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1.
Malar J ; 23(1): 188, 2024 Jun 17.
Article in English | MEDLINE | ID: mdl-38880870

ABSTRACT

BACKGROUND: Effective testing for malaria, including the detection of infections at very low densities, is vital for the successful elimination of the disease. Unfortunately, existing methods are either inexpensive but poorly sensitive or sensitive but costly. Recent studies have shown that mid-infrared spectroscopy coupled with machine learning (MIRs-ML) has potential for rapidly detecting malaria infections but requires further evaluation on diverse samples representative of natural infections in endemic areas. The aim of this study was, therefore, to demonstrate a simple AI-powered, reagent-free, and user-friendly approach that uses mid-infrared spectra from dried blood spots to accurately detect malaria infections across varying parasite densities and anaemic conditions. METHODS: Plasmodium falciparum strains NF54 and FCR3 were cultured and mixed with blood from 70 malaria-free individuals to create various malaria parasitaemia and anaemic conditions. Blood dilutions produced three haematocrit ratios (50%, 25%, 12.5%) and five parasitaemia levels (6%, 0.1%, 0.002%, 0.00003%, 0%). Dried blood spots were prepared on Whatman™ filter papers and scanned using attenuated total reflection-Fourier Transform Infrared (ATR-FTIR) for machine-learning analysis. Three classifiers were trained on an 80%/20% split of 4655 spectra: (I) high contrast (6% parasitaemia vs. negative), (II) low contrast (0.00003% vs. negative) and (III) all concentrations (all positive levels vs. negative). The classifiers were validated with unseen datasets to detect malaria at various parasitaemia levels and anaemic conditions. Additionally, these classifiers were tested on samples from a population survey in malaria-endemic villages of southeastern Tanzania. RESULTS: The AI classifiers attained over 90% accuracy in detecting malaria infections as low as one parasite per microlitre of blood, a sensitivity unattainable by conventional RDTs and microscopy. These laboratory-developed classifiers seamlessly transitioned to field applicability, achieving over 80% accuracy in predicting natural P. falciparum infections in blood samples collected during the field survey. Crucially, the performance remained unaffected by various levels of anaemia, a common complication in malaria patients. CONCLUSION: These findings suggest that the AI-driven mid-infrared spectroscopy approach holds promise as a simplified, sensitive and cost-effective method for malaria screening, consistently performing well despite variations in parasite densities and anaemic conditions. The technique simply involves scanning dried blood spots with a desktop mid-infrared scanner and analysing the spectra using pre-trained AI classifiers, making it readily adaptable to field conditions in low-resource settings. In this study, the approach was successfully adapted to field use, effectively predicting natural malaria infections in blood samples from a population-level survey in Tanzania. With additional field trials and validation, this technique could significantly enhance malaria surveillance and contribute to accelerating malaria elimination efforts.


Subject(s)
Malaria, Falciparum , Plasmodium falciparum , Humans , Malaria, Falciparum/diagnosis , Malaria, Falciparum/blood , Malaria, Falciparum/parasitology , Plasmodium falciparum/isolation & purification , Parasitemia/diagnosis , Parasitemia/parasitology , Anemia/diagnosis , Anemia/blood , Anemia/parasitology , Spectrophotometry, Infrared/methods , Machine Learning , Parasite Load , Adult , Artificial Intelligence , Sensitivity and Specificity , Female , Young Adult , Spectroscopy, Fourier Transform Infrared/methods , Adolescent , Male , Middle Aged , Mass Screening/methods
2.
Sci Rep ; 14(1): 12100, 2024 05 27.
Article in English | MEDLINE | ID: mdl-38802488

