Biology subjects

De Leo, G. A.

Publications and source records attributed to De Leo, G. A..

11 recordsLinked to original sources

bioRxiv2025

Rice-Fish Co-Culturing for Sustainability, Food Security, and Disease and Poverty Reduction

Over 140 million households cultivate rice worldwide. However, rice production contributes to exceedances of planetary boundaries, such as freshwater use and biogeochemical flows. Additionally, rice-farming families may face increased risk of acquiring schistosomiasis, a parasitic disease transmitted by freshwater snails that contributes to reinforcing cycles of poverty and disease. Using data from 405 households in rural Senegal, we show that children in rice-farming households had higher Schistosoma mansoni prevalence and S. haematobium intensities than non-farming peers. To address this environmental-health challenge, we integrated native Nile Tilapia (Oreochromis niloticus) and African Bonytongue (Heterotis niloticus) into rice fields. The fish thrived, suppressed insects and snail pests, improved soil nutrients, and boosted rice yields by >25% with a net benefit of 1,805-3,415 USD/ha/year (benefit-to-cost ratio = 7.42). Hence, low-input rice-fish co-culturing offers a scalable planetary health solution that simultaneously advances sustainability, nutrition, health, and rural livelihoods. ResumePlus de 140 millions de foyers a travers le monde cultivent du riz. Cependant, cette production exerce une pression importante sur les ressources naturelles, notamment les reserves deau douce. Par ailleurs, les menages pratiquant la riziculture peuvent etre plus exposes au risq ue de bilharziose, une maladie parasitaire transmise par des escargots deau douce, qui contribue au cycle de pauvrete. A partir de donnees collectees aupres de 405 menages dans des villages senegalais, nous montrons que les enfants issus de familles pratiquant la riziculture presentent une prevalence plus elevee dinfection a Shistosoma mansoni et des intensites dinfection a S. haematobium plus importantes que ceux issues de familles ne cultivant pas le riz. Pour remedier a cela, nous avons integre deux especes locales de poissons, le tilapia du Nil (Oreochromis niloticus) et lHeterotis (Heterotis niloticus), dans les rizieres, afin de reduire les population descargots hotes, ameliorer les rendements agricoles et augmenter les revenus. Ces poissons ont montre une bonne croissance, ont contribue a la regulation des insectes et des escargots nuisibles, ont enrichi le sol en nutriments, et accru les rendements rizicoles de plus de 25%, avec un benefice net estime entre 1 805 et 3 415 USD/ha/an (ratio benefice-cout = 7,42). Ainsi, la co-culture riz-poisson a faibles intrants constitue une solution reproductible en faveur de la sante publique, permettant de concilier durabilite, nutrition et amelioration des moyens de subsistance en milieu rural.

ecology↗

bioRxiv2025

Pseudomonas superinfection drives Pf phage transmission within airway infections in patients with cystic fibrosis

Pf bacteriophages, lysogenic viruses that infect Pseudomonas aeruginosa (Pa), are implicated in the pathogenesis of chronic Pa infections; phage-infected (Pf+) strains are known to predominate in people with cystic fibrosis (pwCF) who are older and have more severe disease. However, the transmission patterns of Pf underlying the progressive dominance of Pf+ strains are unclear. In particular, it is unknown whether phage transmission commonly occurs horizontally between bacteria within the airway via viral particles or if Pf+ bacteria are mostly acquired via new Pseudomonas infections. Here, we have studied Pa genomic sequences from 3 patient cohorts totaling 663 clinical isolates from 105 pwCF. We identify Pf+ isolates and analyze transmission patterns of Pf within patients between genetically similar groups of bacteria called "clone types". We find that Pf is predominantly passed down vertically within Pa lineages and rarely via horizontal transfer between clone types within the airway. Conversely, we find extensive evidence of Pa superinfection by a new, genetically distinct Pa that is Pf+. Finally, we find that clinical isolates show reduced activity of the type IV pilus and reduced susceptibility to Pf in vitro. These results cast new light on the transmission of virulence-associated phages in the clinical setting.

microbiology↗

bioRxiv2024

A unifying theoretical framework for tick-borne disease risk to explain conflicting results of exclosure experiments across scales

