scholarly journals Persistent Plasmodium falciparum infections enhance transmission-reducing immunity development

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ruth Ayanful-Torgby ◽  
Esther Sarpong ◽  
Hamza B. Abagna ◽  
Dickson Donu ◽  
Evans Obboh ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
Quantitative Polymerase Chain Reaction ◽  
Geographical Area ◽  
Infection Prevalence ◽  
Infection Status ◽  
Individual Level ◽  
Control Programs ◽  
Infection Dynamics ◽  
The Individual

AbstractSubclinical infections that serve as reservoir populations to drive transmission remain a hurdle to malaria control. Data on infection dynamics in a geographical area is required to strategically design and implement malaria interventions. In a longitudinal cohort, we monitored Plasmodium falciparum infection prevalence and persistence, and anti-parasite immunity to gametocyte and asexual antigens for 10 weeks. Of the 100 participants, only 11 were never infected, whilst 16 had persistent infections detected by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), and one participant had microscopic parasites at all visits. Over 70% of the participants were infected three or more times, and submicroscopic gametocyte prevalence was high, ≥ 48% of the parasite carriers. Naturally induced responses against recombinant Pfs48/45.6C, Pfs230proC, and EBA175RIII–V antigens were not associated with either infection status or gametocyte carriage, but the antigen-specific IgG titers inversely correlated with parasite and gametocyte densities consistent with partial immunity. Longitudinal analysis of gametocyte diversity indicated at least four distinct clones circulated throughout the study period. The high prevalence of children infected with distinct gametocyte clones coupled with marked variation in infection status at the individual level suggests ongoing transmission and should be targeted in malaria control programs.

scholarly journals A multiplex qPCR approach for detection of pfhrp2 and pfhrp3 gene deletions in multiple strain infections of Plasmodium falciparum

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Schindler ◽  
Anna C. Deal ◽  
Martina Fink ◽  
Etienne Guirou ◽  
Kara A. Moser ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
High Throughput Screening ◽  
Malaria Diagnosis ◽  
The Novel ◽  
Essential Factor ◽  
Gene Deletions ◽  
Control Programs ◽  
Sub Saharan ◽  
Insight Into

Abstract The rapid and accurate diagnosis of Plasmodium falciparum malaria infection is an essential factor in malaria control. Currently, malaria diagnosis in the field depends heavily on using rapid diagnostic tests (RDTs) many of which detect circulating parasite-derived histidine-rich protein 2 antigen (PfHRP2) in capillary blood. P. falciparum strains lacking PfHRP2, due to pfhrp2 gene deletions, are an emerging threat to malaria control programs. The novel assay described here, named qHRP2/3-del, is well suited for high-throughput screening of P. falciparum isolates to identify these gene deletions. The qHRP2/3-del assay identified pfhrp2 and pfhrp3 deletion status correctly in 93.4% of samples with parasitemia levels higher than 5 parasites/µL when compared to nested PCR. The qHRP2/3-del assay can correctly identify pfhrp2 and pfhrp3 gene deletions in multiple strain co-infections, particularly prevalent in Sub-Saharan countries. Deployment of this qHRP2/3-del assay will provide rapid insight into the prevalence and potential spread of P. falciparum isolates that escape surveillance by RDTs.

Do empowered employees absorb knowledge?

2014 ◽  
Vol 37 (2) ◽  
pp. 130-151 ◽  
Author(s):  
Evangelia Siachou ◽  
Panagiotis Gkorezis
Keyword(s):  
Geographical Area ◽  
Three Dimensions ◽  
Hierarchical Regression ◽  
Cross Sectional ◽  
Content Type ◽  
Individual Level ◽  
Manufacturing Organizations ◽  
The Individual ◽  
The Impact ◽  
The Relationship

Purpose – The present study aims to contribute to the limited empirical research regarding the individual level antecedents of absorptive capacity (AC). In this vein, the authors examined the impact of employees' psychological empowerment (PE) dimensions on their AC. Moreover, the authors explored the magnitude of the relationship between one of PE four dimensions, namely competence, and AC compared to that of the rest three dimensions of PE. Design/methodology/approach – The authors collected data from 100 private employees working in two manufacturing organizations. In order to investigate the hypotheses, the authors conducted hierarchical regression and usefulness analysis. Findings – As predicted, the present results showed that all four PE dimensions affected employees' AC. Furthermore, competence demonstrated the strongest impact among all PE dimensions. Research limitations/implications – Data were drawn from two manufacturing organizations located in specific geographical area. Thus, this may constrain the generalizability of the results. Also, the cross-sectional analysis of the data cannot directly assess causality. Originality/value – To the best of the authors' knowledge, this is the first empirical study examining the relationship between PE and AC.

