Localized recharge processes in the NE Mekong Delta and implications for groundwater quality.

Understanding recharge in the Mekong Delta is critical for the delta's groundwater resources, and requires the investigation of recharge processes at the local scale. In this study of the north eastern area of the Mekong Delta, time-series of environmental tracer data (δ18O, δ2H, major ions and 3H) and markers of rural pollution (NH4 and NO3) were used to highlight localized recharge and impacts on groundwater quality. Results highlighted new hydrological insights into recharge processes, including that the Pleistocene aquifer receives recent recharge (< 60 years), predominantly during high rainfall months (> 100 mm/month). However, due to shallow clay layers there are significant spatial variations in these recharge processes, which were observed in the seasonal fluctuation of groundwater δ18O values in groundwater. Wet season δ18O changes ranged from below analytical uncertainty (≤ 0.10 ‰) to up to 0.56 ‰, and the calculated fraction of rainfall contribution to the aquifer is ≤5 % to 16 %. Rainfall recharge via the acrisol soils results in low groundwater EC (20-55 µS/cm), acidic groundwater (pH 3.6-5.6), and may also have resulted in the low groundwater NO3 concentrations (≤ 5.3 mg NO3/L) at many sites due to adsorption, therefore delaying not reducing NO3 contamination. Site specific variations in nitrogen processes includes increased NO3 (to 29.7 mg/L) from fertiliser transfers or nitrification, and increased NH4 (to 1.4 mg/L) likely due to the recharge of irrigation waters. Unlike other recharge areas across the northern Mekong Delta, this north-eastern region provides a groundwater resource unaffected by arsenic contamination. Therefore, these results should inform on priority areas for protection from further contamination by rural anthropogenic activities.

Seasonal influences on groundwater arsenic concentrations in the irrigated region of the Cambodian Mekong Delta.

Similar to many southern and southeast Asian regions, the mobilisation of arsenic (As) from sediments has driven a widespread contamination problem for groundwater resources in the Cambodian Mekong Delta. For the first time, the seasonal changes in As concentrations and potential links to groundwater pumping for irrigation in shallow aquifers of the Cambodian Mekong Delta are investigated. Using environmental tracers (δ18O, δ2H, 3H, major/trace ions and rare earth elements) the natural and pumping-induced changes in hydrogeological processes are identified. Three conceptual models are proposed: Model 1, where there is limited local recharge or low recharge rates (3H mean residence time > 60 years) and groundwater has a large range in As concentrations (0.2 to 393.8 µg/L). In this semi-confined aquifer, only one of the six groundwater sites has As concentrations that increase (by 10.9 µg/L) potentially due to groundwater pumping and resultant mixing with high-As and low (Pr/Sm)NASC groundwater. However, data on groundwater extraction volumes is required to verify the link with irrigation practices. Model 2, where groundwater is recharged by evaporated surface waters (fractionated δ18O and δ2H). There are moderate As concentrations (64.1-106.1 µg/L) but no significant seasonal changes even though the recharging waters have relatively greater organic carbon contents during the dry season (reduced Ce/Ce*anomaly). Finally model 3, where groundwater is significantly recharged by wet season rainfall (~50% from δ18O data). There is a minor increase in As concentrations with recharge (by 6. µg/L). These combined results highlight an aquifer system in the irrigated region of the Cambodian Mekong Delta where As concentrations are largely impacted by natural rather than irrigation processes. Seasonal-scale recharge processes control As processes where the aquifer is not confined by shallow clay layers, and where the aquifer is semi-confined As concentrations largely reflect longer-term natural processes.

Impact of irrigated agriculture on groundwater resources in a temperate humid region.

