Dengue fever is highly endemic in Vietnam, but scrub typhus-although recognized as an endemic disease-remains underappreciated. These diseases together are likely to account for more than half of the ...acute undifferentiated fever burden in Vietnam. Scrub typhus (ST) is a bacterial disease requiring antimicrobial treatment, while dengue fever (DF) is of viral etiology and does not. The access to adequate diagnostics and the current understanding of empirical treatment strategies for both illnesses remain limited. In this study we aimed to contribute to the clinical decision process in the management of these two important etiologies of febrile illness in Vietnam.
Using retrospective data from 221 PCR-confirmed scrub typhus cases and 387 NS1 protein positive dengue fever patients admitted to five hospitals in Khanh Hoa province (central Vietnam), we defined predictive characteristics for both diseases that support simple clinical decision making with potential to inform decision algorithms in future. We developed models to discriminate scrub typhus from dengue fever using multivariable logistic regression (M-LR) and classification and regression trees (CART). Regression trees were developed for the entire data set initially and pruned, based on cross-validation. Regression models were developed in a training data set involving 60% of the total sample and validated in the complementary subsample. Probability cut points for the distinction between scrub typhus and dengue fever were chosen to maximise the sum of sensitivity and specificity.
Using M-LR, following seven predictors were identified, that reliably differentiate ST from DF; eschar, regional lymphadenopathy, an occupation in nature, increased days of fever on admission, increased neutrophil count, decreased ratio of neutrophils/lymphocytes, and age over 40. Sensitivity and specificity of predictions based on these seven factors reached 93.7% and 99.5%, respectively. When excluding the "eschar" variable, the values dropped to 76.3% and 92.3%, respectively. The CART model generated one further variable; increased days of fever on admission, when eschar was included, the sensitivity and specificity was 95% and 96.9%, respectively. The model without eschar involved the following six variables; regional lymphadenopathy, increased days of fever on admission, increased neutrophil count, increased lymphocyte count, platelet count ≥ 47 G/L and age over 28 years as predictors of ST and provided a sensitivity of 77.4% and a specificity of 90.7%.
The generated algorithms contribute to differentiating scrub typhus from dengue fever using basic clinical and laboratory parameters, supporting clinical decision making in areas where dengue and scrub typhus are co-endemic in Vietnam.
To investigate ventriculo-arterial coupling (VAC) and its components (E
a
, E
es
) in patients with stable ischemic heart disease and changes following percutaneous coronary intervention (PCI). 129 ...patients with stable ischemic heart disease (SIHD) undergoing PCI (study group) and 40 individuals without IHD (control group) were enrolled. VAC was calculated using echocardiography method at baseline and 1, 3, and 6 months after PCI. A linear mixed-effects models with restricted maximum likelihood were used to assess the impact of PCI on E
a
, E
es
, VAC over 6-month follow-up. Mean age of the SIHD group was 67.8 ± 8.1 (years), and predominantly men (73.6%). In the SIHD group, baseline median E
a
, E
es
and VAC were 2.52 (IQR 1.89–3.28) (mmHg/ml), 3.87 (IQR 2.90–4.95) (mmHg/ml), and 0.64 (IQR 0.54–0.79), respectively. Patients with SIHD had significantly lower E
es
and higher VAC when compared to the control group (p < 0.05). E
es
(p = 0.01) and VAC (p < 0.001) were significantly improved over 6 month follow-up after PCI. Notably, the degree of VAC improvement appears to be related to stented artery (Table 3). VAC obtained from echocardiographic methodology demonstrated a significant increase in patients with SIHD at baseline. This observation may represent a plausible mechanism for the benefit of PCI in SIHD. Hence, VAC may be a feasible parameter in the assessment of patients with SIHD.
Composite agricultural systems with permanent maize cultivation in the uplands and irrigated rice in the valleys are very common in mountainous southeast Asia. The soil loss and fertility decline of ...the upland fields is well documented, but little is known about reallocation of these sediments within the landscape. In this study, a turbidity-based linear mixed model was used to quantify sediment inputs, from surface reservoir irrigation water and from direct overland flow, into a paddy area of 13 ha. Simultaneously, the sediment load exported from the rice fields was determined. Mid-infrared spectroscopy was applied to analyze sediment particle size. Our results showed that per year, 64 Mg ha−1 of sediments were imported into paddy fields, of which around 75 % were delivered by irrigation water and the remainder by direct overland flow during rainfall events. Overland flow contributed one-third of the received sandy fraction, while irrigated sediments were predominantly silty. Overall, rice fields were a net sink for sediments, trapping 28 Mg ha−1 a−1 or almost half of total sediment inputs. As paddy outflow consisted almost exclusively of silt- and clay-sized material, 24 Mg ha−1 a−1 of the trapped amount of sediment was estimated to be sandy. Under continued intensive upland maize cultivation, such a sustained input of coarse material could jeopardize paddy soil fertility, puddling capacity and ultimately food security of the inhabitants of these mountainous areas. Preventing direct overland flow from entering the paddy fields, however, could reduce sand inputs by up to 34 %.
