Episodic acidification of 5 rivers in Canada's oil sands during snowmelt: A 25-year record.

Episodic acidification during snowmelt is a natural phenomenon that can be intensified by acidic deposition from heavy industry. In Canada's oil sands region, acid deposition is estimated to be as much as 5% of the Canadian total and large tracks of northeastern Alberta are considered acid-sensitive because of extensive peatland habitats with poorly weathered soils. To identify the frequency, duration and severity of acidification episodes during snowmelt (the predominant hydrological period for delivery of priority pollutants from atmospheric oil sands emissions to surface waters), a 25-year record (1989 to 2014) of automated water quality data (pH, temperature, conductivity) was assembled for 3 rivers along with a shorter record (2012-2014) for another 2 rivers. Acidic episodes (pH<7, ANC<0) were recorded during 39% of all 83 snowmelt events. The severity (duration x magnitude) of episodic acidification increased exponentially over the study period (r2=0.56, P<0.01) and was strongly correlated (P<0.01) with increasing maximum air temperature and weakly correlated with regional land development (P=0.06). Concentrations of aluminum and 11 priority pollutants (Sb, As, Be, Cd, Cr, Cu, Pb, Se, Ag, Tl and Zn) were greatest (P<0.01) during low (<6.5) pH episodes, particularly when coincident with high discharge, such that aluminum and copper concentrations were at times high enough to pose a risk to juvenile rainbow trout (Oncorhynchus mykiss). Although low pH (pH<6.5) was observed during only 8% of 32 acidification episodes, when present, low pH typically lasted 10days. Episodic surface water acidification during snowmelt, and its potential effects on aquatic biota, is therefore an important consideration in the design of long-term monitoring of these typically alkaline (pH=7.72±0.05) rivers.

Killer-cell immunoglobulin-like receptors and malaria caused by Plasmodium falciparum in The Gambia.

The relevance of innate immune responses to Plasmodium falciparum infection, in particular the central role of natural killer (NK) cell-derived interferon gamma (IFN-γ), is becoming increasingly recognised. Recently, it has been shown that IFN-γ production in response to P. falciparum antigens is in part regulated by killer-cell immunoglobulin-like receptor (KIR) genes, and a study from malaria-exposed Melanesians suggested an association between KIR genotypes and susceptibility to infection. This prompted us to determine and compare the frequencies of 15 KIR genes in Gambian children presenting with either severe malaria (n = 133) or uncomplicated malaria (n = 188) and in cord-blood population control samples (n = 314) collected from the same area. While no significant differences were observed between severe and uncomplicated cases, proportions of individuals with KIR2DS2+C1 and KIR2DL2+C1 were significantly higher among malaria cases overall than in population control samples. In an exploratory analysis, activating KIR genes KIR2DS2, KIR3DS1 and KIR2DS5 were slightly higher in children in disease subgroups associated with the highest mortality. In addition, our data suggest that homozygosity for KIR genotype A might be associated with different malaria outcomes including protection from infection and higher blood parasitaemia levels in those that do get infected. These findings are consistent with a probable role of KIR genes in determining susceptibility to malaria, and further studies are warranted in different populations.

Spatial analysis of tuberculosis in an urban west African setting: is there evidence of clustering?

OBJECTIVES: To describe the pattern of tuberculosis (TB) occurrence in Greater Banjul, The Gambia with Geographical Information Systems (GIS) and Spatial Scan Statistics (SaTScan) and to determine whether there is significant TB case clustering. METHODS: In Greater Banjul, where 80% of all Gambian TB cases arise, all patients with TB registered at chest clinics between March 2007 and February 2008 were asked to participate. Demographic, clinical characteristics and GPS co-ordinates for the residence of each consenting TB case were recorded. A spatial scan statistic was used to identify purely spatial and space-time clusters of tuberculosis among permanent residents. RESULTS: Of 1145 recruited patients with TB, 84% were permanent residents with 88% living in 37 settlements that had complete maps available down to settlement level. Significant high- and low-rate spatial and space-time clusters were identified in two districts. The most likely cluster of high rate from both the purely spatial analysis and the retrospective space-time analysis were from the same geographical area. A significant secondary cluster was also identified in one of the densely populated areas of the study region. CONCLUSIONS: There is evidence of significant clustering of TB cases in Greater Banjul, The Gambia. Systematic use of cluster detection techniques for regular TB surveillance in The Gambia may aid effective deployment of resources. However, passive case detection dictates that community-based active case detection and risk factor surveys would help confirm the presence of true clusters and their causes.