ABSTRACT

Field-derived metrics are critical for effective control of malaria, particularly in sub-Saharan Africa where the disease kills over half a million people yearly. One key metric is entomological inoculation rate, a direct measure of transmission intensities, computed as a product of human biting rates and prevalence of Plasmodium sporozoites in mosquitoes. Unfortunately, current methods for identifying infectious mosquitoes are laborious, time-consuming, and may require expensive reagents that are not always readily available. Here, we demonstrate the first field-application of mid-infrared spectroscopy and machine learning (MIRS-ML) to swiftly and accurately detect Plasmodium falciparum sporozoites in wild-caught Anopheles funestus, a major Afro-tropical malaria vector, without requiring any laboratory reagents. We collected 7178 female An. funestus from rural Tanzanian households using CDC-light traps, then desiccated and scanned their heads and thoraces using an FT-IR spectrometer. The sporozoite infections were confirmed using enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), to establish references for training supervised algorithms. The XGBoost model was used to detect sporozoite-infectious specimen, accurately predicting ELISA and PCR outcomes with 92% and 93% accuracies respectively. These findings suggest that MIRS-ML can rapidly detect P. falciparum in field-collected mosquitoes, with potential for enhancing surveillance in malaria-endemic regions. The technique is both fast, scanning 60-100 mosquitoes per hour, and cost-efficient, requiring no biochemical reactions and therefore no reagents. Given its previously proven capability in monitoring key entomological indicators like mosquito age, human blood index, and identities of vector species, we conclude that MIRS-ML could constitute a low-cost multi-functional toolkit for monitoring malaria risk and evaluating interventions.


Subject(s)
Anopheles , Machine Learning , Malaria, Falciparum , Mosquito Vectors , Plasmodium falciparum , Animals , Anopheles/parasitology , Malaria, Falciparum/epidemiology , Malaria, Falciparum/diagnosis , Malaria, Falciparum/parasitology , Plasmodium falciparum/isolation & purification , Mosquito Vectors/parasitology , Female , Humans , Tanzania/epidemiology , Sporozoites , Spectrophotometry, Infrared/methods , Spectroscopy, Fourier Transform Infrared/methods
3.
Parasit Vectors ; 17(1): 143, 2024 Mar 18.
Article in English | MEDLINE | ID: mdl-38500231

ABSTRACT

BACKGROUND: Accurately determining the age and survival probabilities of adult mosquitoes is crucial for understanding parasite transmission, evaluating the effectiveness of control interventions and assessing disease risk in communities. This study was aimed at demonstrating the rapid identification of epidemiologically relevant age categories of Anopheles funestus, a major Afro-tropical malaria vector, through the innovative combination of infrared spectroscopy and machine learning, instead of the cumbersome practice of dissecting mosquito ovaries to estimate age based on parity status. METHODS: Anopheles funestus larvae were collected in rural south-eastern Tanzania and reared in an insectary. Emerging adult females were sorted by age (1-16 days old) and preserved using silica gel. Polymerase chain reaction (PCR) confirmation was conducted using DNA extracted from mosquito legs to verify the presence of An. funestus and to eliminate undesired mosquitoes. Mid-infrared spectra were obtained by scanning the heads and thoraces of the mosquitoes using an attenuated total reflection-Fourier transform infrared (ATR-FT-IR) spectrometer. The spectra (N = 2084) were divided into two epidemiologically relevant age groups: 1-9 days (young, non-infectious) and 10-16 days (old, potentially infectious). The dimensionality of the spectra was reduced using principal component analysis, and then a set of machine learning and multi-layer perceptron (MLP) models were trained using the spectra to predict the mosquito age categories. RESULTS: The best-performing model, XGBoost, achieved overall accuracy of 87%, with classification accuracy of 89% for young and 84% for old An. funestus. When the most important spectral features influencing the model performance were selected to train a new model, the overall accuracy increased slightly to 89%. The MLP model, utilizing the significant spectral features, achieved higher classification accuracy of 95% and 94% for the young and old An. funestus, respectively. After dimensionality reduction, the MLP achieved 93% accuracy for both age categories. CONCLUSIONS: This study shows how machine learning can quickly classify epidemiologically relevant age groups of An. funestus based on their mid-infrared spectra. Having been previously applied to An. gambiae, An. arabiensis and An. coluzzii, this demonstration on An. funestus underscores the potential of this low-cost, reagent-free technique for widespread use on all the major Afro-tropical malaria vectors. Future research should demonstrate how such machine-derived age classifications in field-collected mosquitoes correlate with malaria in human populations.