Disease ecology has focused greatly on determining how changes to biodiversity may drive infectious disease risk for humans. Fencing off experimental areas (exclosures) has been a common experimental approach to assess how removing large-bodied hosts may affect disease risk, especially with tick-borne pathogens (TBPs). However, exclosure experiments have found conflicting results based on the experiments scale, with smaller exclosures tending to increase tick densities inside the exclosure and larger exclosures tending to decrease tick densities inside. Previously, we have lacked a unifying theoretical framework able to reconcile the results of exclosure experiments across spatial scales. We present a spatially explicit model of TBP risk incorporating tick dispersal by small competent mammal hosts which can enter the exclosure and by large incompetent mammal hosts excluded from the exclosure. Our model reproduces the scale-dependence and spatial patterning observed in past exclosure experiments while elucidating their causal mechanisms. Specifically, the modeled exclosures produce high densities of infected ticks near their boundaries, with the densities decreasing towards the exclosures center. Empirical results have found lower tick densities at the exclosures edge than its center, a pattern we demonstrate can also be produced if we additionally allow ticks in their free-living questing stage to disperse.

ecology↗

bioRxiv2024

Marine protected areas promote resilience of kelp forests to marine heatwaves by preserving trophic cascades

Under accelerating threats from climate change impacts, marine protected areas (MPAs) have been proposed as climate adaptation tools to enhance the resilience of marine ecosystems. Yet, debate persists as to whether and how MPAs may promote resilience to climate shocks. Here, we empirically assess whether a network of 85 temperate MPAs in coastal waters promotes resilience against marine heatwaves in Central and Southern California. We use 38 years of satellite-derived kelp cover to test whether MPAs enhance the resistance of kelp forest ecosystems to, and recovery from, the unprecedented 2014-2016 marine heatwave regime. We also leverage a 20-year time series of subtidal community surveys to understand whether protection and recovery of sea urchin predators within MPAs explain emergent patterns in kelp forest resilience through trophic cascades. We find that fully protected MPAs (i.e. no-take marine reserves) significantly enhance the resistance to and recovery of kelp forests to marine heatwaves in Southern California, but not in Central California. Differences in regional responses to the heatwaves may be partly explained by three-level trophic interactions comprising kelp, urchins, and predators of urchins. Urchin abundances in Southern California MPAs are significantly lower within fully protected MPAs during and after the heatwave, while the abundance of their predators are higher. In Central California, there is no significant difference in urchin abundances within protected areas as the current urchin predator, sea otters, are unilaterally protected. Therefore, we provide evidence that fully protected MPAs can be effective climate adaptation tools, but their ability to enhance resilience to extreme climate events depends upon region-specific environmental and ecological dynamics. As nations progress to protect 30% of the oceans by 2030 scientists and managers should consider whether protection will increase resilience to climate-change impacts given their local ecological contexts, and what additional measures may be needed.

ecology↗

bioRxiv2024

Climate variables and urbanization drive changes in the distribution of S. mansoni competent snails in Brazil: novel results from a counterfactual analysis

Schistosomiasis is a neglected tropical disease caused by Schistosoma parasites. Schistosoma are obligate parasites of freshwater Biomphalaria snails, so controlling snail populations is critical to reducing transmission risk. As snails are sensitive to environmental conditions, we expect their distribution is significantly impacted by global change. Here, we leveraged machine learning, remote sensing, and 30 years of snail occurrence records to map the historical and current distribution of competent Biomphalaria throughout Brazil. We identified key features influencing the distribution of suitable habitat and determined how Biomphalaria habitat has changed with climate and urbanization over the last three decades. Our models show that climate change has driven broad shifts in snail host range, whereas expansion of urban and peri-urban areas has driven localized increases in habitat suitability. Elucidating change in Biomphalaria distribution - while accounting for non-linearities that are difficult to detect from local case studies - can help inform schistosomiasis control strategies.

ecology↗

bioRxiv2021

Data-Poor Ecological Risk Assessment of Multiple Stressors

O_LIEcological Risk Assessment is a formal process widely applied to terrestrial, marine, and freshwater ecosystems to evaluate the likelihood of adverse ecological effects occurring as a result of exposure to natural or anthropogenic stressors. For many species, data is sparse and semi-quantitative methodologies provide valuable insight for ecosystem management. Recent statistical developments have improved the quality of these analyses yet a rigorous theoretical framework to assess the cumulative impact of multiple stressors is lacking. C_LIO_LIWe present EcoRAMS, a web application and open-source software module that provides easy-to-use, statistically-robust ecological risk assessments of multiple stressors in data-poor contexts. The software receives attribute scores for two variables (e.g. exposure-sensitivity, productivity-susceptibility, severity-likelihood) via CSV templates and outputs results according to a probabilistic metric of risk. C_LIO_LIWe demonstrate comparative results across a range of assumptions, using simulated and empirical datasets including up to five stressors. Accounting for multiple stressors even when data is limited provides a more detailed analysis of risk that may otherwise be understated in single stressor analyses. C_LIO_LIThis application will allow quantification of risk across data-poor contexts for which statistical results have been previously unavailable. The web app format of EcoRAMS.net lowers the barrier of use for practitioners and scientists at any level of statistical training. C_LI

