MalariaWorld journal最新文献

Background: The spread of artemisinin resistant malaria from SE Asia to the rest of the world remains a threat that will only be ended by eliminating malaria from the region. Novel control approaches are required to mitigate this threat. Spatial repellents (SR) are one such approach. We therefore conducted a multiple cross-over experiment from April 2013 - April 2014, in which all houses in one of two villages in Mondolkiri Province, Cambodia were alternately supplied with an emanator of the spatial repellent metofluthrin per 30 m³ of protected area to cover all potential peridomestic areas where people might spend their time before sleeping. Emanators were replaced every month for a three-month period.

Material and methods: Mosquito densities were simultaneously monitored in each village for two weeks every month using six CDC light-traps/night run from 18.00 to 07.00 hrs inside bedrooms and malaria prevalence, seroconversion and gSG6 protein rates assessed from prevalence surveys. After emanators were installed in the first village they were installed in the second village for a further three-month period and following that were again used in the initial village for a further three months. Surveys were undertaken before the initial installation of the emanators and at each cross-over point.

Results: Anopheles dirus densities were highest in houses closest to the forest. Transmission rates were low even before the application of the emanators. Perhaps due to the low levels of malaria transmission in Mondolkiri no significant relationships were found in Plasmodium cases or seroconversion rates between villages, surveys or by intervention. Adult males, who might spend more time unprotected in the forest at night, appeared to be at greater risk of becoming infected with P. falciparum malaria as compared to women or young children.

Conclusion: At the malaria transmission levels present in Mondolkiri the metofluthrin emanators evaluated had no observable effect on malaria prevalence. This may be due to confounding by low prevalence rates.

Hemozoin is generally considered a waste deposit that is formed for the sole purpose of detoxification of free heme that results from the digestion of hemoglobin by Plasmodium parasites. However, several observations of parasite multiplication, both in vertebrate and invertebrate hosts are suggestive of a wider, but overlooked, metabolic role for this product. The presence of clinical peripheral blood samples of P. falciparum with high parasitemia containing only hemozoin-deficient (non-pigmented) asexual forms has been repeatedly confirmed. Such samples stand in contrast with other samples that contain mostly pigmented circulating trophozoites and gametocytes, indicating that pigment accumulation is a prominent feature of gametocytogenesis. The restricted size, i.e. below detection by light microscopy, of hemozoin in asexual merozoites and ringforms of P. falciparum implies its continuous turnover, supporting a role in metabolism. The prominent interaction of hemozoin with several antimalarial drugs, the involvement of proteins in hemozoin formation, and the finding of plasmodial genes coding for a heme-oxygenase-like protein argue for a wider and more active role for hemozoin in the parasite's metabolism. The observed association of hemozoin with crystalloids during ookinete development is consistent with a useful function to it during parasite multiplication in the invertebrate host. Finally, alternative mechanisms, other than hemozoin formation, provide substitute or additional routes for heme detoxification.

Background: We report cases of gestational and congenital malaria with twin prematurity, low birth weight and bacterial co-infection. Congenital malaria is often misdiagnosed for lack of specific symptoms and a general lack of awareness of this presumably uncommon condition, and its diagnosis and prognosis become even more complex in the event of bacterial co-infections.

Case presentation: A 35-weeks pregnant woman with sickle-cell disease and a history of spontaneous abortions was admitted at Vanga Hospital in DR Congo. She had fever (38.9°C) and microscopy-confirmed P. falciparum malaria and was put on 80/480 mg artemether-lumefantrine. She soon went into active labour, during which both twins developed acute foetal distress and were promptly delivered by C-section. The twins were underweight, and both had P. falciparum malaria at birth and were given 20 mg quinine twice daily. Both developed fever on the third day; a bacterial infection was suspected and 200 mg ceftriaxone was added to their treatment. Fever in both twins quickly resolved, and one twin totally recovered within 2 days of antibiotic treatment. The other twin developed acute respiratory distress and hypoxia and died.

Discussion: This is a case of gestational and congenital malaria with prematurity, low birth weight and bacterial co-infection, but the patients were initially only treated for malaria based on their malaria-positive blood smears at birth.

