Spatio-temporal associations between deforestation and malaria incidence in Lao PDR.
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ABSTRACT:
SUBMITTER: Rerolle F
PROVIDER: S-EPMC8024023 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Knowledge on insecticide resistance in Anopheles species is a basic requirement to guide malaria vector control programs. In Lao PDR, vector control relies on insecticide residual spraying (IRS) and impregnated bed-nets (ITNs) with the use of pyrethroids. Here, the susceptibility of Anopheles species, including several malaria vectors (An. maculatus and An. minimus), to various insecticides was investigated in ten provinces of Lao PDR through a north-south transect. Bioassays were performed on field caught female mosquitoes using the standard WHO susceptibility tests with DDT (4%), deltamethrin (0.05%) and permethrin (0.75%). In addition, the DIIS6 region of the para-type sodium channel gene was amplified and sequenced to identify knockdown resistance mutations (kdr). Resistance to DDT and permethrin was detected in suspected malaria vectors, such as An. nivipes and An. philippinensis in Lao PDR. Resistance to the formerly used DDT was found in a population of An. maculatus s.l. from Luang Prabang province. No resistance to pyrethroids was found in primary vectors, indicating that these insecticides are still adequate for malaria vector control. However, high resistance levels to pyrethroids was found in-vector species and reduced susceptibility to permethrin in An. minimus and An. maculatus was reported in specific localities which raises concerns for pyrethroid-based control in the future. No kdr mutation was found in any of the resistant populations tested hence suggesting a probable role detoxification enzymes in resistance. This study highlights the necessity to continue the monitoring of insecticide susceptibility to early detect potential occurrence and/or migration of insecticide resistance in malaria vectors in Lao PDR.
| S-EPMC5402946 | biostudies-literature
Project description:Malaria remains a major public health problem in the Peruvian Amazon where the persistence of high-risk transmission areas (hotspots) challenges the current malaria control strategies. This study aimed at identifying significant space-time clusters of malaria incidence in Loreto region 2002-2013 and to determine significant changes across years in relation to the control measures applied. Poisson regression and purely temporal, spatial, and space-time analyses were conducted. Three significantly different periods in terms of annual incidence rates (AIR) were identified, overlapping respectively with the pre-, during, and post- implementation control activities supported by PAMAFRO project. The most likely space-time clusters of malaria incidence for P. vivax and P. falciparum corresponded to the pre- and first two years of the PAMAFRO project and were situated in the northern districts of Loreto, while secondary clusters were identified in eastern and southern districts with the latest onset and the shortest duration of PAMAFRO interventions. Malaria in Loreto was highly heterogeneous at geographical level and over time. Importantly, the excellent achievements obtained during 5 years of intensified control efforts totally vanished in only 2 to 3 years after the end of the program, calling for sustained political and financial commitment for the success of malaria elimination as ultimate goal.
| S-EPMC5238441 | biostudies-literature
Project description:BackgroundIn Laos, the malaria burden remains high despite a significant reduction of cases during the last decade. In the context of the disease elimination by 2030, a nationwide entomological survey was conducted to better understand the distribution, abundance and behaviour of major malaria vectors (Anopheles spp.) in the country.MethodsMosquito collections were implemented in ten villages from ten provinces during the rainy and dry seasons of 2014 and 2015 by using human landing catch (HLC) and cow bait collection (CBC) methods. After morphological identification in the field, molecular identification of the sibling species of Anopheles mosquitoes from the Funestus, Leucosphyrus, and Maculatus groups were determined using PCR specific alleles. A screening of Plasmodium falciparum and Plasmodium vivax infections in the vectors was carried out by quantitative PCR assays.ResultsA total of 14,146 adult mosquitoes representing 25 different Anopheles species were collected and morphologically identified. Molecular identification revealed the presence of 12 sibling species within the main primary vector groups, including Anopheles maculatus, Anopheles rampae, Anopheles sawadwongporni, Anopheles pseudowillmori, Anopheles dravidicus, Anopheles minimus, Anopheles aconitus, Anopheles pampanai, Anopheles harrisoni, Anopheles dirus, Anopheles baimaii, Anopheles nemophilous. Anopheles maculatus and An. minimus were predominant during both the dry and rainy seasons, but showed highly zoophilic preferences (Zoophilic index of 98% and 95%, respectively). Overall, 22% of the total malaria vectors were collected between 10:00 PM and 5:00 AM indoors when people are sleeping. Twenty-seven percent of primary and secondary vectors were collected outdoors before 10:00 PM or after 5:00 AM, times when people are usually awake and outdoors. Only two specimens were positive for P. falciparum, one An. aconitus from Phongsaly and one An. minimus from Vientiane Province CONCLUSIONS: The results indicate that people living in rural areas in Laos are constantly exposed to malaria vectors throughout the year and specifically outdoors. The use of LLINs/IRS remains important but innovative tools and new strategies are needed to address locally, the early and outdoor malaria transmission. Lack of expertise in general entomological methods may further exacerbate the situation.