Haematological values from a Gambian cohort--possible reference range for a West African population.

The objective of this study was to establish haematological reference ranges for the West African subregion using a Gambian cohort. We analysed full blood counts from 1279 subjects aged > or =1 year. Anthropometric and body composition measurements were performed. Haematological mean values, medians and 90% reference values were calculated and related to malnutrition in children and thinness and/or obesity in adults. Haemoglobin (Hb) and mean corpuscular volume (MCV) significantly increased with age (P < 0.00001). There were gender-related changes in Hb from 15 years of age (P = 0.001) and for MCV only in adults (P = 0.0002). Hb was significantly reduced in underweight and stunted children (P = 0.0001 and 0.0002, respectively) but was unaffected by thinness or obesity in adults. White blood cell (WBC) and platelet counts were highest under 5 years and declined significantly with age (P < 0.0001 and 0.0001). While, there were no gender-related differences with WBC, there were higher WBC counts in underweight (P = 0.0001) and stunted (P < 0.0001) children. Adult females had significantly higher mean platelet counts compared with males (P = 0.006). The mean and median values of haematological parameters in The Gambia are similar to other standards but the 90% reference range for each parameter encompasses lower values when compared with Western standards.

A general population from Thailand: incidence of common allergens with emphasis on para-phenylenediamine.

BACKGROUND: Most studies on the prevalence of allergy to the permanent hair dye chemical para-phenylenediamine (PPD) are reported from populations of eczema patients attending patch-test clinics, and are assumed to be much higher than in the normal population. No data exist on incidence of senitization to PPD resulting from the use of commercial hair dye preparations over a defined time period. METHOD: A total of 2545 healthy adult volunteers (Bangkok) were screened for PPD allergy through standard patch testing. Volunteers not allergic to PPD were then recruited into two groups: one group applying a commercial hair dye brand as instructed on a monthly basis for 6 months (n=548) and the other group (controls) (n=516) was instructed not to dye their hair for 6 months. Sensitization to PPD resulting from the use of hair dye over this period was then detected by repeat patch testing. RESULTS: The prevalence of PPD allergy in a normal adult population was 2.7% (m=2.4%, f=3.2%). Projected to the adult Thai population, at least 1,000,000 Thai individuals could be allergic to PPD. The incidence of sensitization through the monthly application of standard commercial hair dye preparations over a 6-month period was 1.3%, substantially higher than in controls (0.4%), although numbers were small and not statistically significant. INTERPRETATION: There is a higher prevalence of hair dye allergy among the normal population than previously thought. The incidence of new cases of PPD allergy would indicate that current regulations and practice of hair dye exposure lead to PPD sensitization and allergy, which is a public health problem.

FOXP3 gene expression in a tuberculosis case contact study.

Regulatory T lymphocytes (T(regs)) that express FOXP3 are involved in the beneficial attenuation of immunopathology, but are also implicated in down-regulation of protective responses to infection. Their role in tuberculosis (TB) is unknown. We classified 1272 healthy TB contacts according to their tuberculin skin test (TST) and interferon (IFN)-gamma enzyme-linked immunospot (ELISPOT) results and 128 TB cases, and studied the expression of FOXP3 and interleukin (IL)-10 in blood samples. Compared to the uninfected contact group (TST(-), ELISPOT(-)), we observed higher levels of FOXP3 mRNA in blood from TB patients (< 0.001), but IL-10 expression was slightly lower (P = 0.04). In contrast, FOXP3 expression levels were significantly lower (P = 0.001) in the recently infected contacts (TST(+), ELISPOT(+)) but there was no difference for IL-10 (P = 0.74). We hypothesize that during early/subclinical TB, most of which will become latent, FOXP3(+) T(regs) may be sequestered in the lungs, but when TB becomes progressive, FOXP3 reappears at increased levels in the periphery. While these findings do not reveal the role, beneficial or harmful, of T(regs) in TB, they emphasize the probable importance of these cells.