Conclusions: In malaria-endemic areas, babies should be screened for congenital malaria. Even with a confirmed malaria infection in the new-born, it is important consider the possibility of bacterial co-infections.

Background: In Nigeria, decline in the sensitivity of Plasmodium falciparum to Artemisinin Combination Therapy (ACT) has prompted the unofficial use of chloroquine (CQ) for self-medication. This study was designed to determine the prevalence and distribution of CQ resistant/susceptible alleles of CQ resistance transporter (Pfcrt) and P. falciparum multidrug resistance gene 1 (Pfmdr1) in view of the possible re-introduction of CQ for malaria treatment.

Materials and methods: Four hundred and sixty six (466) P. falciparum positive samples were randomly collected from five states of northwest Nigeria. The samples were amplified using RT- PCR at codon 76 for Pfcrt and codon 86 for Pfmdr1. Data was analysed using chi-square, odds ratios and paired t-tests.

Results: Drug susceptible alleles (N86) were most prevalent in the study population (47.9%; 223/466), followed by the drug resistance alleles 86Y (28.3%; 132/466), followed by the drug susceptible alleles K76 (17.4%; 81/466), the resistant alleles 76T (12.4%; 58/466) and finally the mixed infection mutation K76T (3.6%; 17/466). Differences between the distributions of the Pfmdr1 and Pfcrt alleles were significant (P<0.05). There were significant differences (P<0.05) between N86 and 86Y alleles, but no significant differences between K76 and 76T alleles, including the prevalence of the various alleles across the different age groups.

Conclusion: The results of this study suggest the possibility of (re)introducing CQ for malaria treatment in north-western Nigeria and provide insight in the genetic background of P. falciparum in the study area.

Background: Antimalarial drug-resistant Plasmodium falciparum strains have been a major obstacle to the global efforts of controlling and eliminating malaria. The hope of reintroducing chloroquine for the treatment of uncomplicated malaria follows recent reports on decreases in the prevalence of chloroquine-resistant P. falciparum in several countries and recently, its total disappearance in Malawi and Zambia. In Nigeria, the discontinued use of chloroquine for malaria treatment was officially announced in 2005. A few available reports have shown a persistent high prevalence of the major biomarker of chloroquine resistance in southwest Nigeria. However, information on its prevalence in rural and urban areas is scanty. We investigated possible factors associated with the prevalence of a biomarker for chloroquine-resistance in Ogun State, southwest Nigeria.

Materials and methods: Parasite DNA was extracted from dried blood spots collected by finger-prick in malaria symptomatic and asymptomatic subjects attending the urban-based State General Hospital and a rural-based Primary Health Centre. A structured questionnaire was used to collect data on malaria/fever treatment history. Nested Polymerase Chain Reaction (PCR) followed by Restriction Fragment Length Polymorphisms (RFLP) analysis was used to detect mutations in the P. falciparum chloroquine resistance transporter (Pfcrt).

Results: Of the 243 participants recruited for this study, 56 were found to harbour P. falciparum parasites, of which 62.5% (35/56) showed symptoms of malaria. Prevalence of P. falciparum chloroquine-resistant strains (Pfcrt K76T) was 69.6%. The prevalence of Pfcrt K76T recorded in the rural area (91.7%) was significantly higher (P<0.05) than that in the urban area (53.1%). There was no correlation between prevalence of chloroquine-resistant strains and malaria symptoms in the rural area. However, prevalence of chloroquine-resistant strains was significantly higher in malaria-symptomatic subjects from the urban area.

Conclusions: Drug-resistant P. falciparum strains recorded in the rural area were associated with self-medication and patronage of drug vendors who continue to sell chloroquine. These findings present the importance of continuous surveillance of biomarkers indicating drug resistance especially now that antimalarial drug resistance is a threat to malaria eradication.

Background: Eave tubes are novel mosquito control devices that help to protect households against malaria vectors and other mosquitoes. They are installed in the upper walls of human habitations after the eaves have been closed. Mosquitoes trying to enter through these tubes are intercepted by electrostatic netting that can be treated with a variety of insecticides. Using video, mosquito behaviour and duration of contact with netting in eave tubes was recorded and analysed to assess contamination with insecticides under semi-field and field conditions.

