| 1. |
- Aydin-Schmidt, Berit, et al.
(författare)
-
Carolus Linnaeus, the ash, worm-wood and other anti-malarial plants
- 2010
-
Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 42:11-12, s. 941-942
-
Tidskriftsartikel (refereegranskat)abstract
- 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. The data suggests that the knowledge of the treatment of malaria was already available in Europe some 300 years ago.
|
|
| 2. |
- Aydin-Schmidt, Berit, et al.
(författare)
-
Field Evaluation of a High Throughput Loop Mediated Isothermal Amplification Test for the Detection of Asymptomatic Plasmodium Infections in Zanzibar
- 2017
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- 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. Results The PCR and HTP-LAMP determined malaria prevalences were 1.6% (95% CI 1.3-2.4) and 0.7% (95% CI 0.4-1.1), respectively. The sensitivity of HTP-LAMP compared to PCR was 40.8% (CI95% 27.0-55.8) and the specificity was 99.9% (CI95% 99.8-100). For the PCR positive samples, there was no statistically significant difference between the geometric mean parasite densities among the HTP-LAMP positive (2.5 p/mu L, range 0.2-770) and HTP-LAMP negative (1.4 p/mu L, range 0.1-7) samples (p = 0.088). Two lab technicians analysed up to 282 samples per day and the HTP-LAMP method was experienced as user friendly. Conclusions Although field applicable, this high throughput format of LAMP as used here was not sensitive enough to be recommended for detection of asymptomatic low-density infections in areas like Zanzibar, approaching malaria elimination.
|
|
| 3. |
- Aydin-Schmidt, Berit, et al.
(författare)
-
Loop mediated isothermal amplification (LAMP) accurately detects malaria DNA from filter paper blood samples of low density parasitaemias
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8, s. e103905-
-
Tidskriftsartikel (refereegranskat)abstract
- 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.METHODS AND FINDINGS:Samples from 865 fever patients and 465 asymptomatic individuals collected in Zanzibar were analysed for Pan (all species) and Pf (P. falciparum) DNA with the Loopamp MALARIA Pan/Pf kit. Samples were amplified at 65°C for 40 minutes in a real-time turbidimeter and results were compared with nested PCR. Samples with discordant results between LAMP and nested PCR were analysed with real-time PCR. The real-time PCR corrected nested PCR result was defined as gold standard. Among the 117 (13.5%) PCR detected P. falciparum infections from fever patients (mean parasite density 7491/µL, range 6-782,400) 115, 115 and 111 were positive by Pan-LAMP, Pf-LAMP and nested PCR, respectively. The sensitivities were 98.3% (95%CI 94-99.8) for both Pan and Pf-LAMP. Among the 54 (11.6%) PCR positive samples from asymptomatic individuals (mean parasite density 10/µL, range 0-4972) Pf-LAMP had a sensitivity of 92.7% (95%CI 80.1-98.5) for detection of the 41 P. falciparum infections. Pan-LAMP had sensitivities of 97% (95%CI 84.2-99.9) and 76.9% (95%CI 46.2-95) for detection of P. falciparum and P. malariae, respectively. The specificities for both Pan and Pf-LAMP were 100% (95%CI 99.1-100) in both study groups.CONCLUSION:Both components of the Loopamp MALARIA Pan/Pf detection kit revealed high diagnostic accuracy for parasite detection among fever patients and importantly also among asymptomatic individuals of low parasite densities from minute blood volumes preserved on filter paper. These data support LAMPs potential role for improved detection of low-density malaria infections in pre-elimination settings.
