Desilification of phytolith exacerbates the release of arsenic from rice straw.

Arsenic (As) turnover in rice paddy agro-ecosystems has received much attention because As can enter the food chain through its accumulation in rice, thereby affecting human health. Returning straw to soil is a common practice to retain nutrients for soil and crops, but it also cycles As within the rice paddy field ecosystems. However, there is still a lack of detailed understanding of the fate of As in rice straw, and how or to what extent it is recycled back into the soil environment. This study aims to elucidate the relationship between the microstructure of rice straw and the release of As during rice straw decomposition. The microstructure of rice straw was found to comprise both organic and silica (phytolith) components. These two constituents are inter-embedded to form a composite-like structure that contains up to 6.48 mg As Kg-1. The 30-day batch experiments revealed that the biochemical release of As simultaneously depends upon the decomposition of the organic component and the desilicification of the silica component. Accompanying the release of As was the release of other elements such as Fe, Al, P and S. These elements can further interact with As to form less mobile compounds. The introduction of either Trichoderma harzianum or Bacillus velezensis was expected to accelerate the decomposition of rice straw, and enhance the silica dissolution, hence contributing to an increase in the As release. Despite these expectations, our observations showed the opposite effects. Microorganisms presumably have facilitated the change in solution chemistry or the inclusion of As into the newly-formed precipitates. The biochemical decomposition process can reduce straw particle size, while the negatively-charge surface will involve microsized straw particles in the electrostatic interaction, thereby favoring the dispersibility state. Therefore, the co-transport of micro-sized straw particles with As under field conditions should not be neglected.

Earthworms can mobilize soil arsenic through their casts.

The mobilization of arsenic (As) in paddy soil has received much attention because it might accelerate the transfer of As from soil to rice. This study aims to elucidate whether earthworms can mobilize As through their casts. Cast samples were collected from 23 different paddy fields in the Red River delta. We first analysed different forms of As through fractionation and then performed batch experiments under reducing conditions to identify factors that govern the mobility of As in casts. Because the dissociation of casts may induce colloids that carry As, the colloidal properties of cast suspensions were also examined. The median value of As in casts (obtained from aqua regia digestion) was 5.11 mg kg-1, which was lower than that in the surrounding soil (6.7 mg kg-1). Compared with the surrounding soil, casts contain less As, possibly because cast As is more labile and more easily lost due to leaching. Various processes, including the reductive dissolution of Fe oxides, decomposition of organic matter, and sorption competition of soluble anionic substances, such as P, Si and DOC, were found to strongly correlate with the release of As from casts. We propose that earthworms, via their casts, may accelerate the As cycle in paddy soils, potentially intensifying As exposure to human health. The dissociation of cast could release colloids containing As; therefore, the cotransport of As with cast-induced colloids should also be considered in future works.

Fungicide application can intensify clay aggregation and exacerbate copper accumulation in citrus soils.

Fungicide application for controlling fungal diseases can increase copper (Cu) accumulation in soil. More urgently, Cu released from fungicides can associate with soil clay and favour the mutual aggregation of Cu and soil clay, thereby potentially intensifying the accumulation of Cu. We investigated the effects of Cu salt and six common Cu-based fungicides on colloidal dynamics of a clay fraction from citrus cultivated soil. Batch experiments were carried out to provide the loading capacity of the clay fraction for Cu. The colloidal dynamic experiments were performed over a pH range from 3 to 8 following a test tube method, while surface charge, the key electrochemical factor of the solid-liquid interface, was quantified by a particle charge detector. It was found that all the studied fungicides, via releasing Cu2+, acted to effectively favour clay aggregation. The dissolved organic matter obtained from the dissolution of polymers in fungicides can theoretically stimulate clay dispersion. However, their effects were obscured due to the overwhelming effect of Cu2+. Therefore, Cu2+ appears as the most active agent in the fungicides that intensifies clay aggregation. These findings imply that the intensive application of fungicides for plant protection purposes can inadvertently reduce clay mobility, favour the co-aggregation of clay and fungicides, and hence potentially exacerbate the contamination of the citrus soil.

Progress towards rabies control and elimination in Vietnam.