scholarly journals Parasite-mediated anorexia increases or decreases virulence evolution, depending on dietary context

2018 ◽  
Author(s):  
J. L. Hite ◽  
C. E. Cressler
Keyword(s):  
Food Intake ◽  
Population Level ◽  
Parasite Development ◽  
Infection Prevalence ◽  
Individual Level ◽  
Physiological Processes ◽  
Gastrointestinal Conditions ◽  
The Individual ◽  
Spread Of Infection ◽  
Host Parasite

AbstractParasite-mediated anorexia is a ubiquitous, but poorly understood component of host-parasite interactions. These temporary but substantial reductions in food intake (range: 4-100%) limit exposure to parasites and alter within-host physiological processes that regulate parasite development, production, and survival, such as energy allocation, immune function, host-microbiota interactions, and gastrointestinal conditions. By altering the duration, severity, and spread of infection, anorexia could substantially alter ecological, evolutionary, and epidemiological dynamics. However, these higher-order implications are typically overlooked and remain poorly understood — even though medical (e.g., non-steroidal anti-inflammatory drugs, vaccines, targeted signaling pathways, calorie restriction) and husbandry practices (e.g., antibiotic and diet use for rapid growth, nutrient supplementation) often directly or indirectly alter host appetite and nutrient intake. Here, we develop theory that helps elucidate why reduced food intake (anorexia) can enhance or diminish disease severity and illustrates that the population-level outcomes often contrast with the individual-level outcomes: treatments that increase the intake of high quality nutrients (suppressing anorexia), can drive rapid individual-level recovery, but inadvertently increase infection prevalence and select for more virulent parasites. Such a theory-guided approach offers a tool to improve targeting host nutrition to manage disease in both human and livestock populations by revealing a means to predict how nutrient-driven feedbacks will affect both the host and parasite.

scholarly journals KASP: a genotyping method to rapid identification of resistance in Plasmodium falciparum

2020 ◽  
Author(s):  
Ana Alvarez-Fernandez ◽  
María J. Bernal ◽  
Isabel Fradejas Villajos ◽  
Alexandra Martín Ramírez ◽  
Noor Azian Md Yu ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
Low Cost ◽  
Reference Method ◽  
Rapid Identification ◽  
Control Programs ◽  
Specific Pcr ◽  
Antimalarial Resistance ◽  
Allele Specific ◽  
Almost All

Abstract BackgroundThe emergence and spread of antimalarial resistance continues to hinder malaria control. Plasmodium falciparum, the species that causes most human malaria cases and most deaths, has shown resistance to almost all known antimalarials. This antimalarial resistance arises from the development and subsequent expansion of Single Nucleotide Polymorfisms (SNPs) in specific parasite genes. A quick and cheap tool for the detection of drug resistance can be crucial and very useful for use in hospitals and in malaria control programs. It has been demonstrated in different contexts that genotyping by Kompetitive Allele Specific PCR (KASP), is a simple, fast and economical method that allows a high-precision biallelic characterization of SNPs, hence its possible utility in the study of resistance in P. falciparum.MethodsThree SNPs involved in most cases of resistance to the most widespread antimalarial treatments have been analyzed by PCR plus sequencing and by KASP (C580Y of the Kelch13 gene, Y86N of the Pfmdr1 gene and M133I of the Pfcytb gene). A total of 113 P. falciparum positive samples and 24 negative samples, previously analyzed by PCR and sequencing, were selected for this assay. Likewise, the samples were genotyped for the MSP-1 and MSP-2 genes, and the Multiplicity of Infection (MOI) and parasitaemia were measured to observe their possible influence on the KASP method.ResultsThe KASP results showed the same expected mutations and wild type genotypes as the reference method, with few exceptions that correlated with very low parasitaemia samples. In addition, two cases of heterozygotes that had not been detected by sequencing were found. No correlation was found between the MOI or parasitaemia and the KASP values of the sample. The reproducibility of the technique shows no oscillations between repetitions in any of the three SNPs analyzed.ConclusionsThe KASP assays developed in our study were efficient and versatile for the determination of the Plasmodium genotypes related to resistance. The method is simple, fast, reproducible with low cost in personnel, material and equipment and scalable, being able to core KASP arrays, including numerous SNPs, to complete the main pattern of mutations associated to P. falciparum resistance.

