Epidemiological and ecological consequences of virus manipulation of host and vector in plant virus transmission.

Many plant viruses are transmitted by insect vectors. Transmission can be described as persistent or non-persistent depending on rates of acquisition, retention, and inoculation of virus. Much experimental evidence has accumulated indicating vectors can prefer to settle and/or feed on infected versus noninfected host plants. For persistent transmission, vector preference can also be conditional, depending on the vector's own infection status. Since viruses can alter host plant quality as a resource for feeding, infection potentially also affects vector population dynamics. Here we use mathematical modelling to develop a theoretical framework addressing the effects of vector preferences for landing, settling and feeding-as well as potential effects of infection on vector population density-on plant virus epidemics. We explore the consequences of preferences that depend on the host (infected or healthy) and vector (viruliferous or nonviruliferous) phenotypes, and how this is affected by the form of transmission, persistent or non-persistent. We show how different components of vector preference have characteristic effects on both the basic reproduction number and the final incidence of disease. We also show how vector preference can induce bistability, in which the virus is able to persist even when it cannot invade from very low densities. Feedbacks between plant infection status, vector population dynamics and virus transmission potentially lead to very complex dynamics, including sustained oscillations. Our work is supported by an interactive interface https://plantdiseasevectorpreference.herokuapp.com/. Our model reiterates the importance of coupling virus infection to vector behaviour, life history and population dynamics to fully understand plant virus epidemics

Effects of plant pathogens on population dynamics and community composition in grassland ecosystems: two case studies

Grassland ecosystems comprise a major portion of the earth’s terrestrial surface, ranging from high-input cultivated monocultures or simple species mixtures to relatively unmanaged but dynamic systems. Plant pathogens are a component of these systems with their impact dependent on many interacting factors, including grassland species population dynamics and community composition, the topics covered in this paper. Plant pathogens are affected by these interactions and also act reciprocally by modifying their nature. We review these features of disease in grasslands and then introduce the 150-year long-term Park Grass Experiment (PGE) at Rothamsted Research in the UK. We then consider in detail two plant-pathogen systems present in the PGE, Tragopogon pratensis-Puccinia hysterium and Holcus lanata-Puccinia coronata. These two systems have very different life history characteristics: the first, a biennial member of the Asteraceae infected by its host-specific, systemic rust; the second, a perennial grass infected by a host-non-specific rust. We illustrate how observational, experimental and modelling studies can contribute to a better understanding of population dynamics, competitive interactions and evolutionary outcomes. With Tragopogon pratensis-Puccinia hysterium, characterised as an “outbreak” species in the PGE, we show that pathogen-induced mortality is unlikely to be involved in host population regulation; and that the presence of even a short-lived seed-bank can affect the qualitative outcomes of the host-pathogen dynamics. With Holcus lanata-Puccinia coronata, we show how nutrient conditions can affect adaptation in terms of host defence mechanisms, and that co-existence of competing species affected by a common generalist pathogen is unlikely

Modelling Vector Transmission and Epidemiology of Co-Infecting Plant Viruses.

Co-infection of plant hosts by two or more viruses is common in agricultural crops and natural plant communities. A variety of models have been used to investigate the dynamics of co-infection which track only the disease status of infected and co-infected plants, and which do not explicitly track the density of inoculative vectors. Much less attention has been paid to the role of vector transmission in co-infection, that is, acquisition and inoculation and their synergistic and antagonistic interactions. In this investigation, a general epidemiological model is formulated for one vector species and one plant species with potential co-infection in the host plant by two viruses. The basic reproduction number provides conditions for successful invasion of a single virus. We derive a new invasion threshold which provides conditions for successful invasion of a second virus. These two thresholds highlight some key epidemiological parameters important in vector transmission. To illustrate the flexibility of our model, we examine numerically two special cases of viral invasion. In the first case, one virus species depends on an autonomous virus for its successful transmission and in the second case, both viruses are unable to invade alone but can co-infect the host plant when prevalence is high

Effect of COVID-19 on acute treatment of ST-segment elevation and Non-ST-segment elevation acute coronary syndrome in northwestern Switzerland

To investigate the effect of the corona virus disease 2019 (COVID-19) pandemic on the acute treatment of patients with ST-segment elevation (STEMI) and Non-ST-segment elevation acute coronary syndrome (NSTE-ACS).; We retrospectively identified patients presenting to the emergency department (ED) with suspected ACS. We evaluated the number of percutaneous coronary interventions (PCIs) for STEMI, NSTE-ACS, and elective PCI cases. In STEMI patients, we assessed the time from chest pain onset (cpo) to ED presentation, post-infarction left ventricular ejection fraction (LVEF), and time from ED presentation to PCI. We directly compared cases from two time intervals: January/February 2020 versus March/April 2020 (defined as 2 months before and after the COVID-19 outbreak). In a secondary analysis, we directly compared cases from March/April 2020 with patients from the same time interval in 2019.; From January to April 2020, 765 patients presented with acute chest pain to the ED. A dramatic reduction of ED presentations after compared to before the COVID-19 outbreak (31% relative reduction) was observed. Overall, 398 PCIs were performed, 220/398 PCIs (55.3%) before versus 178/398 PCIs (44.7%) after the outbreak. While numbers for NSTE-ACS and elective interventions declined by 21% and 31%, respectively, the number of STEMI cases remained stable. Time from cpo to ED presentation, post-infarction LVEF, and median door-to-balloon time remained unchanged.; In contrast to previous reports, our findings do not confirm the dramatic drop in STEMI cases and interventions in northwestern Switzerland as observed in other regions and hospitals around the world

Coinfections by noninteracting pathogens are not independent and require new tests of interaction.

