Evaluation of the NOW Malaria Immunochromatographic Test for Quantitative Diagnosis of Falciparum and Vivax Malaria Parasite Density

The NOW® Malaria Test, an immunochromatographic test (ICT), was evaluated to determine its ability to quantitatively detect malaria parasites using 100 blood samples from Thailand, including 50 Plasmodium falciparum (Pf) infections and 50 P. vivax (Pv) infections. Intensities of the thickness of the visible bands of the positive ICT were compared with the parasite densities. In cases of Pf infection, the intensities of both HRP-2 bands (T1 bands: Pf specific bands) and aldolase bands (T2 bands: pan-Plasmodium bands) correlated with the parasite densities. The intensities of T2 bands in Pf positive samples showed better correlation with the parasite densities than the T1 bands. In the cases of Pv infection, the intensities of T2 bands were also well correlated with parasite density. These results suggest that the ICT is useful not only for rapid detection of malaria parasites but also for estimating parasite density.     

合肥市1例输入性卵形疟病例分析

目的　对合肥市1例输入性卵形疟病例进行流行病学调查和实验室诊断分析,为今后预防控制输入性疟疾提供参考依据。方法　对该例输入性卵形疟患者的流行病学史、诊疗经过等资料进行收集、整理和分析。结果　患者从非洲莫桑比克务工返乡,回国数月后因反复发热就医。快速诊断试纸条法（RDT）提示为非恶性疟原虫感染;镜检见被感染红细胞正常大小或略胀大、锯齿状不明显,大滋养体胞浆增多、形态不规则、基本无空泡。荧光定量PCR确诊该病例为卵形疟原虫感染。结论　临床医务人员应加强对有境外流行区生活及工作史人员的疟疾诊断意识,及时早期合理用药,防止疟疾疫情扩散。     

African apes as reservoirs of Plasmodium falciparum and the origin and diversification of the Laverania subgenus

We investigated two mitochondrial genes (cytb and cox1), one plastid gene (tufA), and one nuclear gene (ldh) in blood samples from 12 chimpanzees and two gorillas from Cameroon and one lemur from Madagascar. One gorilla sample is related to Plasmodium falciparum, thus confirming the recently reported presence in gorillas of this parasite. The second gorilla sample is more similar to the recently defined Plasmodium gaboni than to the P. falciparum–Plasmodium reichenowi clade, but distinct from both. Two chimpanzee samples are P. falciparum. A third sample is P. reichenowi and two others are P. gaboni. The other chimpanzee samples are different from those in the ape clade: two are Plasmodium ovale, and one is Plasmodium malariae. That is, we have found three human Plasmodium parasites in chimpanzees. Four chimpanzee samples were mixed: one species was P. reichenowi; the other species was P. gaboni in three samples and P. ovale in the fourth sample. The lemur sample, provisionally named Plasmodium malagasi, is a sister lineage to the large cluster of primate parasites that does not include P. falciparum or ape parasites, suggesting that the falciparum + ape parasite cluster (Laverania clade) may have evolved from a parasite present in hosts not ancestral to the primates. If malignant malaria were eradicated from human populations, chimpanzees, in addition to gorillas, might serve as a reservoir for P. falciparum.     

Novel serologic biomarkers provide accurate estimates of recent Plasmodium falciparum exposure for individuals and communities

Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual’s recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86–0.93), whereas responses to six antigens accurately estimated an individual’s malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs.Many countries have extensive programs to reduce the burden of Plasmodium falciparum (Pf), the parasite responsible for most malaria morbidity and mortality (1). Effectively using limited resources for malaria control or elimination and evaluating interventions require accurate measurements of the risk of being infected with Pf (2–15). To reflect the rate at which individuals are infected with Pf in a useful way, metrics used to estimate exposure in a community need to account for dynamic changes over space and time, especially in response to control interventions (16–18).A variety of metrics can be used to estimate Pf exposure, but tools that are more precise and low cost are needed for population surveillance. Existing metrics have varying intrinsic levels of precision and accuracy and are subject to a variety of extrinsic factors, such as cost, time, and availability of trained personnel (19). For example, entomological measurements provide information on mosquito to human transmission for a community but are expensive, require specially trained staff, and lack standardized procedures, all of which reduce precision and/or make interpretation difficult (19–22). Parasite prevalence can be measured by detecting parasites in the blood of individuals from a cross-sectional sample of a community and is, therefore, relatively simple and inexpensive to perform, but results may be imprecise, especially in areas of low transmission (19, 23), and biased by a number of factors, including immunity and access to antimalarial treatment (5, 6, 19, 23–25). The burden of symptomatic disease in a community can be estimated from routine health systems data; however, such data are frequently unreliable (5, 26–28) and generally underestimate the prevalence of Pf infection in areas of intense transmission. Precise and quantitative information about exposure at an individual level can be reliably obtained from cohort studies by measuring the incidence of asymptomatic and/or symptomatic Pf infection (i.e., by measuring the molecular force of infection) (29–35). Unfortunately, the expense of cohort studies limits their use to research settings. The end result is that most malaria-endemic regions lack reliable, timely data on Pf exposure, limiting the capabilities of malaria control programs to guide and evaluate interventions.Serologic assays offer the potential to provide incidence estimates for symptomatic and asymptomatic Pf infection, which are currently obtained from cohort studies, at the cost of cross-sectional studies (36–38). Although Pf infections are transient, a record of infection remains detectable in an individual’s antibody profile. Thus, appropriately chosen antibody measurements integrated with age can provide information about an individual’s exposure history. Antibodies can be measured by simple ELISAs and obtained from dried blood spots, which are easy to collect, transport, and store (39–41). Serologic responses to Pf antigens have been explored as potential epidemiological tools (42–45), and estimated rates of seroconversion to well-characterized Pf antigens accurately reflect stable rates of exposure in a community, whereas distinct changes in these rates are obtained from successful interventions (22, 39, 41, 46–53). However, current serologic assays are not designed to detect short-term or gradual changes in Pf exposure or measure exposure to infection at an individual level. The ability to calibrate antibody responses to estimates of exposure in individuals could allow for more flexible sampling of a population (e.g., not requiring age stratification), improve accuracy of exposure estimates from small sample sizes, and better characterize heterogeneity in exposure within a community.Different Pf antigens elicit antibody responses with different magnitudes and kinetics, providing a large and diverse set of potential biomarkers for exposure (38, 54–58). We hypothesized that new and more highly informative serologic biomarkers better able to characterize an individual’s recent exposure history could be identified by analyzing antibody responses to a large number of candidate Pf antigens in participants with well-characterized exposure histories. To test this hypothesis, we probed plasma from participants in two cohort studies in Uganda against a protein microarray containing 856 Pf antigens. The primary aim of this analysis was to identify responses to select antigens that were most informative of recent exposure using robust, data-adaptive statistical methods. Each participant’s responses to these selected antigens were used as predictors for two primary outcomes of their recent exposure to Pf: (i) days since last Pf infection and (ii) the incidence of symptomatic malaria in the last year. These individual-level estimates were then aggregated across a population to assess community-level malaria exposure. The selection strategy presented here identified accurate biomarkers of exposure for children living in areas of moderate to high Pf exposure and illustrates the utility of this flexible and broadly applicable approach.     

Wide distribution of Plasmodium ovale in Myanmar

The presence of Plasmodium ovale has never been previously reported in Myanmar. Using blood samples obtained in many villages across the country between 1996 and 2000, molecular diagnosis of Plasmodium species was made with semi- or full-nested polymerase chain reaction (PCR) with species-specific primers, followed by agarose gel electrophoresis to detect amplification products. The presence of P. ovale was also confirmed with the another PCR-based diagnosis, the microtiterplate hybridization (MPH) method using species-specific probes. Both methods target the A type of the small subunit ribosomal RNA gene of the four human malaria parasites. Plasmodium ovale DNA was amplified in samples from 65 (4.9%) of 1323 PCR-positive patients, with perfect agreement between results obtained by nested PCR and MPH. Only four P. ovale-infected patients had single-species infection; all others were coinfected with P. falciparum, P. vivax and/or P. malariae. Quadruple infections were observed in six subjects. Parasites with typical P. ovale morphology were found in only 19 patients by conventional microscopy of Giemsa-stained thin smears or fluorescence microscopy of acridine orange-stained thin smears. Plasmodium ovale infections were found in villages situated in the southern, central and western regions of Myanmar, suggesting that P. ovale may be widely distributed in this country.     

