MalariaWorld journal最新文献

Introduction: The cadherin G-protein coupled receptor BT-R₃ in the mosquito Anopheles gambiae is a single membrane-spanning α-helical (bitopic) protein that represents the most abundant and functionally diverse group of membrane proteins. Binding of the Cry4B toxin of Bacillus thuringiensis subsp. israelensis (Bti) to BT-R₃ triggers a Mg2+-dependent signalling pathway in the mosquito that involves stimulation of G protein α-subunit, which subsequently launches a coordinated signalling cascade involving Na⁺/K⁺-ATPase. Described in this study is the behaviour of the Cry4B purified active protein toxin in solution relative to its protoxin predecessor produced by Bti as well as identification of the region within BT-R₃ of An. gambiae to which the toxin binds.

Materials and methods: The relationship and behaviour of protoxin and toxin were ascertained in vitro by solubility studies in an alkaline environment like that of the mosquito larval midgut. To identify the specific toxin-binding site within BT-R₃, the full-length coding sequence of the bt-r3 gene was amplified and cloned in pENTR/D-TOTO and subcloned in pXINSECT-DEST38 resulting in recombinant pXINSECT-DEST38-bt-r3. Cytotoxicity was analysed using Trichoplusia ni High Five™ insect cells transfected with the pXINSECT-DEST38-bt-r3 plasmid rendering them susceptible to the Cry4B toxin. Truncation mutational analyses, receptor-toxin binding studies and live cell experiments were used to elucidate the toxin-binding site in BT-R₃.

Results: The N-terminal half of the Cry4B protoxin was cleaved releasing active Cry4B toxin. The nontoxic C-terminal portion was degraded into small peptide fragments. The receptor BT-R₃ contained a single toxin-binding site--a 106-amino acid polypeptide bounded by Ile1359 and Ser1464 (¹³⁵⁹IS¹⁴⁶⁴) localized in the 11th cadherin repeat of the receptor.

Conclusions: The structural features of the toxin-binding site are critical to the specificity, selectivity and affinity of the active toxin and for the design and development of novel Bti-based biopesticides.

Plasmodium vivax causes the vast majority of malaria cases in Brazil. The lifecycle of this parasite includes a latent stage in the liver, the hypnozoite. Reactivation of hypnozoites induces repeated relapses. We report a case of two relapses of vivax malaria in a teenage girl after conventional treatment with chloroquine and primaquine. Chloroquine prophylactic treatment for three months was prescribed with a favourable outcome of the case.

It is argued that reducing poverty is likely to alleviate malaria transmission and that the way to do this is by reducing inequality. The present capitalist system (as opposed to a straightforward market) tends to erode equality and promote profit over product. This may extend to the manufacture of bednets, bought by agencies rather than individual consumers, whose products may suffer from built in obsolescence. It is argued that better quality nets that can be re-impregnated locally are both desired and required. Derek Charlwood (aka Mzshensy#1) started his career as a medical entomologist in 1974 as a Research Assistant in the laboratory of the legendary Mick Gillies. By 2012 he had risen to become a Senior Research Assistant working for the Liverpool School of Tropical Medicine and so he is definitely ascending the career ladder. He has worked in numerous malaria endemic countries including Brazil, Papua New Guinea, Tanzania, Cambodia, São Tomé and Príncipe, Mozambique and Eritrea.

A controversy has arisen over whether or not the replacement of PFAS compounds as a binder between insecticides and nets by other compounds has affected the nets' efficacy in preventing malaria transmission. Robert Bos places this matter in a broader and historical context and concludes that now is the time to revisit earlier concepts and provide sustainable malaria prevention and control with a broader foundation aiming for truly resilient results. The need to promote institutional arrangements conducive to inter-sectoral action is as great in WHO Member States as it is within the structure of the World Health Organization itself. Robert Bos is former Executive Secretary, WHO/FAO/UNEP/UN-Habitat Panel of Experts on Environmental Management for Vector Control, WHO, Geneva (1983-1995) former Scientist, Division of Environmental Health, later Department of Sustainable Development and Healthy Environments, later Department of Public Health and Environment, WHO, Geneva (1995-2009) and former Coordinator, Water, Sanitation and Health, WHO, Geneva (2009-2013).

Introduction: Malaria remains a major public health problem in children in endemic areas. This study aimed to determine its prevalence, intensity, and assess how biological parameters like RBC count, haemoglobin, haematocrit, glycaemia, platelet count and WBC count vary with respect to parasitaemia in children <16 years attending the Nkwen District Hospital, northwest Cameroon.

Materials and methods: The study was a hospital-based cross-sectional study conducted between March-May 2023. Structured, closed-ended questionnaires were administered to obtain information. Patients' temperature was measured using an infrared forehead digital thermometer. Malaria was diagnosed by RDT and positive samples Giemsa-stained for parasitaemia. Full blood count was performed using a haemolyser and glycaemia measured using a glucometer.

