Browsing by Author "Rist, Cassidy"

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    Advancing the Global Land Grant Institution: Creating a Virtual Environment to Re-envision Extension and Advance GSS-related Research, Education, and Collaboration
    Hall, Ralph P.; Polys, Nicholas F.; Sforza, Peter M.; Eubank, Stephen D.; Lewis, Bryan L.; Krometis, Leigh-Anne H.; Pollyea, Ryan M.; Schoenholtz, Stephen H.; Sridhar, Venkataramana; Crowder, Van; Lipsey, John; Christie, Maria Elisa; Glasson, George E.; Scherer, Hannah H.; Davis, A. Jack; Dunay, Robert J.; King, Nathan T.; Muelenaer, Andre A.; Muelenaer, Penelope; Rist, Cassidy; Wenzel, Sophie (Virginia Tech, 2017-05-15)
    The vision for this project has emerged from several years of research, teaching, and service in Africa and holds the potential to internationalize education at Virginia Tech and in our partner institutions in Malawi. The vision is simple, to develop a state-of-the-art, data rich, virtual decision-support and learning environment that enables local-, regional-, and national-level actors in developed and developing regions to make decisions that improve resilience and sustainability. Achieving these objectives will require a system that can combine biogeophysical and sociocultural data in a way that enables actors to understand and leverage these data to enhance decision-making at various levels. The project will begin by focusing on water, agricultural, and health systems in Malawi, and can be expanded over time to include any sector or system in any country. The core ideas are inherently scalable...
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    Alternative approaches for creating a wealth index: the case of Mozambique
    Xie, Kexin; Marathe, Achla; Deng, Xinwei; Ruiz-Castillo, Paula; Imputiua, Saimado; Elobolobo, Eldo; Mutepa, Victor; Sale, Mussa; Nicolas, Patricia; Montana, Julia; Jamisse, Edgar; Munguambe, Humberto; Materrula, Felisbela; Casellas, Aina; Rabinovich, Regina; Saute, Francisco; Chaccour, Carlos J.; Sacoor, Charfudin; Rist, Cassidy (BMJ, 2023-08)
    Introduction: The wealth index is widely used as a proxy for a household's socioeconomic position (SEP) and living standard. This work constructs a wealth index for the Mopeia district in Mozambique using data collected in year 2021 under the BOHEMIA (Broad One Health Endectocide-based Malaria Intervention in Africa) project. Methods: We evaluate the performance of three alternative approaches against the Demographic and Health Survey (DHS) method based wealth index: feature selection principal components analysis (PCA), sparse PCA and robust PCA. The internal coherence between four wealth indices is investigated through statistical testing. Validation and an evaluation of the stability of the wealth index are performed with additional household income data from the BOHEMIA Health Economics Survey and the 2018 Malaria Indicator Survey data in Mozambique. Results: The Spearman's rank correlation between wealth index ventiles from four methods is over 0.98, indicating a high consistency in results across methods. Wealth rankings and households' income show a strong concordance with the area under the curve value of ∼0.7 in the receiver operating characteristic analysis. The agreement between the alternative wealth indices and the DHS wealth index demonstrates the stability in rankings from the alternative methods. Conclusions: This study creates a wealth index for Mopeia, Mozambique, and shows that DHS method based wealth index is an appropriate proxy for the SEP in low-income regions. However, this research recommends feature selection PCA over the DHS method since it uses fewer asset indicators and constructs a high-quality wealth index.