万孚疟原虫检测试剂盒检测卵形疟原虫效果评价及影响因素分析

目的 目的 评价万孚疟原虫检测试剂盒 （Pf?LDH/Pan?pLDH） 对卵形疟原虫的检测效果, 并分析原虫密度、 疟原虫乳 酸脱氢酶 （pLDH） 浓度和基因多态性等因素对检测结果的影响。方法 方法 按照万孚疟原虫检测试剂盒的操作说明书, 对经 PCR确认的100份卵形疟患者血样进行检测。采用显微镜镜检法计数患者血片的原虫密度, 以ELISA法检测血样中的 pLDH浓度, 以PCR扩增卵形疟原虫LDH （Po?LDH） 基因并测序, 并分析上述3个因素对检出率的影响。结果 结果 万孚疟原 虫检测试剂盒对上述100份卵形疟患者血样的总体检出率为70.0% （70/100）。当原虫密度 ≤ 500个/μl时, 检出率为 27.3%; 原虫密度> 500个/μl时, 检出率为75.0%～75.4%。当pLDH浓度较低时 （A值 ≤ 0.100）, 检出率为6.7%; pLDH达 到一定浓度时 （A值 > 0.100）, 检出率为95.1%～100%。Po?LDH基因序列分析结果显示所有卵形疟样本可分为2种亚 型, 分别为卵形疟原虫curtisi亚种 （P. o. curtisi） 和卵形疟原虫wallikeri亚种 （P. o. wallikeri）。2种亚型的LDH基因同源 性为97%, 共有24个单核苷酸多态性 （SNP）, 其中3个SNPs为非同义突变, 其余均为同义突变。2种亚型的LDH编码氨 基酸序列同源性为99%, 共有3个氨基酸的差异。万孚疟原虫检测试剂盒对P. o. curtisi的检出率为73.1% （38/52）, 对 P. o. wallikeri的检出率为66.7% （32/48）, 两者差异无统计学意义 （P > 0.05）。结论 结论 万孚疟原虫检测试剂盒对卵形疟原虫的 检测效果优于大部分同类产品, 其检出率与原虫密度、 pLDH浓度关系密切, 与pLDH基因多态性无关。     

CD47 regulates the phagocytic clearance and replication of the Plasmodium yoelii malaria parasite