Materials and methods: Off-the-shelf action cameras were used to observe behaviour of mosquitoes in eave tubes near Ifakara, Tanzania. In an experimental hut in a screen house, we observed Anopheles arabiensis females on electrostatic eave tube netting treated with bendiocarb powder or with Beauveria bassiana spores, both in comparison to untreated netting. In village houses that had been equipped with eave tubes we observed the behaviour of wild mosquitoes towards electrostatic netting treated with bendiocarb. Results were evaluated using a short-contact assay (5 second exposure).

Results: In the semi-field setup, the median contact time of An. arabiensis on bendiocarb-powdered eave tube nets was 276.4 sec (n=56), compared to 26.3 sec on the control (n=59). Of all the mosquitoes observed on the treated net, 94.6% had contact times of more than 5 seconds on the bendiocarb-powdered netting. The median time on nets powdered with B. bassiana spores was 34.4 sec (n=26), compared 37.1 sec in the untreated control (n=22). 88.5% of the mosquitoes spent more than 5 seconds on the treated nets. In the field we recorded 106 individual mosquitoes of unknown species inside tubes. They spent a median time of 70.9 sec on the bendiocarb-treated netting, with 90.6% remaining there for more than 5 seconds.

Conclusions: We have found no indication that the behaviour of mosquitoes on electrostatic eave tube netting, treated either with bendiocarb powder or with B. bassiana spores, interferes with successful transfer of lethal doses of these insecticidal actives. The videographic set-up used in this study is simple, sturdy and reliable enough to observe and analyse mosquito behaviour under field conditions.

Background: Initiation of specific antimalarial treatment within 24 hrs of fever onset at home and before presentation to the hospital is one of the strategies to reduce mortality from malaria in sub-Saharan Africa. In order to determine whether this strategy is being implemented we describe the use and factors associated with the use of pre-hospital medications among children admitted with malaria in one of the tertiary hospitals in Uganda.

Materials and methods: Use of pre-hospital medications was assessed in 205 children aged 6-59 months and diagnosed with malaria at admission in Mulago hospital. Data were obtained on the type, source, and dose adequacy of medicines used before presentation to the hospital as well as the socio-demographical characteristics of the children. The proportion of children using pre-hospital medication was determined and logistic regression analysis used to determine factors associated with use of pre-hospital medication.

Results: Overall, 147/205 (72%) of the children were given some medication for their illness before presentation to the hospital. The common pre-hospital medicines used were paracetamol (107/147, 72.8 %) and antimalarial medicines (91/147, 61.9 %). Antibiotics were used in only 12 (8.2 %) of the cases. The majority (62/91, 68%) of the cases got medicines from a health facility but only 41/91 (45%) received an adequate dose. Having fever for more than three days was significantly associated with use of pre-hospital medicines (OR = 2.2; 95% CI 1.12-4.35; p = 0.02).

Conclusions: The pre-hospital use of medicines is common amongst children presenting with malaria to this tertiary Ugandan hospital. The practice is, however, associated with use of inadequate doses of antimalarials and delay in presentation to the hospital. More effort is therefore needed to educate communities on the importance of proper home management of malaria.

Background: During pregnancy, malaria poses a great health risk to both mother and foetus. In Kenya, to prevent and control infections, mothers receive intermittent preventive treatment during pregnancy (IPTp) and are provided with a bednet (ITN). Uptake of these control strategies, however, is not optimal. In Kajiado County, for instance, only ITNs are given to pregnant women, without IPTp. We assessed utilisation of health facilities and WHO-recommended maternal malaria control strategies in Kajiado County.

Materials and methods: A total of eleven health facilities were recruited, in which 6899 pregnant women were divided in three groups. Group 1 were women attending a clinic and used ITNs, group 2 did not attend a clinic but used ITNs and group 3, which did neither. 86% Of deliveries were assessed; 84% of these in clinics and 16% at home. Throughout pregnancy, data on abortion and premature births were collected. Upon delivery, data on stillbirths, birth weight and neonatal mortality was noted. Mother's cord and placental blood was examined for malaria parasites and parasitaemia using microscopy; haemoglobin levels were determined.