The groundwater irrigation expansion, and its multiple potential impacts on the quantity and quality of water resources, is not just restricted to areas that are water limited. In this study we present the seasonal impacts irrigation practices can have on groundwater resources in a temperate humid region, where the average annual rain/PET ratio is 1.0. In this system the irrigation expansion is solely supported by groundwater pumping, but despite this only 5 boreholes are monitored for hydraulic head data. In this study, we compensate the scarce hydrophysical dataset by incorporating environmental tracers (major ions, δ18O, δ2H and δ13C) and dating tracers (3H, CFC, SF6 and 14C). Results indicate that at 9 of the 15 irrigation sites investigated, groundwater pumping for irrigation has induced the mixing of recent groundwater (up to <1year) with older waters. The origin of the older waters was from either the deeper marl aquifer, or the shallow sand-clay aquifer (SCB) that has a 14C mean residence time (MRT) of up to 9700years. Secondly, although high nitrate loads in infiltrating waters were being diverted via the artificial subsurface drainage system, increases in fertiliser loads have resulted in higher NO3 concentrations in younger groundwater (NO3: 9-45mg/L, MRT <20years), compared with older groundwater (NO3≤9mg/L, MRT>20years). The changes in flow pathways, induced by irrigation, also results in seasonal declines in groundwater NO3 concentrations due to mixing with older waters. In temperate humid areas, such evaluations of the seasonal evolution of water residence time, mixing process, and agrochemical contaminants are an important contribution to real water resources management in irrigated catchments.

Rapid decline of influenza vaccine-induced antibody in the elderly: is it real, or is it relevant?

Advisory committees have cautioned that influenza vaccine-induced antibody declines more rapidly in the elderly, falling below seroprotective levels within 4 months. We conducted a literature review to assess this assertion. The articles that were included in this review reported antibody levels > or =4 months after influenza immunization in persons > or =60 years old, interpretable in the context of annual influenza vaccine-approval criteria (seroprotection/seroconversion) specified by the Committee for Proprietary Medicinal Products (CPMP) for the elderly. The final review included 14 studies; 8 of which reported seroprotection rates. Seroprotection exceeding CPMP criteria was maintained > or =4 months after influenza immunization in all 8 of the studies reporting this for the H3N2 component and in 5 of the 7 studies reporting this for the H1N1 and B components. In determining whether CPMP criteria were met at season's end, primary antibody response appeared to be more relevant than secondary antibody decline. Both studies reporting seroprotection rates that failed CPMP criteria > or =4 months after influenza immunization for each of the H1N1 and B components had also reported failed seroprotection at 1 month after immunization. If initially achieved after immunization, seroprotection rates of 70%-100% were maintained not just at 4 months (2 studies) but also at 5 months (2 studies) and even at >6 months (4 studies), for the H3N2 and H1N1 vaccine components. Seroprotection rates appeared less consistent for the B vaccine component, throughout the postimmunization period. Seroconversion appears to vary substantially and inversely with preimmunization titers but not with age. In 2 of 6 studies reporting seroconversion alone, CPMP criteria were still met at 4 months. In the other 4 studies, the main reason for failure at 4 months was primary failure at 1 month. A total of 6 studies compared antibody persistence by age, and no consistent differences were found on that basis. The historic concern that the influenza vaccine-induced antibody response in the elderly declines more rapidly and below seroprotective levels within 4 months of immunization should be reconsidered.

Protective measures and human antibody response during an avian influenza H7N3 outbreak in poultry in British Columbia, Canada.

