Malaria is an important cause of global morbidity and mortality. The fact that some people are bitten more often than others has a large effect on the relationship between risk factors and prevalence ...of vector-borne diseases. Here we develop a mathematical framework that allows us to estimate the heterogeneity of infection rates from the relationship between rates of infectious bites and community prevalence. We apply this framework to a large, published data set that combines malaria measurements from more than 90 communities. We find strong evidence that heterogeneous biting or heterogeneous susceptibility to infection are important and pervasive factors determining the prevalence of infection: 20% of people receive 80% of all infections. We also find that individual infections last about six months on average, per infectious bite, and children who clear infections are not immune to new infections. The results have important implications for public health interventions: the success of malaria control will depend heavily on whether efforts are targeted at those who are most at risk of infection.
Ultrafine particles (UFPs, diameter
<
100
nm) and co-emitted pollutants from traffic are a potential health threat to nearby populations. During summertime in Raleigh, North Carolina, UFPs were ...simultaneously measured upwind and downwind of a major roadway using a spatial matrix of five portable industrial hygiene samplers (measuring total counts of 20–1000
nm particles). While the upper sampling range of the portable samplers extends past the defined “ultrafine” upper limit (100
nm), the 20–1000
nm number counts had high correlation (Pearson
R
=
0.7–0.9) with UFPs (10–70
nm) measured by a co-located research-grade analyzer and thus appear to be driven by the ultrafine range. Highest UFP concentrations were observed during weekday morning work commutes, with levels at 20
m downwind from the road nearly fivefold higher than at an upwind station. A strong downwind spatial gradient was observed, linearly approximated over the first 100
m as an 8% drop in UFP counts per 10
m distance. This result agreed well with UFP spatial gradients estimated from past studies (ranging 5–12% drop per 10
m). Linear regression of other vehicle-related air pollutants measured in near real-time (10-min averages) against UFPs yielded moderate to high correlation with benzene (
R
2
=
0.76), toluene (
R
2
=
0.49), carbon monoxide (
R
2
=
0.74), nitric oxide (
R
2
=
0.80), and black carbon (
R
2
=
0.65). Overall, these results support the notion that near-road levels of UFPs are heavily influenced by traffic emissions and correlate with other vehicle-produced pollutants, including certain air toxics.
Numerous health studies conducted worldwide suggest an increase in the occurrence of adverse health effects for populations living, working, or going to school near large roadways. A study was ...designed to assess traffic emission impacts on air quality near a heavily traveled highway. The portion of highway studied included a section of open field and a section with a noise barrier adjacent to the road. In addition, the section containing the noise barrier included a portion with vegetation in the vicinity of the barrier. Thus, this field study provided an opportunity to evaluate near-road air quality with no barriers, with a noise barrier only, and with a noise barrier and vegetation adjacent to the road. Pollutants measured under these scenarios included carbon monoxide (CO) and particulate matter (PM).
Measurements showed the effects of a noise barrier on near-road air quality. The presence of this structure often led to pollutant concentration reductions behind the barrier during meteorological conditions with winds directionally from the road. CO and PM number concentrations generally decreased between 15 and 50% behind the barrier. However, conditions occurred when pollutant concentrations were greater behind the barrier than when no barrier was present. These results imply that the presence of a noise barrier can lead to higher pollutant concentrations on the road during certain wind conditions. In addition, the study results suggested that the presence of mature trees in addition to the barrier further lowered PM number concentrations.
Malaria burden is increasing in sub-Saharan cities because of rapid and uncontrolled urbanization. Yet very few studies have studied the interactions between urban environments and malaria. ...Additionally, no standardized urban land-use/land-cover has been defined for urban malaria studies. Here, we demonstrate the potential of local climate zones (LCZs) for modeling malaria prevalence rate (PfPR 2−10) and studying malaria prevalence in urban settings across nine sub-Saharan African cities. Using a random forest classification algorithm over a set of 365 malaria surveys we: (i) identify a suitable set of covariates derived from open-source earth observations; and (ii) depict the best buffer size at which to aggregate them for modeling PfPR 2−10. Our results demonstrate that geographical models can learn from LCZ over a set of cities and be transferred over a city of choice that has few or no malaria surveys. In particular, we find that urban areas systematically have lower PfPR 2−10 (5%-30%) than rural areas (15%-40%). The PfPR 2−10 urban-to-rural gradient is dependent on the climatic environment in which the city is located. Further, LCZs show that more open urban environments located close to wetlands have higher PfPR 2−10. Informal settlements-represented by the LCZ 7 (lightweight lowrise)-have higher malaria prevalence than other densely built-up residential areas with a mean prevalence of 11.11%. Overall, we suggest the applicability of LCZs for more exploratory modeling in urban malaria studies.
The contribution of malaria to morbidity and mortality among people in Africa has been a subject of academic interest, political advocacy, and speculation. National statistics for much of sub-Saharan ...Africa have proved to be an unreliable source of disease-specific morbidity and mortality data. Credible estimates of disease-specific burdens are required for setting global and national priorities for health in order to rationalize the use of limited resources and lobby for financial support. We have taken an empirical approach to defining the limits of Plasmodium falciparum transmission across the continent and interpolated the distributions of projected populations in 1995. By combining a review of the literature on malaria in Africa and models of acquired functional immunity, we have estimated the age-structured rates of the fatal, morbid and disabling sequelae following exposure to malaria infection under different epidemiological conditions.
Milk fat globule membrane is a protein-lipid complex that may strengthen the gut barrier. The main objective of this study was to assess the ability of a membrane-rich milk fat diet to promote the ...integrity of the gut barrier and to decrease systemic inflammation in lipopolysaccharide (LPS)-challenged mice. Animals were randomly assigned to one of 2 American Institute of Nutrition (AIN)-76A formulations differing only in fat source: control diet (corn oil) and milk fat diet (anhydrous milk fat with 10% milk fat globule membrane). Each diet contained 12% calories from fat. Mice were fed diets for 5 wk, then injected with vehicle or LPS (10mg/kg of BW) and gavaged with dextran-fluorescein to assess gut barrier integrity. Serum was assayed for fluorescence 24h after gavage, and 16 serum cytokines were measured to assess the inflammatory response. Gut permeability was 1.8-fold higher in LPS-challenged mice fed the control diet compared with the milk fat diet. Furthermore, mice fed the milk fat diet and injected with LPS had lower serum levels of IL-6, IL-10, IL-17, monocyte chemotactic protein (MCP)-1, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and IL-3 compared with LPS-injected mice fed the control diet. The results indicate that the membrane-rich milk fat diet decreases the inflammatory response to a systemic LPS challenge compared with corn oil, and the effect coincides with decreased gut permeability.
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