Optimal health and disease management using spatial uncertainty: a geographic characterization of emergent artemisinin-resistant Plasmodium falciparum distributions in Southeast Asia.

Background: Artemisinin-resistant Plasmodium falciparum malaria parasites are now present across much of mainland Southeast Asia, where ongoing surveys are measuring and mapping their spatial distribution. These efforts require substantial resources. Here we propose a generic 'smart surveillance' methodology to identify optimal candidate sites for future sampling and thus map the distribution of artemisinin resistance most efficiently.

Spread of artemisinin-resistant Plasmodium falciparum in Myanmar: a cross-sectional survey of the K13 molecular marker.

Background: Emergence of artemisinin resistance in southeast Asia poses a serious threat to the global control of Plasmodium falciparum malaria. Discovery of the K13 marker has transformed approaches to the monitoring of artemisinin resistance, allowing introduction of molecular surveillance in remote areas through analysis of DNA. We aimed to assess the spread of artemisinin-resistant P falciparum in Myanmar by determining the relative prevalence of P falciparum parasites carrying K13-propeller mutations.

Water quality guidelines for chemicals: learning lessons to deliver meaningful environmental metrics.

Many jurisdictions around the globe have well-developed regulatory frameworks for the derivation and implementation of water quality guidelines (WQGs) or their equivalent (e.g. environmental quality standards, criteria, objectives or limits).

A Bayesian mixture model for estimating intergeneration chronic toxicity.

Understanding toxic effects on biological populations across generations is crucial for determining the long-term consequences of chemical pollution in aquatic environments. As a consequence, there is considerable demand for suitable statistical methods to analyze complex multigeneration experimental data. We demonstrate the application of a Bayesian mixture model (with random-effects) to assess the effect of intergeneration copper (Cu) exposure on the reproductive output of the copepod, Tigriopus japonicus, using experimental data across three generations.

Acclimation effect and fitness cost of copper resistance in the marine copepod Tigriopus japonicus.

Copper (Cu) contamination is common and widespread in coastal marine environments. This study used the marine copepod Tigriopus japonicus to test whether Cu resistance can be developed through multigeneration acclimation to elevated Cu levels and whether the resistance has a fitness cost. T.

Chronic toxicity of tributyltin to development and reproduction of the European freshwater snail Lymnaea stagnalis (L.).

Chronic toxicity, growth and reproduction were measured in the freshwater gastropod Lymnaea stagnalis exposed to waterborne bis(tri-n-butyltin) oxide (TBTO) over a range of four nominal concentrations (0-10microg TBTl(-1)). Egg development was completely inhibited at 10microg TBTl(-1), whilst abnormal embryonic development was observed at 1microg TBTl(-1). For the solvent control and the 0.

An evaluation of United Kingdom environmental bovine spongiform encephalopathy risk assessment.

As a member of the group of diseases known as transmissible spongiform encephalopathies (TSEs), bovine spongiform encephalopathy (BSE) has been causally associated with a new variant of Creutzfeldt-Jakob disease (vCJD) in humans. Given the many uncertainties on the transmission and persistence of TSE pathogens in the environment, quantitative assessment of risks to humans and animals continues to remain a public health issue. This paper reviews quantitative BSE risk assessments undertaken in the United Kingdom since 1997 to address the potential for human exposure and theoretical health risks through environmental pathways.

Bayesian and time-independent species sensitivity distributions for risk assessment of chemicals.

Species sensitivity distributions (SSDs) are increasingly used to analyze toxicity data but have been criticized for a lack of consistency in data inputs, lack of relevance to the real environment, and a lack of transparency in implementation. This paper shows how the Bayesian approach addresses concerns arising from frequentist SSD estimation. Bayesian methodologies are used to estimate SSDs and compare results obtained with time-dependent (LC50) and time-independent (predicted no observed effect concentration) endpoints for the insecticide chlorpyrifos.

Transmissible spongiform encephalopathy risk assessment: the UK experience.

Transmissible spongiform encephalopathy (TSE) risk assessments undertaken in the United Kingdom have mainly had the objective of determining the risks posed to humans from exposure to the causal agents associated with bovine spongiform encephalopathy (BSE) and variant Creutzfeld-Jakob disease (vCJD). In this article, I examine 19 of these risk assessments published to date and consider how their results might be influenced by underlying model assumptions and methodology. Three separate aspects common to all the assessments are infective load estimation, exposure pathway identification, and risk estimation.

Chronic toxicity of tributyltin on development and reproduction of the hermaphroditic snail Physa fontinalis: Influence of population density.

Tributyltin (TBT) is toxic to aquatic organisms and occurs widely in sediments and surface waters of American and European rivers and lakes. This study investigated TBT effects on development and population growth rate (r) of the common, hermaphroditic European freshwater snail Physa fontinalis. Egg ropes of similar age (1-3 days old) were exposed to a control (solvent only) and nominal concentrations of 0.

Uptake and depuration of 4-nonylphenol by the benthic invertebrate Gammarus pulex: how important is feeding rate?

The major exposure and uptake route for soluble toxins by aquatic organisms is generally considered to be through the water column. In the case of hydrophobic chemicals, exposure and uptake through diet often take on greater importance as the chemicals adsorb onto organic sediments and food. A chemical that has recently come under close scrutiny because of its toxicity and possible endocrine disrupting effects in aquatic life is 4-nonylphenol (NP).

Estimating the effects of 17alpha-ethinylestradiol on populations of the fathead minnow Pimephales promelas: are conventional toxicological endpoints adequate?

Environmental benchmarks have recently been proposed for several steroids including the synthetic steroid, 17alpha-ethinylestradiol (EE2). These benchmarks are based on extrapolation from studies involving long-term exposure of various fish species to EE2. One of the critical studies was a complete life-cycle experiment performed with the fathead minnow Pimephales promelas over a 289 day exposure period.

Estimation of demographic toxicity through the double bootstrap.

Toxicity to organisms is usually expressed in terms of an observable effect on individuals from which a summary endpoint (such as the NOEC or ECx) is derived for risk assessment and environmental quality standards. However, toxicity evaluated in terms of a demographic endpoint may be more relevant to such regulatory applications. In this paper the effect of toxicity on population growth rate r is explored in tandem with a 'double bootstrap' to incorporate uncertainty.

Time should be considered in developmental ecotoxicity test.

Developmental toxicity tests are often used for the hazard assessment of chemicals and environmental media. One of the most widely used is the oyster embryo larval test (OEL), in which the development of oyster larvae is arrested at a single fixed time (e.g.

Better bootstrap estimation of hazardous concentration thresholds for aquatic assemblages.

The introduction of species sensitivity distribution (SSD) approaches to ecological risk assessment offers the potential for a more transparent scientific basis for the derivation of predicted no-effect concentrations. However, conventional SSD methodologies have relied on standard distributions (e.g.