|
|
| 4. |
- Aydin Schmidt, Berit
(författare)
-
New diagnostic tools for malaria-challenges and opportunities
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nearly half of the world’s population is at risk for malaria and over 600,000 die from the disease every year. Access to prompt and correct parasite based diagnosis in order to target treatment to those with a confirmed malaria infection and improved malaria surveillance are cornerstones in malaria control. The availability of modern diagnostic tools such as rapid diagnostic test (RDT), polymerase chain reaction (PCR) and loop mediated isothermal amplification (LAMP) represent new opportunities besides microscopy for improved sensitive and accurate parasite-based diagnosis. However, there are different demands on diagnostic tools for different health care settings and endemic contexts. The performance of RDT was compared to blood smear microscopy and PCR among febrile patients in a low endemic/pre elimination area (Zanzibar). Although the sensitivity of RDT was found to be relatively low (76.5%) the health care workers were highly adherent to test results in prescribing antimalarial drugs. Parasite clearance and detection of recurrent infections was assessed by different diagnostic methods after malaria treatment in febrile children in a relatively high endemic area of mainland Tanzania. Median clearance time was two days for PCR and microscopy whereas the clearance times were seven and 28 days for the pLDH and HRP2 based RDTs, respectively. pLDH based RDT was a better tool than HRP2 based for treatment follow up and detection of recurrent infection. The usefulness of RDT as a source of parasite DNA was evaluated through different parasite DNA extraction methods. DNA extraction efficacy varied with test device and extraction method. There was no difference in PCR detection rates between RDT and filter paper samples collected from the field. This confirms the usefulness of RDTs stored under field conditions as a modern tool for molecular malaria surveillance and RDT quality control. A LAMP kit was compared to conventional PCR methods for detection of parasite DNA from dried blood spots collected among both fever patients and asymptomatic individuals in Zanzibar. The LAMP kit had a sensitivity of 98% for detection of Plasmodium(P) falciparum among fever patients and a sensitivity of > 92% and 77% for detection of P. falciparum and P. malariae among asymptomatic individuals. The high diagnostic accuracy of the LAMP kit for detection of low density parasitaemias from minute blood volumes preserved on filter papers supports its role for improved case detection in areas of low density malaria infections. The results in this thesis provide important data on the usefulness of new diagnostic tools for improved case detection and surveillance of malaria in different endemic contexts.
|
|
| 5. |
- Aydin-Schmidt, Berit, et al.
(författare)
-
Usefulness of Plasmodium falciparum-specific rapid diagnostic tests for assessment of parasite clearance and detection of recurrent infections after artemisinin-based combination therapy.
- 2013
-
Ingår i: Malaria journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- 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. falciparum infections after artemisinin-based combination therapy (ACT) in a moderately high endemic area of rural Tanzania.
|
|
| 6. |
- Cook, Jackie, et al.
(författare)
-
Loop-mediated isothermal amplification (LAMP) for point-of-care detection of asymptomatic low-density malaria parasite carriers in Zanzibar
- 2015
-
Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 14, s. 43-
-
Tidskriftsartikel (refereegranskat)abstract
- 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. Finger-prick blood was taken for screening by rapid diagnostic test (RDT) and LAMP and collected on filter paper for subsequent polymerase chain reaction (PCR) analyses. LAMP results were compared to RDT and to PCR using McNemar's test. Results: Approximately 1,000 people were screened. RDT detected ten infections (1.0% (95% CI 0.3-1.6)) whilst both LAMP and PCR detected 18 (1.8% (95% CI 0.9-2.6)) infections. However, PCR identified three infections that LAMP did not detect and vice versa. LAMP testing was easy to scale-up in field conditions requiring minimal training and equipment, with results ready one to three hours after screening. Conclusions: Despite lower than expected prevalence, LAMP detected a higher number of infections than the currently used diagnostic, RDT. LAMP is a field-friendly, sensitive diagnostic test that could be useful for MSAT malaria campaigns which require quick results to enable prompt treatment.
|
|
| 7. |
- Holmström, Oscar, et al.
(författare)
-
A novel deep learning-based point-of-care diagnostic method for detecting Plasmodium falciparum with fluorescence digital microscopy.
- 2020
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:11
-
Tidskriftsartikel (refereegranskat)abstract
- 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.METHODS: Thin blood smears (n = 125) were collected from patients with microscopy-confirmed P. falciparum infections in rural Tanzania, prior to and after initiation of artemisinin-based combination therapy. The samples were stained using the 4',6-diamidino-2-phenylindole fluorogen and digitized using the prototype microscope scanner. Two DL algorithms were trained to detect malaria parasites in the samples, and results compared to the visual assessment of both the digitized samples, and the Giemsa-stained thick smears.RESULTS: Detection of P. falciparum parasites in the digitized thin blood smears was possible both by visual assessment and by DL-based analysis with a strong correlation in results (r = 0.99, p < 0.01). A moderately strong correlation was observed between the DL-based thin smear analysis and the visual thick smear-analysis (r = 0.74, p < 0.01). Low levels of parasites were detected by DL-based analysis on day three following treatment initiation, but a small number of fluorescent signals were detected also in microscopy-negative samples.CONCLUSION: Quantification of P. falciparum parasites in DAPI-stained thin smears is feasible using DL-supported, point-of-care digital microscopy, with a high correlation to visual assessment of samples. Fluorescent signals from artefacts in samples with low infection levels represented the main challenge for the digital analysis, thus highlighting the importance of minimizing sample contaminations. The proposed method could support malaria diagnostics and monitoring of treatment response through automated quantification of parasitaemia and is likely to be applicable also for diagnostics of other Plasmodium species and other infectious diseases.
|
|
| 8. |
- Mhamilawa, Lwidiko E, et al.
