Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Hedge J[original query] |
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Novel Wolbachia strains in Anopheles malaria vectors from Sub-Saharan Africa (preprint)
Jeffries CL , Lawrence GG , Golovko G , Kristan M , Orsborne J , Spence K , Hurn E , Bandibabone J , Tantely LM , Raharimalala FN , Keita K , Camara D , Barry Y , Wat'senga F , Manzambi EZ , Afrane YA , Mohammed AR , Abeku TA , Hedge S , Khanipov K , Pimenova M , Fofanov Y , Boyer S , Irish SR , Hughes GL , Walker T . bioRxiv 2018 338434 Anopheles (An.) mosquitoes contain bacteria that can influence Plasmodium parasites. Wolbachia, a common insect endosymbiont, has historically been considered absent from Anopheles but has recently been found in An. gambiae populations. Here, we assessed a range of Anopheles species from five malaria-endemic countries for Wolbachia and Plasmodium infection. Strikingly, we found Wolbachia infections in An. coluzzii, An. gambiae s.s, An. arabiensis, An. moucheti and An. species ‘A’ increasing the number of Anopheles species known to be naturally infected by this endosymbiont. Molecular analysis suggests the presence of phylogenetically diverse novel strains, while qPCR and 16S rRNA sequencing indicates that Wolbachia is the dominant member of the microbiota in An. moucheti and An. species ‘A’. We found no evidence of Wolbachia/Asaia co-infections, and presence of these endosymbionts did not have significant effects on malaria prevalence. We discuss the importance of novel Wolbachia strains in Anopheles and potential implications for disease control. |
Ideational factors associated with consistent use of insecticide-treated nets: a multi-country, multilevel analysis
Babalola S , Kumoji K , Awantang GN , Oyenubi OA , Toso M , Tsang S , Bleu T , Achu D , Hedge J , Schnabel DC , Cash S , Van Lith LM , McCartney-Melstad AC , Nkomou Y , Dosso A , Lahai W , Hunter GC . Malar J 2022 21 (1) 374 BACKGROUND: Malaria remains a major cause of morbidity and mortality in sub-Saharan Africa. Using insecticide-treated nets (ITNs) every night, year-round is critical to maximize protection against malaria. This study describes sociodemographic, psychosocial, and household factors associated with consistent ITN use in Cameroon, Côte d'Ivoire and Sierra Leone. METHODS: Cross-sectional household surveys employed similar sampling procedures, data collection tools, and methods in three countries. The survey sample was nationally representative in Côte d'Ivoire, representative of the North and Far North regions in Cameroon, and representative of Bo and Port Loko districts in Sierra Leone. Analysis used multilevel logistic regression and sociodemographic, ideational, and household independent variables among households with at least one ITN to identify correlates of consistent ITN use, defined as sleeping under an ITN every night the preceding week. FINDINGS: Consistent ITN use in Côte d'Ivoire was 65.4%, 72.6% in Cameroon, and 77.1% in Sierra Leone. While several sociodemographic and ideational variables were correlated with consistent ITN use, these varied across countries. Multilevel logistic regression results showed perceived self-efficacy to use ITNs and positive attitudes towards ITN use were variables associated with consistent use in all three countries. The perception of ITN use as a community norm was positively linked with consistent use in Cameroon and Côte d'Ivoire but was not significant in Sierra Leone. Perceived vulnerability to malaria was positively linked with consistent use in Cameroon and Sierra Leone but negatively correlated with the outcome in Côte d'Ivoire. Household net sufficiency was strongly and positively associated with consistent use in all three countries. Finally, the findings revealed strong clustering at the household and enumeration area (EA) levels, suggesting similarities in net use among respondents of the same EA and in the same household. CONCLUSIONS: There are similarities and differences in the variables associated with consistent ITN use across the three countries and several ideational variables are significant. The findings suggest that a social and behaviour change strategy based on the ideation model is relevant for increasing consistent ITN use and can inform specific strategies for each context. Finally, ensuring household net sufficiency is essential. |
Novel Wolbachia strains in Anopheles malaria vectors from Sub-Saharan Africa.
