Sudden oak death management in Oregon tanoak forests

Sudden oak death (SOD) caused by Phytophthora ramorum was first discovered in Oregon forests in July 2001. There appear to have been three separate introductions of P. ramorum into Oregon; in approximately 1998, 2008, and 2014. The most recent of these was the EU1 clonal lineage; all others were the NA1 clonal lineage. Since 2001 an interagency team has been attempting to eradicate the pathogen though a program of early detection (aerial and ground surveys, stream baiting) and destruction (herbicide treatment, felling and burning) of infected and nearby host plants; the program has evolved over time. Post-treatment monitoring indicates that although the pathogen has been eliminated from many of the sites, spread continues. From 2001 to 2015 the quarantine area expanded from 23 km2 to 1,333 km2, where it remains to date. Within a 145 km2 Generally Infested Area near the center of the quarantine area, most sites have not been treated and the disease has been allowed to intensify and spread. Where eradication treatments have stopped, canopy tanoak mortality increased from nearly zero to 87 percent during the 2012-2016 period. Managing sudden oak death in Oregon forests is challenging for many reasons and Oregon’s program is likely to change in the future

Sources of resistance to grapevine fanleaf virus (GFV) in Vitis species

A diverse array of Vitis germplasm was screened to identify sources of resistance to grapevine fanleaf virus (GFV). The 173 accessions screened included Vitis species, cultivars, and interspecific hybrids. Since Vitis vinifera and GFV are thought to have a common origin in the Middle East, particular attention was paid to this species - 27 Middle Eastern vinifera accessions and 9 vinifera cultivars were surveyed. In addition, North American accessions of 24 Euvitis species and 2 Muscadinia species were tested, including cultivars of rotundifolia, as were accessions of 5 Asian species. The interspecific hybrids included 3 vinifera x rotundifolia (VR) hybrids known to be resistant to the feeding of Xiphinema index, the nematode vector of GFV. The vines to be tested were approach grafted to infected Cabernet Sauvignon vines and subsequently screened for the presence of the virus by ELISA. 3 GFV-resistant accessions were identified - a Middle Eastern vinifera, rotundifolia cv. Bountiful, and one of the VR hybrids. Several vinifera accessions (including some cultivars) previously reported to be GFV-resistant were susceptible in this study. These results suggest that two forms of GFV resistance, hast plant resistance and nonhost resistance, exist in Vitis germplasm

Efficacy and safety of hepcidin-based screen-and-treat approaches using two different doses versus a standard universal approach of iron supplementation in young children in rural Gambia: a double-blind randomised controlled trial.

BACKGROUND: Iron deficiency prevalence rates frequently exceed 50 % in young children in low-income countries. The World Health Organization (WHO) recommended universal supplementation of young children where anaemia rates are >40 %. However, large randomized trials have revealed that provision of iron to young children caused serious adverse effects because iron powerfully promotes microbial growth. Hepcidin - the master regulator of iron metabolism that integrates signals of infection and iron deficiency - offers the possibility of new solutions to diagnose and combat global iron deficiency. We aim to evaluate a hepcidin-screening-based iron supplementation intervention using hepcidin cut-offs designed to indicate that an individual requires iron, is safe to receive it and will absorb it. METHODS: The study is a proof-of-concept, three-arm, double blind, randomised controlled, prospective, parallel-group non-inferiority trial. Children will be randomised to receive, for a duration of 12 weeks, one of three multiple micronutrient powders (MNP) containing: A) 12 mg iron daily; B) 12 mg or 0 mg iron daily based on a weekly hepcidin screening indicating if iron can be given for the next seven days or not; C) 6 mg or 0 mg iron daily based on a weekly hepcidin screening indicating if iron can be given for the next seven days or not. The inclusion criteria are age 6-23 months, haemoglobin (Hb) concentration between 7 and 11 g/dL, z-scores for Height-for-Age, Weight-for-Age and Weight-for-Height > -3 SD and free of malaria. Hb concentration at 12 weeks will be used to test whether the screen-and-treat approaches are non-inferior to universal supplementation. Safety will be assessed using caregiver reports of infections, in vitro bacterial and P. falciparum growth assays and by determining the changes in the gut microbiota during the study period. DISCUSSION: A screen-and-treat approach using hepcidin has the potential to make iron administration safer in areas with widespread infections. If this proof-of-concept study shows promising results the development of a point-of-care diagnostic test will be the next step. TRIAL REGISTRATION: ISRCTN07210906 , 07/16/2014

