ResearchPad - agrochemicals https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Indoor and outdoor residual spraying of a novel formulation of deltamethrin K-Othrine<sup>®</sup> (Polyzone) for the control of simian malaria in Sabah, Malaysia]]> https://www.researchpad.co/article/elastic_article_14704 Since 2000, human malaria cases in Malaysia were rapidly reduced with the use of insecticides in Indoor Residual Spray (IRS) and Long-Lasting Insecticide Net (LLIN). Unfortunately, monkey malaria in humans has shown an increase especially in Sabah and Sarawak. The insecticide currently used in IRS is deltamethrin K-Othrine® WG 250 wettable granule, targeting mosquitoes that rest and feed indoor. In Sabah, the primary vector for knowlesi malaria is An. balabacensis a species known to bite outdoor. This study evaluates an alternative method, the Outdoor Residual Spray (ORS) using a novel formulation of deltamethrin K-Othrine® (PolyZone) to examine it suitability to control knowlesi malaria vector in Sabah, compared to the current method. The study was performed at seven villages in Sabah having similar type of houses (wood, bamboo and concrete). Houses were sprayed with deltamethrin K-Othrine® (PolyZone) at two different dosages, 25 mg/m2 and 30 mg/m2 and deltamethrin K-Othrine® WG 250 wettable granule at 25 mg/m2, sprayed indoor and outdoor. Residual activity on different walls was assessed using standard cone bioassay techniques. For larval surveillances, potential breeding sites were surveyed. Larvae were collected and identified, pre and post spraying. Adult survey was done using Human Landing Catch (HLC) performed outdoor and indoor. Detection of malaria parasite in adults was conducted via microscopy and molecular methods. Deltamethrin K-Othrine® (PolyZone) showed higher efficacy when sprayed outdoor. The efficacy was found varied when sprayed on different types of wall surfaces. Deltamethrin K-Othrine® (PolyZone) at 25 mg/m2 was the most effective with regards to ability to high mortality and effective knock down (KD). The vector population was reduced significantly post-spraying and reduction in breeding sites as well. The number of simian malaria infected vector, human and simian malaria transmission were also greatly reduced.

]]>
<![CDATA[Kala-azar elimination in a highly-endemic district of Bihar, India: A success story]]> https://www.researchpad.co/article/elastic_article_14634 The World Health Organization (WHO) has set a target to eliminate visceral leishmaniasis (VL), commonly known as “Kala-azar,” as a public health problem in India by 2020. The elimination target is defined as achieving less than 1 case per 10,000 people at the block level. Although India has made substantial progress in the elimination of the disease since 2012, VL remains a stable public health problem in four middle-eastern states including Bihar. Bihar contributes >61% of the total Indian cases annually, and a few districts of the state have reported more than 600 cases annually. In this study, the results indicate that an intensive integrated VL control strategy including epidemiological analysis based on a geographical information system (GIS), hot-spot mapping, active case detection, vector control using the indoor residual spraying (IRS) of chemical insecticides, awareness campaigns, human resource development, the close monitoring of control activities, and active epidemiological surveillance and entomological monitoring can achieve the elimination target in the highly endemic region of Bihar. The elimination of VL from highly endemic zones is urgently required to control any new outbreak. Therefore, the implementation of the Vaishali VL control strategy is strongly recommended in all highly endemic districts of Bihar, India.

]]>
<![CDATA[Sublethal and transgenerational effects of sulfoxaflor on the demography and feeding behaviour of the mirid bug <i>Apolygus lucorum</i>]]> https://www.researchpad.co/article/elastic_article_14540 Sulfoxaflor, the first commercially available sulfoximine insecticide, has been used for the control of sap-feeding insect pests such as plant bugs and aphids on a variety of crops. However, its sublethal effects on the mirid bug Apolygus lucorum, one of the key insect pests of Bt cotton and fruit trees in China, have not been fully examined. Here, we evaluated the demography and feeding behaviour of A. lucorum exposed to sulfoxaflor. The leaf-dipping bioassay showed that the LC10 and LC30 of sulfoxaflor against 3rd-instar nymphs of this insect were 1.23 and 8.37 mg L-1, respectively. The LC10 significantly extended the nymphal duration and decreased the oviposition period by 5.29 days and female fecundity by 56.99% in the parent generation (F0). The longer duration of egg, 5th-instar nymphs, preadult, and male adult longevity were observed in the F1 generation (F1) at LC10. At the LC30, the duration of egg and 1st-instar nymph, female adult longevity, and oviposition period of the F1 were significantly shorter, while the nymphal duration in the F0 and duration of 5th-instar nymphs, preadult survival rate, and male adult longevity in the F1 significantly increased. The net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) in the F1 were not significantly affected by these two concentrations, whereas the mean generation time (T) was lower at the LC30. Additionally, the probe counts and cells mixture feeding time were markedly lengthened by the LC10 and LC30, respectively, when A. lucorum nymphs exposed to sulfoxaflor fed on Bt cotton plants without insecticides. These results clearly indicate that sulfoxaflor causes sublethal effects on A. lucorum and the transgenerational effects depend on the tested concentrations.

