Atmospheric deposition of phosphorus to land and freshwater.

We compiled published and newly-obtained data on the directly-measured atmospheric deposition of total phosphorus (TP), filtered total phosphorus (FTP), and inorganic phosphorus (PO4-P) to open land, lakes, and marine coasts. The resulting global data base includes data for c. 250 sites, covering the period 1954 to 2012. Most (82%) of the measurement locations are in Europe and North America, with 44 in Africa, Asia, Oceania, and South-Central America. The deposition rates are log-normally distributed, and for the whole data set the geometric mean deposition rates are 0.027, 0.019 and 0.14 g m(-2) a(-1) for TP, FTP and PO4-P respectively. At smaller scales there is little systematic spatial variation, except for high deposition rates at some sites in Germany, likely due to local agricultural sources. In cases for which PO4-P was determined as well as one of the other forms of P, strong parallels between logarithmic values were found. Based on the directly-measured deposition rates to land, and published estimates of P deposition to the oceans, we estimate a total annual transfer of P to and from the atmosphere of 3.7 Tg. However, much of the phosphorus in larger particles (principally primary biological aerosol particles) is probably redeposited near to its origin, so that long-range transport, important for tropical forests, large areas of peatland and the oceans, mainly involves fine dust from deserts and soils, as described by the simulations of Mahowald et al. (Global Biogeochemical Cycles 22, GB4026, 2008). We suggest that local release to the atmosphere and subsequent deposition bring about a pseudo-diffusive redistribution of P in the landscape, with P-poor ecosystems, for example ombrotrophic peatlands and oligotrophic lakes, gaining at the expense of P-rich ones. Simple calculations suggest that atmospheric transport could bring about significant local redistribution of P among terrestrial ecosystems. Although most atmospherically transported P is natural in origin, local transfers from fertilised farmland to P-poor ecosystems may be significant, and this requires further research.

Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland-lowland land-use continuum, under low-flow conditions.

An assessment is made of the role of riverine colloids in macronutrient (nitrogen, phosphorus and carbon), metal and trace element partitioning and transport, for five rivers in the Ribble and Wyre catchments in north-western England, under baseflow/near-baseflow conditions. Cross-flow ultrafiltration was used to separate colloidal (<0.45 µm >1 kDa) and truly dissolved (<1 kDa) fractions from river water. Clear patterns were observed, along the upland-lowland land use continuum, in the partitioning and transport of macronutrients and metals between the colloidal, truly dissolved and acid-available particulate (>0.45 µm, suspended) fractions. Of these operationally-defined fractions measured, colloids were generally more important for both macronutrient and metal transport in the upland than in the lowland rivers. The results suggest that organic moieties in truly dissolved form from sewage effluent may have a greater capacity to chelate metals. Organic-rich colloids in the upland moorlands and metal oxide colloidal precipitates in the industrial rivers had a higher capacity for binding metals than the colloidal fractions in the urban and agricultural lowland rivers. Aggregation of these colloids may provide an important mechanism for formation of larger suspended particulates, accounting for a higher degree of metal enrichment in the acid-available particulate fractions of the upland moorland and lowland industrial rivers, than in the lowland agricultural and urban rivers. This mechanism of transfer of contaminants to larger aggregates via colloidal intermediates, known as 'colloidal pumping' may also provide a mechanism for particulate P formation and the high proportion of P being transported in the particulate fraction in the uplands. The cross-flow ultrafiltration data also allowed refinement of partition coefficients, by accounting for colloids within the solids phase and replacing the filtered (<0.45 µm) fraction with the truly dissolved (<1 kDa) concentrations. These provided a clearer description of the controls on metal and P partitioning along the upland-lowland continuum.

Background wet deposition of mercury in Great Britain.

Precipitation samples have been collected on a monthly basis from a network of 10 sites in Great Britain (GB) in order to estimate background mercury (Hg) deposition in the rural environment. Collection started in February 2005 and results presented here cover the period up to June 2009. The annual volume-weighted mean (AVWM) Hg concentrations range from 1.0 ng L(-1) at Cockley Beck in the Lake District in 2006 to 8.8 ng L(-1) at Heigham Holmes on the Norfolk Coast England in 2008. The largest validated solution concentrations were 33.7 ng L(-1) Hg measured at Cockley Beck in May 2008. The large difference in rainfall amount between sites means that the remote site at Cockley Beck has both the lowest long-term AVWM concentration (1.6 ng L(-1)) and the greatest annual flux is greatest at 43 mg ha(-1) yr(-1). Predicted deposition tends to be much greater in western Britain where the greater rainfall occurs. Because some observations are very close to the analytical detection limit (1.0 ng L(-1)), rigorous cleaning procedures, the use of replicate samplers to monitor contamination, and the inclusion of 'bottle blanks' are required to obtain valid measurements of Hg in the bulk deposition. Deposition in rural sites is equivalent to about 10% of the estimated magnitude of known emissions in GB.