Detection of ranavirus in endemic and threatened amphibian populations of the Australian Wet Tropics Region

2020 ◽  
Vol 26 (1) ◽  
pp. 93
Author(s):  
Felicity J. Wynne
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Quantitative Polymerase Chain Reaction ◽  
Amphibian Declines ◽  
Chain Reaction ◽  
Individual Level ◽  
Frog Species ◽  
Wet Tropics ◽  
Polymerase Chain ◽  
The Individual ◽  
Amphibian Chytrid Fungus

The amphibian chytrid fungus (Batrachochytrium dendrobatidis) has driven severe amphibian declines in the Australian tropics. These declines have resulted in species extirpations and extinctions, with many surviving in small, highly threatened populations. Despite the fragility of remaining populations, another group of lethal pathogens, ranaviruses, have rarely been investigated among native amphibians. Ranaviruses have previously been associated with fish, reptile and amphibian mortality events in Australia, yet remain poorly understood here, especially among amphibian hosts. Here, quantitative polymerase chain reaction assays were used to detect ranavirus presence from eight of 17 tested sites containing populations of endangered and critically endangered Australian frog species. Although present in these populations, ranavirus seems to be at the lower bounds of detectability of the assay, which makes firm diagnosis at the individual level unreliable. Repeated (n=14) detections of this pathogen, however, are highly indicative of its presence at each area where it was detected. Therefore, these populations are likely often exposed to ranavirus. The results of this study are not characteristic of populations experiencing rapid disease-associated die-offs or declines, but further investigations should be undertaken to examine the potential drivers of these pathogens to predict future emergence and potential threats to endangered Australian amphibians.

scholarly journals Socioeconomic inequalities in the consumption of fruits and vegetables: Colombian National Nutrition Survey, 2010

2019 ◽  
Vol 35 (2) ◽  
Author(s):  
Oscar Fernando Herran ◽  
Gonzalo Alberto Patiño ◽  
Edna Magaly Gamboa
Keyword(s):  
Fruits And Vegetables ◽  
Fruit Juice ◽  
Vegetable Consumption ◽  
Geographical Area ◽  
Nutrition Survey ◽  
Cross Sectional ◽  
Individual Level ◽  
National Nutrition Survey ◽  
Using Data ◽  
The Individual

The objective of this study was to estimate inequalities in the consumption of fruits and vegetables. A multilevel study was performed based on cross-sectional data of adults from 18 to 64 years of age (n = 5,217) and in geodemographic units (n = 33). The consumption of fruits and vegetables was estimated with a food frequency questionnaire administered as part of the 2010 Colombian National Nutrition Survey (ENSIN). Inequality indices for the consumption of whole fruits and fruit juice and for raw and cooked vegetables were estimated using data on wealth, food security, geographical area and monetary poverty. The prevalence of the consumption of cooked vegetables was 64.8% (95%CI: 59.2-70.4) among men and the prevalence of the consumption of fruit juice was 86.1% (95%CI: 82.4-89.8) among women. The frequency of the consumption of fruit juice was 1.03 times/day (95%CI: 0.93-1.14) among women. The prevalence and frequency fruits and vegetables consumption per day for the three socioeconomic variables considered in this study are higher according to the higher socioeconomic level (p < 0.05), except for the consumption frequency of whole fruits/day (p = 0.24). At the individual level, the Gini coefficient for frequency/day ranged from 0.51 to 0.62. At the ecological level, the Gini index for prevalence ranged from 0.04 to 0.14; and for frequency/day ranged from 0.03 to 0.11. The Colombian population does not meet fruits and vegetables consumption recommendations. Men and women favor the consumption of fruit juice over whole fruits. The inequality in vegetable consumption is clear, with men at a disadvantage. The poor eat fewer fruits and vegetables.

scholarly journals KASP: a genotyping method to rapid identification of resistance in Plasmodium falciparum

