Chloroquine-susceptible and -resistant Plasmodium falciparum strains survive high chloroquine concentrations by becoming dormant but are eliminated by prolonged exposure.

Background: Plasmodium falciparum strains that are resistant to standard-dose chloroquine can be treated by higher chloroquine concentrations maintained for a longer time in vivo.

Objectives: To determine the relative importance of chloroquine concentrations versus exposure time for elimination of chloroquine-susceptible and -resistant P. falciparum in vitro.

Performance and Application of Commercially Available Loop-Mediated Isothermal Amplification (LAMP) Kits in Malaria Endemic and Non-Endemic Settings.

Loop-mediated isothermal amplification (LAMP) is a sensitive molecular tool suitable for use as a near point-of-care test for the diagnosis of malaria. Recent meta-analyses have detailed high sensitivity and specificity of malaria LAMP when compared to microscopy, rapid diagnostic tests, and polymerase chain reaction in both endemic and non-endemic settings. Despite this, the use of malaria LAMP has primarily been limited to research settings to date.

A novel deep learning-based point-of-care diagnostic method for detecting Plasmodium falciparum with fluorescence digital microscopy.

Background: Malaria remains a major global health problem with a need for improved field-usable diagnostic tests. We have developed a portable, low-cost digital microscope scanner, capable of both brightfield and fluorescence imaging. Here, we used the instrument to digitize blood smears, and applied deep learning (DL) algorithms to detect Plasmodium falciparum parasites.

Surveillance of genetic markers associated with Plasmodium falciparum resistance to artemisinin-based combination therapy in Pakistan, 2018-2019.

Background: The spread of artemisinin resistance in the Greater Mekong Subregion of Southeast Asia poses a significant threat for current anti-malarial treatment guidelines globally. The aim of this study was to assess the current prevalence of molecular markers of drug resistance in Plasmodium falciparum in the four provinces with the highest malaria burden in Pakistan, after introducing artemether-lumefantrine as first-line treatment in 2017.

Methods: Samples were collected during routine malaria surveillance in Punjab, Sindh, Baluchistan, and Khyber Pakhtunkhwa provinces of Pakistan between January 2018 and February 2019.

Detection of by Light Microscopy, Loop-Mediated Isothermal Amplification, and Polymerase Chain Reaction on Day 3 after Initiation of Artemether-Lumefantrine Treatment for Uncomplicated Malaria in Bagamoyo District, Tanzania: A Comparative Trial.

Microscopy-determined positivity rates exceeding 10% on day 3 after initiation of artemisinin-based combination therapy (ACT) is an important indicator of artemisinin resistance. However, microscopy does not detect low-density parasitemia, contrary to molecular tools such as loop-mediated isothermal amplification (LAMP) and polymerase chain reaction (PCR). We compared microscopy, LAMP, and PCR for detection of on day 3 after ACT in 256 patients with uncomplicated malaria in Bagamoyo District, Tanzania.

A cluster randomised controlled trial of two rounds of mass drug administration in Zanzibar, a malaria pre-elimination setting-high coverage and safety, but no significant impact on transmission.

Background: Mass drug administration (MDA) has the potential to interrupt malaria transmission and has been suggested as a tool for malaria elimination in low-endemic settings. This study aimed to determine the effectiveness and safety of two rounds of MDA in Zanzibar, a pre-elimination setting.

Methods: A cluster randomised controlled trial was conducted in 16 areas considered as malaria hotspots, with an annual parasite index of > 0.

Absence of K13 Propeller Domain Polymorphisms among Field Isolates Collected from the Brazilian Amazon Basin between 1984 and 2011.

Artemisinin resistance, presently confined to Southeast Asia and associated with mutations in the K13 (PfK13) propeller domain, represents a serious threat to global malaria control. This study aimed to provide baseline information for future artemisinin resistance surveillance, by analyzing the PfK13 propeller domain in field isolates collected from the Brazilian Amazon Basin between 1984 and 2011. A total of 152 mono-infections were assessed, of which 118 (78%) were collected before and 34 (22%) after the introduction of artemisinin-based combination therapy (ACT) in 2006.