| S-EPMC7654023 | biostudies-literature
Project description:BACKGROUND:Malaria transmission is influenced by a complex interplay of factors including climate, socio-economic, environmental factors and interventions. Malaria control efforts across Africa have shown a mixed impact. Climate driven factors may play an increasing role with climate change. Efforts to strengthen routine facility-based monthly malaria data collection across Africa create an increasingly valuable data source to interpret burden trends and monitor control programme progress. A better understanding of the association with other climatic and non-climatic drivers of malaria incidence over time and space may help guide and interpret the impact of interventions. METHODS:Routine monthly paediatric outpatient clinical malaria case data were compiled from 27 districts in Malawi between 2004 and 2017, and analysed in combination with data on climatic, environmental, socio-economic and interventional factors and district level population estimates. A spatio-temporal generalized linear mixed model was fitted using Bayesian inference, in order to quantify the strength of association of the various risk factors with district-level variation in clinical malaria rates in Malawi, and visualized using maps. RESULTS:Between 2004 and 2017 reported childhood clinical malaria case rates showed a slight increase, from 50 to 53 cases per 1000 population, with considerable variation across the country between climatic zones. Climatic and environmental factors, including average monthly air temperature and rainfall anomalies, normalized difference vegetative index (NDVI) and RDT use for diagnosis showed a significant relationship with malaria incidence. Temperature in the current month and in each of the 3 months prior showed a significant relationship with the disease incidence unlike rainfall anomaly which was associated with malaria incidence at only three months prior. Estimated risk maps show relatively high risk along the lake and Shire valley regions of Malawi. CONCLUSION:The modelling approach can identify locations likely to have unusually high or low risk of malaria incidence across Malawi, and distinguishes between contributions to risk that can be explained by measured risk-factors and unexplained residual spatial variation. Also, spatial statistical methods applied to readily available routine data provides an alternative information source that can supplement survey data in policy development and implementation to direct surveillance and intervention efforts.
| S-EPMC6945411 | biostudies-literature
Project description:IntroductionThe effect of malaria exposure on mortality using health facility incidence data as a measure of transmission has not been well investigated. Health and demographic surveillance systems (HDSS) routinely capture data on mortality, interventions and other household related indicators, offering a unique platform for estimating and monitoring the incidence-mortality relationship in space and time.MethodsMortality data from the HDSS located in Western Kenya collected from 2007 to 2012 and linked to health facility incidence data were analysed using Bayesian spatio-temporal survival models to investigate the relation between mortality (all-cause/malaria-specific) and malaria incidence across all age groups. The analysis adjusted for insecticide-treated net (ITN) ownership, socio-economic status (SES), distance to health facilities and altitude. The estimates obtained were used to quantify excess mortality due to malaria exposure.ResultsOur models identified a strong positive relationship between slide positivity rate (SPR) and all-cause mortality in young children 1-4 years (HR = 4.29; 95% CI: 2.78-13.29) and all ages combined (HR = 1.55; 1.04-2.80). SPR had a strong positive association with malaria-specific mortality in young children (HR = 9.48; 5.11-37.94), however, in older children (5-14 years), it was associated with a reduction in malaria specific mortality (HR = 0.02; 0.003-0.33).ConclusionSPR as a measure of transmission captures well the association between malaria transmission intensity and all-cause/malaria mortality. This offers a quick and efficient way to monitor malaria burden. Excess mortality estimates indicate that small changes in malaria incidence substantially reduce overall and malaria specific mortality.