Clinical presentation and outcome of tuberculosis patients infected by M. africanum versus M. tuberculosis.

SETTING: A tuberculosis (TB) case contact study in the Gambia. OBJECTIVE: To test whether Mycobacterium africanum, which has lost around 68 kb compared with M. tuberculosis sensu stricto, causes less severe TB disease. DESIGN: We genotyped mycobacterial isolates and compared clinical and radiological characteristics as well as outcome data of M. africanum-infected TB patients with those infected with M. tuberculosis. RESULTS: Of 317 index cases, 301 had a mycobacterial isolate available, 290 of which had an interpretable spoligotype pattern. Of these, 110 isolates (38%) were M. africanum and 180 (62%) were M. tuberculosis. M. africanum cases had lower body mass indices (17 vs. 17.45 for M. tuberculosis-infected patients, P = 0.029) and their radiographic disease was more extensive (96% vs. 89% had at least moderately severe radiographic changes, P = 0.031). Outcome on treatment was similar (2.8% of human immunodeficiency virus [HIV] negative M. africanum patients died on treatment vs. 3.0% of M. tuberculosis patients, P = 0.95). CONCLUSION: M. africanum causes sputum smear-positive tuberculosis disease that is at least as severe as that caused by M. tuberculosis sensu stricto. Further clinical comparisons may be helpful in smear-negative patients and HIV-TB co-infected patients, and to identify whether there is any difference in time to develop disease.

Long-term protection against carriage of hepatitis B virus after infant vaccination.

BACKGROUND: Carriage of hepatitis B virus (HBV) is a major risk factor for liver cirrhosis and hepatocellular carcinoma. Infant vaccination has been effective in preventing horizontal transmission during early childhood. It is unknown whether protection is maintained into early adulthood. METHODS: In 1984, early childhood vaccination was introduced in 2 rural Gambian villages. In 2003, serological assessment of 81.5% of 1,350 eligible participants 1-24 years old was done, to determine vaccine efficacy against infection and carriage. RESULTS: Overall vaccine efficacy against infection and carriage was 83.4% (95% confidence interval [CI], 79.8%-86.6%) and 96.5% (85% CI, 93.9%-98.9%), respectively. Vaccine efficacy against infection was similar when restricted to primary responders (85.3%), but a significant effect of peak antibody concentration was found. Both vaccine efficacy and levels of hepatitis B surface antibody (anti-HBs) decreased with age, resulting in a vaccine efficacy against infection and carriage among 20-24-year-old participants of 70.9% (95% CI, 60.4%-80.5%) and 91.1% (95% CI, 75.8%-100%), respectively. Fifteen years after vaccination, fewer than half of the vaccinees had detectable anti-HBs. The prevalence of carriage in the unvaccinated population was similar to the prevalence 20 years earlier. CONCLUSIONS: HBV vaccination early during life can provide long-lasting protection against carriage, despite decreasing antibody levels. The role played by subclinical boosting and the necessity of a booster need to be evaluated.

Identifying ELISPOT and skin test cut-offs for diagnosis of Mycobacterium tuberculosis infection in The Gambia.