Rabies is a fatal viral disease that causes an estimated 59,000 human deaths each year. The majority of these deaths occur in developing countries in Asia. Canine rabies is endemic to Vietnam, which is, however, moving towards the disease's elimination. Many countries, such as Vietnam, have invested tremendous resources in controlling rabies, highlighting the goal of regional and global elimination of this neglected disease. In Vietnam, rabies is recognised as one of five high-priority, zoonotic diseases by the Ministry of Health and the Ministry of Agriculture and Rural Development. Investment by the government and by international partners for rabies prevention and control has played a substantial role in reducing human rabies deaths from 404 cases in 1992 to 74 cases in 2017. The catalyst for this effort was the Prime Minister's creation of the National Rabies Program in 1996, which led to increased support and resources for rabies prevention and control. Interventions carried out since then include the expansion of post-exposure prophylaxis centres throughout the country, the introduction or revision of key legislation and guidelines, and improved multisectoral One Health collaboration. In addition, support from international partners, such as the World Organisation for Animal Health (OIE), the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO), and the Centers for Disease Control and Prevention (CDC), has helped to increase awareness, manage dog populations more effectively, and improve Vietnam's surveillance and diagnostic capabilities. To pursue the goal of eliminating dog-mediated rabies in Vietnam, political commitment is crucial. Resources must be made available to enforce the regulations and guidelines that will enable Vietnam to achieve greater canine rabies vaccination coverage. In this paper, the authors provide an overview of the animal and human health systems in Vietnam, as well as past, current and future directions of rabies prevention and control.

La rage est une maladie virale à l'issue mortelle faisant chaque année un nombre estimé de 59 000 victimes humaines. La plupart de ces décès surviennent dans les pays en développement d'Asie. Au Vietnam, la rage canine est endémique mais le pays poursuit activement l'objectif d'éliminer la rage de son territoire. À l'instar du Vietnam, plusieurs pays ont investi des ressources colossales pour contrôler la rage, renforçant ainsi la dimension régionale et mondiale de l'objectif d'élimination de cette maladie négligée. Au Vietnam, la rage figure parmi les cinq zoonoses hautement prioritaires prises en compte par le ministère de la Santé et le ministère de l'Agriculture et du développement rural. Les investissements consacrés à la prévention et au contrôle de la rage par le gouvernement et ses partenaires internationaux ont joué un rôle déterminant dans la réduction du nombre de décès humains dus à la rage, qui est passé de 404 cas en 1992 à 74 cas en 2017. L'élément catalyseur de cet effort a été la création en 1996 du Programme national de lutte contre la rage par le premier ministre de l'époque, ce qui a permis de renforcer les ressources et le soutien dédiés à la prévention et à la lutte contre la rage. Depuis lors, les interventions ont porté sur la création de centres de prophylaxie post-exposition sur tout le territoire, l'introduction ou la révision de la législation et des lignes directrices applicables et l'amélioration de la collaboration Une seule santé. En outre, le soutien de partenaires internationaux tels que l'Organisation mondiale de la santé animale (OIE), l'Organisation mondiale de la santé (OMS), l'Organisation des Nations Unies pour l'alimentation et l'agriculture (FAO) et les Centres pour le contrôle et la prévention des maladies (CDC, États-Unis d'Amérique) a abouti à une meilleure sensibilisation, à une gestion plus efficace des populations de chiens et à un renforcement des capacités de surveillance et de diagnostic au Vietnam. Un engagement politique fort est indispensable pour réussir à éliminer totalement la rage transmise par les chiens au Vietnam. Des ressources doivent être rendues disponibles afin de mettre en oeuvre la réglementation et les lignes directrices pertinentes et d'augmenter ainsi la couverture vaccinale de la population canine du pays. Les auteurs décrivent les systèmes de santé animale et publique du Vietnam ainsi que les orientations passées, actuelles et futures de la prévention et du contrôle de la rage dans le pays.