Abstract
A field trial was conducted at a site in Cam Binh commune, Ha Tinh province, Vietnam, highly contaminated with organo-pesticides. The phyto-Fenton process was applied to remove pesticide ...residues in soils. In addition to magnetite (Fe
3
O
4
) materials added to the soils, fertilizers and elicitors for oxidative burst were also added in the different experimental treatments. Dichloro-diphenyl-trichloroethane (DDT) and isomers were removed in all experimental lots. The removal efficiency was highest in lot B1, a site where only iron materials were added. The removal efficiency and the final content of DDTs in B1 were 98.4% and 0.009 mg kg
−1
, respectively. In the presence of elicitors, the conversion of DDT to dichloro-diphenyl-dichloroethylene was more favorable. Analysis of soil properties indicated that the phyto-Fenton process can occur at neutral soil pH, and when there are only small changes in soil organic carbon content and cation exchange capacities. Shifts in the composition of the microbial communities were observed. Further studies on the interactions between materials added to soil, plants, and the soil microbiome are needed to understand the mechanism of action of the phyto-Fenton process during soil remediation.
The present study revealed how local socioecological knowledge elucidated during participatory rural appraisals and historical remote sensing data can be combined for analyzing land use change ...patterns from 1954 to 2007 in northwestern Vietnam. The developed approach integrated farmer decision rules on cropping preferences and location, visual and supervised classification methods, and qualitative information obtained during various forms of participatory appraisals. The integration of historical remote sensing data (aerial photo, Landsat, LISS III) with farmer decision rules showed the feasibility of the proposed method to explain crop distribution patterns for the assessment period of 53 years. Our approach is beneficial for data-limited environments, which is a prevalent situation for many developing regions. The derived land use and crop type dataset was used for understanding how anthropogenic activities altered the study area of the Chieng Khoi commune during the assessment period of five decades, and what potential impact this can have on the natural resource base. The newly developed approach offers a methodological pathway that can be easily transferred to local government authorities for a better understanding of cropping transitions and agricultural expansion trends in data-limited rural landscapes. The detected land use change patterns and upland cropping expansion of more than two hundred percent in 53 years not only revealed the consequences of the interactions and feedback between farmers and their land, but further highlighted the urgent need for implementing sustainable land management practices in the case study watershed of the Chieng Khoi commune and northwestern Vietnam in general.
•Turbidity was a good predictor of suspended sediment in a mountainous catchment.•The same model performed better for particulate organic carbon.•Serial correlation was the most important factor to ...obtain good predictions.
The aim of this study was to develop a method to continuously monitor sediment, carbon and nitrogen concentrations in streams using turbidity sensors. Field experiments were conducted in an irrigated and intensely cultivated watershed in Northwest Vietnam. Turbidity, discharge and rainfall were monitored during two successive rainy seasons from 2010 to 2011, and manual water samples were collected using a storm-based approach. Samples were analyzed for concentrations of suspended sediment (SSC), particulate organic carbon (POC) and particulate nitrogen (PN). A linear mixed model was developed to account for serial correlation, with turbidity, discharge and rainfall as predictor variables. Turbidity was the most important predictor variable in all models. Fivefold cross-validation showed best model performance for POC with a Pearson’s correlation coefficient of 0.91, while predictions for SSC and PN achieved a satisfying correlation of 0.86 and 0.87, respectively. Laboratory testing of the turbidity sensors showed that the turbidity signal is sensitive to differences in organic matter content, and has the smallest variance for fine textures, both of which are correlated to POC and thus supporting the higher predictive accuracy for this variable. The developed methodology is widely applicable and can be used to simultaneously obtain reliable, cost-effective and continuous estimates of SSC, POC and PN with a single sensor.
We conducted a field experiment on a 53 %-slope in Northwest Vietnam using¹⁵N-labelled urea to trace its fate in maize (Zea mays) under intensive tillage and fertilization (T1, control) versus maize ...with Panicum maximum grass barriers (T2), under minimum tillage (MT) with Arachis pintoi as cover crop (T3) or relay cropped with Phaseolus calcaratus (T4).¹⁵N-labelled urea was applied to one maize row at the top of each plot one year after trial establishment. At harvest, 21.6 % of the labelled¹⁵N were recovered by maize in T1, 8.9 % in T2, 29 % in T3, and 30.9 % in T4. In T2, maize and P. maximum competed heavily for N with a total 38.1 % of¹⁵N recovered in barriers. Less than 6 % of¹⁵N applied was found in maize rows along the slope regardless of the treatment. MT reduced¹⁵N translocation to deeper soil layers (40–80 cm), indicating a safety net function. Less than 0.1 kg N ha⁻¹of applied¹⁵N reached the collection devices at the bottom of plots; the majority of added¹⁵N was intercepted by plants along the slope. Current farming practice (T1) induced a negative N balance of −142 kg N ha⁻¹in which residue burning and erosion were major pathways for N losses. Reduced N losses by erosion in T2 contributed to a less negative N balance as compared to T1. Positive N balances of MT treatments were associated with strongly reduced N losses by erosion and abandonment of burning residues, indicating a viable option for hillside cropping.