]]>
<![CDATA[Identification and detection of a novel point mutation in the Chitin Synthase gene of <i>Culex pipiens</i> associated with diflubenzuron resistance]]> https://www.researchpad.co/article/elastic_article_14502 Diflubenzuron is one of the main larvicides used for the control of the West Nile Virus vector Culex pipiens in the Mediterranean. However, the efficiency of control is now under threat due to the selection of insecticide resistance. Two point mutations were previously identified at the Chitin synthase and shown to confer low and high levels of resistance and a diagnostic was developed to monitor the trait. This study reports the identification of a third mutation associated with high levels of diflubenzuron resistance in Italy. This mutation was also detected in France, whereas no resistance mutations were found in Cx. pipiens mosquitoes sampled from Greece, Portugal and Israel. The findings are of major concern for mosquito control programs in S. Europe, which rely on the use of a limited number of larvicides.

]]>
<![CDATA[A screening of the MMV Pathogen Box® reveals new potential antifungal drugs against the etiologic agents of chromoblastomycosis]]> https://www.researchpad.co/article/elastic_article_13863 Chromoblastomycosis (CBM) is a chronic subcutaneous mycosis caused by traumatic implantation of many species of black fungi. Due to the refractoriness of some cases and common recurrence of CBM, a more effective and less time-consuming treatment is mandatory. The aim of this study was to identify compounds with in vitro antifungal activity in the Pathogen Box® compound collection against different CBM agents. Synergism of these compounds with drugs currently used to treat CBM was also assessed. An initial screening of the drugs present in this collection at 1 μM was performed with a Fonsecaea pedrosoi clinical strain according to the EUCAST protocol. The compounds with activity against this fungus were also tested against other seven etiologic agents of CBM (Cladophialophora carrionii, Phialophora verrucosa, Exophiala jeanselmei, Exophiala dermatitidis, Fonsecaea monophora, Fonsecaea nubica, and Rhinocladiella similis) at concentrations ranging from 0.039 to 10 μM. The analysis of potential synergism of these compounds with itraconazole and terbinafine was performed by the checkerboard method. Eight compounds inhibited more than 60% of the F. pedrosoi growth: difenoconazole, bitertanol, iodoquinol, azoxystrobin, MMV688179, MMV021013, trifloxystrobin, and auranofin. Iodoquinol produced the lowest MIC values (1.25–2.5 μM) and MMV688179 showed MICs that were higher than all compounds tested (5 - >10 μM). When auranofin and itraconazole were tested in combination, a synergistic interaction (FICI = 0.37) was observed against the C. carrionii isolate. Toxicity analysis revealed that MMV021013 showed high selectivity indices (SI ≥ 10) against the fungi tested. In summary, auranofin, iodoquinol, and MMV021013 were identified as promising compounds to be tested in CBM models of infection.

]]>
<![CDATA[Using morphological attributes for the fast assessment of nutritional responses of Buddhist pine (Podocarpus macrophyllus [Thunb.] D. Don) seedlings to exponential fertilization]]> https://www.researchpad.co/article/N5094337c-fdbe-414d-8545-a46f7fbb230f