SETTING: An urban area, The Gambia. OBJECTIVE: To identify ELISPOT and PPD skin test cut-offs, targeting sensitivity and specificity equivalence. DESIGN: Tuberculosis cases >5 years of age and their household contacts underwent ELISPOT, HIV and PPD skin tests. Cases and contacts sleeping in a different house were used to estimate sensitivity and specificity, providing two planes for estimating cut-offs. Specificity was adjusted for infection from previous exposure using a multivariate discrimination algorithm. RESULTS: The point on the line of intersection of the planes that maximised sensitivity and specificity equivalence occurred at 4 spots (95% confidence interval [CI] 3.5-5, multiplier=0 ) for CFP-10 and 5.5 spots (4.5-8, multiplier=0 for ESAT-6), yielding a sensitivity and specificity of 76% for both antigens. Combining ESAT-6 and CFP-10 using an 'or' statement yielded a maximum equivalence sensitivity and specificity of 76.5% at 6 spots for ESAT-6 and 11.5 spots for CFP-10. For the PPD skin test sensitivity and specificity, an equivalence of 78% occurred at 11 mm induration (9-13 mm). CONCLUSION: An ELISPOT cut-off for ESAT-6 or CFP-10 could be set at 4-8 spot forming units (20-40 spots per million), with little benefit from combining the results. A cut-off of 9-13 mm for the PPD skin test is reasonable when comparing with the ELISPOT.

Dr Bruno Sachs addresses an audience of first year medical students: an extract from the writing of Martin Winckler, French doctor and writer.

One of the authors of this paper (DJ) has been impressed by the work of the second author (MW) for some time. On reading one of his works, Les Trois Médecins, DJ was so struck by a particular passage that he attempted a translation. He received not only permission from Winckler to seek publication but also help with the translation. Along with that translation, which forms the body of this article, the passage has been set in context by MW, who also provides some explanation of it. It is DJ's hope that the article will prove stimulating in its own right, and also lead some readers at least to seek out more of Winckler's work.

Estimation of critical loads of acidity for lakes in northeastern United States and eastern Canada.

The New England Governors and Eastern Canadian Premiers (NEG/ECP) adopted the Acid Rain Action Plan in June 1998, and issued a series of action items to support its work toward a reduction of sulfur dioxide (SO(2)) and nitrogen oxide (NO(x)) emissions in northeastern North America. One of these action items was the preparation of an updated critical load map using data from lakes in the NEG/ECP area. Critical load maps provide a more complete index of the surface water sensitivity to acidification. Combined sulfur and nitrogen critical loads and deposition exceedances were computed using Henriksen's Steady-State Water Chemistry (SSWC) model. Results show that 28% of all 2053 lakes studied have a critical load of 20 kg/ha/year or less, making them vulnerable to acid deposition. Emission reductions, and more specifically SO(2) emission reductions have proven beneficial because critical loads were exceeded in 2002 for 12.3% of all studied lakes. Those lakes are located in the more sensitive areas where geology is carbonate-poor. Of these lakes, 2.9% will never recover even with a complete removal of SO(4) deposition. Recovery from acidification for the remaining 9.4% of the lakes will require additional emission SO(2) reductions.

Comparison of non-invasive sampling methods for detection of HPV in rural African women.

BACKGROUND: The prevalence of cervical cancer is extremely high in low income countries, primarily because of a lack of cytological screening. The link between human papillomavirus (HPV) and cervical cancer has long been recognised, and it has been suggested that isolated HPV testing in women who do not participate in existing screening programmes may be used to identify women at higher risk of developing cervical cancer. This community based study compares two self administered techniques for detecting HPV (tampons and self administered swabs) with a clinician directed technique, the cervical cytobrush. METHODS: 377 rural women were interviewed and of these 210 women had full gynaecological examination, and accepted all three sampling methods for HPV. HPV typing of DNA extracts was performed using polymerase chain reaction and enzyme linked immunosorbent assay techniques. RESULTS: Using the cervical cytobrush as the gold standard, self administered swabs (SAS) showed a sensitivity of 63.9%, and tampons showed a sensitivity of 72.4%. The acceptability of these two tests was 97.1% and 84.6% respectively. When combining acceptability with sensitivity, the SAS detected 61.9% and the tampons detected 60.9% of the true positives. CONCLUSION: In a setting where women are at a considerable risk of developing cervical cancer, with no access to a formal screening programme, self directed HPV testing could be a useful screening tool in identifying those women at increased risk who may require further investigation.

