Month: February 2013

Decelerating Spread of West Nile Virus by Percolation in a Heterogeneous Urban Landscape

/ Matt Artz

PLoS Comput BiolPLoS Computational Biology 7(7), 2011

Krisztian Magori, Waheed I. Bajwa, Sarah Bowden, and John M. Drake

“Vector-borne diseases are emerging and re-emerging in urban environments throughout the world, presenting an increasing challenge to human health and a major obstacle to development. Currently, more than half of the global population is concentrated in urban environments, which are highly heterogeneous in the extent, degree, and distribution of environmental modifications. Because the prevalence of vector-borne pathogens is so closely coupled to the ecologies of vector and host species, this heterogeneity has the potential to significantly alter the dynamical systems through which pathogens propagate, and also thereby affect the epidemiological patterns of disease at multiple spatial scales. One such pattern is the speed of spread. Whereas standard models hold that pathogens spread as waves with constant or increasing speed, we hypothesized that heterogeneity in urban environments would cause decelerating travelling waves in incipient epidemics.

The spatial structure of annual WNV outbreaks in NYC, demonstrated for the year of 2003.

The spatial structure of annual WNV outbreaks in NYC, demonstrated for the year of 2003. Speed of WNV spread was estimated from point locations of WNV-positive mosquito pools (circles) and WNV-positive dead birds (triangles). Dark and light cyan areas represent transmission-inhibiting and transmission-promoting land-cover types. The black crosses represent the approximate location of Central Park, La Guardia Airport and the John F. Kennedy International Airport respectively, where NOAA collects weather data. The first five locations where WNV was detected in 2003 are labeled as A, B, C, D, and E, respectively. The first estimate of wave-speed was calculated using the convex hull method as (1) the increase of the square root area of the polygon encompassing ABCDE (black) relative to the square root area of the polygon encompassing ABCD (red) locations (convex hull method).

“To test this hypothesis, we analysed data on the spread of West Nile virus (WNV) in New York City (NYC), the 1999 epicentre of the North American pandemic, during annual epizootics from 2000–2008. These data show evidence of deceleration in all years studied, consistent with our hypothesis. To further explain these patterns, we developed a spatial model for vector-borne disease transmission in a heterogeneous environment. An emergent property of this model is that deceleration occurs only in the vicinity of a critical point. Geostatistical analysis suggests that NYC may be on the edge of this criticality. Together, these analyses provide the first evidence for the endogenous generation of decelerating travelling waves in an emerging infectious disease. Since the reported deceleration results from the heterogeneity of the environment through which the pathogen percolates, our findings suggest that targeting control at key sites could efficiently prevent pathogen spread to remote susceptible areas or even halt epidemics.”

Forest Elephant Crisis in the Congo Basin

/ Matt Artz

PLoS Biology, 5(4), 2007

Stephen Blake, Samantha Strindberg, Patrick Boudjan, Calixte Makombo, Inogwabini Bila-Isia, Omari Ilambu, Falk Grossmann, Lambert Bene-Bene, Bruno de Semboli, Valentin Mbenzo, Dino S’hwa, Rosine Bayogo, Liz Williamson, Mike Fay, John Hart, and Fiona Maisels

“Debate over repealing the ivory trade ban dominates conferences of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Resolving this controversy requires accurate estimates of elephant population trends and rates of illegal killing. Most African savannah elephant populations are well known; however, the status of forest elephants, perhaps a distinct species, in the vast Congo Basin is unclear. We assessed population status and incidence of poaching from line-transect and reconnaissance surveys conducted on foot in sites throughout the Congo Basin.

Interpolated Elephant Dung Count and Human-Sign Frequency across the Ndoki-Dzanga MIKE Site

Interpolated Elephant Dung Count and Human-Sign Frequency across the Ndoki-Dzanga MIKE Site

“Results indicate that the abundance and range of forest elephants are threatened from poaching that is most intense close to roads. The probability of elephant presence increased with distance to roads, whereas that of human signs declined. At all distances from roads, the probability of elephant occurrence was always higher inside, compared to outside, protected areas, whereas that of humans was always lower. Inside protected areas, forest elephant density was correlated with the size of remote forest core, but not with size of protected area. Forest elephants must be prioritised in elephant management planning at the continental scale.”

World Ocean Council to Facilitate Industry Action on US Ocean Policy and Marine Spatial Planning

/ Matt Artz

World Ocean CouncilProgram Will Develop Coordinated, Pro-active Business Community Involvement in U.S. Ocean Policy and Planning

The World Ocean Council (WOC) is launching a two-year effort to improve ocean business community understanding, collaboration and participation in U.S. ocean policy and marine spatial planning (MSP) developments.

The WOC program includes:

  • Organizing a national business conference on U.S. ocean policy in 2014.
  • Developing an ocean business community roster in each of the 9 MSP regions.
  • Establishing ocean business leadership fora in 3 of the MSP regions.

Private sector involvement is essential to achieving balanced and lasting outcomes to marine policy and management efforts. For example, without business involvement in MSP – which seeks to guide the intensity and location of uses in an area – there is a significant risk that planning will not fully consider existing and potential economic activities and will miss out on key marine resource, use and ecosystem information held by industry. Business participation in MSP is critical to ensuring it delivers its proposed benefits to responsible industry operators, such as streamlined permitting.