Zero-sum, the niche,and metacommunities: long-term dynamics of community assembly

Recent models of community assembly, structure, and dynamics have incorporated, to varying degrees, three mechanistic processes: resource limitation and interspecific competition, niche requirements of species, and exchanges between a local community and a regional species pool. Synthesizing 30 years of data from an intensively studied desert rodent community, we show that all of these processes, separately and in combination, have influenced the structural organization of this community and affected its dynamical response to both natural environmental changes and experimental perturbations. In addition, our analyses suggest that zero-sum constraints, niche differences, and metacommunity processes are inextricably linked in the ways that they affect the structure and dynamics of this system. Explicit consideration of the interaction of these processes should yield a deeper understanding of the assembly and dynamics of other ecological communities. This synthesis highlights the role that long-term data, especially when coupled with experimental manipulations, can play in assessing the fundamental processes that govern the structure and function of ecological communities

RBC barcoding allows for the study of erythrocyte population dynamics and P. falciparum merozoite invasion.

Plasmodium falciparum invasion of host erythrocytes is essential for the propagation of the blood stage of malaria infection. Additionally, the brief extracellular merozoite stage of P. falciparum represents one of the rare windows during which the parasite is directly exposed to the host immune response. Therefore, efficient invasion of the host erythrocyte is necessary not only for productive host erythrocyte infection, but also for evasion of the immune response. Host traits, such as hemoglobinopathies and differential expression of erythrocyte invasion ligands, can protect individuals from malaria by impeding parasite erythrocyte invasion. Here we combine RBC barcoding with flow cytometry to study P. falciparum invasion. This novel high-throughput method allows for the (i) direct comparison of P. falciparum invasion into different erythrocyte populations and (ii) assessment of the impact of changing erythrocyte population dynamics on P. falciparum invasion

Artemisinin Activity in Red Blood Cells from Anemic Children.

Artemisinin combination therapies are the current frontline therapy for falciparum malaria. Artemisinin is activated by heme iron, and the consequent production of reactive oxygen species and carbon-centered radicals results in rapid parasite clearance. Red blood cells (RBCs) from anemic iron-deficient individuals have decreased levels of heme, and such deficiencies are highly prevalent among children and pregnant women in malaria-endemic countries. We, therefore, investigated the possibility that host anemia could impair artemisinin activity and alter the drug sensitivity of artemisinin-resistant strains of Plasmodium falciparum. We collected RBCs from anemic (n = 35) and nonanemic (n = 11) Gambian children between the ages of 2 and 24 months. Parasites grown in RBCs from both groups were assessed in vitro using the ring-stage survival assay with artemisinin-resistant and artemisinin-sensitive strains of P. falciparum. No differences were found in artemisinin sensitivity (P > 0.05), and there was no correlation between artemisinin activity and host hemoglobin levels. Standard antimalarial drug activity assays for representatives of the major classes of antimalarial drugs found no differences in the IC50 values against P. falciparum between anemic and nonanemic RBCs. We conclude that host anemia does not influence artemisinin activity

Influence of host iron status on Plasmodium falciparum infection

Iron deficiency affects one quarter of the world's population and causes significant morbidity, including detrimental effects on immune function and cognitive development. Accordingly, the World Health Organization (WHO) recommends routine iron supplementation in children and adults in areas with a high prevalence of iron deficiency. However, a large body of clinical and epidemiological evidence has accumulated which clearly demonstrates that host iron deficiency is protective against falciparum malaria and that host iron supplementation may increase the risk of malaria. Although many effective antimalarial treatments and preventive measures are available, malaria remains a significant public health problem, in part because the mechanisms of malaria pathogenesis remain obscured by the complexity of the relationships that exist between parasite virulence factors, host susceptibility traits, and the immune responses that modulate disease. Here we review (i) the clinical and epidemiological data that describes the relationship between host iron status and malaria infection and (ii) the current understanding of the biological basis for these clinical and epidemiological observations

Perceptions of an Ideal Point-of-Care Test for Sexually Transmitted Infections – A Qualitative Study of Focus Group Discussions with Medical Providers