Travel as a risk factor for uncomplicated Plasmodium falciparum malaria in the highlands of western Kenya.

In the 1980s, highland malaria returned to the tea estates of western Kenya after an absence of nearly a generation. In order to determine the importance of travel for the spread of malaria in this region, we prospectively collected blood films and travel, demographic and geographic information on well persons and outpatients on tea estates near the western rim of the Rift Valley. Risk factors for malaria asexual parasitaemia included: tribal/ethnic group, home province and home district malaria endemicity. Travel away from the Kericho tea estates within the previous two months showed an odds ratio (OR) for parasitaemia of 1.59 for well persons and 2.38 for outpatients. Sexual stages of malaria parasites (gametocytes) had an OR of 3.14 (well persons) and 2.22 (outpatients) for those who had travelled. Increased risk of malaria parasitaemia with travel was concentrated in children aged <5 years. An increase in population gametocytaemia is possibly due to increased chloroquine resistance and suppressed infections contracted outside of the tea estates.

Use of intermittent presumptive treatment and insecticide treated bed nets by pregnant women in four Kenyan districts.

The roll back malaria (RBM) movement promotes the use of insecticide-treated bednets (ITNs) and intermittent presumptive treatment (IPT) of malaria infection as preventive measures against the adverse effects of malaria among pregnant women in Africa. To determine the use of these preventive measures we undertook a community-based survey of recently pregnant women randomly selected from communities in four districts of Kenya in December 2001. Of the 1814 women surveyed, only 5% had slept under an ITN. More than half of the 13% of women using a bednet (treated or untreated) had bought their nets from shops or markets. Women from rural areas used bednets less than urban women (11% vs. 27%; P < 0.001), and 41% of the bednets used by rural women had been obtained free of charge from a research project in Bondo or a nationwide UNICEF donation through antenatal clinics (ANCs). Despite 96% of ANC providers being aware of IPT with sulphadoxine-pyrimethamine (SP), only 5% of women interviewed had received two or more doses of SP as a presumptive treatment. The coverage of pregnant women with at least one dose of IPT with SP was 14%, though a similar percentage also had received at least a single dose as a curative treatment. The coverage of nationally recommended strategies to prevent malaria during pregnancy during 2001 was low across the diverse malaria ecology of Kenya. Rapid expansion of access to these services is required to meet international and national targets by the year 2005. The scaling up of malaria prevention programmes through ANC services should be possible with 74% of women visiting ANCs at least twice in all four districts. Issues of commodity supply and service costs to clients will be the greatest impediments to reaching RBM targets.

Comparative cost-effectiveness of diagnostic tests for urinary schistosomiasis and the implications for school health programmes.

The use of self-reported schistosomiasis or blood in urine has received a great deal of interest as a cheap and simple technique for diagnosing individuals infected with Schistosoma haematobium and identifying schools with a high prevalence of infection. Although the answers to questions about the signs and symptoms of urinary schistosomiasis have been shown to be good markers of parasitological infection, a formal cost-effectiveness analysis of their performance in relation to urine filtration and parasitological examination (assumed to be the gold standard) is lacking. Using empirical data on the costs and effectiveness of these techniques in 15 schools in Tanzania, the cost for every correct diagnosis or for every infected child identified was assessed. Although self-reported schistosomiasis was shown to be three times more cost-effective than urine filtration in identifying infected individuals, it would have resulted in a third of the infected children being missed. Use of self-reported schistosomiasis first to identify high-risk schools for mass treatment and then to identify infected children in low-risk schools (for individual treatment) also appeared more cost-effective than urine filtration and would have resulted in only 8% of the infected children not being treated. The use of self-reported schistosomiasis or self-reported blood in urine should be continually supported as a simple, cheap and cost-effective tool for identifying schools at high-risk of schistosomiasis.

A comparative cost analysis of insecticide-treated nets and indoor residual spraying in highland Kenya.