Regional scale evidence for improvements in surface water chemistry 1990-2001.

The main aim of the international UNECE monitoring program ICP Waters under the Convention of Long-range Transboundary Air Pollution (CLRTAP) is to assess, on a regional basis, the degree and geographical extent of the impact of atmospheric pollution, in particular acidification, on surface waters. Regional trends are calculated for 12 geographical regions in Europe and North America, comprising 189 surface waters sites. From 1990-2001 sulphate concentrations decreased in all but one of the investigated regions. Nitrate increased in only one region, and decreased in three North American regions. Improvements in alkalinity and pH are widely observed. Results from the ICP Waters programme clearly show widespread improvement in surface water acid-base chemistry, in response to emissions controls programs and decreasing acidic deposition. Limited site-specific biological data suggest that continued improvement in the chemical status of acid-sensitive lakes and streams will lead to biological recovery in the future.

Climate-induced episodic acidification of streams in central ontario.

In this study we have analyzed the hydrochemical effect of drought conditions during 311 hydrological episodes in nine headwater streams in central Ontario over the past 20 years. Acid Neutralization Capacity (ANC) was logarithmically correlated (p<0.05) to antecedent discharge in eight of the nine streams, with the largest decline in ANC occurring after low antecedent flow. In eight of the nine streams SO4(2-) was the most important driving mechanism of ANC decline, but dilution as well as organic acidity was important in several streams. No decrease in the SO4(2-) driven ANC decline was observed over the 20 year study period despite a approximately 40% reduction in SO4(2-) deposition. The strong correlation between ANC decline and low antecedent discharge demonstrates that episodic acidification during rain events is strongly associated with preceding drought conditions, especially in wetland-dominated catchments. The results have important implications for recoveryfrom acidification, especially in northern ecosystems where climate scenarios forecast that warmer and drier conditions will be more common.

Design and implementation of relational databases relevant to the diverse needs of a tuberculosis case contact study in the Gambia.

The data requirements of a large multidisciplinary tuberculosis case contact study are complex. We describe an ACCESS-based relational database system that meets our rigorous requirements for data entry and validation, while being user-friendly, flexible, exportable, and easy to install on a network or stand alone system. This includes the development of a double data entry package for epidemiology and laboratory data, semi-automated entry of ELISPOT data directly from the plate reader, and a suite of new programmes for the manipulation and integration of flow cytometry data. The double entered epidemiology and immunology databases are combined into a separate database, providing a near-real-time analysis of immuno-epidemiological data, allowing important trends to be identified early and major decisions about the study to be made and acted on. This dynamic data management model is portable and can easily be applied to other studies.

Detection of severe protein-energy malnutrition by nurses in The Gambia.

AIM: To test whether nurses can use the WHO integrated management of childhood illness (IMCI) nutrition algorithm to identify reliably severe protein-energy malnutrition in children. METHODS: Nurses were trained to identify severe protein-energy malnutrition using IMCI training materials. They identified visible severe wasting and bipedal oedema, and categorised weight-for-age using a growth chart, in consecutive children attending outpatient clinics. Their findings were compared with weight for height Z (WHZ) score, bipedal oedema assessed by a trained observer, and weight-for-age Z score. RESULTS: A total of 352 children were recruited, of whom 34 (9.7%) were severely wasted (WHZ score <-3) and 18 (5.1%) had bipedal oedema. In the detection of severe wasting, the nurses' assessments showed 56% sensitivity, 95% specificity, and 56% positive predictive value (PPV), and for bipedal oedema 22%, 99%, and 57% respectively. Overall, the nurses identified only half of 50 children with severe wasting and/or bipedal oedema and wrongly identified a further 13 children as severely malnourished. Plotting weight for age by the nurses showed 62% sensitivity, 99% specificity, and 89% PPV for the detection of children with very low weight. CONCLUSIONS: Severe malnutrition was both under-diagnosed and wrongly diagnosed by nurses trained in the use of the IMCI nutrition algorithm in a clinic setting in The Gambia. These guidelines for health workers and the training materials, particularly with respect to calculation of age, need further development to improve the detection of malnourished children.