2020 ◽  
Author(s):  
Ana Alvarez-Fernandez ◽  
María J. Bernal ◽  
Isabel Fradejas Villajos ◽  
Alexandra Martín Ramírez ◽  
Noor Azian Md Yu ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
Low Cost ◽  
Reference Method ◽  
Rapid Identification ◽  
Control Programs ◽  
Specific Pcr ◽  
Antimalarial Resistance ◽  
Allele Specific ◽  
Almost All

Abstract Background The emergence and spread of antimalarial resistance continues to hinder malaria control. Plasmodium falciparum, the species that causes most human malaria cases and most deaths, has shown resistance to almost all known antimalarials. This antimalarial resistance arises from the development and subsequent expansion of Single Nucleotide Polymorfisms (SNPs) in specific parasite genes. A quick and cheap tool for the detection of drug resistance can be crucial and very useful for use in hospitals and in malaria control programs. It has been demonstrated in different contexts that genotyping by Kompetitive Allele Specific PCR (KASP), is a simple, fast and economical method that allows a high-precision biallelic characterization of SNPs, hence its possible utility in the study of resistance in P. falciparum. Methods Three SNPs involved in most cases of resistance to the most widespread antimalarial treatments have been analyzed by PCR plus sequencing and by KASP (C580Y of the Kelch13 gene, Y86N of the Pfmdr1 gene and M133I of the Pfcytb gene). A total of 113 P. falciparum positive samples and 24 negative samples, previously analyzed by PCR and sequencing, were selected for this assay. Likewise, the samples were genotyped for the MSP-1 and MSP-2 genes, and the Multiplicity of Infection (MOI) and parasitaemia were measured to observe their possible influence on the KASP method. Results The KASP results showed the same expected mutations and wild type genotypes as the reference method, with few exceptions that correlated with very low parasitaemia samples. In addition, two cases of heterozygotes that had not been detected by sequencing were found. No correlation was found between the MOI or parasitaemia and the KASP values of the sample. The reproducibility of the technique shows no oscillations between repetitions in any of the three SNPs analyzed. Conclusions The KASP assays developed in our study were efficient and versatile for the determination of the Plasmodium genotypes related to resistance. The method is simple, fast, reproducible with low cost in personnel, material and equipment and scalable, being able to core KASP arrays, including numerous SNPs, to complete the main pattern of mutations associated to P. falciparum resistance.

scholarly journals Diagnosis of tuberculosis in groups of badgers: an exploration of the impact of trapping efficiency, infection prevalence and the use of multiple tests

2016 ◽  
Vol 144 (8) ◽  
pp. 1717-1727 ◽  
Author(s):  
S. N. BUZDUGAN ◽  
M. A. CHAMBERS ◽  
R. J. DELAHAY ◽  
J. A. DREWE
Keyword(s):  
Diagnostic Tests ◽  
Field Studies ◽  
Trapping Efficiency ◽  
Infection Prevalence ◽  
Group Level ◽  
Tuberculosis Control ◽  
Individual Level ◽  
The Individual ◽  
The Impact ◽  
Diagnosis Of Infection

SUMMARYAccurate detection of infection with Mycobacterium bovis in live badgers would enable targeted tuberculosis control. Practical challenges in sampling wild badger populations mean that diagnosis of infection at the group (rather than the individual) level is attractive. We modelled data spanning 7 years containing over 2000 sampling events from a population of wild badgers in southwest England to quantify the ability to correctly identify the infection status of badgers at the group level. We explored the effects of variations in: (1) trapping efficiency; (2) prevalence of M. bovis; (3) using three diagnostic tests singly and in combination with one another; and (4) the number of badgers required to test positive in order to classify groups as infected. No single test was able to reliably identify infected badger groups if <90% of the animals were sampled (given an infection prevalence of 20% and group size of 15 badgers). However, the parallel use of two tests enabled an infected group to be correctly identified when only 50% of the animals were tested and a threshold of two positive badgers was used. Levels of trapping efficiency observed in previous field studies appear to be sufficient to usefully employ a combination of two existing diagnostic tests, or others of similar or greater accuracy, to identify infected badger groups without the need to capture all individuals. To improve on this, we suggest that any new diagnostic test for badgers would ideally need to be >80% sensitive, at least 94% specific, and able to be performed rapidly in the field.

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