Publications by authors named "R Brent Thomson"

1,463 Publications

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Eliminating onchocerciasis within the Meme River Basin of Cameroon: A social-ecological approach to understanding everyday realities and health systems.

PLoS Negl Trop Dis 2021 Jun 2;15(6):e0009433. Epub 2021 Jun 2.

Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.

Background: Onchocerciasis affects some of the world's most marginalized people, perpetuating poverty and inequalities. Mass Drug Administration (MDA) with Ivermectin has taken place within the Meme River basin region in Cameroon for over 15 years. Despite this, onchocerciasis is still prevalent in the region due to existing and emerging contextual challenges. Using a social-ecological approach we explore the everyday realities of communities, highlighting the challenges and potential solutions that could support Neglected Tropical Disease (NTD) programmes when transitioning from control to elimination of onchocerciasis in this highly endemic area and other similar communities.

Methodology/principal Finding: In-depth interviews (71) with community members and Community Drug Distributors (CDDs) were conducted to understand current knowledge, attitudes, and behaviours in relation to transmission, prevention and treatment of onchocerciasis. Through application of the social-ecological model, four key themes were identified: 1. Contextual factors on health promotion interventions (Onchocerciasis history and understanding of the disease, prevention and mitigation strategies and MDA experience); 2. Social determinants (poverty and livelihoods, economic and social impacts on CDD volunteers and stigma); 3. Environmental determinants (exposure, housing, occupation and poverty); and 4. health seeking pathways and decision making for treatment (access, cost and preferable treatment routes). We discuss these core and cross cutting themes (gender differences and community participation/ownership) in relation to intersectoral collaboration, gender equity and health systems support, making recommendations for NTD programmes within the context of integrated and interdisciplinary approaches. These include the need for; intersectional and gender analysis at the local level, addressing environmental dimensions of onchocerciasis through integrated and regular health promotion, vector control strategies and access to safe water sources; reflection and action that embeds responses to social and economic barriers to MDA; integrated case detection and management that is responsive to onchocerciasis symptoms and related stigma and a fair and just support network for CDDs.

Conclusion/significance: NTD programmes need to respond to diverse community circumstances and behaviours. Communities are not a homogeneous risk group and treating them in this way will delay elimination. A deeper understanding of individual needs and their capacity to seek prevention and treatment must be considered if onchocerciasis is to be eliminated and the remaining impacts managed.
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http://dx.doi.org/10.1371/journal.pntd.0009433DOI Listing
June 2021

Prevalence and factors associated with hypertension among people living with HIV/AIDS on antiretroviral therapy in Uganda.

Pan Afr Med J 2021 25;38:216. Epub 2021 Feb 25.

School of Medicine, University of California at San Francisco, San Francisco, United States of America.

Introduction: antiretroviral therapy (ART) has improved survival of People Living with HIV (PLWH); however, this has resulted in an increasingly high prevalence of non-communicable diseases (NCD) like hypertension. Hypertension is a major risk factor for cardiovascular and cerebral vascular disease, which are both associated with high morbidity and mortality rates. We studied the prevalence and factors associated with hypertension among PLWH on ART.

Methods: we conducted a retrospective data analysis of PLWH on ART enrolled between 2011 and 2014 into a randomized double-blinded placebo-controlled trial investigating the safety of discontinuing cotrimoxazole prophylaxis (COSTOP) among PLWH in Central Uganda. We used the mean blood pressure (BP) measurements of the first four monthly clinic visits to define hypertension. Patients were categorised as: having normal BP (≤120/80mmHg), elevated BP (systolic >120-129, and diastolic ≤80), Stage 1 hypertension (systolic 130-139, or diastolic >80-89) and Stage 2 hypertension (systolic ≥140 or diastolic ≥90). Multiple logistic regression was used to evaluate factors associated with hypertension.

Results: data from 2026 COSTOP trial study participants were analysed, 74.1% were women and 77.2% were aged 35 years and above. The overall prevalence of hypertension was 29%, of whom 19.5% had Stage 1 hypertension and 9.5% had Stage 2 hypertension. About 21.4% were overweight or obese. Factors independently associated with hypertension among PLWH on ART included increasing age (p≤0.001) and high body mass index (p≤0.001). Efavirenz (p≤0.001) and lopinavir/ritonavir (p=0.036) based regimen had lower odds of hypertension than Nevirapine based regimens.

Conclusion: PLWH on ART have a high prevalence of hypertension, which rises with increasing age and body mass index (BMI) and among those on nevirapine-based ART. Implementation of hypertension prevention measures among PLWH on ART and integration of NCD and HIV care to improve patients' management outcomes are required.
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http://dx.doi.org/10.11604/pamj.2021.38.216.28034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8140674PMC
June 2021

High spatial resolution dosimetry with uncertainty analysis using Raman micro-spectroscopy readout of radiochromic films.

Med Phys 2021 May 27. Epub 2021 May 27.

Department of Physics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada.

Purpose: The purpose of this work is to develop a new approach for high spatial resolution dosimetry based on Raman micro-spectroscopy scanning of radiochromic film (RCF). The goal is to generate dose calibration curves over an extended dose range from 0-50 Gy and with improved sensitivity to low (< 2 Gy) doses, in addition to evaluating the uncertainties in dose estimation associated with the calibration curves.