Culturing slowly growing tree seedlings is a potential approach for managing the conflict between the increasing demand for ornamental stock and the decreasing area of farmlands due to urbanization. In this study, Buddhist pine (Podocarpus macrophyllus [Thunb.] D. Don) seedlings were raised in multishelves with light-emitting diode lighting in the spectrum of 17:75:8 (red:green:blue) at 190–320 μmol m-2 s-1 with controlled temperature and relative humidity at 19.5°C and 60%, respectively. Seedlings were fed by exponential fertilization (EF) (nitrogen [N]-phosphorus [P]2O5-K2O, 10-7-9) at eight rates of 0 (control), 20 (E20), 40 (E40), 60 (E60), 80 (E80), 100 (E100), 120 (E120), and 140 (E140) mg N seedling-1 for four months through 16 fertilizer applications. The nutritional responses of Buddhist pine seedlings can be identified and classified into various stages in response to increasing doses, up to and over 120 N seedling-1. Morphological traits, i.e., the green color index and leaf area (LA) obtained by digital analysis and the fine root growth, all remained constant in response to doses that induced steady nutrient loading. LA had a positive relationship with most of the nutritional parameters. A dose range between 60 and 120 mg N seedling-1 was recommended for the culture of Buddhist pine seedlings. At this range of fertilizer doses, measuring the leaf area through digital scanning can easily and rapidly indicate the inherent nutrient status of the seedlings.

]]>
<![CDATA[PDIP38/PolDIP2 controls the DNA damage tolerance pathways by increasing the relative usage of translesion DNA synthesis over template switching]]> https://www.researchpad.co/article/5c897795d5eed0c4847d30a7

Replicative DNA polymerases are frequently stalled at damaged template strands. Stalled replication forks are restored by the DNA damage tolerance (DDT) pathways, error-prone translesion DNA synthesis (TLS) to cope with excessive DNA damage, and error-free template switching (TS) by homologous DNA recombination. PDIP38 (Pol-delta interacting protein of 38 kDa), also called Pol δ-interacting protein 2 (PolDIP2), physically associates with TLS DNA polymerases, polymerase η (Polη), Polλ, and PrimPol, and activates them in vitro. It remains unclear whether PDIP38 promotes TLS in vivo, since no method allows for measuring individual TLS events in mammalian cells. We disrupted the PDIP38 gene, generating PDIP38-/- cells from the chicken DT40 and human TK6 B cell lines. These PDIP38-/- cells did not show a significant sensitivity to either UV or H2O2, a phenotype not seen in any TLS-polymerase-deficient DT40 or TK6 mutants. DT40 provides a unique opportunity of examining individual TLS and TS events by the nucleotide sequence analysis of the immunoglobulin variable (Ig V) gene as the cells continuously diversify Ig V by TLS (non-templated Ig V hypermutation) and TS (Ig gene conversion) during in vitro culture. PDIP38-/- cells showed a shift in Ig V diversification from TLS to TS. We measured the relative usage of TLS and TS in TK6 cells at a chemically synthesized UV damage (CPD) integrated into genomic DNA. The loss of PDIP38 also caused an increase in the relative usage of TS. The number of UV-induced sister chromatid exchanges, TS events associated with crossover, was increased a few times in PDIP38-/- human and chicken cells. Collectively, the loss of PDIP38 consistently causes a shift in DDT from TLS to TS without enhancing cellular sensitivity to DNA damage. We propose that PDIP38 controls the relative usage of TLS and TS increasing usage of TLS without changing the overall capability of DDT.

]]>
<![CDATA[Analysis of genetic control and QTL mapping of essential wheat grain quality traits in a recombinant inbred population]]> https://www.researchpad.co/article/5c897730d5eed0c4847d2663

Wheat cultivars are genetically crossed to improve end-use quality for traits as per demands of baking industry and broad consumer preferences. The processing and baking qualities of bread wheat are influenced by a variety of genetic make-ups, environmental factors and their interactions. Two wheat cultivars, WL711 and C306, derived recombinant inbred lines (RILs) with a population of 206, were used for phenotyping of quality-related traits. The genetic analysis of quality traits showed considerable variation for measurable quality traits, with normal distribution and transgressive segregation across the years. From the 206 RILs, few RILs were found to be superior to those of the parental cultivars for key quality traits, indicating their potential use for the improvement of end-use quality and suggesting the probability of finding new alleles and allelic combinations from the RIL population. Mapping analysis identified 38 putative QTLs for 13 quality-related traits, with QTLs explaining 7.9–16.8% phenotypic variation spanning over 14 chromosomes, i.e., 1A, 1B, 1D, 2A, 2D, 3B, 3D, 4A, 4B, 4D, 5D, 6A, 7A and 7B. In-silico analysis based on homology to the annotated wheat genes present in database, identified six putative candidate genes within QTL for total grain protein content, qGPC.1B.1 region. Major QTL regions for other quality traits such as TKW have been identified on 1B, 2A, and 7A chromosomes in the studied RIL population. This study revealed the importance of the combination of stable QTLs with region-specific QTLs for better phenotyping, and the QTLs presented in our study will be useful for the improvement of wheat grain and bread-making quality.