Subject(s)
Anopheles , Malaria , Animals , Female , Humans , Infant , Child, Preschool , Child , Infant, Newborn , Anopheles/parasitology , Mosquito Vectors/parasitology , Spectroscopy, Fourier Transform Infrared , Tanzania
4.
Malar J ; 23(1): 86, 2024 Mar 26.
Article in English | MEDLINE | ID: mdl-38532415

ABSTRACT

BACKGROUND: The degree to which Anopheles mosquitoes prefer biting humans over other vertebrate hosts, i.e. the human blood index (HBI), is a crucial parameter for assessing malaria transmission risk. However, existing techniques for identifying mosquito blood meals are demanding in terms of time and effort, involve costly reagents, and are prone to inaccuracies due to factors such as cross-reactivity with other antigens or partially digested blood meals in the mosquito gut. This study demonstrates the first field application of mid-infrared spectroscopy and machine learning (MIRS-ML), to rapidly assess the blood-feeding histories of malaria vectors, with direct comparison to PCR assays. METHODS AND RESULTS: Female Anopheles funestus mosquitoes (N = 1854) were collected from rural Tanzania and desiccated then scanned with an attenuated total reflectance Fourier-transform Infrared (ATR-FTIR) spectrometer. Blood meals were confirmed by PCR, establishing the 'ground truth' for machine learning algorithms. Logistic regression and multi-layer perceptron classifiers were employed to identify blood meal sources, achieving accuracies of 88%-90%, respectively, as well as HBI estimates aligning well with the PCR-based standard HBI. CONCLUSIONS: This research provides evidence of MIRS-ML effectiveness in classifying blood meals in wild Anopheles funestus, as a potential complementary surveillance tool in settings where conventional molecular techniques are impractical. The cost-effectiveness, simplicity, and scalability of MIRS-ML, along with its generalizability, outweigh minor gaps in HBI estimation. Since this approach has already been demonstrated for measuring other entomological and parasitological indicators of malaria, the validation in this study broadens its range of use cases, positioning it as an integrated system for estimating pathogen transmission risk and evaluating the impact of interventions.


Subject(s)
Anopheles , Malaria , Animals , Humans , Female , Mosquito Vectors , Malaria/epidemiology , Machine Learning , Spectrophotometry, Infrared , Feeding Behavior
5.
Malar J ; 22(1): 346, 2023 Nov 10.
Article in English | MEDLINE | ID: mdl-37950315

ABSTRACT

Studies on the applications of infrared (IR) spectroscopy and machine learning (ML) in public health have increased greatly in recent years. These technologies show enormous potential for measuring key parameters of malaria, a disease that still causes about 250 million cases and 620,000 deaths, annually. Multiple studies have demonstrated that the combination of IR spectroscopy and machine learning (ML) can yield accurate predictions of epidemiologically relevant parameters of malaria in both laboratory and field surveys. Proven applications now include determining the age, species, and blood-feeding histories of mosquito vectors as well as detecting malaria parasite infections in both humans and mosquitoes. As the World Health Organization encourages malaria-endemic countries to improve their surveillance-response strategies, it is crucial to consider whether IR and ML techniques are likely to meet the relevant feasibility and cost-effectiveness requirements-and how best they can be deployed. This paper reviews current applications of IR spectroscopy and ML approaches for investigating malaria indicators in both field surveys and laboratory settings, and identifies key research gaps relevant to these applications. Additionally, the article suggests initial target product profiles (TPPs) that should be considered when developing or testing these technologies for use in low-income settings.


Subject(s)
Culicidae , Malaria , Animals , Humans , Artificial Intelligence , Evidence Gaps , Malaria/epidemiology , Mosquito Vectors , Spectrophotometry, Infrared/methods
6.
BMC Bioinformatics ; 24(1): 11, 2023 Jan 09.
Article in English | MEDLINE | ID: mdl-36624386

ABSTRACT

BACKGROUND: Old mosquitoes are more likely to transmit malaria than young ones. Therefore, accurate prediction of mosquito population age can drastically improve the evaluation of mosquito-targeted interventions. However, standard methods for age-grading mosquitoes are laborious and costly. We have shown that Mid-infrared spectroscopy (MIRS) can be used to detect age-specific patterns in mosquito cuticles and thus can be used to train age-grading machine learning models. However, these models tend to transfer poorly across populations. Here, we investigate whether applying dimensionality reduction and transfer learning to MIRS data can improve the transferability of MIRS-based predictions for mosquito ages. METHODS: We reared adults of the malaria vector Anopheles arabiensis in two insectaries. The heads and thoraces of female mosquitoes were scanned using an attenuated total reflection-Fourier transform infrared spectrometer, which were grouped into two different age classes. The dimensionality of the spectra data was reduced using unsupervised principal component analysis or t-distributed stochastic neighbour embedding, and then used to train deep learning and standard machine learning classifiers. Transfer learning was also evaluated to improve transferability of the models when predicting mosquito age classes from new populations. RESULTS: Model accuracies for predicting the age of mosquitoes from the same population as the training samples reached 99% for deep learning and 92% for standard machine learning. However, these models did not generalise to a different population, achieving only 46% and 48% accuracy for deep learning and standard machine learning, respectively. Dimensionality reduction did not improve model generalizability but reduced computational time. Transfer learning by updating pre-trained models with 2% of mosquitoes from the alternate population improved performance to ~ 98% accuracy for predicting mosquito age classes in the alternative population. CONCLUSION: Combining dimensionality reduction and transfer learning can reduce computational costs and improve the transferability of both deep learning and standard machine learning models for predicting the age of mosquitoes. Future studies should investigate the optimal quantities and diversity of training data necessary for transfer learning and the implications for broader generalisability to unseen datasets.


