimental results show that the hydrogen pumping from the vacuum chamber runs at constant rate during the RF discharge for each mode. After RF power switching-off the inverse desorption of hydrogen, accumulated during the RF discharge in the vacuum chamber walls and helical coil surfaces, is observed. When the antenna anode voltages and the RF pulse duration in both modes are increasing, the character of the time dependences of hydrogen pressure does not change significantly.Изучено поведение рециклинга водорода во время плазменных экспериментов на торсатроне У-3М. Для этой цели было проведено измерение временных зависимостей давления водорода в вакуумной камере торсатрона У-3М в режимах ВЧ-чистки стенок камеры и ВЧ-нагрева плазмы. Экспериментальные результаты показали, что в обоих режимах во время ВЧ-разряда скорость откачки водорода из вакуумной камеры остается постоянной для каждого из режимов. После выключения ВЧ-мощности наблюдается обратная десорбция водорода, накопленного во время ВЧ-разряда в стенках вакуумной камеры и винтовых катушек. Повышение анодных напряжений на ВЧ-антеннах и увеличение длительности ВЧ-импульса существенно не влияют на характер временных зависимостей давления водорода.Вивчено поведінку рециклінгу водню під час плазмових експериментів на торсатроні У-3М. Для цієї мети було проведено вимірювання часових залежностей тиску водню у вакуумній камері торсатрона У-3М в режимах ВЧ-чистки стінок камери і ВЧ-нагріву плазми. Експериментальні результати показали, що в обох режимах під час ВЧ-розряду швидкість відкачування водню з вакуумної камери залишається постійною для кожного з режимів. Після виключення ВЧ-потужності спостерігається зворотна десорбція водню, накопиченого під час ВЧ-розряду в стінках вакуумної камери і гвинтових котушок. Підвищення анодних напруг на ВЧ-антенах і збільшення тривалості ВЧ-імпульсу істотно не впливають на характер тимчасових залежностей тиску водню

Genetic Determination and Linkage Mapping of Plasmodium falciparum Malaria Related Traits in Senegal

Plasmodium falciparum malaria episodes may vary considerably in their severity and clinical manifestations. There is good evidence that host genetic factors contribute to this variability. To date, most genetic studies aiming at the identification of these genes have used a case/control study design for severe malaria, exploring specific candidate genes. Here, we performed a family-based genetic study of falciparum malaria related phenotypes in two independent longitudinal survey cohorts, as a first step towards the identification of genes and mechanisms involved in the outcome of infection. We studied two Senegalese villages, Dielmo and Ndiop that differ in ethnicity, malaria transmission and endemicity. We performed genome-scan linkage analysis of several malaria-related phenotypes both during clinical attacks and asymptomatic infection. We show evidence for a strong genetic contribution to both the number of clinical falciparum malaria attacks and the asymptomatic parasite density. The asymptomatic parasite density showed linkage to chromosome 5q31 (LOD = 2.26, empirical p = 0.0014, Dielmo), confirming previous findings in other studies. Suggestive linkage values were also obtained at three additional chromosome regions: the number of clinical malaria attacks on chromosome 5p15 (LOD = 2.57, empirical p = 0.001, Dielmo) and 13q13 (LOD = 2.37, empirical p = 0.0014 Dielmo), and the maximum parasite density during asymptomatic infection on chromosome 12q21 (LOD = 3.1, empirical p<10−4, Ndiop). While regions of linkage show little overlap with genes known to be involved in severe malaria, the four regions appear to overlap with regions linked to asthma or atopy related traits, suggesting that common immune related pathways may be involved

Assessment of rodent communities in two provinces of Cambodia

Rodents play an important role in regulating ecosystems, in particular through seed dispersion and predation, and constitute a prey for mesopredators. However, rodents are considered pests in rural areas because they can cause significant damage to crops, especially during episodes of sudden population growth (Singleton, 2003). Rodents are also carriers or reservoirs for numerous zoonotic diseases that represent a serious threat to human health (Meerburg et al., 2009; Luis et al., 2013; Olival et al., 2017). Multi-site assessments of rodent communities are consequently needed to understand the implications of various spatio-temporal factors on these ecosystem services, the epidemiology of rodent-borne diseases, and other interactions with humans

Pair-wise correlation between phenotypes studied.

<p>PFA, Number of visits Pf+; NMF, Number of non-malaria fever visits; PVA, Number of visits Pv+; mx-PFD, Pf max parasite density; PFD, Overall Pf parasite densities; mx-PVD, Pv max parasite density; PVD, Overall Pv parasite densities. In bold, highly significant p value (≤10⁻⁴); in italic, significant p value that becomes not significant after Bonferroni correction for multiple testing (21 hypotheses tested).</p

Contribution (%) of genetic (heritability, h²) and house (c²) effects to variability in malaria and non-malaria clinical and biological phenotypes of <i>P. falciparum</i> (Pf) and <i>P. vivax</i> (Pv).

<p>h², variance due to genetics, c², variance due to house effect, S.E. the standard error; NS, not significant (<i>p-value</i>>0.05); NE, not estimated.</p>a<p>Retained because of marginal significance.</p

Family statistics.

<p>Family statistics.</p

Percentage of variation in <i>P. falciparum</i> (Pf) and <i>P. vivax</i> (Pv) phenotypes explained by environmental factors (and their interactions) in the statistical analyses.

<p>In parentheses, <i>p</i> is the <i>p-value</i>; in bold, <i>p-value</i><10⁻³.</p>a<p>Retained because of significant interaction with Age.</p

Number of pairs of individuals as defined by genetic relationship (phi2) and household relationship.

<p>Number of pairs of individuals as defined by genetic relationship (phi2) and household relationship.</p