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    BOHEMIA: Broad One Health Endectocide-based Malaria Intervention in Africa—a phase III cluster-randomized, open-label, clinical trial to study the safety and efficacy of ivermectin mass drug administration to reduce malaria transmission in two African settings
    Chaccour, Carlos; Casellas, Aina; Hammann, Felix; Ruiz-Castillo, Paula; Nicolas, Patricia; Montaña, Julia; Mael, Mary; Selvaraj, Prashant; Duthaler, Urs; Mrema, Sigilbert; Kakolwa, Mwaka; Lyimo, Issa; Okumu, Fredros; Marathe, Achla; Schürch, Roger; Elobolobo, Eldo; Sacoor, Charfudin; Saute, Francisco; Xia, Kang; Jones, Caroline; Rist, Cassidy; Maia, Marta; Rabinovich, N. R. (2023-02-21)
    Background Residual malaria transmission is the result of adaptive mosquito behavior that allows malaria vectors to thrive and sustain transmission in the presence of good access to bed nets or insecticide residual spraying. These behaviors include crepuscular and outdoor feeding as well as intermittent feeding upon livestock. Ivermectin is a broadly used antiparasitic drug that kills mosquitoes feeding on a treated subject for a dose-dependent period. Mass drug administration with ivermectin has been proposed as a complementary strategy to reduce malaria transmission. Methods A cluster randomized, parallel arm, superiority trial conducted in two settings with distinct eco-epidemiological conditions in East and Southern Africa. There will be three groups: human intervention, consisting of a dose of ivermectin (400 mcg/kg) administered monthly for 3 months to all the eligible population in the cluster (>15 kg, non-pregnant and no medical contraindication); human and livestock intervention, consisting human treatment as above plus treatment of livestock in the area with a single dose of injectable ivermectin (200 mcg/kg) monthly for 3 months; and controls, consisting of a dose of albendazole (400 mg) monthly for 3 months. The main outcome measure will be malaria incidence in a cohort of children under five living in the core of each cluster followed prospectively with monthly RDTs Discussion The second site for the implementation of this protocol has changed from Tanzania to Kenya. This summary presents the Mozambique-specific protocol while the updated master protocol and the adapted Kenya-specific protocol undergo national approval in Kenya. BOHEMIA will be the first large-scale trial evaluating the impact of ivermectin-only mass drug administration to humans or humans and cattle on local malaria transmission.
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    The Burden of Livestock Parasites on the Poor
    Rist, Cassidy; Garchitorena, Andres; Ngonghala, Calistus N.; Gillespie, Thomas R.; Bonds, Matthew H. (2015-11)
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    The Effects of Land Cover Change on the Spatial Distribution of Lyme disease in Northern Virginia Since 2005
    Stevenson, Megan N. (Virginia Tech, 2019-10-11)
    Lyme disease has been a growing problem in the United States over the last few decades, and is currently the most common vector-borne disease in the country. This research evaluates the land cover within specified counties of northern Virginia to determine if a correlation exists between forest fragmentation, suburbanization, and cases of human Lyme disease as has been demonstrated in other Lyme endemic regions in the United States. Few studies have focused specifically on northern Virginia when considering the impacts of land cover change on Lyme disease. Discovered through the use of geospatial and statistical analysis, the cluster of Lyme disease cases in northern Virginia are associated with forest fragmentation within the study region, which creates an ideal habitat for black-legged ticks and the white-footed mouse, allowing for an increase in Lyme disease transfer from vector to humans. The goal is for the research findings to be applicable to other regions with similar land cover types. Regions with similar characteristics would then be able to recognize the potential risk of human Lyme disease and implement ways to reduce the Lyme disease risk associated with suburban development. The purpose of this study is to answer the following research questions: 1) How has the spatial distribution of Lyme disease in Northern Virginia changed since 2005 with respect to land cover? 2) Which suburban communities are more at risk for Lyme disease when considering their land cover types and the increasing spatial distribution of Lyme disease?
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    Environmental Fate of Ivermectin and its biological metabolites in Soils: Potential implications for the Environmental Impact of Ivermectin Mass Drug Administration for Malaria Control
    Shija, Gerald Enos (Virginia Tech, 2023-02-02)
    Despite significant vector control advancements in the past years, the current malaria trends suggest that new control strategies are urgently required. These new approaches should address the current frontline intervention challenges like increasing insecticide resistance in mosquitoes and residual transmission issues. Insecticide-treated livestock (ITL) is one of the novel potential strategies to overcome the above challenges. ITL involves treating livestock near humans with an insecticide like ivermectin (IVM) to kill zoophagic malaria vectors. However, ivermectin pharmacokinetics data suggests that most IVM-administered drugs remain intact, and more than 90 % of this drug is eliminated in feces. Biological metabolites: 3′′-O-demethylivermectin (3DI) and 24-hydroxymethyl ivermectin (24OHI) are also excreted in feces. Therefore, using manure from treated cattle as fertilizers contaminates the soil, ground, and surface water with IVM or its metabolites through leaching and hydraulic water flow affecting the soil and aquatic ecosystems. Contemplating the contamination impacts, these drugs' environmental fate and effects could be regarded before massive IVM applications. Many researchers have tried to address this subject in temperate regions compared to the tropics, where IVM is urgently needed. Regional discrepancies such as soil types and climate can independently and dependently determine the fate and impact of ivermectin. Our research investigates the environmental fate of IVM and its primary biological metabolites. Laboratory and field studies in Tanzania and Virginia were conducted to simulate the difference between tropical and temperate climates. Soil and soil-manure mixture spiked with IVM were layered into two 5 mm layers in columns exposed to natural sunlight. The remaining IVM and its primary metabolite were quantified using Liquid Chromatography with a tandem mass spectrometry detector (LC-MS/MS. These compounds degraded up to 1.5 times faster in Tanzania than in Virginia, depending on temperature, soil depths and type, organic matter, and soil moisture. When IVM is subcutaneously injected into cattle, drug residues and metabolites: 3DI and 24OHI are excreted in feces following a positive skewed Poisson distribution profile. IVM, 3DI, and 24OH were found to degrade rapidly when cattle pats when exposed to the field. Since we conducted our study in the Summer, no IVM or its metabolites leached into the soil beneath. The obtained half-lives suggest that ivermectin's massive drug administration has little to worry about, primarily when the dung from treated cattle is spread into the field in thin layers in the Summer before farm application.