(författare)
-
Detection of Plasmodium falciparum 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
- 2019
-
Ingår i: American Journal of Tropical Medicine and Hygiene. - : American Society of Tropical Medicine and Hygiene. - 0002-9637 .- 1476-1645. ; 101:5, s. 1144-1147
-
Tidskriftsartikel (refereegranskat)abstract
- Microscopy-determined Plasmodium falciparum 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 P. falciparum on day 3 after ACT in 256 patients with uncomplicated malaria in Bagamoyo District, Tanzania. Day 3 positivity rates were 0%, 84.8%, and 84.4% for each method, respectively. The sensitivity and specificity of LAMP against PCR was 100% (95% CI, 96.1-100) and 77.4% (95% CI, 58.9-90.4) when quantitative PCR-determined parasite densities were ≥ two parasites/µL. Loop-mediated isothermal amplification had comparable diagnostic accuracy to PCR and could potentially represent a field-friendly tool for determining day 3 positivity rates. However, what day 3 P. falciparum positivity determined using molecular methods represents needs to be further elucidated.
|
|
| 9. |
- Morris, Ulrika, et al.
(författare)
-
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.
- 2018
-
Ingår i: BMC Medicine. - : Springer Science and Business Media LLC. - 1741-7015. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- 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 > 0.8%. The areas were randomised to eight intervention and eight control clusters. The intervention included two rounds of MDA with dihydroartemisinin-piperaquine and single low-dose primaquine 4 weeks apart in May-June 2016. Primary and secondary outcomes were cumulative confirmed malaria case incidences 6 months post-MDA and parasite prevalences determined by PCR 3 months post-MDA. Additional outcomes included intervention coverage, treatment adherence, occurrence of adverse events, and cumulative incidences 3, 12, and 16 months post-MDA.RESULTS: Intervention coverage was 91.0% (9959/10944) and 87.7% (9355/10666) in the first and second rounds, respectively; self-reported adherence was 82.0% (881/1136) and 93.7% (985/1196). Adverse events were reported in 11.6% (147/1268) and 3.2% (37/1143) of post-MDA survey respondents after both rounds respectively. No serious adverse event was reported. No difference in cumulative malaria case incidence was observed between the control and intervention arms 6 months post-MDA (4.2 and 3.9 per 1000 population; p = 0.94). Neither was there a difference in PCR-determined parasite prevalences 3 months post-MDA (1.4% and 1.7%; OR = 1.0, p = 0.94), although having received at least the first MDA was associated with reduced odds of malaria infection (aOR = 0.35; p = 0.02). Among confirmed malaria cases at health facilities, 26.0% and 26.3% reported recent travel outside Zanzibar in the intervention and control shehias (aOR ≥ 85; p ≤ 0.001).CONCLUSIONS: MDA was implemented with high coverage, adherence, and tolerability. Despite this, no significant impact on transmission was observed. The findings suggest that two rounds of MDA in a single year may not be sufficient for a sustained impact on transmission in a pre-elimination setting, especially when the MDA impact is restricted by imported malaria. Importantly, this study adds to the limited evidence for the use of MDA in low transmission settings in sub-Saharan Africa.TRIAL REGISTRATION: ClinicalTrials.gov, NCT02721186 (registration date: March 29, 2016).
|
|
| 10. |
- Morris, Ulrika, et al.
(författare)
-
Field deployment of loop-mediated isothermal amplification for centralized mass-screening of asymptomatic malaria in Zanzibar : a pre-elimination setting
- 2015
-
Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- 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). In 50 % of the study households, participants were asked to provide 60 μL of finger-prick blood for additional LAMP screening. LAMP was conducted in two centralized laboratories in Zanzibar, by trained technicians with limited or no previous experience of molecular methods. The LAMP assay was performed with Loopamp(TM) MALARIA Pan/Pf Detection Kit (Eiken Chemical Company, Japan). Samples positive for Plasmodium genus (Pan)-LAMP were re-tested using Plasmodium falciparum-specific LAMP kits.RESULTS: Paired RDT and LAMP samples were available from 3983 individuals. The prevalence of asymptomatic malaria was 0.5 % (CI 95 % 0.1-0.8) and 1.6 % (CI 95 % 1.1-2.2) by RDT and Pan-LAMP, respectively. LAMP detected 3.4 (CI 95 % 2.2-5.2) times more Plasmodium positive samples than RDT. DNA contamination was experienced, but solved by repetitive decontamination of all equipment and reagents.CONCLUSIONS: LAMP is a simple and sensitive molecular tool, and has potential in active surveillance and mass-screening programmes for detection of low-density asymptomatic malaria in pre-elimination settings. However, in order to deploy LAMP more effectively in field settings, protocols may need to be adapted for processing larger numbers of samples. A higher throughput, affordable closed system would be ideal to avoid contamination.
|
|
| 11. |
- Morris, Ulrika, et al.