Subject(s)
Anopheles , Malaria , Animals , Adult , Female , Humans , Mosquito Vectors , Machine Learning
7.
Malar J ; 21(1): 365, 2022 Dec 02.
Article in English | MEDLINE | ID: mdl-36461058

ABSTRACT

BACKGROUND: Malaria transmission can be highly heterogeneous between and within localities, and is influenced by factors such as survival and biting frequencies of Anopheles mosquitoes. This study investigated the relationships between the biological age, distance from aquatic habitats and pyrethroid resistance status of Anopheles funestus mosquitoes, which currently dominate malaria transmission in south-east Tanzania. The study also examined how such relationships may influence malaria transmission and control. METHODS: Female An. funestus were collected in houses located 50-100 m, 150-200 m or over 200 m from the nearest known aquatic habitats. The mosquitoes were exposed to 1×, 5× and 10× the diagnostic doses of deltamethrin or permethrin, or to the synergist, piperonyl butoxide (PBO) followed by the pyrethroids, then monitored for 24 h-mortality. Ovaries of exposed and non-exposed mosquitoes were dissected to assess parity as a proxy for biological age. Adults emerging from larval collections in the same villages were tested against the same insecticides at 3-5, 8-11 or 17-20 days old. FINDINGS: Mosquitoes collected nearest to the aquatic habitats (50-100 m) had the lowest mortalities compared to other distances, with a maximum of 51% mortality at 10× permethrin. For the age-synchronized mosquitoes collected as larvae, the insecticide-induced mortality assessed at both the diagnostic and multiplicative doses (1×, 5× and 10×) increased with mosquito age. The highest mortalities at 1× doses were observed among the oldest mosquitoes (17-20 days). At 10× doses, mortalities were 99% (permethrin) and 76% (deltamethrin) among 8-11 day-olds compared to 80% (permethrin) and 58% (deltamethrin) among 3-5 day-olds. Pre-exposure to PBO increased the potency of both pyrethroids. The proportion of parous females was highest among mosquitoes collected farthest from the habitats. CONCLUSION: In this specific setting, older An. funestus and those collected farthest from the aquatic habitats (near the centre of the village) were more susceptible to pyrethroids than the younger ones and those caught nearest to the habitats. These findings suggest that pyrethroid-based interventions may remain at least moderately effective despite widespread pyrethroid-resistance, by killing the older, less-resistant and potentially-infective mosquitoes. Further studies should investigate how and whether these observations could be exploited to optimize malaria control in different settings.


Subject(s)
Anopheles , Insecticides , Humans , Adult , Animals , Female , Permethrin/pharmacology , Tanzania , Larva , Ecosystem , Aging
8.
Malar J ; 21(1): 161, 2022 Jun 03.
Article in English | MEDLINE | ID: mdl-35658961