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    The Impact of Ivermectin Treatment in Cattle on Dung Degradation and Fauna Abundance and Diversity in Tanzania
    Ruhinda, Miriam Shani (Virginia Tech, 2023-06-08)
    Ivermectin also called the wonder drug has been used over the years to control internal and external parasites in livestock. In humans it has been used for the control of several neglected tropical diseases. With regards to efforts to control malaria, mass drug administration (MDA) of ivermectin in humans and livestock has been considered as a potential tool. This is due to challenges in malaria preventive strategies such as insecticide resistance in mosquitoes, shift in their behaviors and residual transmission. Ivermectin reduces malaria transmission by targeting the mosquito nervous system resulting in their death. Ivermectin and its metabolites could have great impacts on the environment as well as human and health. In temperate settings, impacts of ivermectin in the environment were studied due to intense use of the drug in livestock. There is also a necessity to study effects of ivermectin in the tropics before MDA for malaria vector control. Despite its great potential, previous studies done recorded toxicity and sensitivity of the drug to most arthropods mainly dung organisms because ivermectin is released in dung at high concentrations for the case of livestock. With dung organism activity being affected the dung decomposition process is disrupted, cattle avoid these grazing areas leading to financial losses. In the tropics where there is a high number of malaria cases, there is no information on the impacts of the drug in the environment. We placed standardized dung pats from ivermectin-treated and control cattle to determine the effect of ivermectin on dung degradation and dung fauna in Tanzania. For the dung degradation study, at 15, 30 and 45 days post placement, we observed a total of 220 dung pats in the field. We measured termite colonization; wet weight of the entire pat; water content; dry weight of the 10 g subsamples and organic matter from subsamples and the whole pat. For the dung fauna study, we collected fresh dung 3, 10 and 29 days post treatment and put the pats out in the field to be colonized by insects before being transferred to emergence traps. We also did a semi field study where we collected dung pats 1,2,3 and 5 days post treatment to obtain larvae counts. We qualitatively assessed insect larvae activity in the field experiment and observed and counted larvae in the semi field study. We found that termites colonized pats from cattle treated with ivermectin more readily compared to controls (p < 0.001). Compared to control pats, the treated pats' wet weight decreased more slowly on day 15 (p < 0.001), day 30 (p < 0.001), and on day 45 (p = 0.037). Percent dry weight increased over time and similarly between the treatments as water content decreased. Organic matter of the 10g sub samples was similar between the treatments. Total organic matter in the whole pats showed significant differences on day 15 (p < 0.001), and day 30 (p = 0.003), but not on day 45 (p = 0.291). Qualitatively, we observed that pats from treated cattle had less insect larvae activity as compared to controls in the field study. In the semi field study, we counted less larvae in the pats from ivermectin-treated cattle than in the control pats (p < 0.001). Our results indicate that ivermectin and its residues affect dung degradation and dung fauna in tropical savanna settings, and the environmental safety may be at risk upon mass drug administration in livestock.
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    Insecticide-treated livestock: a potential One Health approach to malaria control in Africa
    Ruiz-Castillo, Paula; Rist, Cassidy; Rabinovich, Regina; Chaccour, Carlos J. (Elsevier, 2022-02-01)
    New vector-control tools are urgently needed to reduce malaria in areas where there is significant transmission after deployment of indoor residual spraying (IRS) and insecticide treated nets. Insecticide-treated livestock (ITL) is a potential novel strategy by which zoophagic mosquitos are killed after feeding upon animals treated with an insecticide. Although there are several insecticide candidates in the pipeline with a wide efficacy range against mosquitos, additional field studies with epidemiological outcomes are required to test the impact of this intervention on malaria transmission. Insecticides under consideration have long been used in livestock to improve animal health and productivity, but each has food and environmental safety considerations. Therefore, moving ITL from a concept to implementation will require a One Health framework.