BACKGROUND: In 2004 an outbreak of avian influenza of the H7N3 subtype occurred among poultry in British Columbia, Canada. We report compliance with recommended protective measures and associated human infections during this outbreak. METHODS: We sought voluntary participation by anyone (cullers, farmers and their families) involved in efforts to control the poultry outbreak. Recruitment was by advertisements at the worker deployment site, in local media and through newsletters sent directly to farmers. Sera were tested for antibody to H7N3 by microneutralization assay. A subset of 16 sera (including convalescent sera from 2 unprotected workers with conjunctivitis from whom virus had been isolated) was further tested by Western blot and routine and modified hemagglutination inhibition assays. RESULTS: A total of 167 people (20% to 25% of all workers) participated between May 7 and July 26, 2004. Of these, 19 had experienced influenza-like illness and 21 had experienced red or watery eyes. There was no significant association between illness reports and exposure to infected birds. Among 65 people who entered barns with infected birds, 55 (85%) had received influenza vaccine, 48 (74%) had received oseltamivir, and 55 (85%), 54 (83%) and 36 (55%) reported always wearing gloves, mask or goggles, respectively. Antibody to the H7 subtype was not detected in any sera. INTERPRETATION: During the BC outbreak, compliance with recommended protective measures, especially goggles, was incomplete. Multiple back-up precautions, including oseltamivir prophylaxis, may prevent human infections and should be readily accessible and consistently used by those involved in the control of future outbreaks of avian influenza in poultry. Localized human avian influenza infections may not result in serologic response despite confirmed viral detection and culture.

Coordinated response to SARS, Vancouver, Canada.

Two Canadian urban areas received travelers with severe acute respiratory syndrome (SARS) before the World Health Organization issued its alert. By July 2003, Vancouver had identified 5 cases (4 imported); Toronto reported 247 cases (3 imported) and 43 deaths. Baseline preparedness for pandemic threats may account for the absence of sustained transmission and fewer cases of SARS in Vancouver.

Potential cost-effectiveness of annual influenza immunization for infants and toddlers: experience from Canada.

BACKGROUND: In 2004, expert groups in North America recommended annual influenza immunization for healthy infants and toddlers aged 6-23 months with a goal of reducing high hospitalization rates (HR). We assess cost-effectiveness of this program in Canada. METHODS: Analysis was from third-party payer and societal perspectives in preventing hospitalization and other outcomes among 500,000 vaccinated or non-vaccinated infants/toddlers. Base-case assumptions include: 25% attack rate (AR), 1% case hospitalization rate (HR), 0.002% case fatality, vaccine effectiveness (VE) of 66%, CDN dollar 15 per dose for vaccine and administration, half of mothers requiring 2h from work per dose to immunize and two doses required by 100% (first year) or 33% (subsequent years) of infants/toddlers immunized. RESULTS: After the first year, infant/toddler influenza immunization costs the third-party approximately CDN dollar 9 per day of illness averted, CDN dollar 120 per physician visit averted, CDN dollar 7000 per hospitalization averted, CDN dollar 3 million per death averted and CDN dollar 450,000 per life year gained. Corresponding costs from societal perspective are approximately CDN dollar 3, CDN dollar 45, CDN dollar 2500, CDN dollar 1 million and CDN dollar 170,000. The program becomes cost-saving from the third-party perspective at AR>55%, HR>4%, or cost per dose (for vaccine and its administration) 74%. CONCLUSIONS: In the base case, infant/toddler influenza immunization is not cost-saving but could become more cost-effective in settings of higher attack rate and lower immunization cost. In this context, immunization of children in daycare or other group settings should be preferentially considered. Economic analyses should routinely inform expansions to influenza immunization programs.

Novel avian influenza H7N3 strain outbreak, British Columbia.

Genome sequences of chicken (low pathogenic avian influenza [LPAI] and highly pathogenic avian influenza [HPAI]) and human isolates from a 2004 outbreak of H7N3 avian influenza in Canada showed a novel insertion in the HA0 cleavage site of the human and HPAI isolate. This insertion likely occurred by recombination between the hemagglutination and matrix genes in the LPAI virus.

Human illness from avian influenza H7N3, British Columbia.

Avian influenza that infects poultry in close proximity to humans is a concern because of its pandemic potential. In 2004, an outbreak of highly pathogenic avian influenza H7N3 occurred in poultry in British Columbia, Canada. Surveillance identified two persons with confirmed avian influenza infection. Symptoms included conjunctivitis and mild influenzalike illness.

The five most frequently asked questions about private duty home care.