]]>
<![CDATA[Nitrogen- and phosphorus-starved Triticum aestivum show distinct belowground microbiome profiles]]> https://www.researchpad.co/article/5c76fe27d5eed0c484e5b5dd

Many plants have natural partnerships with microbes that can boost their nitrogen (N) and/or phosphorus (P) acquisition. To assess whether wheat may have undiscovered associations of these types, we tested if N/P-starved Triticum aestivum show microbiome profiles that are simultaneously different from those of N/P-amended plants and those of their own bulk soils. The bacterial and fungal communities of root, rhizosphere, and bulk soil samples from the Historical Dryland Plots (Lethbridge, Canada), which hold T. aestivum that is grown both under N/P fertilization and in conditions of extreme N/P-starvation, were taxonomically described and compared (bacterial 16S rRNA genes and fungal Internal Transcribed Spacers—ITS). As the list may include novel N- and/or P-providing wheat partners, we then identified all the operational taxonomic units (OTUs) that were proportionally enriched in one or more of the nutrient starvation- and plant-specific communities. These analyses revealed: a) distinct N-starvation root and rhizosphere bacterial communities that were proportionally enriched, among others, in OTUs belonging to families Enterobacteriaceae, Chitinophagaceae, Comamonadaceae, Caulobacteraceae, Cytophagaceae, Streptomycetaceae, b) distinct N-starvation root fungal communities that were proportionally enriched in OTUs belonging to taxa Lulworthia, Sordariomycetes, Apodus, Conocybe, Ascomycota, Crocicreas, c) a distinct P-starvation rhizosphere bacterial community that was proportionally enriched in an OTU belonging to genus Agrobacterium, and d) a distinct P-starvation root fungal community that was proportionally enriched in OTUs belonging to genera Parastagonospora and Phaeosphaeriopsis. Our study might have exposed wheat-microbe connections that can form the basis of novel complementary yield-boosting tools.

]]>
<![CDATA[Genomic insights into neonicotinoid sensitivity in the solitary bee Osmia bicornis]]> https://www.researchpad.co/article/5c61e8f0d5eed0c48496f48d

The impact of pesticides on the health of bee pollinators is determined in part by the capacity of bee detoxification systems to convert these compounds to less toxic forms. For example, recent work has shown that cytochrome P450s of the CYP9Q subfamily are critically important in defining the sensitivity of honey bees and bumblebees to pesticides, including neonicotinoid insecticides. However, it is currently unclear if solitary bees have functional equivalents of these enzymes with potentially serious implications in relation to their capacity to metabolise certain insecticides. To address this question, we sequenced the genome of the red mason bee, Osmia bicornis, the most abundant and economically important solitary bee species in Central Europe. We show that O. bicornis lacks the CYP9Q subfamily of P450s but, despite this, exhibits low acute toxicity to the N-cyanoamidine neonicotinoid thiacloprid. Functional studies revealed that variation in the sensitivity of O. bicornis to N-cyanoamidine and N-nitroguanidine neonicotinoids does not reside in differences in their affinity for the nicotinic acetylcholine receptor or speed of cuticular penetration. Rather, a P450 within the CYP9BU subfamily, with recent shared ancestry to the Apidae CYP9Q subfamily, metabolises thiacloprid in vitro and confers tolerance in vivo. Our data reveal conserved detoxification pathways in model solitary and eusocial bees despite key differences in the evolution of specific pesticide-metabolising enzymes in the two species groups. The discovery that P450 enzymes of solitary bees can act as metabolic defence systems against certain pesticides can be leveraged to avoid negative pesticide impacts on these important pollinators.

]]>
<![CDATA[Spatial and temporal development of deltamethrin resistance in malaria vectors of the Anopheles gambiae complex from North Cameroon]]> https://www.researchpad.co/article/5c75ac7cd5eed0c484d088a5