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    Integrative Analyses of Environmental Factors Impacting Animal and Human Health Through Perturbations of Microbial Communities
    Caswell, Clayton C.; Ahmed, S. Ansar; Sriranganathan, Nammalwar; Allen, Irving C.; Luo, Xin; Meng, Xiang-Jin; Theus, Michelle H.; Yuan, Lijuan; Hungerford, Laura L.; Pierson, Bill; Rist, Cassidy (Virginia Tech, 2017-05-15)
    The term ‘microbiome’ defines the vast microscopic communities collectively composed of bacteria, viruses, fungi, and eukaryotic protozoans that inhabit myriad niches, including environmental locales, as well as the surfaces and organ systems of animals and humans. Recent empirical evidence clearly demonstrates the substantial role that microbiomes play in facilitating the homeostasis of complex biological systems, and as such, perturbation of these microbial communities can lead to dysregulation of environmental ecosystems, significant declines in animal and human health, and the emergence of detrimental conditions, such as infectious diseases, inflammatory disorders, and neurodegenerative aliments. A variety of factors are involved in shifting the composition and complexity (i.e., the functionality) of microbiomes, including the contamination of soil, water, and food sources with toxicants, pharmaceuticals, and antimicrobial compounds...
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    Livestock and avermectins in Sub-Saharan Africa: protocol for a restricted systematic review of the impacts on productivity and documentation of resistance
    Rist, Cassidy; Zheng, Rose; DeBose, Kyrille (Virginia Tech, 2020-07-13)
    This document provides the protocol for a restricted systematic review (rapid review) intended to summarize the impacts of avermectins on livestock productivity and document resistance to avermectins in livestock in Sub-Saharan Africa. The protocol is written in alignment with the PRISMA-P statement, with modifications for a restricted systematic review.
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    Mapping the potential use of endectocide-treated cattle to reduce malaria transmission
    Imbahale, Susan S.; Montana Lopez, Julia; Brew, Joe; Paaijmansz, Krijn; Rist, Cassidy; Chaccour, Carlos J. (Springer Nature, 2019-04-09)
    Treating cattle with endectocide is a longstanding veterinary practice to reduce the load of endo and ectoparasites, but has the potential to be added to the malaria control and elimination toolbox, as it also kills malaria mosquitoes feeding on the animals. Here we used openly available data to map the areas of the African continent where high malaria prevalence in 2-10 year old children coincides with a high density of cattle and high density of the partly zoophilic malaria vector Anopheles arabiensis. That is, mapping the areas where treating cattle with endectocide would potentially have the greatest impact on reducing malaria transmission. In regions of Africa that are not dominated by rainforest nor desert, the map shows a scatter of areas in several countries where this intervention shows potential, including central and eastern sub-Saharan Africa. The savanna region underneath the Sahel in West Africa appears as the climatic block that would benefit to the largest extent from this intervention, encompassing several countries. West Africa currently presents the highest under-10 malaria prevalence and elimination within the next twenty years cannot be contemplated there with currently available interventions alone, making the use of endectocide treated cattle as a complementary intervention highly appealing.
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    Modeling the burden of poultry disease on the rural poor in Madagascar
    Rist, Cassidy; Ngonghala, Calistus N.; Garchitorena, Andres; Brook, Cara E.; Ramananjato, Ranto; Miller, Ann C.; Randrianarivelojosia, Milijaona; Wright, Patricia C.; Gillespie, Thomas R.; Bonds, Matthew H. (2015-12)
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    One Health Approach to Emerging Viral and Vector-borne Diseases
    Bertke, Andrea S.; Paulson, Sally L.; Rist, Cassidy; Kolivras, Korine N.; Hungerford, Laura L.; Alexander, Kathleen A.; Ragan, Valerie; Gohlke, Julia M. (Virginia Tech, 2017-05-15)
    Understanding the spatial and temporal distribution of novel infectious diseases is among the most important and challenging tasks for the coming century. Emerging viral and vector-borne diseases are a significant threat to humans, animals, and plants across the globe. In the previous 40 years, the number of new emergent pathogens affecting humans have increased more than 300%. Approximately 60% of these organisms are zoonotic, transferred to humans from animals, and the number of vector-borne pathogens have increased more than 300% in the same time frame. Viruses affecting plants impact agricultural food sources, as well as regional and global economies. Understanding how these pathogens emerge and evolve, transmit from animals to humans and adapt to new hosts to increase morbidity and mortality, spread geospatially and temporally through regions or the global community, and how human behavior and beliefs impact these processes are of critical importance...