Several Plasmodium species exhibit a strong age-based preference for the red blood cells (RBC) they infect, which in turn is a major determinant of disease severity and pathogenesis. The molecular basis underlying this age constraint on the use of RBC and its influence on parasite burden is poorly understood. CD47 is a marker of self on most cells, including RBC, which, in conjunction with signal regulatory protein alpha (expressed on macrophages), prevents the clearance of cells by the immune system. In this report, we have investigated the role of CD47 on the growth and survival of nonlethal Plasmodium yoelii 17XNL (PyNL) malaria in C57BL/6 mice. By using a quantitative biotin-labeling procedure and a GFP-expressing parasite, we demonstrate that PyNL parasites preferentially infect high levels of CD47 (CD47^hi)-expressing young RBC. Importantly, C57BL/6 CD47^−/− mice were highly resistant to PyNL infection and developed a 9.3-fold lower peak parasitemia than their wild-type (WT) counterparts. The enhanced resistance to malaria observed in CD47^−/− mice was associated with a higher percentage of splenic F4/80⁺ cells, and these cells had a higher percentage of phagocytized parasitized RBC than infected WT mice during the acute phase of infection, when parasitemia was rapidly rising. Furthermore, injection of CD47-neutralizing antibody caused a significant reduction in parasite burden in WT C57BL/6 mice. Together, these results strongly suggest that CD47^hi young RBC may provide a shield to the malaria parasite from clearance by the phagocytic cells, which may be an immune escape mechanism used by Plasmodium parasites that preferentially infect young RBC.Malaria, caused by Plasmodium parasites, remains a major cause of mortality and morbidity in the developing world. Among the four principal human Plasmodium species, Plasmodium falciparum is the most virulent, being responsible for more than 90% of malaria-associated deaths. Likewise, Plasmodium species that infect rodents and nonhuman primates also differ widely in their fulminant nature and in the mortality they cause (1–3). How different Plasmodium species have evolved to exhibit this wide array of virulence and disease severity remains one of the major unsolved questions in malaria biology and pathogenesis.One important factor that is associated with Plasmodium parasite burden and disease severity is the age constraint of the host red blood cells (RBC) they infect. The age-based preference for restricted invasion of RBC by the Plasmodium parasite is characterized as young RBC (reticulocyte), aged RBC (mature), or both young and aged RBC. Plasmodium species that preferentially infect and grow inside young RBC generally cause a low-grade, self-resolving infection that is rarely fatal (e.g., Plasmodium vivax and Plasmodium ovale), whereas those that infect both young and aged RBC cause more fulminant infection that can be fatal in the absence of immunity (e.g., P. falciparum) (1, 4–6). Thus, along with host genetic background and immune response, restriction for age-specific RBC invasion is a major determinant of the severity and outcome of malaria infection.Malaria parasites have evolved to use redundant receptors and pathways to invade the RBC. For example, sialic acid (7) and Duffy antigen (8) are the major RBC receptors for invasion of P. falciparum and P. vivax, respectively, although other receptors and invasion pathways are known to exist (9, 10). Although a redundancy in RBC receptor use would ensure successful invasion by mitigating the effects of polymorphism and immune targeting, the reasons behind the RBC age-based preference for invasion are not fully clear and remain a subject of debate.Survival of normal cells through the course of their life cycle is essential to maintain homeostasis, and aberrant cells (e.g., senescent or foreign antigen-expressing cells) are eliminated through a sophisticated programmed cell removal system that relies on the recognition of self and nonself determinants (11). CD47, a cell surface molecule in the Ig superfamily, is ubiquitously expressed on many cell types, including RBC, and is a marker of self to avoid early clearance by phagocytic cells through ligation of signal regulatory protein alpha (12). In contrast, altered expression or conformational changes in CD47 may lead to a molecular switch that triggers a phagocytic signal to remove aged or damaged cells (11). Recent studies have shown that the level of CD47 expression is higher in progenitor cells and declines as they undergo maturation and are subsequently aged (13). This age-dependent difference in CD47 expression shields young cells but allows clearance of aging and damaged cells from the system.CD47 is overexpressed in cancer cells (11, 14, 15), and the CD47–signal regulatory protein alpha interaction is considered a major pathway of immune evasion by tumor cells (15). Administration of anti-CD47 antibodies enabled the phagocytosis of tumor cells in vitro, reduced their growth, and prevented the metastasis of human patient tumor cells (14). In this article, using the murine Plasmodium yoelii nonlethal model, we provide quantitative evidence for age of RBC as the basis for the survival and growth of malaria parasites and provide supporting data that suggest that P. yoelii nonlethal parasites prefer to grow inside younger RBC, which allows them to evade immune clearance by phagocytic cells through a CD47-mediated process, and that CD47 modulates the clearance of malaria infection. To our knowledge, this is the first report that provides a molecular basis for the age-dependent preference for infection of RBC by a Plasmodium parasite and sheds light on its implications for the severity of malaria infection in a host.     