If pathogen species, strains, or clones do not interact, intuition suggests the proportion of coinfected hosts should be the product of the individual prevalences. Independence consequently underpins the wide range of methods for detecting pathogen interactions from cross-sectional survey data. However, the very simplest of epidemiological models challenge the underlying assumption of statistical independence. Even if pathogens do not interact, death of coinfected hosts causes net prevalences of individual pathogens to decrease simultaneously. The induced positive correlation between prevalences means the proportion of coinfected hosts is expected to be higher than multiplication would suggest. By modelling the dynamics of multiple noninteracting pathogens causing chronic infections, we develop a pair of novel tests of interaction that properly account for nonindependence between pathogens causing lifelong infection. Our tests allow us to reinterpret data from previous studies including pathogens of humans, plants, and animals. Our work demonstrates how methods to identify interactions between pathogens can be updated using simple epidemic models

Long-Term Results After Drug-Eluting Versus Bare-Metal Stent Implantation in Saphenous Vein Grafts: Randomized Controlled Trial

Background Efficacy data on drug-eluting stents (DES) versus bare-metal stents (BMS) in saphenous vein grafts are controversial. We aimed to compare DES with BMS among patients undergoing saphenous vein grafts intervention regarding long-term outcome. Methods and Results In this multinational trial, patients were randomized to paclitaxel-eluting or BMS. The primary end point was major adverse cardiac events (cardiac death, nonfatal myocardial infarction, and target-vessel revascularization at 1 year. Secondary end points included major adverse cardiac events and its individual components at 5-year follow-up. One hundred seventy-three patients were included in the trial (89 DES versus 84 BMS). One-year major adverse cardiac event rates were lower in DES compared with BMS (2.2% versus 16.0%, hazard ratio, 0.14; 95% CI, 0.03-0.64,; P; =0.01), which was mainly driven by a reduction of subsequent myocardial infarctions and need for target-vessel revascularization. Five-year major adverse cardiac event rates remained lower in the DES compared with the BMS arm (35.5% versus 56.1%, hazard ratio, 0.40; 95% CI, 0.23-0.68,; P; <0.001). A landmark-analysis from 1 to 5 years revealed a persistent benefit of DES over BMS (hazard ratio, 0.33; 95% CI, 0.13-0.74,; P; =0.007) in terms of target-vessel revascularization. More patients in the BMS group underwent multiple target-vessel revascularization procedures throughout the study period compared with the DES group (DES 1.1% [n=1] versus BMS 9.5% [n=8],; P; =0.013). Enrollment was stopped before the target sample size of 240 patients was reached. Conclusions In this randomized controlled trial with prospective long-term follow-up of up to 5 years, DES showed a better efficacy than BMS with sustained benefits over time. DES may be the preferred strategy in this patient population. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT00595647

Scientific Opinion on the pest categorisation of Strawberry vein banding virus

The Panel on Plant Health performed a pest categorisation of Strawberry vein banding virus (SVBV) for the European Union (EU) territory. SVBV is a well-defined virus species of the genus Caulimovirus for which the entire genome sequence is known and molecular detection assays are available. SVBV is transmitted by vegetative multiplication of infected hosts and through the activity of aphid vectors, the most efficient being Chaetosiphon spp. The virus is reported from all continents and is present in three EU Member States: the Czech Republic, Italy and Slovakia. The host range of SVBV is restricted to cultivated and wild strawberries. It is listed in Annex IAI of Directive 2000/29/EC. SVBV is not expected to be affected by ecoclimatic conditions wherever its hosts are present and has the potential to establish in large parts of the EU territory, and to subsequently spread through the action of its Chaetosiphon fragaefolii vector, which is present in many Member States. SVBV does not cause severe symptoms, and modern cultivars are mostly symptomless if infected with SVBV alone. SVBV can, however, contribute to more severe symptoms when it occurs in mixed infections with other strawberry viruses. Despite this, SVBV is considered a minor problem in strawberry production as a consequence of modern practices including the systematic use of certified planting materials and the use of short crop cycles, which have greatly reduced the impact of strawberry viruses. Overall, SVBV does not have the potential to be a quarantine pest as, given current agricultural practices, it does not fulfil the pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 11 of having a severe impact. However, SVBV has the potential to be a regulated non-quarantine pest because it fulfils all pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 21