Where are the growth opportunities in home care? How can I reduce my dependency on Medicare? What can I do to improve the bottom line? These are some of the questions being asked by successful home care leaders as they work to recover from the effects of the Balanced Budget Act and the Interim Payment System and prepare for the Prospective Payment System.

Intervening in adolescent substance abuse.

Substance use and abuse is a major public health problem that affects adolescents of both genders and of every socioeconomic level. Because of the nature of the nursing profession, nurses are often trusted with confidential queries from family members and friends and clients concerned about substance use by teenagers they know and love. The purpose of this article is to provide nurses information and strategies for helping adolescents and their families with this problem. Specifically, this article includes information about current trends in teenage substance use and abuse, risk factors that influence use and abuse, and strategies for prevention, identification, and treatment.

Recent advances in chromatographic and electrophoretic methods for the study of drug-protein interactions.

Drug-protein binding is an important process in determining the activity and fate of a pharmaceutical agent once it has entered the body. This review examines various chromatographic and electrophoretic methods that have been developed to study such interactions. An overview of each technique is presented along with a discussion of its strengths, weaknesses and potential applications. Formats that are discussed include the use of both soluble and immobilized drugs or proteins, and approaches based on zonal elution, frontal analysis or vacancy peak measurements. Furthermore, examples are provided that illustrate the use of these methods in determining the overall extent of drug-protein binding, in examining the displacement of a drug by other agents and in measuring the equilibrium or rate constants for drug-protein interactions. Examples are also given demonstrating how the same methods, particularly when used in high-performance liquid chromatography or capillary electrophoresis systems, can be employed as rapid screening tools for investigating the binding of different forms of a chiral drug to a protein or the binding of different proteins and peptides to a given pharmaceutical agent.

Effects of ligand heterogeneity in the characterization of affinity columns by frontal analysis.

This study examined how the binding capacities and equilibrium constants measured by frontal analysis are affected by ligand heterogeneity in affinity columns. Equations derived for n- and two-site systems gave good agreement with results obtained for the binding of L-thyroxine to a column containing human serum albumin (HSA) and for the binding of (R)-warfarin to coupled columns containing HSA or pigeon serum albumin. The same equations were used to examine how different degrees of ligand heterogeneity affected the apparent binding capacities or equilibrium constants measured using the linear range of double-reciprocal frontal analysis plots. A large proportion of two-site systems gave good estimates (i.e., less than 10-20% error) for the true total column capacity and for the association constant of the highest affinity ligand in the column. A smaller, but still appreciable, fraction of all three- and four-site cases also produced good estimates of these values. The results of this work are not limited to protein-based affinity columns but should be applicable to any type of stationary phase that has well-defined binding regions and relatively fast, reversible interactions with solutes.

Action steps to prepare for the new managed care.

Remaining competitive under a managed care system requires skills and talents that were not necessarily important in home care until recent years. And as we get used to it, the current managed care model will undergo even more disruptions in the near future. Providers that want to succeed in the 21st century must learn to adapt and re-adapt to the managed care of tomorrow.

Family climate and parent-child relationships: recollections from a nonclinical sample of adult children of alcoholic fathers.

Past family climate and past parent-child relationships of a nonclinical sample of young adult children of alcoholic fathers (n = 87) were compared to a sociodemographically similar sample of young adults with nonalcoholic parents (n = 106). Self-reports indicated that, compared to respondents from nonalcoholic families, respondents with alcoholic fathers described a more negative family climate with higher levels of conflict and lower levels of cohesion and expressiveness. Adult children of alcoholics described more negative relationships with their alcoholic fathers. However, contrary to clinical literature, adult children of alcoholics' descriptions of their relationships with their nonalcoholic mothers did not differ from the descriptions provided by young adults with nonalcoholic parents. Daughters of alcoholic fathers reported more negative relationships with their fathers in the areas of role performance, affective expression, and control than did sons. Implications for practice include reinforcing the nurturing relationship between nonalcoholic mothers and their children in families with alcoholic fathers.