Results: In total, 321 children were examined. Overall prevalence of malaria (all P. falciparum) was 22.7% (73/321), with 24.7% (18/73), 34.2% (25/73) and 41.1% (30/73) having low, moderate and high parasitaemias, respectively. Overall GMPD was 2.670.8±179.9/μL; children aged 6-10 years were hit hardest (5.377.7 ± 3.2/μL). Malaria-positive children had significantly lower RBC count, Hb concentration, Hct, blood sugar, WBC and platelet counts (p<0.05) compared to those that were negative. Among positive children, RBC count, Hct, Hb, lymphocyte and platelet count each showed a significant (p<0.05) decrease while total WBC and granulocyte count each showed a significant (p<0.05) increase with increasing levels of parasitaemia.

Conclusions: Changes in biological parameters during malaria are sensitive but poor specific indicators of malaria because they may overlap with symptoms of other infections. More attention should be given to children aged 6-10 years during strategic planning and design of malaria control programmes.

Introduction: In the current study we assessed clinical laboratories' staff ability across the city of Kinshasa with particular focus on their practices and performance regarding malaria microscopy.

Materials and methods: This was a non-random cross-sectional study included clinical laboratories in Kinshasa and focused on cross-checking of blood slides, a questionnaire and checklist according to standardised analytic malaria microscopy procedures. Regarding the cross-checking of slides, participant responses were considered 'corrects' in cases of complete congruence with the reference; 'acceptable' for malaria-positive slides but no identification of Plasmodium species, stage of development, parasite density and/or reported as P. falciparum instead of 'P. non falciparum'; and 'incorrect' if 'false positive' and 'false negative' cases.

Results: Eighty-eight among the 90 targeted clinical laboratories (participation 97.8%) took part in the investigation from February to July 2019. The ability assessment revealed that individuals qualified to perform thick blood films (TBF) according to the national malaria control program (NMCP) procedures ranged from 48.6% to 100.0%. Overall cross-checking performance of 167 eligible routine slides was relatively low: 37.7%; 25.8% and 36.5% of correct, acceptable and incorrect responses, respectively. The first routine slide was correctly and acceptably scored respectively by 35.3% and 28.2% of participating laboratories (n = 85); and the second, by 40.2% and 23.2% respectively (n = 82). The sensitivity and specificity were found to be 79.4% and 53.8%, respectively. However, the relative high scores reported in relation with the ability needed to perform TBF based on NMCP standards contrasted with the poor performance from cross-checking slides. Consecutively, only one-third of the 88 participating laboratories reached a score > 60% in agreement with NMCP procedures and had acceptable responses to cross-checked slides.

Conclusions: The study was conducted as part of the activities relating to "Ensuring early diagnosis and prompt malaria treatment" component of the national malaria control strategy with NMCP support. More laboratories must implement clear and standardised malaria microscopy procedures, and need to include more rigorous quality control.

Introduction: Human habitats remain the main point of human-vector interaction leading to malaria transmission despite the sustained use of insecticide-treated nets and indoor residual spraying. Simple structural modifications involving screening of doors, windows and eaves have great potential for reducing indoor entry of mosquitoes. Moreover, insecticide treatment of the screen material may provide additional benefit in mosquito population reduction.

Materials and methods: Four huts, each constructed inside a semi-field structure, were used in the study. Two had untreated eave and door screens and screened air cavities in place of windows (experiment 1) or were similar but with the eave screens treated with Actellic® 300CS insecticide (experiment 2). The other two huts remained unscreened throughout the study. Two hundred, 3-day old adults of F1 generation Anopheles funestus collected by aspiration or F0 reared from An. arabiensis larvae or An. arabiensis (Dongola strain) were released in each semi-field structure at dusk and recaptured the following morning. A single volunteer slept in each hut under an untreated bednet each night of the study. Recaptured mosquitoes were counted and recorded by location, either indoor or outdoor of each hut in the different semi-field structures.

Results: Based on modelled estimates, significantly fewer, 10% An. arabiensis from Ahero, 11% An. arabiensis Dongola strain and 10% An. funestus from Siaya were observed inside modified huts compared to unmodified ones. Treating of eave screen material with Actellic® 300CS significantly reduced indoor numbers of An. arabiensis from Ahero, to nearly 0%, and An. arabiensis Dongola strain, to 3%, compared to huts with untreated eave screens, while eliminating An. funestus indoors. These modifications cost US$180 /structure and have been observed to last more than 15 years in a different location.

Conclusions: Eave, door and window screening are effective ways of reducing mosquito entry into houses. Additionally, treatment of eave screen material with an effective insecticide further reduces the Anopheles population in and around the screened huts under semi-field conditions and could greatly complement existing vector control efforts.