ABSTRACT

BACKGROUND: It is often assumed that the population dynamics of the malaria vector Anopheles funestus, its role in malaria transmission and the way it responds to interventions are similar to the more elaborately characterized Anopheles gambiae. However, An. funestus has several unique ecological features that could generate distinct transmission dynamics and responsiveness to interventions. The objectives of this work were to develop a model which will: (1) reconstruct the population dynamics, survival, and fecundity of wild An. funestus populations in southern Tanzania, (2) quantify impacts of density dependence on the dynamics, and (3) assess seasonal fluctuations in An. funestus demography. Through quantifying the population dynamics of An. funestus, this model will enable analysis of how their stability and response to interventions may differ from that of An. gambiae sensu lato. METHODS: A Bayesian State Space Model (SSM) based on mosquito life history was fit to time series data on the abundance of female An. funestus sensu stricto collected over 2 years in southern Tanzania. Prior values of fitness and demography were incorporated from empirical data on larval development, adult survival and fecundity from laboratory-reared first generation progeny of wild caught An. funestus. The model was structured to allow larval and adult fitness traits to vary seasonally in response to environmental covariates (i.e. temperature and rainfall), and for density dependency in larvae. The effects of density dependence and seasonality were measured through counterfactual examination of model fit with or without these covariates. RESULTS: The model accurately reconstructed the seasonal population dynamics of An. funestus and generated biologically-plausible values of their survival larval, development and fecundity in the wild. This model suggests that An. funestus survival and fecundity annual pattern was highly variable across the year, but did not show consistent seasonal trends either rainfall or temperature. While the model fit was somewhat improved by inclusion of density dependence, this was a relatively minor effect and suggests that this process is not as important for An. funestus as it is for An. gambiae populations. CONCLUSION: The model's ability to accurately reconstruct the dynamics and demography of An. funestus could potentially be useful in simulating the response of these populations to vector control techniques deployed separately or in combination. The observed and simulated dynamics also suggests that An. funestus could be playing a role in year-round malaria transmission, with any apparent seasonality attributed to other vector species.


Subject(s)
Anopheles , Malaria , Animals , Anopheles/physiology , Bayes Theorem , Female , Malaria/prevention & control , Mosquito Vectors/physiology , Population Dynamics , Tanzania
9.
Int J Pharm ; 620: 121741, 2022 May 25.
Article in English | MEDLINE | ID: mdl-35421533

ABSTRACT

Targeted delivery of nucleic acids is gaining momentum due to improved efficacy, selectivity, increased circulation time and enhanced tissue retention in target cells. Using nucleic acid-based therapies previously undruggable targets have proven now to be amenable for treatment. Currently, several methods for preparing targeted or labelled delivery vehicles for nucleic acids are based on liposomal formulations. Lipid nanoparticles (LNPs) are structurally different from liposomes and these methods should therefore be evaluated before being translated to siRNA LNPs preparation protocols. Here, we describe a robust and facile method for the preparation of targeted or fluorescently labelled siRNA LNPs. Using a copper free strain-promoted azide-alkyne cycloaddition (SPAAC) we demonstrate that post-insertion of ligand-lipid conjugates into preformed LNPs is superior to direct-surface modification because it preserves the physicochemical parameters of the LNPs. We found that the time point of solvent removal by dialysis is critical and affects the hydrodynamic diameter of the LNPs; post-insertion after dialysis shows the smallest increase in hydrodynamic diameter and polydispersity index (PDI). The post-insertion of ligand-lipid conjugates also proceeded with rapid kinetics and high efficacy over a wide temperature range. Using this optimised protocol, we generated siRNA LNPs containing both targeting and fluorescent tracking ligands allowing us to monitor siRNA LNP uptake kinetics in dependence of the targeting ligand. In aggregate, we describe a robust approach for the generation of targeted and labelled siRNA LNPs that allows their controlled and facile decoration with ligand combinations.


Subject(s)
Liposomes , Nanoparticles , Ligands , Lipids , RNA, Small Interfering/genetics , Renal Dialysis
10.
Health sci. dis ; 23(7): 18-22, 2022. figures, tables
Article in English | AIM (Africa) | ID: biblio-1379119

ABSTRACT

Introduction. We studied malaria in HIV infected subjects hospitalized in the department of infectious diseases at Point G Teaching Hospital in Mali, with the objective to have current data on malaria in patients infected by HIV. Materials and methods. We conducted a prospective study from October, 1st 2016 to September 30th 2018 in patients seropositive for HIV having positive thick smear for Plasmodium and hospitalized in the department of infectious diseases at Point G Teaching Hospital. We collected sociodemographic, clinical and lab data form those patients. Data have been entered and analyzed using SPSS20.0 software. Results. Hospital frequency of malaria among People living with HIV was 24.4% (151/618). This population has a mean-age of 44.1±12.4 y/o and a sex ratio (M/F) of 0.86. Majority of patients were at WHO stage IV of HIV infection (63.4%). Symptoms were by decreasing frequency: fever (98.3%); headache (86.4%); anorexia (72.9%); asthenia (61.0%) and vomiting (42.4%). the mean parasitemia was 172.9±352.1 trophozoite/mm3 . Mean hemoglobin level was 9.1±3.2 g/dl and the mean CD4 count was 9±3 cell/mm3 . Severe malaria was independent from WHO HIV stage and from immunologic deficiency. The malaria treatment when correctly followed conduct to good improvement of the anemia (p = 0.03) and the negativity of the parasitemia (p = 0.00). Death in our HIV patient is linked to association with severe malaria (p = 0,012). Conclusion. Malaria is relatively common and severe among PLWHA in Mali. Prompt treatment is still effective and must be implemented to ensure a good prognosis. Despite cotrimoxazole chemoprophylaxis, a certain number of PLHIV suffer from malaria, raising the hypothesis of plasmodium resistance to antifolates.