福建省3例输入性卵形疟的实验诊断分析

目的 随着输入性疟疾的增加,通过镜检结合PCR方法,提高检出率。方法 福建省2013年成立基因诊断参比实验室,用PCR方法回顾性筛查过往病例时发现有3例卵形疟原虫误诊为间日疟。结果 镜检结合PCR扩增和序列分析发现FJ1、FJ2为卵形疟亚种curtisi和恶性疟混合感染,FJ3为单一卵形疟亚种curtisi感染。结论 福建省以往卵形疟报道很少,需要加强诊断培训,镜检结合PCR检查提高检出率。     

Development of Monoclonal Antibodies That Target 1-Cys Peroxiredoxin and Differentiate Plasmodium falciparum from P. vivax and P. knowlesi

Prompt and accurate diagnosis of malarial patients is a crucial factor in controlling the morbidity and mortality of the disease. Effective treatment decisions require a correct diagnosis among mixed-species malarial patients. Differential diagnosis is particularly important in cases of Plasmodium vivax, a species that shares endemicity with P. falciparum in most endemic areas. Moreover, it is difficult to identify P. knowlesi on the basis of morphology alone, and rapid diagnostic tests are still not available for this malaria species. Therefore, the development of diagnostic tests applicable to the field is urgently needed. 1-Cys peroxiredoxin (1-Cys-Prx) in P. falciparum is abundantly expressed in the mature asexual stages, making it a promising candidate as a diagnostic antigen. In this study, we produced five monoclonal antibodies (mAbs) against P. falciparum 1-Cys-Prx (Pf1-Cys-Prx) by immunizing BALB/c mice with recombinant Pf1-Cys-Prx and subsequent hybridoma production. Cross reactivity of established mAbs with the orthologous molecule of Pf1-Cys-Prx in P. vivax (Pv1-Cys-Prx) and P. knowlesi (Pk1-Cys-Prx) was examined. Western blot analyses showed that three mAbs reacted with Pv1-Cys-Prx and Pk1-Cys-Prx but two mAbs did not. These results indicate that the two mAbs were effective in differentiating P. falciparum from P. vivax and P. knowlesi and could be used in differential diagnosis as well as comparative molecular studies of human Plasmodium species.     

山东省14例输入性卵形疟原虫wallikeri亚种的鉴定

目的 对山东省14例输入性卵形疟原虫wallikeri亚种进行鉴定分析。方法 收集14例输入性疟疾病例,进行快速疟疾诊断试纸条检测(RDT)、血涂片镜检、NP-1993常规巢式PCR鉴定和卵形疟原虫wallikeri(P. ovale wallikeri)亚种的特异性PCR检测。PCR扩增产物测序后,进行Blast比对分析。结果 14例患者RDT检测结果:泛疟原虫(非恶性疟)阳性12例,阴性2例;镜检结果,13例卵形疟原虫,1例间日疟原虫;NP-1993常规巢式PCR结果,14例样本4种疟原虫引物扩增结果均为阴性。P. ovale wallikeri亚种的特异性PCR检测结果:14例样本均能扩增到P. ovale wallikeri亚种特异性条带780 bp。Blast分析测序结果,检索结果为P. ovale wallikeri亚种。结论 14 例镜检阳性、NP-1993常规巢式PCR检测阴性的输入性疟疾病例均确诊为P. ovale wallikeri亚种感染。     

The Cytoplasmic Region of Plasmodium falciparum SURFIN4.2 Is Required for Transport from Maurer’s Clefts to the Red Blood Cell Surface

Background: Plasmodium, the causative agent of malaria, exports many proteins to the surface of the infected red blood cell (iRBC) in order to modify it toward a structure more suitable for parasite development and survival. One such exported protein, SURFIN_4.2, from the parasite of human malignant malaria, P. falciparum, was identified in the trypsin-cleaved protein fraction from the iRBC surface, and is thereby inferred to be exposed on the iRBC surface. SURFIN_4.2 also localize to Maurer’s clefts—parasite-derived membranous structures established in the RBC cytoplasm and tethered to the RBC membrane—and their role in trafficking suggests that they are a pathway for SURFIN_4.2 transport to the iRBC surface. It has not been determined the participation of protein domains and motifs within SURFIN_4.2 in transport from Maurer’s clefts to the iRBC surface; and herein we examined if the SURFIN_4.2 intracellular region containing tryptophan-rich (WR) domain is required for its exposure on the iRBC surface. Results: We generated two transgenic parasite lines which express modified SURFIN_4.2, with or without a part of the intracellular region. Both recombinant SURFIN_4.2 proteins were exported to Maurer’s clefts. However, only SURFIN_4.2 possessing the intracellular region was efficiently cleaved by surface treatment of iRBC with proteinase K. Conclusions: These results indicate that SURFIN_4.2 is exposed on the iRBC surface and that the intracellular region containing WR domain plays a role on the transport from Maurer’s clefts to the iRBC membrane.     