Methods: Samples of RCF (EBT3) were irradiated at a broad dose-range of 0.03 Gy-50 Gy using an Elekta Synergy clinical linear accelerator. Raman spectra were acquired with a custom-built Raman micro-spectroscopy setup involving a 500 mW, multimode 785 nm laser focused to a lateral spot diameter of 30 µm on the RCF. The depth of focus of 34 µm enabled the concurrent collection of Raman spectra from the RCF active layer and the polyester laminate. The pre-processed Raman spectra were normalized to the intensity of the 1614 cm Raman peak from the polyester laminate that was unaltered by radiation. The mean intensities and the corresponding standard deviation of the active layer Raman peaks at 696, 1445 and 2060 cm were determined for the 150 × 100 µm scan area per dose value. This was used to generate three calibration curves that enabled the conversion of the measured Raman intensity to dose values. The experimental, fitting and total dose uncertainty was determined across the entire dose range for the dosimetry system of Raman micro-spectroscopy and RCF.

Results: In contrast to previous work that investigated the Raman response of RCFs using different methods, high resolution in the dose response of the RCF, even down to 0.03 Gy, was obtained in this study. The dynamic range of the calibration curves based on all three Raman peaks in the RCF extended up to 50 Gy with no saturation. At a spatial resolution of 30 × 30 µm , the total uncertainty in estimating dose in the 0.5 Gy to 50 Gy dose range was [6 - 9]% for all three Raman calibration curves. This consisted of the experimental uncertainty of [5 - 8]%, and the fitting uncertainty of [2.5 - 4.5]%. The main contribution to the experimental uncertainty was determined to be from the scan area inhomogeneity which can be readily reduced in future experiments. The fitting uncertainty could be reduced by performing Raman measurements on RCF samples at further intermediate dose values in the high and low dose range.

Conclusions: The high spatial resolution experimental dosimetry technique based on Raman micro-spectroscopy and RCF presented here, could become potentially useful for applications in microdosimetry to produce meaningful dose-estimates in cellular targets, as well as for applications based on small field dosimetry that involve high dose gradients.
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http://dx.doi.org/10.1002/mp.15000DOI Listing
May 2021

Ecological engineering across a temporal gradient: Sociable weaver colonies create year-round animal biodiversity hotspots.

J Anim Ecol 2021 May 26. Epub 2021 May 26.

FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch, South Africa.

Animal distribution in a landscape depends mostly on the availability of resources. This can be facilitated by other species that have positive effects on local species diversity and impact community structure. Species that significantly change resource availability are often termed ecosystem engineers. Identifying these species is key but predicting where they have large or small impacts is an even greater challenge. The stress-gradient hypothesis predicts that the importance of facilitative interactions that shape community structure and function will increase in stressful and harsh environments. In most environments, conditions will fluctuate between harsh and benign periods, yet how the impacts of ecosystem engineers will change in different conditions has received little attention. Monitoring for extended periods will increase the understanding of how engineers may mitigate the extreme differences between changing seasons. We investigated the role of sociable weavers Philetairus socius as ecosystem engineers and examined how the association of species to weaver colonies may vary across a seasonal (temporal) gradient. Sociable weavers build large colonies that are home to hundreds of weaver individuals but also host a wide range of other animal species. We investigated the use of weaver colonies by terrestrial and arboreal vertebrates and birds throughout a calendar year, encompassing harsh and benign periods. We demonstrate that the presence of sociable weaver colonies creates centres of animal activity. Colonies were used by the local Kalahari animal community for foraging, shade, territorial behaviours and roosting sites. Furthermore, animal activity increased with increased primary productivity, but this was not restricted to weaver colonies, suggesting that the importance of colonies does not directionally change across environmental conditions. Our results were not consistent with predictions of the stress-gradient hypothesis across a temporal gradient. We demonstrate the importance of sociable weavers as ecological engineers and the significance of their colonies in structuring the surrounding animal community. Colonies appear to provide a range of different resources for different species. Sociable weaver colonies have large ecological importance to local animal communities and, by mitigating environmental stress, may be increasingly important as human-driven climate change advances.
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http://dx.doi.org/10.1111/1365-2656.13544DOI Listing
May 2021

The mental health of Australian medical practitioners during Covid-19.

Australas Psychiatry 2021 May 19:10398562211010807. Epub 2021 May 19.

Hobart Clinic, Hobart, TAS, Australia.

Objectives: To ascertain whether doctors were experiencing higher rates of distress during Covid-19 and whether this was impacted by demographic factors. Our hypotheses were that being a junior doctor, having a previous mental health diagnosis and treating Covid-19 positive patients would predict higher rates of distress.

Methods: Cross-sectional survey conducted via Survey Monkey. Voluntary participants were recruited from the mailing list of a national-based referral service for doctors to psychiatrists. Distress was measured using the Kessler Psychological Distress Scale (K10). Demographic factors were analysed for predictive value of a higher rating on the K10. Areas of concern in relation to Covid-19 and preference for support services were measured on a Likert scale and compared to levels of distress.

Results: The rate of very high distress was 15%. Being a junior doctor and having a previous mental health diagnosis were predictive factors of a higher K10 score. K10 was not affected by likelihood of contact with Covid-19-positive patients. Social isolation had a larger impact on mental health in the context of a previous psychiatric diagnosis. Face-to-face assessments were preferred.

Conclusions: Rates of distress in doctors have been higher than baseline during Covid-19. Some groups have been particularly vulnerable.
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http://dx.doi.org/10.1177/10398562211010807DOI Listing
May 2021