ecology↗

bioRxiv2021

Modeling the efficacy of CRISPR gene drive for schistosomiasis control

CRISPR gene drives could revolutionize the control of infectious diseases by accelerating the spread of engineered traits that limit parasite transmission in wild populations. While much effort has been spent developing gene drives in mosquitoes, gene drive technology in molluscs has received little attention despite the role of freshwater snails as obligate, intermediate hosts of parasitic flukes causing schistosomiasis - a disease of poverty affecting more than 200 million people worldwide. A successful drive in snails must overcome self-fertilization, which prevents a drives spread. Simultaneous hermaphroditism is a feature of snails - distinct from gene drive model organisms - and is not yet incorporated in gene drive models of disease control. Here we developed a novel population genetic model accounting for snails sexual and asexual reproduction, susceptibility to parasite infection regulated by multiple alleles, fitness differences between genotypes, and a range of drive characteristics. We then integrated this model with an epidemiological model of schistosomiasis transmission and snail population dynamics. Simulations showed that gene drive establishment can be hindered by a variety of biological and ecological factors, including selfing. However, our model suggests that, under a range of conditions, gene drive mediated immunity in snails could maintain rapid disease reduction achieved by annual chemotherapy treatment of the human population, leading to long-term elimination. These results indicate that gene drives, in coordination with existing public health measures, may become a useful tool to reduce schistosomiasis burden in selected transmission settings with effective CRISPR construct design and close evaluation of the genetic and ecological landscape.

genetics↗

bioRxiv2021

Identifying low risk insecticides to address both food shortages and the biocontrol of human schistosomiasis

Use of agrochemicals, including insecticides, is vital to food production and predicted to increase 2-5 fold by 2050. Previous studies have shown a positive association between agriculture and the human infectious disease schistosomiasis, which is problematic as this parasitic disease infects approximately 250 million people worldwide. Certain insecticides might runoff fields and be highly toxic to invertebrates, such as prawns in the genus Macrobrachium, that are biocontrol agents for snails that transmit the parasites causing schistosomiasis. We used a laboratory dose-response experiment and an observational field study to determine the relative toxicities of three pyrethroid (esfenvalerate, {lambda}-cyhalothrin, and permethrin) and three organophosphate (chlorpyrifos, malathion, and terbufos) insecticides to Macrobrachium prawns. In the lab, pyrethroids were consistently several orders of magnitude more toxic than organophosphate insecticides, and more likely to runoff fields at lethal levels according to modeling data. In the field, we found that Macrobrachium prawn survival at 31 water contact sites in the lower basin of the Senegal River where schistosomiasis is endemic was predicted by pyrethroid application rates to nearby crop fields after controlling for abiotic and prawn-level factors. Our findings suggest that widely used pyrethroid insecticides can have strong non-target effects on Macrobrachium prawns that are biocontrol agents where 400 million people are at risk of human schistosomiasis. Understanding the ecotoxicology of high-risk insecticides may help improve human health in schistosomiasis-endemic regions undergoing agricultural expansion.

ecology↗

bioRxiv2020

The Impact of Pf Bacteriophages on the Fitness of Pseudomonas aeruginosa; A Mathematical Modeling Approach

Pseudomonas aeruginosa (Pa) is a major bacterial pathogen responsible for chronic lung infections in cystic fibrosis patients. Recent work by ourselves and others has implicated Pf bacteriophages, non-lytic filamentous viruses produced by Pa, in the chronicity and severity of Pa infections. Pf phages act as structural elements in Pa biofilms and sequester aerosolized antibiotics, thereby contributing to antibiotic tolerance. Consistent with a selective advantage in this setting, the prevalence of Pf+ bacteria increases over time in these patients. However, the production of Pf phages comes at a metabolic cost to bacteria, such that Pf+ strains grow more slowly than Pf- strains in vitro. Here, we use a mathematical model to investigate how these competing pressures might influence the relative abundance of Pf+ versus Pf- strains in different settings. Our model predicts that Pf+ strains of Pa can only outcompete Pf- strains if the benefits of phage production falls solely onto Pf+ strains and not onto the overall bacterial community in the lung. Further, phage production only leads to a net positive gain in fitness at antibiotic concentrations slightly above the minimum inhibitory concentration (i.e., concentrations for which the benefits of antibiotic sequestration outweigh the metabolic cost of phage production), but which are not lethal for Pf+ strains. As a result, our model predicts that frequent administration of intermediate doses of antibiotics with low decay rates favors Pf+ over Pf- strains. These models inform our understanding of the ecology of Pf phages and suggest potential treatment strategies for Pf+ Pa infections. ImportanceFilamentous phages are a frontier in bacterial pathogenesis, but the impact of these phages on bacterial fitness is unclear. In particular, Pf phages produced by Pa promote antibiotic tolerance but are metabolically expensive to produce, suggesting that competing pressures may influence the prevalence of Pf+ versus Pf- strains of Pa in different settings. Our results identify conditions likely to favor Pf+ strains and thus antibiotic tolerance. This study contributes to a better understanding of the unique ecology of filamentous phages and may facilitate improved treatment strategies for combating antibiotic tolerance.