Field Evaluation of a High Throughput Loop Mediated Isothermal Amplification Test for the Detection of Asymptomatic Plasmodium Infections in Zanzibar.

Background: New field applicable diagnostic tools are needed for highly sensitive detection of residual malaria infections in pre-elimination settings. Field performance of a high throughput DNA extraction system for loop mediated isothermal amplification (HTP-LAMP) was therefore evaluated for detecting malaria parasites among asymptomatic individuals in Zanzibar.

Methods: HTP-LAMP performance was evaluated against real-time PCR on 3008 paired blood samples collected on filter papers in a community-based survey in 2015.

Adding a single low-dose of primaquine (0.25 mg/kg) to artemether-lumefantrine did not compromise treatment outcome of uncomplicated Plasmodium falciparum malaria in Tanzania: a randomized, single-blinded clinical trial.

Background: The World Health Organization (WHO) recently recommended the addition of a single low-dose of the gametocytocidal drug primaquine (PQ) to artemisinin-based combination therapy (ACT) in low transmission settings as a component of pre-elimination or elimination programmes. However, it is unclear whether that influences the ACT cure rate. The study assessed treatment outcome of artemether-lumefantrine (AL) plus a single PQ dose (0.

Field deployment of loop-mediated isothermal amplification for centralized mass-screening of asymptomatic malaria in Zanzibar: a pre-elimination setting.

Background: Molecular tools for detection of low-density asymptomatic Plasmodium infections are needed in malaria elimination efforts. This study reports results from the hitherto largest implementation of loop-mediated isothermal amplification (LAMP) for centralized mass screening of asymptomatic malaria in Zanzibar.

Methods: Healthy individuals present and willing to participate in randomly selected households in 60 villages throughout Zanzibar were screened for malaria by rapid diagnostic tests (RDT).

SYBR Green real-time PCR-RFLP assay targeting the plasmodium cytochrome B gene--a highly sensitive molecular tool for malaria parasite detection and species determination.

A prerequisite for reliable detection of low-density Plasmodium infections in malaria pre-elimination settings is the availability of ultra-sensitive and high-throughput molecular tools. We developed a SYBR Green real-time PCR restriction fragment length polymorphism assay (cytb-qPCR) targeting the cytochrome b gene of the four major human Plasmodium species (P. falciparum, P.

Loop-mediated isothermal amplification (LAMP) for point-of-care detection of asymptomatic low-density malaria parasite carriers in Zanzibar.

Background: Asymptomatic, low parasite density malaria infections are difficult to detect with currently available point-of-care diagnostics. This study piloted a loop-mediated isothermal amplification (LAMP) kit for field-friendly, high-throughput detection of asymptomatic malaria infections during mass screening and treatment (MSAT) in Zanzibar, a malaria pre-elimination setting.

Methods: Screening took place in three known hotspot areas prior to the short rains in November.

Loop mediated isothermal amplification (LAMP) accurately detects malaria DNA from filter paper blood samples of low density parasitaemias.

Background: Loop mediated isothermal amplification (LAMP) provides an opportunity for improved, field-friendly detection of malaria infections in endemic areas. However data on the diagnostic accuracy of LAMP for active case detection, particularly low-density parasitaemias, are lacking. We therefore evaluated the performance of a new LAMP kit compared with PCR using DNA from filter paper blood spots.

Usefulness of Plasmodium falciparum-specific rapid diagnostic tests for assessment of parasite clearance and detection of recurrent infections after artemisinin-based combination therapy.

Background: Rapid diagnostic test (RDT) is an important tool for parasite-based malaria diagnosis. High specificity of RDTs to distinguish an active Plasmodium falciparum infection from residual antigens from a previous infection is crucial in endemic areas where residents are repeatedly exposed to malaria. The efficiency of two RDTs based on histidine-rich protein 2 (HRP2) and lactate dehydrogenase (LDH) antigens were studied and compared with two microscopy techniques (Giemsa and acridine orange-stained blood smears) and real-time polymerase chain reaction (PCR) for assessment of initial clearance and detection of recurrent P.