| S-EPMC5509217 | biostudies-literature
Project description:Epidemiology of acute respiratory viral infections in children in Vientiane, Lao People’s Democratic Republic
| PRJEB42813 | ENA
Project description:BackgroundIn the context of national and regional goals to eliminate malaria by 2030, the Center for Malaria Parasitology and Entomology in the Lao PDR is implementing strategies to ensure all malaria cases are detected and appropriately treated with first-line artemisinin combination therapy, artemether-lumefantrine (AL). Timely and relevant evidence to inform policies and strategies is needed to ensure the most effective and efficient use of resources, and to accelerate progress towards elimination goals. A 2015 outlet survey conducted in five provinces of the southern Lao PDR was the first of its kind to study the total market for malaria treatments and diagnostics. The sub-national outlet survey was designed to describe the market and to assess public and private sector readiness and performance for malaria case management. Additionally, key indicators were estimated among private outlets within districts with and without a Public Private Mix (PPM) programme.ResultsOver half of anti-malarial stockists were public sector (65.1%). In the private sector, pharmacies most commonly stocked anti-malarials, although anti-malarials were also found in private health facilities, drug stores, general retailers, and itinerant drug vendors. Nearly all anti-malarial stocking public health facilities had AL (99.5%) and 90.8% had confirmatory testing. Fewer than half of anti-malarial stocking private outlets stocked AL (40.8%) and malaria testing (43.5%). Chloroquine has not been a first-line treatment for Plasmodium falciparum malaria since 2005 and Plasmodium vivax since 2011 yet private sector availability was 77.6% and chloroquine accounted for 62.2% of the total anti-malarial market share. AL and confirmatory testing availability were higher in private outlets in PPM (68.1, 72.6%) versus non-PPM districts (2.5, 12.1%). Chloroquine was available in 63.6% of PPM and 96.7% of non-PPM-district outlets, and was the most commonly distributed anti-malarial among private outlets in both PPM (61.7%) and non-PPM districts (99.1%).ConclusionsPublic sector outlets in the southern Lao PDR are typically equipped to test and appropriately treat malaria. There is need to address widespread private sector availability and distribution of chloroquine. The PPM programme has improved private provider readiness to manage malaria according to national guidelines. However, supporting interventions to address provider and consumer behaviours are needed to further drive uptake.
| S-EPMC5404290 | biostudies-literature
Project description:The current study aims to provide a fine-scale spatiotemporal estimate of malaria incidence among Cameroonian under-5, and to determine its associated environmental factors, to set up preventive interventions that are adapted to each health district of Cameroon. Routine data on symptomatic malaria in children under-5 collected in health facilities, between 2012 and 2018 were used. The trend of malaria cases was assessed by the Mann-Kendall (M-K) test. A time series decomposition was applied to malaria incidence to extract the seasonal component. Malaria risk was estimated by the standardised incidence ratio (SIR) and smoothed by a hierarchical Bayesian spatiotemporal model. In total, 4,052,216 cases of malaria were diagnosed between 2012 and 2018. There was a gradual increase per year, from 369,178 in 2012 to 652,661 in 2018. After adjusting the data for completeness, the national incidence ranged from 489‰ in 2012 to 603‰ in 2018, with an upward trend (M-K test p-value < 0.001). At the regional level, an upward trend was observed in Adamaoua, Centre without Yaoundé, East, and South regions. There was a positive spatial autocorrelation of the number of malaria incident-cases per district per year as suggested by the Moran's I test (statistic range between 0.11 and 0.53). The crude SIR showed a heterogeneous malaria risk with values ranging from 0.00 to 8.90, meaning that some health districts have a risk 8.9 times higher than the national annual level. The incidence and risk of malaria among under-5 in Cameroon are heterogeneous and vary significantly across health districts and seasons. It is crucial to adapt malaria prevention measures to the specificities of each health district, in order to reduce its burden in health districts where the trend is upward.