Subject(s)
HIV Infections , Trimethoprim, Sulfamethoxazole Drug Combination , Inpatients , Malaria , Chemoprevention
11.
Parasit Vectors ; 14(1): 514, 2021 Oct 07.
Article in English | MEDLINE | ID: mdl-34620227

ABSTRACT

BACKGROUND: Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings. METHOD: Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps. RESULTS: Proportions of inseminated females inside the experimental huts in the village increased from approximately 60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps. CONCLUSION: Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers.


Subject(s)
Anopheles/physiology , Housing , Malaria/transmission , Mosquito Vectors/physiology , Sexual Behavior, Animal , Animals , Anopheles/classification , Anopheles/parasitology , Female , Humans , Insect Bites and Stings , Malaria/parasitology , Male , Mosquito Control/methods , Rural Population
12.
PeerJ ; 6: e4480, 2018.
Article in English | MEDLINE | ID: mdl-29527419

ABSTRACT

"Candidatus Phytoplasma aurantifolia" is associated with witches' broom disease of lime in Oman and the UAE. A previous study showed that an infection by phytoplasma may not necessarily result in the physical appearance of witches' broom symptoms in some locations in Oman and the UAE. This study investigated whether phytoplasma strains belonging to "Ca. P. aurantifolia" (based on the 16S rRNA gene analysis) in locations where disease symptoms are expressed are different from phytoplasma in locations where disease symptoms are not expressed. About 21 phytoplasma strains (15 from areas and trees with disease symptoms and six from areas and trees without disease symptoms) were included in the analysis. The study utilized sequences of the imp and SAP11 genes to characterize the 21 strains. Phylogenetic analysis of both genes showed that the 21 strains are similar to each other and to reference strains in GenBank. The study shows that there is a low level of diversity among all phytoplasma strains. In addition, it shows that phytoplasma in places where witches' broom symptoms are not expressed are similar to phytoplasma in places where disease symptoms are expressed. This may suggest that disease expression is not linked to the presence of different phytoplasma strains, but may be due to other factors such as weather conditions.

13.
Plant Dis ; 102(1): 202-208, 2018 Jan.
Article in English | MEDLINE | ID: mdl-30673464

ABSTRACT

A study was conducted to characterize the common Pythium spp. in greenhouses in Oman and their level of resistance to hymexazol, a widely used fungicide in the country. Pythium isolates were obtained from soil samples, cocopeat bags, and cucumber roots collected from seven regions in the country. Identification of 80 Pythium isolates to the species level using sequences of the internal transcribed spacer region of the ribosomal RNA showed that they belong to four species: Pythium aphanidermatum (77 isolates), P. spinosum (1 isolate), P. myriotylum (1 isolate), and P. catenulatum (1 isolate). Investigating the aggressiveness of three Pythium spp. on cucumber showed that P. aphanidermatum, P. myriotylum, and P. spinosum are pathogenic. Phylogenetic analysis of P. aphanidermatum isolates showed that most of the isolates obtained from cocopeat clustered separately from isolates obtained from soil and roots. This may indicate a difference in the origin of the cocopeat isolates. Evaluating the resistance of 27 P. aphanidermatum isolates to hymexazol showed that most isolates were sensitive (0.9 to 31.2 mg liter-1) whereas one isolate was resistant (142.9 mg liter-1). This study is the first to report P. myriotylum and P. catenulatum in Oman. It is also the first to report the development of resistance to hymexazol among P. aphanidermatum populations from greenhouses. Growers should use integrated disease management strategies to avoid further development of resistance to hymexazol.