The usefulness of rapid diagnostic tests in the new context of low malaria transmission in Zanzibar.

Background: We assessed if histidine-rich-protein-2 (HRP2) based rapid diagnostic test (RDT) remains an efficient tool for Plasmodium falciparum case detection among fever patients in Zanzibar and if primary health care workers continue to adhere to RDT results in the new epidemiological context of low malaria transmission. Further, we evaluated the performance of RDT within the newly adopted integrated management of childhood illness (IMCI) algorithm in Zanzibar.

Methods And Findings: We enrolled 3890 patients aged ≥ 2 months with uncomplicated febrile illness in this health facility based observational study conducted in 12 primary health care facilities in Zanzibar, between May-July 2010.

Rapid diagnostic tests for molecular surveillance of Plasmodium falciparum malaria -assessment of DNA extraction methods and field applicability.

Background: The need for new malaria surveillance tools and strategies is critical, given improved global malaria control and regional elimination efforts. High quality Plasmodium falciparum DNA can reliably be extracted from malaria rapid diagnostic tests (RDTs). Together with highly sensitive molecular assays, wide scale collection of used RDTs may serve as a modern tool for improved malaria case detection and drug resistance surveillance.

Prevalence of PCR detectable malaria infection among febrile patients with a negative Plasmodium falciparum specific rapid diagnostic test in Zanzibar.

We screened for malaria in 594 blood samples from febrile patients who tested negative by a Plasmodium falciparum-specific histidine-rich protein-2-based rapid diagnostic test at 12 health facilities in Zanzibar districts North A and Micheweni, from May to August 2010. Screening was with microscopy, polymerase chain reaction (PCR) targeting the cytochrome b gene (cytbPCR) of the four major human malaria species, and quantitative PCR (qPCR). The prevalence of cytbPCR-detectable malaria infection was 2% (12 of 594), including 8 P.

Novel polymorphisms in Plasmodium falciparum ABC transporter genes are associated with major ACT antimalarial drug resistance.

Chemotherapy is a critical component of malaria control. However, the most deadly malaria pathogen, Plasmodium falciparum, has repeatedly mounted resistance against a series of antimalarial drugs used in the last decades. Southeast Asia is an epicenter of emerging antimalarial drug resistance, including recent resistance to the artemisinins, the core component of all recommended antimalarial combination therapies.

Carolus Linnaeus, the ash, worm-wood and other anti-malarial plants.

In 1735 Carolus Linnaeus wrote that quinine was the preferred treatment for malaria but that the bark of the ash (Fraxinus excelsior) and worm-wood (Artemisia absinthium) also had effects on the disease. We here report that lipo- and hydrophilic extracts of the bark of the ash inhibit the in vitro growth of the asexual stages of P. falciparum.

Antimalarial exposure delays Plasmodium falciparum intra-erythrocytic cycle and drives drug transporter genes expression.

Background: Multi-drug resistant Plasmodium falciparum is a major obstacle to malaria control and is emerging as a complex phenomenon. Mechanisms of drug evasion based on the intracellular extrusion of the drug and/or modification of target proteins have been described. However, cellular mechanisms related with metabolic activity have also been seen in eukaryotic systems, e.

Chloroquine resistant P. falciparum prevalence is low and unchanged between 1990 and 2005 in Guinea-Bissau: an effect of high chloroquine dosage?

Chloroquine resistant malaria was first reported in Guinea-Bissau in 1990 but chloroquine remains the most commonly used antimalarial in the country. Since 1990, we have conducted nearly annual standardized WHO in vitro micro-tests to assess chloroquine resistance. We have identified pfcrt 76T and other genetic polymorphisms in samples from 1992, 1993, 1995, 2004 and 2005.