四川省输入性卵形疟原虫wallikeri亚种实验室检测分析

目的 鉴定四川省疑似输入性卵形疟原虫感染病例wallikeri亚种感染情况,并对2014-2017年全省1 079份复核血样卵形疟原虫wallikeri亚种感染情况进行分析。方法 对2018年1-4月四川省10例疑似输入性卵形疟原虫感染病例进行血涂片镜检、快速诊断试纸条（RDT）检测和巢式PCR检测并进行测序分析,同时回顾性检测2014-2017年全省 1 079份复核血样卵形疟原虫wallikeri亚种感染情况。结果 2018年1-4月四川省10例疑似输入性卵形疟原虫感染病例镜检结果均为卵形疟原虫阳性,其中2例存在恶性疟原虫混合感染;RDT检测结果均为疟原虫阳性;常规巢式PCR检测除2例结果为恶性疟原虫阳性外,其余均为阴性;采用卵形疟原虫wallikeri亚种特异性引物进行PCR检测,10例均为阳性,序列分析结果显示为卵形疟原虫wallikeri亚种。对2014-2017年全省1 079份复核血样进行回顾性检测,发现2例卵形疟原虫wallikeri亚种与恶性疟原虫混合感染病例,均为2017年报告,此前检测结果为单纯恶性疟原虫感染。结论 四川省首次鉴定发现输入性卵形疟原虫wallikeri亚种感染病例。     

A prospective analysis of the Ab response to Plasmodium falciparum before and after a malaria season by protein microarray

Abs are central to malaria immunity, which is only acquired after years of exposure to Plasmodium falciparum (Pf). Despite the enormous worldwide burden of malaria, the targets of protective Abs and the basis of their inefficient acquisition are unknown. Addressing these knowledge gaps could accelerate malaria vaccine development. To this end, we developed a protein microarray containing ∼23% of the Pf 5,400-protein proteome and used this array to probe plasma from 220 individuals between the ages of 2–10 years and 18–25 years in Mali before and after the 6-month malaria season. Episodes of malaria were detected by passive surveillance over the 8-month study period. Ab reactivity to Pf proteins rose dramatically in children during the malaria season; however, most of this response appeared to be short-lived based on cross-sectional analysis before the malaria season, which revealed only modest incremental increases in Ab reactivity with age. Ab reactivities to 49 Pf proteins measured before the malaria season were significantly higher in 8–10-year-old children who were infected with Pf during the malaria season but did not experience malaria (n = 12) vs. those who experienced malaria (n = 29). This analysis also provided insight into patterns of Ab reactivity against Pf proteins based on the life cycle stage at which proteins are expressed, subcellular location, and other proteomic features. This approach, if validated in larger studies and in other epidemiological settings, could prove to be a useful strategy for better understanding fundamental properties of the human immune response to Pf and for identifying previously undescribed vaccine targets.     