Land use planning is an important task for every country in the world to ensure the sustainable use of land resources for economic and social development activities. However, many land use plans have ...not achieved their desired effectiveness due to a lack of consideration and evaluation of factors affecting the land use planning implementation process. This study was conducted to answer the following question: what are the main factors influencing the land use planning process in Vietnam? In this study, we use multivariate regression to identify the main factors influencing land use planning in Vietnam, including the economic factor group; institutional and policy factor group; urbanisation factor group; planning factor group; social factor group; environmental factor group; and organisational and implementation factor group. The results identified five groups of factors influencing land use planning in the Dan Phuong district through the influencing factor analysis method, including policy (Po), economy (Ec), society (So), environment (En), and others (Ot). In addition, the linear regression model obtained for land use planning in Dan Phuong district is as follows: land use planning = 0.408Po + 0.454Ec + 0.398So + 0.368En + 0.259Ot. In which the group of factors with the strongest influence was the Eco factors (β = 0.454), the second was the Po factors (β = 0.408), the third was the So factors (β = 0.398), the fourth was the En factors (β = 0.368), and lastly, there were the Ot factors (β = 0.259). The results of the analysis were used to plan land use effectively and according to local conditions. This can help managers to find solutions for the sustainable use of land resources in the future.
Measurements of saturated hydraulic conductivity (
K
s) and indices of Horton overland flow (HOF) generation are used to assess the influence of landscape fragmentation on near-surface hydrologic ...response in two upland watersheds in northern Vietnam. The fragmented landscape, which results from timber extraction and swidden agriculture, is a mosaic of surfaces having distinct infiltration characteristics. In general, human activity has reduced infiltration and altered near-surface flow paths on all disturbed land covers. Compacted roads, paths, and dwelling sites, for example, have the propensity to generate HOF for small rainfall depths. Although these surfaces occupy a small fraction of a basin land area (estimated at <1%), they contribute disproportionately to overland flow response during typical rainfall events. Recently abandoned fields have the lowest
K
s of all non-consolidated, post-cultivation surfaces tested. Beginning 1–2 years following abandonment, diminished
K
s recovers over time with the succession to more advanced types of secondary regrowth. If a grassland emerges on the abandoned site, rather than a bamboo-dominated cover,
K
s recovers more rapidly. The decrease in
K
s with depth below disturbed surfaces is more acute than that found at undisturbed sites. This enhanced anisotropy in near-surface
K
s increases the likelihood of the development of a lateral subsurface flow component during large storms of the monsoon rain season. Subsequently, the likelihood of return flow generation is increased. Because the recovery time of subsurface
K
s is greater than that for the surface
K
s, the impact human activity has on hydrologic response in the fragmented basin may linger long after the surface vegetation has evolved to a mature forested association.
We use a hydrology-based fragmentation index to explore the influence of land-cover distribution on the generation and buffering of Hortonian overland flow (HOF) in two disturbed upland basins in ...northern Vietnam (Tan Minh). Both the current degree of fragmentation in Tan Minh and the current spatial arrangement of buffers (relative to HOF source areas) provide only limited opportunities for infiltrating surface runoff from upslope source areas, in part because of the high connectivity of swidden fields on long hillslopes. The intentional placement of buffers below HOF sources and the reduction of the down-slope lengths of swidden fields could reduce the occurrence of HOF on individual hillslopes. Reduction of the total watershed total depth of HOF would require maintaining a sufficient area of buffering land covers; and this may necessitate the use of longer fallow periods. These measures are, however, counter to the land-practice trends witnessed in the last several decades (i.e., no buffers, cultivation of long slopes, and increasingly shorter fallow periods). The two most likely scenarios of future land-cover change in Tan Minh—one representing increased fragmentation, the other decreased—both lead to an increase in HOF because of reduced buffering potential. The unlikely scenario of abandonment of agriculture and subsequent regeneration of forest, leads to both less fragmentation and less HOF. The study highlights the hydrological impacts associated with fragmentation at Tan Minh, which is the product of decades of local and regional forcing factors that have dictated the degree and timing of timber removal and swiddening at the site.
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