Monitoring the results of Canada/U.S.A. acid rain control programs: some lake responses.

Aquatic acidification by deposition of airborne pollutants emerged as an environmental issue in southeastern Canada during the 1970s. Drawing information from the extensive research and monitoring programs, a sequence of issue assessments demonstrated the necessity of reducing the anthropogenic emissions of acidifying pollutants, particularly sulphur dioxide (SO2). The 1991 Canada-U.S. Air Quality Agreement (AQA) was negotiated to reduce North American SO2 emissions by approximately 40% relative to 1980 levels by 2010, and at present, both countries have reduced emissions beyond their AQA commitment. In response to reduced SO2 emissions, atmospheric deposition of sulphate (SO4(2-)) and SO4(2-) concentrations in many lakes have declined, particularly in south-central Ontario and southern Québec. Sulphate deposition still exceeds aquatic critical loads throughout southeastern Canada however. Increasing pH or alkalinity (commonly deemed 'recovery') has been observed in only some lakes. Several biogeochemical factors have intervened to modify the lake chemistry response to reduced SO4(2-) input, notably release of stored SO4(2-) from wetlands following periods of drought and reduction in the export of base cations from terrestrial soils. Three examples from Ontario are presented to illustrate these responses. Significant increases in pH and alkalinity have been observed in many lakes in the Sudbury area of Ontario due to the large reductions in local SO2 emissions; 'early-stage' biological recovery is evident in these lakes. An integrated assessment model predicts that AQA emission reductions will not be sufficient to promote widespread chemical or biological recovery of Canadian lakes. Monitoring and modeling are mutually supporting assessment activities and both must continue.

Absence of association between delayed type hypersensitivity to tuberculin and atopy in children in The Gambia.

BACKGROUND: An inverse association between delayed type hypersensitivity to tuberculin and atopy has been observed in children, suggesting that exposure to mycobacteria may influence the immune response to allergens. OBJECTIVE: To investigate the relationship between tuberculin responses and atopy in children living in three different environments in The Gambia. METHODS: In this cross-sectional study a total of 507 school-aged children were recruited from rural, urban poor or urban affluent communities. They were assessed for skin responses to five common allergens and tuberculin, presence of bacille Calmette-Guérin (BCG) scar, presence of intestinal parasites, and total serum IgE. Atopy was defined as the presence of a skin prick test response > or = 3 x 3 mm to at least one allergen. RESULTS: The overall prevalence of atopy was 33% but there was a significant variation among the three study groups. The prevalence of atopy was 22% in urban poor, 36% in urban affluent, and 43% in rural children. Controlling for potential confounding factors, children in the rural community had a significantly higher odds ratio, 3.3 (95% confidence interval 1.8-6.0) of being atopic than children from the urban poor community. No association between atopy and tuberculin response or BCG scar was observed in any of the three groups. Serum IgE levels were higher among children of the urban poor group but were not associated with tuberculin response or BCG scar in any of the groups. CONCLUSION: Environmental factors have an important influence on the development of atopy in children in The Gambia but delayed type hypersensitivity to tuberculin is not a protective factor.

Congenital rubella syndrome: a risk in immigrant populations.

An infant with congenital rubella syndrome was born to a young mother who had recently arrived in the UK. The infection was not detected before birth, and transmission to another infant was documented. This case highlights the emerging importance of rubella as an imported infection in the developed world and the need to maintain a high index of suspicion for this disorder in recent immigrants from countries with no immunisation programme. Targeted immunisation for such groups is recommended.