La rabia es una enfermedad vírica fatal, que según las estimaciones mata a 59 000 personas al año, mayoritariamente en países en desarrollo asiáticos. La rabia canina es endémica en el Vietnam, país que no obstante avanza ahora hacia la eliminación de la enfermedad. Como el Vietnam, muchos países han invertido cantidades colosales de recursos en la lucha antirrábica, subrayando con ello su compromiso con el objetivo de eliminar esta enfermedad desatendida a escala regional y mundial. El Ministerio de Salud y el Ministerio de Agricultura y Desarrollo Rural del Vietnam tienen catalogada la rabia como una de las cinco enfermedades zoonóticas que revisten máxima prioridad. Las inversiones en prevención y control de la rabia realizadas por el gobierno y por asociados internacionales han ayudado sensiblemente a reducir el número de personas muertas por la rabia, que ha pasado de 404 casos en 1992 a 74 en 2017. El catalizador de este esfuerzo fue la creación en 1996, por iniciativa del Primer Ministro, del Programa Nacional contra la Rabia, que se tradujo en un aumento del apoyo y los recursos destinados a prevenir y combatir la enfermedad. Entre otras intervenciones, desde entonces se ha multiplicado en todo el país el número de centros donde se dispensa profilaxis tras la exposición, se han promulgado o revisado leyes, decretos y directrices fundamentales y se ha mejorado la colaboración multisectorial en clave de Una sola salud. Además, el respaldo de asociados internacionales como la Organización Mundial de Sanidad Animal (OIE), la Organización Mundial de la Salud (OMS), la Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO) o los Centros para el Control y la Prevención de Enfermedades (CDC) de los Estados Unidos ha ayudado a generar una mayor conciencia del problema, a gestionar más eficazmente las poblaciones de perros y a dotar al país de mejores medios de vigilancia y diagnóstico. Para hacer realidad el objetivo de eliminar del Vietnam la rabia transmitida por perros, la voluntad política es un factor clave, pues hay que poner sobre la mesa los recursos necesarios para aplicar los reglamentos y normas que permitirán al país ampliar la cobertura de vacunación canina antirrábica. Tras trazar una panorámica de los sistemas sanitario y zoosanitario del Vietnam, los autores describen el rumbo pasado, presente y futuro de las labores de prevención y control de la rabia en el país.

Copper encapsulated in grass-derived phytoliths: Characterization, dissolution properties and the relation of content to soil properties.

The formation of phytoliths as a result of the precipitation of Si in many Si-rich plant species is known to encapsulate organic matter. This work aims to examine the possible encapsulation of Cu in grass phytoliths in an orange growing area, where Cu-rich fungicides have been excessively applied. Batch experiments, in combination with SEM-EDS and microscopy, were conducted for the grass-derived phytoliths and phytoliths separated from soil, thus revealing their dissolution properties, morphotypes and contents, in relation to soil properties. By measuring the Cu release accompanying the dissolution of phytoliths by different extractants, especially an Na2CO3/HNO3 solution, it was revealed that Cu was encapsulated within the silica body of the phytolith. This sink of Cu in the grass can be cycled to serve as a new Cu source in soils. Phytolith contents in the soil were up to 17.7 g kg-1 and tended to accumulate in soil depths from 0 to 20 cm. A positive correlation was found for soil phytolith and phytCu contents and may be indicative of the role of phytoliths as an enhancer of Cu accumulation in soil. It would be worth developing suitable techniques for the determination of phytCu, because common extraction/digestion methods are not suited for evaluating this Cu pool.

Isolation of the ornithine-delta-aminotransferase cDNA and effect of salt stress on its expression in Arabidopsis thaliana.

To evaluate the relative importance of ornithine (Orn) as a precursor in proline (Pro) synthesis, we isolated and sequenced a cDNA encoding the Orn-delta-aminotransferase (delta-OAT) from Arabidopsis thaliana. The deduced amino acid sequence showed high homology with bacterial, yeast, mammalian, and plant sequences, and the N-terminal residues exhibited several common features with a mitochondrial transit peptide. Our results show that under both salt stress and normal conditions, delta-OAT activity and mRNA in young plantlets are slightly higher than in older plants. This appears to be related to the necessity to dispose of an easy recycling product, glutamate. Analysis of the expression of the gene revealed a close association with salt stress and Pro production. In young plantlets, free Pro content, Delta1-pyrroline-5-carboxylate synthase mRNA, delta-OAT activity, and delta-OAT mRNA were all increased by salt-stress treatment. These results suggest that for A. thaliana, the Orn pathway, together with the glutamate pathway, plays an important role in Pro accumulation during osmotic stress. Conversely, in 4-week-old A. thaliana plants, although free Pro level also increased under salt-stress conditions, the delta-OAT activity appeared to be unchanged and delta-OAT mRNA was not detectable. Delta1-pyrroline-5-carboxylate synthase mRNA was still induced at a similar level. Therefore, for the adult plants the free Pro increase seemed to be due to the activity of the enzymes of the glutamate pathway.