microbiology↗

bioRxiv2019

Identification of snails and parasites of medical importance via convolutional neural network: an application for human schistosomiasis

Schistosomiasis is a debilitating parasitic disease infecting over 250 million people with nearly 800 million people at risk worldwide, primarily in sub-Saharan Africa. Transmission to humans involves freshwater snails as intermediate hosts, which are particularly prevalent in developing countries where dams and water resource projects have expanded freshwater snail habitat. At our study sites in the lower Senegal River Basin, we have collected more than 5,500 images of the 7 freshwater snail species (grouped into 4 categories) most frequently encountered in this aquatic ecosystem, 5 of which amplify and transmit either urinary or intestinal human schistosomiasis, with the other 2 species responsible for the transmission of less common parasitic diseases of humans and/or livestock. We have also collected over 5,100 images of 11 classes of trematodes, including human and non-human schistosomes. It takes a great deal of training and expertise to accurately classify these organisms morphologically. In recent years, deep convolutional neural networks (CNNs) have proven to be highly efficient for image recognition tasks across many object categories. Here we demonstrate classification capacity for snail and parasite images and test our models performance against 8 highly-trained human parasitologists with experience taxonomically classifying snail and parasite species from the Senegal River Basin in West Africa. We establish and train a single CNN end-to-end directly from images with only pixels and labels as inputs. Applying this state-of-the-art algorithm, we are able to classify images of 4 snail categories with 99.64% accuracy and images of 11 parasite categories with 88.14% accuracy, which rivals highly-trained human parasitologists. The trained algorithm could next be deployed to mobile devices for use in remote field settings by local technicians, and significantly improve monitoring snail and parasite occurrence in the field for disease control purposes.\n\nAuthor SummarySchistosomiasis is a neglected tropical disease (NTD) infecting over 250 million people worldwide. The current approach to mitigate this disease in endemic regions is community or school-based mass drug administration. However, parasites are primarily transmitted through environmental reservoirs where freshwater snails serve as intermediate hosts. People use the contaminated water sources for their daily tasks and get re-infected after drug treatment. Therefore, drug administration alone is not effective for schistosomiasis control in such high transmission settings. Recent studies show that snail population control is essential to reduce disease transmission risks. To discern between parasitic worms of humans in snails and those of other non-human species is a necessary step to precisely quantify transmission risk for human schistosomiasis. However, it takes a great deal of expertise to train lab and field technicians to accurately classify snail and parasite species. Artificial intelligence (AI)-powered computer vision algorithms have recently proven to be highly efficient for image recognition tasks. We have collected thousands of snail and parasite images in Senegal during 2015-2018. Using these images as training data, we developed an AI model that classifies images of 4 snail categories and 11 parasite categories with, in some cases, higher accuracy than well-trained human parasitologists. This model could next be deployed to mobile devices for use in remote field settings to support local technicians to identify transmission hotspots and target control.

bioinformatics↗

bioRxiv2018

Prawn aquaculture as a method for schistosomiasis control and poverty alleviation: a win-win approach to address a critical infectious disease of poverty

Recent evidence suggests crustacean snail predators may aid schistosomiasis control programs by targeting the environmental component of the parasites life cycle through predation of the snail species that serve as intermediate hosts of the parasite. We evaluate costs, benefits, and potential synergies between schistosomiasis control and aquaculture of giant prawns using an integrated bio-economic-epidemiologic model. We identified combinations of stocking density and aquaculture cycle length that maximize profit and offer disease control benefits for sustainable schistosomiasis control. We consider two prawn species in sub-Saharan Africa: the endemic, non-domesticated Macrobrachium vollenhovenii, and the non-native, domesticated Macrobrachium rosenbergii. We find that, at profit-optimal densities, both M. rosenbergii and M. vollenhovenii can complement conventional control approaches (mass drug treatment of people) and lead to sustainable schistosomiasis control. We conclude that integrated aquaculture strategies can be a win-win strategy in terms of health and sustainable development in schistosomiasis endemic regions of the world.

epidemiology↗