The relative cost of indoor residual house-spraying (IRS) versus insecticide-treated bednets (ITNs) forms part of decisions regarding selective malaria prevention. This paper presents a cost comparison of these two approaches as recently implemented by Merlin, a UK emergency relief organization funded through international donor support and working in the highland districts of Gucha and Kisii in Kenya. The financial costs (cash expenditures) and the economic costs (including the opportunity costs of using existing staff and volunteers, and an annualized cost for capital items) were assessed. The financial cost for IRS was US dollars 0.86 per person protected, compared with 4.21 dollars for ITNs (reducing to 3.42 dollars to the provider assuming cost recovery). The economic cost per person protected for IRS was 0.88 dollars, compared with 2.34 dollars for ITNs. The costs for ITNs were sensitive to the number of nets sold per community group ('efficiency'), as the delivery costs constituted upwards of 40% of the total cost. However, even marked increases in efficiency of these groups could not reduce the costs of ITNs to that comparable with IRS, except if more than one cycle of IRS was needed. The implications of predicted reductions in the cost of insecticide for both IRS and ITNs are also explored. The provision of itemized cost data allows predictions to be made on changes in the design of these programmes. Under almost all design scenarios, IRS would appear to be a more cost-efficient means of vector control in the Kenyan highlands.

Evaluation of efficacy of school-based anthelmintic treatments against anaemia in children in the United Republic of Tanzania.

OBJECTIVE: To determine the impact of deworming on anaemia as part of a large-scale school-based anthelmintic treatment programme in the Tanga Region of the United Republic of Tanzania. METHODS: Both the reduction in the prevalence of anaemia and the cost per case prevented were taken into consideration. Cross-sectional studies involved parasitological examination and anaemia evaluation before and at 10 months and 15 months after schoolchildren were dewormed. FINDINGS: Baseline studies indicated that the prevalence of anaemia (haemoglobin < 110 g/l) was high (54%) among schoolchildren, particularly those with high intensities of hookworm and schistosomiasis. Attributable fraction analysis suggested that hookworm and schistosomiasis were responsible for 6% and 15% of anaemia cases, respectively. Fifteen months after deworming with albendazole and praziquantel the prevalence of anaemia was reduced by a quarter and that of moderate-to-severe anaemia (haemoglobin <90 g/l) was reduced by nearly a half. The delivery of these anthelmintics through the school system was achieved at the relatively low cost of US$ 1 per treated child. The cost per anaemia case prevented by deworming schoolchildren was in the range US$ 6-8, depending on the haemoglobin threshold used. CONCLUSIONS: The results suggested that deworming programmes should be included in public health strategies for the control of anaemia in schoolchildren where there are high prevalences of hookworm and schistosomiasis.

The effects of sex and age of responders on the reliability of self-diagnosed infection: a study of self-reported urinary schistosomiasis in Tanzanian school children.

Self-reported schistosomiasis has been proven to be a reliable estimation of the prevalence of infection in school children. For the first time, this paper presents an investigation into the use of self-reported schistosomiasis to estimate the prevalence of urinary schistosomiasis, due to Schistosoma haematobium, in school children with particular emphasis on whether the age and sex of respondents influences the reliability of diagnosis. It is shown first, that the prevalence and intensity of infection vary with sex; infection in boys is always more prevalent and more intense than in girls of the same age and second, that age and sex influence the reliability of self-reported schistosomiasis as a diagnostic method. Age and sex are factors that should be considered when implementing control measures in endemic areas.

The potential of rapid screening methods for Schistosoma mansoni in western Kenya.

Data from 46 schools in western Kenya were used to investigate the performance of school-based questionnaires, on reported blood in stool and water-contact patterns, as indicators of the prevalence of human infection with Schistosoma mansoni. Prevalence of infection was associated with the prevalence of self-reported blood in stool, recent history of swimming and recent history of fishing. It was shown that use of a threshold of 30% of subjects reporting blood in stool would identify 42.9% of the 'high-prevalence' schools (i.e. prevalence > or = 50%) and 87.5% of the 'low-prevalence' schools (i.e. prevalence < 50%). A threshold of 25% reporting swimming would identify 57.1% and 93.7% of the high- and low-prevalence schools, respectively. Blood in stool appears to be too coarse an indicator to identify schools for mass treatment correctly. Although the use of multiple questions improved the diagnostic performance of the questionnaire in identifying the high-prevalence schools, it was unclear how questions can best be combined in other settings. However, there is a direct relationship between prevalence of S. mansoni infection and distance of the school from the lakeshore; analysis indicated that use of a threshold of 5 km from the lakeshore would correctly identify most (90%) of both the low- and high-prevalence schools. Distance to the lakeshore may therefore be used to screen schools in much of East Africa (i.e. those areas close to the Great Lakes where the infection is known to be prevalent and where much of the region's population is concentrated). In other areas of transmission, such as irrigation areas, further studies are still required.