| S-EPMC8169670 | biostudies-literature
Project description:BACKGROUND:Plasmodium falciparum malaria is a threat to public health, but Plasmodium vivax malaria is most prevalent in Latin America, where the incidence rate has been increasing since 2016, particularly in Venezuela and Brazil. The Brazilian Amazon reported 193,000 cases in 2017, which were mostly confirmed as P. vivax (~?90%). Herein, the relationships among malaria incidence rates and the proportion of accumulated deforestation were contrasted using data from the states of Acre and Rondônia in the south-western Brazilian Amazon. The main purpose is to test the hypothesis that the observed difference in incidence rates is associated with the proportion of accumulated deforestation. METHODS:An ecological study using spatial and temporal models for mapping and modelling malaria risk was performed. The municipalities of Acre and Rondônia were the spatial units of analysis, whereas month and year were the temporal units. The number of reported malaria cases from 2009 until 2015 were used to calculate the incidence rate per 1000 people at risk. Accumulated deforestation was calculated using publicly available satellite images. Geographically weighted regression was applied to provide a local model of the spatial heterogeneity of incidence rates. Time-series dynamic regression was applied to test the correlation of incidence rates and accumulated deforestation, adjusted by climate and socioeconomic factors. RESULTS:The malaria incidence rate declined in Rondônia but remained stable in Acre. There was a high and positive correlation between the decline in malaria and higher proportions of accumulated deforestation in Rondônia. Geographically weighted regression showed a complex relationship. As deforestation increased, malaria incidence also increased in Acre, while as deforestation increased, malaria incidence decreased in Rondônia. Time-series dynamic regression showed a positive association between malaria incidence and precipitation and accumulated deforestation, whereas the association was negative with the human development index in the westernmost areas of Acre. CONCLUSION:Landscape modification caused by accumulated deforestation is an important driver of malaria incidence in the Brazilian Amazon. However, this relationship is not linearly correlated because it depends on the overall proportion of the land covered by forest. For regions that are partially degraded, forest cover becomes a less representative component in the landscape, causing the abovementioned non-linear relationship. In such a scenario, accumulated deforestation can lead to a decline in malaria incidence.
| S-EPMC6727495 | biostudies-literature
Project description:BackgroundPrimaquine is effective against the latent liver stage of Plasmodium vivax. Eliminating the latent liver stage of P. vivax is one of the necessary conditions to achieve the goal of malaria elimination in Lao People's Democratic Republic (PDR) by 2030. However, people with glucose-6-phosphate dehydrogenase (G6PD) deficiency are at risk of haemolysis when ingesting primaquine. The aim of this study was to detect the prevalence of the G6PD Viangchan variant, which is said to be common in Lao PDR and which can result in severe haemolysis in patients exposed to primaquine.MethodsBlood samples were collected from villagers in three malaria endemic provinces: Champasak and Savannakhet in the south, and Phongsaly in the north. Each blood sample was semi-quantitatively assayed for G6PD enzyme activity using the G6PD Assay Kit-WST Lyophilized (DOJINDO Laboratories, Japan). Blood samples that were found to be G6PD deficient were sequenced to detect G6PD Viangchan mutation.ResultsIn total, 2043 blood samples were collected from Phongsaly (n = 426, 20.9%), Savannakhet (n = 924, 45.2%), and Champasak (n = 693, 33.9%) provinces in Lao PDR from 2016 to 2017. Of these, 964 (47.2%) were taken from male villagers and 1079 (52.8%) were taken from female villagers. G6PD Viangchan mutation was not detected in Phongsaly province in this study. In Savannakhet province, 48 of the 924 samples (45 males, 3 females) had the G6PD Viangchan mutation (n = 48, 5.2%). In Champasak province, 42 of the 693 samples (18 males, 24 females) had the G6PD Viangchan mutation (n = 42, 6.1%).ConclusionsG6PD Viangchan variant, which can cause severe haemolysis in the carrier when exposed to primaquine, was detected among 6.1% of the villagers in Champasak and 5.2% in Savannakhet but not in Phongsaly in this study. G6PD Viangchan variant might be common in the south of Laos but not so in the north. In the north, other G6PD deficiency variants might be more prevalent. However, in order not to overlook anyone and ensure a safe primaquine therapy for people living in malaria endemic areas in Lao PDR, G6PD testing is necessary.
| S-EPMC6416863 | biostudies-literature