An in vitro system for assessing the sensitivity of Plasmodium vivax to chloroquine

Following earlier observations on short-term culture of Plasmodium vivax, an in vitro test system has been developed for assessing the parasite's sensitivity to chloroquine. Fresh isolates with predominantly young trophozoites are diluted 1:19 with a (v/v=1/1) mixture of RPMI 1640 and Waymouth medium. The blood-medium mixture (BMM) is inoculated into the predosed microtitre plates before incubation in a candle jar. Incubation for 30 or 42 h yielded the best results. Incubation for 18 or 24 h was generally insufficient for an adequate development of the parasites. The reading of the test is based on stage-specific differential counts in the Giemsa-stained pre-incubation and post-incubation thick films, the evaluation on log-probit analysis of drug-related inhibition of parasite development. The test system has been evaluated on 200 fresh P. vivax isolates in an area with satisfactory clinical-parasitological response to chloroquine. At 30 or 42 h incubation 121 isolates (61.5%) showed adequate control growth and yielded valid sensitivity tests. Complete inhibition of parasite development occurred within the concentration range of 40-1280 nM. The mean EC50 for 30 h of incubation was 50.3 nM, as compared to 49.7 nM with 42 h of incubation. The geometric mean cut-off concentration of parasite development was 488 nM with 30 h of incubation as against 470 nM with 42 h of incubation.     

Rapid clearance of Plasmodium falciparum hyperparasitaemia after oral amodiaquine treatment in patients with uncomplicated malaria

Amodiaquine is one of the possible alternative therapeutic options to treat chloroquine-resistant Plasmodium falciparum infections in Africa. In this study, its efficacy to treat patients with acute uncomplicated falciparum malaria and high parasitaemia (> or =5% of infected erythrocytes in the peripheral blood) was assessed by using the standard protocol developed by the World Health Organization. The mean pre-treatment parasitaemia was 10.8% (range, 5.0-35%). All 32 patients who completed the study (four lost to follow-up) had an adequate clinical and parasitological response on day 14. As compared with the pre-treatment parasitaemia, the mean parasitaemia decreased by 97.8% on day 2 (two patients with negative smears) and 99.97% on day 3 (22 patients with negative smears; the other ten patients had low residual parasitaemia ranging from 24 to 400 asexual parasites/microl). Our results suggest that, in areas of stable transmission in Africa, hyperparasitaemic patients with uncomplicated malaria can be safely treated with oral amodiaquine provided that their clinical and parasitological responses are closely monitored for the first 3 days and controlled on day 7 and 14.     

2012—2020年江苏省输入性卵形疟流行病学特征

目的　分析2012—2020年江苏省输入性卵形疟病例流行病学特征,为该省制定输入性疟疾防控策略提供科学依据。方法　在传染病报告信息管理系统和寄生虫病防治信息管理系统中,收集2012—2020年江苏省卵形疟确诊病例相关信息,包括出国、回国时间,在国外患病次数,发病、初诊和确诊时间,初诊和确诊单位等资料,进行描述性统计分析。结果　2012—2020年江苏省累计报告卵形疟病例347例,其中2015年报告例数最多（71例）。347例卵形疟病例均为实验室确诊的境外输入性病例,占该阶段江苏省报告疟疾病例总数的14.32%。全省卵形疟报告例数居前5位的地级市依次为连云港市（53例,占15.27%）、南通市（44例,占12.68%）、淮安市（44例,占12.68%）、泰州市（44例,占12.68%）和扬州市（36例,占10.37%）。报告病例数以10月最多,达39例（占11.24%）;12月最少,为21例（占6.05%）。卵形疟病例境外感染来源地主要为赤道几内亚（97例,占37.95%）、安哥拉（60例,占17.29%）、尼日利亚（40例,占11.53%）。卵形疟病例从回国到发病中位时间为64（144） d,其中7.49%（26/347）的病例回国1年后发病。病例初诊单位主要集中在县级医疗机构（117例,占33.72%）,确诊单位主要集中在地市级医疗机构（122例,占35.16%）。2012—2020年江苏省卵形疟病例初诊正确率从2012年的0提升到2020年的78.26%,呈逐年上升趋势（[χ2] = 50.90,P＜0.01）。结论　2012—2020年江苏省每年均有输入性卵形疟病例报告,感染来源地主要为非洲,初诊和确诊单位主要集中在地市级和县级等基层医疗机构。今后应重点开展基层镜检人员疟原虫检测能力培训,以提高卵形疟诊断能力、巩固消除疟疾成果。