(författare)
-
Rapid diagnostic tests for molecular surveillance of Plasmodium falciparum malaria -assessment of DNA extraction methods and field applicability.
- 2013
-
Ingår i: Malaria journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- 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. However, comparative studies of DNA extraction efficiency from RDTs and the field applicability are lacking. The aim of this study was to compare and evaluate different methods of DNA extraction from RDTs and to test the field applicability for the purpose of molecular epidemiological investigations.
|
|
| 12. |
- Mwaiswelo, Richard, et al.
(författare)
-
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
- 2016
-
Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- 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 (0.25 mg/kg) versus standard AL regimen for treatment of acute uncomplicated Plasmodium falciparum malaria in Tanzania. Methods: A randomized, single-blinded, clinical trial was conducted in Yombo, Bagamoyo district, Tanzania. Acute uncomplicated P. falciparum malaria patients aged >= 1 year, with the exception of pregnant and lactating women, were enrolled and treated with AL plus a single PQ dose (0.25 mg/kg) or AL alone under supervision. PQ was administered together with the first AL dose. Clinical and laboratory assessments were performed at 0, 8, 24, 36, 48, 60, and 72 h and on days 7, 14, 21, and 28. The primary end-point was a polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR) on day 28. Secondary outcomes included: fever and asexual parasitaemia clearance, proportion of patients with PCR-determined parasitaemia on day 3, and proportion of patients with Pfmdr1 N86Y and Pfcrt K76T on days 0, 3 and day of recurrent infection. Results: Overall 220 patients were enrolled, 110 were allocated AL + PQ and AL, respectively. Parasite clearance by microscopy was fast, but PCR detectable parasitaemia on day 3 was 31/109 (28.4 %) and 29/108 (26.9 %) in patients treated with AL + PQ and AL, respectively (p = 0.79). Day 28 PCR-adjusted ACPR and re-infection rate was 105/105 (100 %) and 101/102 (99 %) (p = 0.31), and 5/107 (4.7 %) and 5/8 (4.8 %) (p = 0.95), in AL + PQ and AL arm, respectively. There was neither any statistically significant difference in the proportion of Pfmdr1 N86Y or Pfcrt K76T between treatment arms on days 0, 3 and day of recurrent infection, nor within treatment arms between days 0 and 3 or day 0 and day of recurrent infection. Conclusion: The new WHO recommendation of adding a single low-dose of PQ to AL did not compromise treatment outcome of uncomplicated P. falciparum malaria in Tanzania.
|
|
| 13. |
- Ursing, Johan, et al.
(författare)
-
Chloroquine-susceptible and -resistant Plasmodium falciparum strains survive high chloroquine concentrations by becoming dormant but are eliminated by prolonged exposure
- 2022
-
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 77:4, s. 1005-1011
-
Tidskriftsartikel (refereegranskat)abstract
- 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.Methods: Chloroquine-susceptible (3D7) and -resistant (FCR3) strains were exposed in vitro to 1, 2, 4, 8, 16 or 32 times their respective 90% inhibitory chloroquine concentrations for 3, 5, 7 or 14 days and then followed until recrudescence, or not, by 42 days after the end of exposure.Results: Exposure to chloroquine appeared to eliminate susceptible and resistant parasites, leaving small pyknotic apparently dead parasites. Chloroquine-susceptible and -resistant parasites recrudesced after 3 and 5 days of chloroquine exposure. Recrudescence occurred in one out of four 7 day exposure series but not after 14 days exposure. The median time to recrudescence was 13 to 28 days with a range of 8 to 41 days after the end of exposure. Time to recrudescence after the end of exposure increased with duration of exposure for susceptible and resistant strains (P < 0.001). Time to recrudescence did not correlate with concentrations greater than 1x IC90.Conclusions: Chloroquine-susceptible and -resistant P. falciparum probably become dormant. Elimination of dormant parasites is primarily dependent upon the duration of chloroquine exposure. Exposure to effective drug concentrations for 7 days eliminates most parasites in vitro. The results support in vivo data indicating that elimination of chloroquine-resistant P. falciparum correlates with Day 7 chloroquine concentrations.
|
|