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    The potential health impact of ivermectin mass drug administration for malaria control on swine in Mozambique
    Assenga, Alphonce Alexander (Virginia Tech, 2023-01-23)
    BACKGROUND: Both endo- and ectoparasites pose a great challenge to the health of pigs worldwide, placing a significant burden on low-resource countries where veterinary care is minimal. As part of a larger clinical trial assessing the use of ivermectin (IVM) mass drug administration to humans and pigs for the control of malaria vectors in the Mopeia district in Mozambique, a longitudinal study to assess the impact of IVM administration on pig health was performed. METHODS: Beginning in March 2022, IVM was administered to pigs in the intervention area once a month for three consecutive months. Seventy pigs from the treatment group and 70 pigs from the control group were randomly selected for inclusion in the study. Fecal samples were collected monthly for three months and analyzed for the presence of strongyle eggs, strongyle eggs in the larval stage (strongyles – larval) and Ascaris suum using the modified McMaster test. Fecal samples were also collected two weeks after each dose of IVM was given to pigs in the treatment group for determination of a fecal egg reduction count. Juvenile pigs were measured twice a month for the first 3 months of the study, then once monthly for another three months. Visual exam for ectoparasites was performed on all pigs for the presence of ticks, lice or scabies at the same time points. RESULTS: Overall, 55% [95% CI: 48-62%] of pigs were positive for Ascaris suum, 95.2% [95% CI: 91-98%] were positive for strongyle eggs, and 72.5% [95% CI: 65.5-79%] were positive for strongyle – larval. A significant difference in the ivermectin treatment group was only seen one month after the second dose of ivermectin was administered: pigs in the treatment group had a 23.6% lower prevalence of strongyles (p = 0.003) and 18% lower prevalence of strongyles – larval (p = 0.03). Pigs in the treatment group also had lower EPG for Ascaris suum (diff = 102 EPG; p = 0.006), strongyles (diff = 642 EPG; p < 0.001), and strongyles - larval (diff = 217 EPG; p < 0.001). Analysis of covariance regression found no significant difference(P>0.05) in average daily weight gain (ADG) between the treatment and control groups. CONCLUSION: IVM delivered once monthly for three months has a small impact on pig health. To counteract the multiple health challenges pigs face in these settings, different dosing schedules along with education on husbandry issues related to nutrition and sanitation should be investigated in order to maximize impact on pig health.
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    Potential impact of 5 years of ivermectin mass drug administration on malaria outcomes in high burden countries
    Marathe, Achla; Shi, Ruoding; Mendez-Lopez, Ana; Hu, Zhihao; Lewis, Bryan L.; Rabinovich, Regina; Chaccour, Carlos J.; Rist, Cassidy (2021-11)
    Introduction The global progress against malaria has slowed significantly since 2017. As the current malaria control tools seem insufficient to get the trend back on track, several clinical trials are investigating ivermectin mass drug administration (iMDA) as a potential additional vector control tool; however, the health impacts and cost-effectiveness of this new strategy remain unclear. Methods We developed an analytical tool based on a full factorial experimental design to assess the potential impact of iMDA in nine high burden sub-Saharan African countries. The simulated iMDA regimen was assumed to be delivered monthly to the targeted population for 3 months each year from 2023 to 2027. A broad set of parameters of ivermectin efficacy, uptake levels and global intervention scenarios were used to predict averted malaria cases and deaths. We then explored the potential averted treatment costs, expected implementation costs and cost-effectiveness ratios under different scenarios. Results In the scenario where coverage of malaria interventions was maintained at 2018 levels, we found that iMDA in these nine countries has the potential to reverse the predicted growth of malaria burden by averting 20-50 million cases and 36 000-90 000 deaths with an assumed efficacy of 20%. If iMDA has an efficacy of 40%, we predict between 40-99 million cases and 73 000-179 000 deaths will be averted with an estimated net cost per case averted between US$2 and US$7, and net cost per death averted between US$1460 and US$4374. Conclusion This study measures the potential of iMDA to reverse the increasing number of malaria cases for several sub-Saharan African countries. With additional efficacy information from ongoing clinical trials and country-level modifications, our analytical tool can help determine the appropriate uptake strategies of iMDA by calculating potential marginal gains and costs under different scenarios.