The effectiveness of insecticide-based malaria vector control interventions in Africa is threatened by the spread and intensification of pyrethroid resistance in targeted mosquito populations. The present study aimed at investigating the temporal and spatial dynamics of deltamethrin resistance in An. gambiae s.l. populations from North Cameroon. Mosquito larvae were collected from 24 settings of the Garoua, Pitoa and Mayo Oulo Health Districts (HDs) from 2011 to 2015. Two to five days old female An. gambiae s.l. emerging from larval collections were tested for deltamethrin resistance using the World Health Organization’s (WHO) standard protocol. Sub samples of test mosquitoes were identified to species using PCR-RFLP and genotyped for knockdown resistance alleles (Kdr 1014F and 1014S) using Hot Ligation Oligonucleotide Assay (HOLA). All the tested mosquitoes were identified as belonging to the An. gambiae complex, including 3 sibling species mostly represented by Anopheles arabiensis (67.6%), followed by Anopheles coluzzii (25.4%) and Anopheles gambiae (7%). Deltamethrin resistance frequencies increased significantly between 2011 and 2015, with mosquito mortality rates declining from 70–85% to 49–73% in the three HDs (Jonckheere-Terstra test statistic (JT) = 5638, P< 0.001), although a temporary increase of mortality rates (91–97%) was seen in the Pitoa and Mayo Oulo HDs in 2012. Overall, confirmed resistance emerged in 10 An. gambiae s.l. populations over the 24 field populations monitored during the study period, from 2011 to 2015. Phenotypic resistance was mostly found in urban settings compared with semi-urban and rural settings (JT = 5282, P< 0.0001), with a spatial autocorrelation between neighboring localities. The Kdr 1014F allelic frequencies in study HDs increased from 0–30% in 2011 to 18–61% in 2014–2015 (JT = 620, P <0.001), especially in An. coluzzii samples. The overall frequency of the Kdr 1014S allele was 0.1%. This study revealed a rapid increase and widespread deltamethrin resistance frequency as well as Kdr 1014F allelic frequencies in An. gambiae s.l. populations over time, emphasizing the urgent need for vector surveillance and insecticide resistance management strategies in Cameroon.

]]>
<![CDATA[Pesticide distribution and depletion kinetic determination in honey and beeswax: Model for pesticide occurrence and distribution in beehive products]]> https://www.researchpad.co/article/5c76fe5bd5eed0c484e5b94e

Beehive products such as honey, beeswax and recently pollen have been regarded for many years as appropriate sentinels for environmental pesticide pollutions. However, despite yearly application of hundreds of approved pesticides in agricultural fields, only a minor fraction of these organic compounds were actually detected in honey and beeswax samples. This observation has led us to question the general suitability of beehive products as a sentinel for synthetic organic pesticides applied in the field. The aim of the present study was to experimentally determine the distribution (logarithmic ratio of beeswax to honey pesticide concentration, LogD) and depletion kinetics (half-life) of selected pesticides in honey and beeswax as a measure of the latter matrixes to serve as a pesticide sentinel. The obtained parameters were used to extrapolate to pesticide burden in honey and beeswax samples collected from German and Israeli apiaries. In addition, we aimed to establish a mathematical model, enabling us to predict distribution of selected pesticides between honey to beeswax, by utilizing simple substance descriptors, namely, octanol/water partitioning coefficient, molar weight and Henry coefficient. Based on the present results, it appears that pesticides with LogD values > 1 and half-life in beeswax > 1 day, were likely to accumulate and detected in beeswax samples, and less likely to be found in honey. On the other hand, pesticides with negative LogD values were highly likely to be found in honey and less so in beeswax samples. Finally, pesticides with LogD values between 0–1 were expected to be found in both matrixes. The developed model was successfully applied to predict LogD values, thereby identifying octanol/water partitioning and molar weight as the most prominent substance descriptors, which affect pesticide distribution between honey and beeswax.

]]>
<![CDATA[Rainfall affects leaching of pre-emergent herbicide from wheat residue into the soil]]> https://www.researchpad.co/article/5c5df35fd5eed0c4845811ca