Jeffries CL , Lawrence GG , Golovko G , Kristan M , Orsborne J , Spence K , Hurn E , Bandibabone J , Tantely LM , Raharimalala FN , Keita K , Camara D , Barry Y , Wat'senga F , Manzambi EZ , Afrane YA , Mohammed AR , Abeku TA , Hedge S , Khanipov K , Pimenova M , Fofanov Y , Boyer S , Irish SR , Hughes GL , Walker T . Wellcome Open Res 2018 3 113 Background: Wolbachia, a common insect endosymbiotic bacterium that can influence pathogen transmission and manipulate host reproduction, has historically been considered absent from the Anopheles (An.) genera, but has recently been found in An. gambiae s.l. populations. As there are numerous Anopheles species that have the capacity to transmit malaria, we analysed a range of species to determine Wolbachia prevalence rates, characterise novel Wolbachia strains and determine any correlation between the presence of Plasmodium, Wolbachia and the competing endosymbiotic bacterium Asaia. Methods: Anopheles adult mosquitoes were collected from five malaria-endemic countries: Guinea, Democratic Republic of the Congo (DRC), Ghana, Uganda and Madagascar, between 2013 and 2017. Molecular analysis of samples was undertaken using quantitative PCR, Sanger sequencing, Wolbachia multilocus sequence typing (MLST) and high-throughput amplicon sequencing of the bacterial 16S rRNA gene. Results: Novel Wolbachia strains were discovered in five species: An. coluzzii, An. gambiae s.s., An. arabiensis, An. moucheti and An. species 'A', increasing the number of Anopheles species known to be naturally infected. Variable prevalence rates in different locations were observed and novel strains were phylogenetically diverse, clustering with Wolbachia supergroup B strains. We also provide evidence for resident strain variants within An. species 'A'. Wolbachia is the dominant member of the microbiome in An. moucheti and An. species 'A', but present at lower densities in An. coluzzii. Interestingly, no evidence of Wolbachia/Asaia co-infections was seen and Asaia infection densities were also shown to be variable and location dependent. Conclusions: The important discovery of novel Wolbachia strains in Anopheles provides greater insight into the prevalence of resident Wolbachia strains in diverse malaria vectors. Novel Wolbachia strains (particularly high-density strains) are ideal candidate strains for transinfection to create stable infections in other Anopheles mosquito species, which could be used for population replacement or suppression control strategies. |
An animal model of marginal iodine deficiency during development: the thyroid axis and neurodevelopmental outcome
Gilbert ME , Hedge JM , Valentin-Blasini L , Blount BC , Kannan K , Tietge J , Zoeller RT , Crofton KM , Jarrett JM , Fisher JW . Toxicol Sci 2013 132 (1) 177-95 Thyroid hormones (THs) are essential for brain development, and iodine is required for TH synthesis. Environmental chemicals that perturb the thyroid axis result in modest reductions in TH, yet there is a paucity of data on the extent of neurological impairments associated with low-level TH disruption. This study examined the dose-response characteristics of marginal iodine deficiency (ID) on parameters of thyroid function and neurodevelopment. Diets deficient in iodine were prepared by adding 975, 200, 125, 25, or 0 microg/kg potassium iodate to the base casein diet to produce five nominal iodine levels ranging from ample (Diet 1: 1000 microg iodine/kg chow, D1) to deficient (Diet 5: 25 microg iodine/kg chow, D5). Female Long Evans rats were maintained on these diets beginning 7 weeks prior to breeding until the end of lactation. Dams were sacrificed on gestational days 16 and 20, or when pups were weaned on postnatal day (PN) 21. Fetal tissue was harvested from the dams, and pups were sacrificed on PN14 and PN21. Blood, thyroid gland, and brain were collected for analysis of iodine, TH, and TH precursors and metabolites. Serum and thyroid gland iodine and TH were reduced in animals receiving two diets that were most deficient in iodine. T4 was reduced in the fetal brain but was not altered in the neonatal brain. Neurobehavior, assessed by acoustic startle, water maze learning, and fear conditioning, was unchanged in adult offspring, but excitatory synaptic transmission was impaired in the dentate gyrus in animals receiving two diets that were most deficient in iodine. A 15% reduction in cortical T4 in the fetal brain was sufficient to induce permanent reductions in synaptic function in adults. These findings have implications for regulation of TH-disrupting chemicals and suggest that standard behavioral assays do not readily detect neurotoxicity induced by modest developmental TH disruption. |
Marginal iodide deficiency and thyroid function: dose-response analysis for quantitative pharmacokinetic modeling
Gilbert ME , McLanahan ED , Hedge J , Crofton KM , Fisher JW , Valentin-Blasini L , Blount BC . Toxicology 2011 283 (1) 41-8 Severe iodine deficiency (ID) results in adverse health outcomes and remains a benchmark for understanding the effects of developmental hypothyroidism. The implications of marginal ID, however, remain less well known. The current study examined the relationship between graded levels of ID in rats and serum thyroid hormones, thyroid iodine content, and urinary iodide excretion. The goals of this study were to provide parametric and dose-response information for development of a quantitative model of the thyroid axis. Female Long Evans rats were fed casein-based diets containing varying iodine (I) concentrations for 8 weeks. Diets were created by adding 975, 200, 125, 25, or 0 mcg/kg I to the base diet ( approximately 25 mcg I/kg chow) to produce 5 nominal I levels, ranging from excess (basal+added I, Treatment 1: 1000 mcg I/kg chow) to deficient (Treatment 5: 25 mcg I/kg chow). Food intake and body weight were monitored throughout and on 2 consecutive days each week over the 8-week exposure period, animals were placed in metabolism cages to capture urine. Food, water intake, and body weight gain did not differ among treatment groups. Serum T4 was dose-dependently reduced relative to Treatment 1 with significant declines (19 and 48%) at the two lowest I groups, and no significant changes in serum T3 or TSH were detected. Increases in thyroid weight and decreases in thyroidal and urinary iodide content were observed as a function of decreasing I in the diet. Data were compared with predictions from a recently published biologically based dose-response (BBDR) model for ID. Relative to model predictions, female Long Evans rats under the conditions of this study appeared more resilient to low I intake. These results challenge existing models and provide essential information for development of quantitative BBDR models for ID during pregnancy and lactation. |
Can we "hedge" against the development of antiviral resistance among pandemic influenza viruses?
Shay DK , Ridenhour BJ . PLoS Med 2009 6 (6) e1000103 David K. Shay and Benjamin Ridenhour discuss a modeling study predicting that stockpiling a secondary antiviral for use early in a flu pandemic can forestall resistance to the primary stockpiled drug. |
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