Anaemia in schoolchildren in eight countries in Africa and Asia.

OBJECTIVE: To report on the haemoglobin concentrations and prevalence of anaemia in schoolchildren in eight countries in Africa and Asia. DESIGN: Blood samples were collected during surveys of the health of schoolchildren as a part of programmes to develop school-based health services. SETTING: Rural schools in Ghana, Indonesia, Kenya, Malawi, Mali, Mozambique, Tanzania and Vietnam. SUBJECTS: Nearly 14 000 children enrolled in basic education in three age ranges (7-11 years, 12-14 years and > or =15 years) which reflect the new UNICEF/WHO thresholds to define anaemia. RESULTS: Anaemia was found to be a severe public health problem (defined as >40% anaemic) in five African countries for children aged 7-11 years and in four of the same countries for children aged 12-14 years. Anaemia was not a public health problem in the children studied in the two Asian countries. More boys than girls were anaemic, and children who enrolled late in school were more likely to be anaemic than children who enrolled closer to the correct age. The implications of the four new thresholds defining anaemia for school-age children are examined. CONCLUSIONS: Anaemia is a significant problem in schoolchildren in sub-Saharan Africa. School-based health services which provide treatments for simple conditions that cause blood loss, such as worms, followed by multiple micronutrient supplements including iron, have the potential to provide relief from a large burden of anaemia.

The epidemiology and burden of Plasmodium falciparum-related anemia among pregnant women in sub-Saharan Africa.

The paucity of precise information on the burden of malaria among pregnant women has hampered effective lobbying for the inclusion of preventative strategies against malaria in Safe Motherhood Initiatives. This article reviews the evidence on the coincidental risks of malaria and anemia in Africa and attempts to estimate the probable burden of malaria-related severe anemia in this susceptible group. Twenty-six studies on hemoglobin levels in all-parity pregnant women throughout this region could be matched with a malaria parasite ratio in children < 15 yr old (a measure of the intensity of transmission). In areas with no malaria, the mean hemoglobin levels were markedly higher than those found in areas with stable malaria transmission, though changes with increasing intensity of transmission were unclear. Eighteen studies from areas with stable malaria transmission in sub-Saharan Africa suggested that the median prevalence of severe anemia in all-parity pregnant women is approximately 8.2%. Assuming that 26% of these cases are due to malaria, it is suggested that as many as 400,000 pregnant women may have developed severe anemia as a result of infection with malaria in sub-Saharan Africa in 1995.

Malaria in pregnancy as an indirect cause of infant mortality in sub-Saharan Africa.

Although randomized controlled trials of interventions to reduce malaria in pregnancy have demonstrated an increase in the birthweight of the newborn in primigravidae, the subsequent impact on infant mortality in all-parities has not been assessed. The aim of this paper was to model the possible impact of placental malarial infection on infant mortality through reduced birthweight. An extensive literature search was undertaken to define a series of parameters describing the associations between placental infection, birthweight and premature mortality in sub-Saharan Africa. It was shown that a baby is twice as likely to be born of low birthweight if the mother has an infected placenta at the time of delivery (all-parities: 23% vs 11%, primigravidae only: 32% vs 16%), and that the probability of premature mortality of African newborns in the first year of life is 3 times higher in babies of low birthweight than in those of normal birthweight (16% vs 4.6%). Assuming 25% of pregnant women in malaria-endemic areas of Africa harbour placental malarial infection, it is suggested that 5.7% of infant deaths in malarious areas could be an indirect cause of malaria in pregnancy. This would imply that, in 1997, malaria in pregnancy could have been responsible for around 3700 infant deaths under the diverse epidemiological conditions in Kenya. Placental infection with Plasmodium falciparum appears to have a more significant role in infant survival in Africa than has been previously assumed. This may explain the high reduction in infant mortality rates from interventions aimed at reducing transmission, over and above that expected from a decline in direct malaria-specific mortality alone.