No-tillage with stubble retention is a widely used cropping system for its conservation and yield benefits. The no-tillage farming system in southern Australia relies heavily on herbicides for weed management, but heavy crop residues may have a negative impact on the activity of pre-emergent herbicides applied. Any herbicide intercepted by the crop residue may not reach the soil surface without timely rainfall and may dissipate due to volatilisation, photo-degradation and/or microbial activity. Two experiments were carried out to investigate the interception of prosulfocarb, pyroxasulfone, and trifluralin herbicides by wheat residue and retention following simulated rainfall. For the first experiment, there were four simulated rainfall amounts (0, 5, 10, and 20 mm), three intensities (5, 10, and 20 mm h–1) and five application times (immediately after spraying herbicide, 6 h, 1, 7, and 14 days after spraying). In the second experiment, 20 mm of rainfall was applied at 10 mm h–1 in either 4 × 5 mm rainfall events over two days, 2 × 10 mm rainfall events over one day, or a single 20 mm rainfall event, with a no-rainfall control treatment. Bioassays were used to assess the herbicide activity/availability in the soil and remaining on the residue, using cucumber (Cucumis sativus L.) and Italian ryegrass (Lolium multiflorum Lam.) as indicator plants. At higher rainfall amounts, most of the herbicide leached from the stubble into the soil soon after application; more so with rain in one event rather than multiple events. However, the intensity of rainfall had no effect. Pyroxasulfone leached easily from the residue to the soil to potentially offer good weed control, prosulfocarb had an intermediary leaching effect, while only a small amount of trifluralin leached from stubble after rain. Therefore, in no-tillage situations with large amounts of crop residue present on the soil surface, herbicides that leach easily from the residue should be considered, like pyroxasulfone.

]]>
<![CDATA[Contrasting patterns of gene expression indicate differing pyrethroid resistance mechanisms across the range of the New World malaria vector Anopheles albimanus]]> https://www.researchpad.co/article/5c5b5298d5eed0c4842bcc50

Decades of unmanaged insecticide use and routine exposure to agrochemicals have left many populations of malaria vectors in the Americas resistant to multiple classes of insecticides, including pyrethroids. The molecular basis of pyrethroid resistance is relatively uncharacterised in American malaria vectors, preventing the design of suitable resistance management strategies. Using whole transcriptome sequencing, we characterized the mechanisms of pyrethroid resistance in Anopheles albimanus from Peru and Guatemala. An. albimanus were phenotyped as either deltamethrin or alpha-cypermethrin resistant. RNA from 1) resistant, 2) unexposed, and 3) a susceptible laboratory strain of An. albimanus was sequenced and analyzed using RNA-Seq. Expression profiles of the three groups were compared based on the current annotation of the An. albimanus reference genome. Several candidate genes associated with pyrethroid resistance in other malaria vectors were found to be overexpressed in resistant An. albimanus. In addition, gene ontology terms related to serine-type endopeptidase activity, extracellular activity and chitin metabolic process were also commonly overexpressed in the field caught resistant and unexposed samples from both Peru and Guatemala when compared to the susceptible strain. The cytochrome P450 CYP9K1 was overexpressed 14x in deltamethrin and 8x in alpha-cypermethrin-resistant samples from Peru and 2x in deltamethrin-resistant samples from Guatemala, relative to the susceptible laboratory strain. CYP6P5 was overexpressed 68x in deltamethrin-resistant samples from Peru but not in deltamethrin-resistant samples from Guatemala. When comparing overexpressed genes between deltamethrin-resistant and alpha-cypermethrin-resistant samples from Peru, a single P450 gene, CYP4C26, was overexpressed 9.8x (p<0.05) in alpha-cypermethrin-resistant samples. In Peruvian deltamethrin-resistant samples, the knockdown resistance mutation (kdr) variant alleles at position 1014 were rare, with approximately 5% frequency, but in the alpha-cypermethrin-resistant samples, the frequency of these alleles was approximately 15–30%. Functional validation of the candidate genes and the kdr mutation as a resistance marker for alpha-cypermethrin will confirm the role of these mechanisms in conferring pyrethroid resistance.

]]>
<![CDATA[Socio-economic and demographic disparities in ownership and use of insecticide-treated bed nets for preventing malaria among rural reproductive-aged women in northern Ghana]]> https://www.researchpad.co/article/5c59fed1d5eed0c48413562d

Background

Malaria continues to be a leading cause of morbidity and mortality in most countries in Sub-Saharan Africa. Insecticide-treated bed nets (ITNs) is one of the cost-effective interventions for preventing malaria in endemic settings. Ghana has made tremendous efforts to ensure widespread ownership and use of ITNs. However, national coverage statistics can mask important inequities that demand targeted attention. This study assesses the disparities in ownership and utilization of ITNs among reproductive-aged women in a rural impoverished setting of Ghana.

Methods

Population-based cross-sectional data of 3,993 women between the age of 15 and 49 years were collected in seven districts of the Upper East region of Ghana using a two-stage cluster sampling approach. Bivariate and multivariate regression models were used to assess the social, economic and demographic disparities in ownership and utilization of ITN and to compare utilization rates among women in households owning at least one ITN.