Results: 86% Of the women visited a health facility, 97% used an ITN. Only 3% went without visits or bednet usage. Although the number of cases was low, attending a clinic and using a bednet increased maternal Hb and reduced maternal mortality. Use of nets decreased maternal malaria cases and mortality due to malaria whilst maternal Hb increased. Across the study groups, infant outcomes improved, with fewer abortions, premature births, still births, neonatal mortality and an increase in mean body weight at birth.

Conclusion: Women should be sensitised to visit clinics and use ITNs for better maternal and new-born health outcomes.

Background: Microscopic diagnosis of Giemsa-stained thick and thin blood films has remained the standard laboratory method for diagnosing malaria. High quality performance of microscopists that examine blood slides in health facilities remains critically important.

Materials and methods: A cross-sectional study was conducted to assess the performance of 107 malaria microscopists working at 23 malaria rechecking laboratories in Ethiopia. A set of 12 blood film slides was distributed to each microscopist. Data was collected and exported to SPSS version 20 for analysis. Chi-square, sensitivity, specificity, percent agreement, and kappa scores were calculated to assess performance in detecting and identification of Plasmodium species.

Results: The mean age of the participants was 30 ± 5 yrs and most of them (54; 50.5%) were working at regional reference laboratories. Overall, the sensitivity of participants in detecting and identifying malaria parasite species was 96.8% and 56.7%, respectively. The overall agreement on detection and identification of malaria species was 96.8% (Kappa = 0.9) and 64.8% (Kappa = 0.33), respectively. The least accurately identified malaria parasite species was P. malariae (3/107; 2.8%) followed by P. ovale (35/107; 32.7%). Participants working at hospital laboratories had the highest percentage (72.3 %, Kappa=0.51) of accurate species identification. Study participants that had participated in malaria microscopy and quality assurance trainings were significantly better at quantifying parasite densities (P<0.001).

Conclusion: The accuracy of parasite identification and quantification differed strongly between participants and expert microscopists. Therefore, regular competency assessment and training for malaria microscopists should be mandatory to assure proper diagnosis and management of malaria in Ethiopia.

Background: Asymptomatic malaria parasitaemia remains an effective transmission pool for malaria during pregnancy, which can result in placenta parasitaemia and adverse pregnancy outcomes. This study examined asymptomatic malaria parasitaemia among pregnant women in the antenatal clinic in General Hospital, Nassarawa-Eggon, Nasarawa State, Nigeria.

Materials and methods: A cross-sectional hospital based survey was carried out among 242 apparently healthy pregnant women presenting for booking in an antenatal clinic between June and August 2014. An interviewer-administered semi-structured questionnaire was used to obtain information on socio-demographic data and possible risk factors for asymptomatic malaria parasitaemia. These women should not have taken antimalarial medicines two weeks prior to the interview. Microscopy was used to identify malaria parasites and haemoglobin levels were estimated. Data was analysed using Epi Info 3.5.3. Descriptive statistics such as means, standard deviations, proportions, and range were used to summarise the data and the Chi square test was used to test association between categorical explanatory variables and outcome variables.

Results: Mean age (± SD) was 25.5 ± 5.5 years, 118 (48.8%) of the women were in the 25-34 years age group, while 153 (63.2%) were multigravidae. Asymptomatic Plasmodium falciparum infection was found in 55 women (22.7%; 95% CI: 18.0-28.7%) Among these, 36 (65.5%) were anaemic [OR: 2.0, CI: 1.1-3.8]. Long lasting insecticidal net (LLIN) was not used by 17 (30.9%) of the respondents. Younger age group (below 25 years) [AOR: 2.4, CI: 1.2-4.9] and non-usage of LLIN [AOR: 2.4, CI: 1.1-5.1] were significant predictors of asymptomatic malaria parasitaemia.

Conclusion: Asymptomatic malaria parasitaemia is a health challenge among pregnant women, especially in the younger age group and can predispose them to maternal anaemia. The supply and appropriate use of LLIN should be intensified.