A population dynamic approach to evaluating the impact of school attendance on the unit cost and effectiveness of school-based schistosomiasis chemotherapy programmes.

This paper presents a first attempt at modelling the possible cost and effectiveness of reaching non-enrolled children through school-based programmes using empirical data from Egypt. A sex/school-attendance/age-structured population dynamic model was used to predict trends in infection and early disease. Four treatment delivery strategies were compared: school-based (coverage of 85 %) and school-aged targeted (coverage of 25, 50 and 85 %). The school-aged targeted strategies also included the school-based programme. For each alternative strategy, the maximum unit cost was calculated to obtain a cost-effectiveness ratio equal or smaller to the one obtained with the school-based programme (unit cost of US$ 0.60). The analysis showed that, for S. mansoni in Lower Egypt, a programme where only 85% of children attending school were treated would still prevent 77 % of the early disease cases prevented with a programme where 85 % of all school-age children were treated. However, using the school-aged targeted strategy, from US $ 0.06 to US $ 1.03 extra unit costs could be spent to reach non-enrolled children and still be more cost-effective. Treating non-enrolled children is an important consideration in maximizing the effectiveness of treatment programmes while maintaining a cost-effectiveness comparable to school-based delivery.

The impact of lymphatic filariasis on labour inputs in southern India: results of a multi-site study.

A multi-site study was undertaken, in the rural areas of three districts in Tamil Nadu state, in southern India, to examine the impact of acute and chronic forms of lymphatic filariasis, caused by infection with Wuchereria bancrofti, on labour inputs. More than half of the acute episodes of adenolymphangitis (ADL) observed in the study communities caused total disability. The mean (S.D.) time that each ADL case was able to allocate to economic activity each day during these acute episodes was much less than seen in the controls matched for sex, age and occupation [0.97 (2.36) v. 4.48 (3.82) h; P < 0.01]. The acute disease also severely affected domestic activities, with female ADL cases spending only 1.54 (2.12) h/day on domestic activity, compared with 4.18 (2.61) h by controls. The subjects with chronic filariasis also spent significantly less time in economic activity than their matched controls [4.40 (3.79) v. 5.13 (3.83) h/day; P < 0.01). Although the acute episodes have a dramatic effect on the productivity of the affected individual, the labour loss caused by chronic disease is more serious, as the manifestations of chronic disease mostly affect the most productive age-groups, persist for life and are mostly irreversible. The adverse impact of acute and chronic filariasis was observed in males and females, farmers and non-farmers and during the rainy, winter and summer seasons. It is estimated that about 3.8% of the potential labour inputs of the men and 0.77% of those of the women were lost because of lymphatic filariasis. In addition to this loss, the total economic burden of the disease must include the costs of treatment and other health care and of the resources spent on control programmes. Estimates of the disease burden are likely to be useful in determining the costs and benefits of the recently launched campaign to eliminate lymphatic filariasis.

The economic burden of lymphatic filariasis in India.

Lymphatic filariasis affects 119 million people living in 73 countries, with India accounting for 40% of the global prevalence of infection. Despite its debilitating effects, lymphatic filariasis is given very low control priority. One of the reasons for this is paucity of information on the economic burden of the disease. Recent studies in rural areas of south India have shown that the treatment costs and loss of work time due to the disease are considerable. Based on the results of these studies, Kapa Ramaiah et al. here estimate the annual economic loss because of lymphatic filariasis for India and discuss the implications of their findings.

Sex-dependent neutralizing humoral response to Schistosoma mansoni 28GST antigen in infected human populations.

The reduction of Schistosoma fecundity observed after experimental vaccination with the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm28GST) antigen has been related to the inhibition of glutathione S-transferase (GST) enzymatic activity by specific antibody. The humoral immune response to the protective antigen Sm28GST and to the epitopes involved in the enzymatic site (amino acid ¿aa sequences 10-43 and 190-211) was evaluated in infected individuals before chemotherapy treatment. The capacity of the serum samples to inhibit GST enzymatic activity was assessed. Specific IgG3 response was predominant in the male population with a low intensity of infection and was associated with maximal GST inhibition. In contrast, the neutralizing activity of serum samples from women with a low intensity of infection was correlated with high specific IgA response specifically directed toward the 190-211 epitope. These results strongly support the hypothesis that GST-neutralizing IgG3 and IgA isotypes are sex dependent. The relationship of this specific acquired immune response with the level of intensity of infection is discussed.