Results

As high as 79% of respondents were found to own ITN while 62% of ITN owners used them the night preceding the survey. We identified disparities in both ownership and utilization of ITNs in wealth index, occupational status, religion, and district of residence. Respondents in the relative richest wealth quintile were 74% more likely to own ITNs compared to those in the poorest quintile (p-value< 0.001, CI = 1.29–2.34) however, they were 33% less likely to use ITNs compared to the poorest (p-value = 0.01, CI = 0.50–0.91).

Conclusion

Interventions aimed at preventing and controlling malaria through the use of bed nets in rural Ghana and other similar settings should give more attention to disadvantage populations such as the poor and unemployed. Tailored massages and educational campaigns are required to ensure consistent use of treated bed nets.

]]>
<![CDATA[Fire, CO2, and climate effects on modeled vegetation and carbon dynamics in western Oregon and Washington]]> https://www.researchpad.co/article/5c57e67cd5eed0c484ef33e4

To develop effective long-term strategies, natural resource managers need to account for the projected effects of climate change as well as the uncertainty inherent in those projections. Vegetation models are one important source of projected climate effects. We explore results and associated uncertainties from the MC2 Dynamic Global Vegetation Model for the Pacific Northwest west of the Cascade crest. We compare model results for vegetation cover and carbon dynamics over the period 1895–2100 assuming: 1) unlimited wildfire ignitions versus stochastic ignitions, 2) no fire, and 3) a moderate CO2 fertilization effect versus no CO2 fertilization effect. Carbon stocks decline in all scenarios, except without fire and with a moderate CO2 fertilization effect. The greatest carbon stock loss, approximately 23% of historical levels, occurs with unlimited ignitions and no CO2 fertilization effect. With stochastic ignitions and a CO2 fertilization effect, carbon stocks are more stable than with unlimited ignitions. For all scenarios, the dominant vegetation type shifts from pure conifer to mixed forest, indicating that vegetation cover change is driven solely by climate and that significant mortality and vegetation shifts are likely through the 21st century regardless of fire regime changes.

]]>
<![CDATA[Effects of long-term fertilization on soil organic carbon mineralization and microbial community structure]]> https://www.researchpad.co/article/5c57e66bd5eed0c484ef30c6

Soil microorganisms play a pivotal role in carbon mineralization and their diversity is crucial to the function of soil ecosystems. However, the effects of long-term fertilization on microbial-mediated carbon mineralization are poorly understood. To identify the relative roles of microbes in carbon mineralization of yellow paddies, we investigated the long-term fertilization effects on soil properties and microbial communities and their relationships with carbon mineralization. The treatments included: no fertilization (CK), chemical fertilizer (NPK), organic fertilizer (M), and constant organic-inorganic fertilizer (MNPK). NPK treatment significantly increased soil water content (WC), while M and MNPK treatments significantly increased the content of soil organic carbon (SOC), total nitrogen (TN), soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and WC. Strong increases in CO2 emissions, potential mineralized carbon, and turnover rate constant were observed in both organic-fertilizer treatments (M and MNPK), relative to the CK treatment. These changes in soil properties can be attributed to the variation in microbial communities. NPK treatment had no significant effect. Different fertilization treatments changed soil microbial community; SOC and SMBN were the most important contributors to the variance in microbial community composition. The variations in community composition did not significant influence carbon mineralization; however, carbon mineralization was significantly influenced by the abundance of several non-dominant bacteria. The results suggest that SOC, SMBN, and non-dominant bacteria (Gemmatimonadetes and Latescibacteria), have a close relationship to carbon mineralization, and should be preferentially considered in predicting carbon mineralization under long-term fertilization.

]]>
<![CDATA[Matching the genetics of released and local Aedes aegypti populations is critical to assure Wolbachia invasion]]> https://www.researchpad.co/article/5c3e5090d5eed0c484d8308d

Background

Traditional vector control approaches such as source reduction and insecticide spraying have limited effect on reducing Aedes aegypti population. The endosymbiont Wolbachia is pointed as a promising tool to mitigate arbovirus transmission and has been deployed worldwide. Models predict a rapid increase on the frequency of Wolbachia-positive Ae. aegypti mosquitoes in local settings, supported by cytoplasmic incompatibility (CI) and high maternal transmission rate associated with the wMelBr strain.