A point-of-care test (POCT) for sexually transmitted infections (STIs), which offers immediate diagnosis resulting in patients receiving diagnosis and treatment in a single visit, has the ability to address some of the STI control needs. However, needs assessment from STI experts and end users about currently available STI POCTs and their future new development has not been evaluated since World Health Organization Sexually Transmitted Diseases Diagnostics Initiative was formed over 15 years ago. Therefore, our objective was to explore the perceptions of the ideal types of STI POCT for use in health care settings.A qualitative study, encompassing eight focus groups, was conducted from March 2008 through April 2009. Participants included 6 STD clinic directors, 63 clinicians, and 7 public health/laboratory/epidemiology professionals in the STI field. Discussion topics included currently available POCT, perceived barriers to using POCT in clinics, priority STI for the development of new POCT, and characteristics of the ideal POCT. All discussions were recorded and transcribed verbatim. Themes raised as barriers for current POCT included complexity, long time frames of the so-called "rapid" test, multiple time-driven steps, requiring laboratory technician, difficulty in reading result, interruption of workflow, unreliability, and invasiveness. Chlamydia trachomatis was identified as the priority organism for development of a new STI POCT. Themes indicated for the ideal POCT included rapid turnaround (up to 20 minutes), ease of use, non-invasive, accurate (preferred sensitivity and specificity in the range of high 90s), Clinical Laboratory Improvement Amendments (CLIA)-waived, user-friendly (for both patients and staff), compact, durable, and sturdy.Focus group discussions with STI experts and professionals highlighted chlamydia as the top priority pathogen for POCT development, and identified the qualities of new POCT for STIs. Participants endorsed ease of use, rapid turnaround and high accuracy as essential characteristics of an ideal POCT

Host iron status and iron supplementation mediate susceptibility to erythrocytic stage Plasmodium falciparum.

Iron deficiency and malaria have similar global distributions, and frequently co-exist in pregnant women and young children. Where both conditions are prevalent, iron supplementation is complicated by observations that iron deficiency anaemia protects against falciparum malaria, and that iron supplements increase susceptibility to clinically significant malaria, but the mechanisms remain obscure. Here, using an in vitro parasite culture system with erythrocytes from iron-deficient and replete human donors, we demonstrate that Plasmodium falciparum infects iron-deficient erythrocytes less efficiently. In addition, owing to merozoite preference for young erythrocytes, iron supplementation of iron-deficient individuals reverses the protective effects of iron deficiency. Our results provide experimental validation of field observations reporting protective effects of iron deficiency and harmful effects of iron administration on human malaria susceptibility. Because recovery from anaemia requires transient reticulocytosis, our findings imply that in malarious regions iron supplementation should be accompanied by effective measures to prevent falciparum malaria

Strong but opposing effects of associational resistance and susceptibility on defense phenotype in an African savanna plant

The susceptibility of plants to herbivores can be strongly influenced by the identity, morphology and palatability of neighboring plants. While the defensive traits of neighbors often determine the mechanism and strength of associational resistance and susceptibility, the effect of neighbors on plant defense phenotype remains poorly understood. We used field surveys and a prickle-removal experiment in a semi-arid Kenyan savanna to evaluate the efficacy of physical defenses against large mammalian herbivores in a common understory plant, Solanum campylacanthum. We then quantified the respective effects of spinescent Acacia trees and short-statured grasses on browsing damage and prickle density in S. campylacanthum. We paired measurements of prickle density beneath and outside tree canopies with long-term herbivore-exclusion experiments to evaluate whether associational resistance reduced defense investment by decreasing browsing damage. Likewise, we compared defense phenotype within and outside pre-existing and experimentally created clearings to determine whether grass neighbors increased defense investment via associational susceptibility. Removing prickles increased the frequency of browsing by ~25%, and surveys of herbivory damage on defended leaves suggested that herbivores tended to avoid prickles. As predicted, associational resistance and susceptibility had opposing effects on plant phenotype: individuals growing beneath Acacia canopies (or, analogously, within large-herbivore exclosures) had a significantly lower proportion of their leaves browsed and produced ~ 70–80% fewer prickles than those outside refuges, whereas plants in grass-dominated clearings were more heavily browsed and produced nearly twice as many prickles as plants outside clearings. Our results demonstrate that associational resistance and susceptibility have strong, but opposing, effects on plant defense phenotype, and that variable herbivore damage is a major source of intraspecific variation in defense phenotype in this system