Subject(s)
Cucumis sativus/microbiology , Drug Resistance, Fungal , Fungicides, Industrial/pharmacology , Oxazoles/pharmacology , Pythium/drug effects , Oman , Plant Diseases/prevention & control
15.
Cell Mol Biol (Noisy-le-grand) ; 62(3): 10-4, 2016 Mar 20.
Article in English | MEDLINE | ID: mdl-27064867

ABSTRACT

The zinc finger transcription factor GATA4, located on chromosome 8p23.1-p22, has been implicated as a critical regulator of cardiac development during embryogenesis. Mutations of GATA4 appear to be responsible for some cardiac septal defects. The aim of this work was to screen for mutations in the GATA4 gene in sample of Egyptian patients affected by isolated and non-isolated cardiac septal defects. We examined 20 patients with atrial septal defect (ASD), ventricle septal defect (VSD), atrioventricular septal defects (AVSD) and A-V canal disturbance defect and compared with examined 10 unaffected individuals as normal control. The patients were referred from Congenital Heart Disease Clinic of the Clinical Genetics department at the National Research Centre. All patients were subjected to clinical evaluation, echocardiography and karyotyping. Genomic DNA was extracted from all cases and subjected to PCR followed by direct sequencing. The predicted effect of variants was done by a variety of proper prediction tools. We detected six variants in GATA4 gene, two of them are novel variants. Predicted functional analysis of the relevant variants was performed by In silico analysis. Further confirmatory studies on familial segregation and in vitro / in vivo functional analysis are recommended to support our results.


Subject(s)
GATA4 Transcription Factor/genetics , Heart Septal Defects/genetics , Mutation , Case-Control Studies , Child , Child, Preschool , DNA Mutational Analysis , Egypt/epidemiology , Female , Genetic Variation , Heart Septal Defects/epidemiology , Humans , Infant , Male , Models, Molecular , Nucleic Acid Conformation , Prospective Studies , RNA, Messenger/chemistry , RNA, Messenger/genetics
17.
Appl Radiat Isot ; 105: 47-51, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26248083

ABSTRACT

Statistical analysis based on chemical composition, using radioisotope X-ray fluorescence, have been applied on 39 ancient pottery fragments coming from the excavation at Tell Al-Kasra archaeological site, Syria. Three groups were defined by applying Cluster and Factor analysis statistical methods. Thermoluminescence (TL) dating was investigated on three sherds taken from the bathroom (hammam) on the site. Multiple aliquot additive dose (MAAD) was used to estimate the paleodose value, and the gamma spectrometry was used to estimate the dose rate. The average age was found to be 715±36 year.

18.
Phytopathology ; 105(9): 1229-44, 2015 Sep.
Article in English | MEDLINE | ID: mdl-25822187

ABSTRACT

Ceratocystis wilt is among the most important diseases on mango (Mangifera indica) in Brazil, Oman, and Pakistan. The causal agent was originally identified in Brazil as Ceratocystis fimbriata, which is considered by some as a complex of many cryptic species, and four new species on mango trees were distinguished from C. fimbriata based on variation in internal transcribed spacer sequences. In the present study, phylogenetic analyses using DNA sequences of mating type genes, TEF-1α, and ß-tubulin failed to identify lineages corresponding to the four new species names. Further, mating experiments found that the mango isolates representing the new species were interfertile with each other and a tester strain from sweet potato (Ipomoea batatas), on which the name C. fimbriata is based, and there was little morphological variation among the mango isolates. Microsatellite markers found substantial differentiation among mango isolates at the regional and population levels, but certain microsatellite genotypes were commonly found in multiple populations, suggesting that these genotypes had been disseminated in infected nursery stock. The most common microsatellite genotypes corresponded to the four recently named species (C. manginecans, C. acaciivora, C. mangicola, and C. mangivora), which are considered synonyms of C. fimbriata. This study points to the potential problems of naming new species based on introduced genotypes of a pathogen, the value of an understanding of natural variation within and among populations, and the importance of phenotype in delimiting species.


Subject(s)
Ascomycota/classification , Ipomoea batatas/microbiology , Mangifera/microbiology , Plant Diseases/microbiology , Ascomycota/genetics , Ascomycota/isolation & purification , Brazil , DNA Barcoding, Taxonomic , DNA, Fungal/chemistry , DNA, Fungal/genetics , DNA, Ribosomal Spacer/genetics , Fungal Proteins/genetics , Genetic Variation , Genotype , Microsatellite Repeats/genetics , Phylogeny , Sequence Analysis, DNA
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