Methodology/principle findings

Wolbachia wMelBr strain was released for 20 consecutive weeks after receiving >87% approval of householders of the isolated community of Tubiacanga, Rio de Janeiro. wMelBr frequency plateued~40% during weeks 7–19, peaked 65% but dropped as releases stopped. A high (97.56%) maternal transmission was observed. Doubling releases and deploying mosquitoes with large wing length and low laboratory mortality produced no detectable effects on invasion trend. By investigating the lab colony maintenance procedures backwardly, pyrethroid resistant genotypes in wMelBr decreased from 68% to 3.5% after 17 generations. Therefore, we initially released susceptible mosquitoes in a local population highly resistant to pyrethroids which, associated with the over use of insecticides by householders, ended jeopardizing Wolbachia invasion. A new strain (wMelRio) was produced after backcrossing wMelBr females with males from field to introduce mostly pyrethroid resistance alleles. The new strain increased mosquito survival but produced relevant negative effects on Ae. aegypti fecundity traits, reducing egg clutche size and egg hatch. Despite the cost on fitness, wMelRio successful established where wMelBr failed, revealing that matching the local population genetics, especially insecticide resistance background, is critical to achieve invasion.

Conclusions/significance

Local householders support was constantly high, reaching 90% backing on the second release (wMelRio strain). Notwithstanding the drought summer, the harsh temperature recorded (daily average above 30°C) did not seem to affect the expression of maternal transmission of wMel on a Brazilian background. Wolbachia deployment should match the insecticide resistance profile of the wild population to achieve invasion. Considering pyrethroid-resistance is a widely distributed phenotype in natural Ae. aegypti populations, future Wolbachia deployments must pay special attention in maintaining insecticide resistance in lab colonies for releases.

]]>
<![CDATA[<i>PLoS Biology</i> Issue Image | Vol. 17(1) January 2019]]> https://www.researchpad.co/article/5c5ca274d5eed0c48441e400

Identification and characterization of a mosquito-specific eggshell organizing factor in Aedes aegypti mosquitoes

Mosquito-borne pathogens infect millions of people worldwide, and the rise in insecticide resistance is exacerbating this problem. A new generation of environmentally safe insecticides will be essential to control insecticide-resistant mosquitoes. One potential route to such novel insecticide targets is the identification of proteins specifically needed for mosquito reproduction. Using RNA interference to screen mosquito-specific genes in Aedes aegypti (the mosquito that transmits yellow fever), Isoe et al. identified the eggshell organizing factor 1 (EOF1) protein as playing an essential role in eggshell melanization and embryonic development. Nearly 100% of the eggs laid by EOF1-deficient females had a defective eggshell and were non-viable. Additional experiments revealed that EOF1 also plays an essential role in eggshell formation in Aedes albopictus, a carrier of Zika virus and dengue fever. The image shows a scanning electron micrograph of a small region (about 20 µm across) of the shell from a normal Aedes aegypti egg.

Image Credit: pbio.3000068

]]>
<![CDATA[Alternative strategies for mosquito-borne arbovirus control]]> https://www.researchpad.co/article/5c37b78cd5eed0c4844903f9

Background

Mosquito-borne viruses—such as Zika, chikungunya, dengue fever, and yellow fever, among others—are of global importance. Although vaccine development for prevention of mosquito-borne arbovirus infections has been a focus, mitigation strategies continue to rely on vector control. However, vector control has failed to prevent recent epidemics and arrest expanding geographic distribution of key arboviruses, such as dengue. As a consequence, there has been increasing necessity to further optimize current strategies within integrated approaches and advance development of alternative, innovative strategies for the control of mosquito-borne arboviruses.

Methods and findings

This review, intended as a general overview, is one of a series being generated by the Worldwide Insecticide resistance Network (WIN). The alternative strategies discussed reflect those that are currently under evaluation for public health value by the World Health Organization (WHO) and represent strategies of focus by globally recognized public health stakeholders as potential insecticide resistance (IR)-mitigating strategies. Conditions where these alternative strategies could offer greatest public health value in consideration of mitigating IR will be dependent on the anticipated mechanism of action. Arguably, the most pressing need for endorsement of the strategies described here will be the epidemiological evidence of a public health impact.

Conclusions

As the burden of mosquito-borne arboviruses, predominately those transmitted by Aedes aegypti and A. albopictus, continues to grow at a global scale, new vector-control tools and integrated strategies will be required to meet public health demands. Decisions regarding implementation of alternative strategies will depend on key ecoepidemiological parameters that each is intended to optimally impact toward driving down arbovirus transmission.

]]>