Although the WOC effort is focused on the U.S., the outputs will be of importance to the ocean business community in other countries and regions where ocean policies and MSP are under development, e.g. Europe, Canada, Australia and elsewhere.

The Sustainable Ocean Summit (SOS) – 22-24 April, 2013, Washington, D.C. – includes an important session on MSP that will provide input to the new WOC program by addressing:

  • What is the business case for MSP?
  • How can ocean industries ensure they are informed and engaged in a coordinated, pro-active manner?
  • What is needed to make sure that MSP reflects the needs and opportunities of industry involvement?

The WOC is recruiting an ocean policy/marine spatial planning program officer. Information is available at: http://www.oceancouncil.org/site/opportunities.php

The WOC project on ocean policy and planning in the U.S. is possible thanks to support from the Gordon and Betty Moore Foundation.

[Source: World Ocean Council  press release]

Global Mapping of Infectious Disease

/ Matt Artz / 1 Comment

Philosophical Transactions of the Royal Society B, 04 February 2013

Simon I. Hay, Katherine E. Battle, David M. Pigott, David L. Smith, Catherine L. Moyes, Samir Bhatt, John S. Brownstein, Nigel Collier, Monica F. Myers, Dylan B. George, and Peter W. Gething

“The primary aim of this review was to evaluate the state of knowledge of the geographical distribution of all infectious diseases of clinical significance to humans. A systematic review was conducted to enumerate cartographic progress, with respect to the data available for mapping and the methods currently applied. The results helped define the minimum information requirements for mapping infectious disease occurrence, and a quantitative framework for assessing the mapping opportunities for all infectious diseases. This revealed that of 355 infectious diseases identified, 174 (49%) have a strong rationale for mapping and of these only 7 (4%) had been comprehensively mapped.

A schematic overview of a niche/occurrence mapping process (for example boosted regression trees (BRT)) that uses pseudo-absence data guided by expert opinion. Consensus based definitive extent layers of infectious disease occurrence at the national level (a) are combined with accurately geo-positioned occurrence (presence) locations (b) to generate pseudo-absence data (c). The presence (b) and pseudo-absence data (c) are then used in the BRT analyses, alongside a suite of environmental covariates (d ) to predict the probability of occurrence of the target disease (e).

A schematic overview of a niche/occurrence mapping process (for example boosted regression trees (BRT)) that uses pseudo-absence data guided by expert opinion. Consensus based definitive extent layers of infectious disease occurrence at the national level (a) are combined with accurately geo-positioned occurrence (presence) locations (b) to generate pseudo-absence data (c). The presence (b) and pseudo-absence data (c) are then used in the BRT analyses, alongside a suite of environmental covariates (d ) to predict the probability of occurrence of the target disease (e).

“A variety of ambitions, such as the quantification of the global burden of infectious disease, international biosurveillance, assessing the likelihood of infectious disease outbreaks and exploring the propensity for infectious disease evolution and emergence, are limited by these omissions. An overview of the factors hindering progress in disease cartography is provided. It is argued that rapid improvement in the landscape of infectious diseases mapping can be made by embracing non-conventional data sources, automation of geo-positioning and mapping procedures enabled by machine learning and information technology, respectively, in addition to harnessing labour of the volunteer ‘cognitive surplus’ through crowdsourcing.”

Resource Diversity and Landscape-level Homogeneity Drive Native Bee Foraging

/ Matt Artz

PNAS-2.coverPNAS, 08 January 2013

Shalene Jha and Claire Kremen

“Given widespread declines in pollinator communities and increasing global reliance on pollinator-dependent crops, there is an acute need to develop a mechanistic understanding of native pollinator population and foraging biology. Using a population genetics approach, we determine the impact of habitat and floral resource distributions on nesting and foraging patterns of a critical native pollinator, Bombus vosnesenskii. Our findings demonstrate that native bee foraging is far more plastic and extensive than previously believed and does not follow a simple optimal foraging strategy. Rather, bumble bees forage further in pursuit of species-rich floral patches and in landscapes where patch-to-patch variation in floral resources is less, regardless of habitat composition. Thus, our results reveal extreme foraging plasticity and demonstrate that floral diversity, not density, drives bee foraging distance. Furthermore, we find a negative impact of paved habitat and a positive impact of natural woodland on bumble bee nesting densities. Overall, this study reveals that natural and human-altered landscapes can be managed for increased native bee nesting and extended foraging, dually enhancing biodiversity and the spatial extent of pollination services.”

2013 URISA Student Competition Opens

/ Matt Artz

URISAURISA is pleased to announce that submissions are now being accepted for the 2013 Student Competition. URISA hosts an annual Student Competition to encourage students in a variety of academic settings and disciplines to write and publish papers and posters to share with the URISA membership and others in the geospatial technologies industry.  The submission may include research projects, case studies, projects, or any type of methodology in which geospatial technology and skills were used or could be used.

Submissions will be accepted until June 3, 2013 in two categories:

PAPERS – Students are invited to submit a paper for the competition and possible inclusion in the URISA Journal. The papers will undergo a review process under the direction of an esteemed panel of academic and practitioner members of URISA. Lead authors of the top papers receive an award of a one-year membership in URISA and free registration to GIS-Pro 2013 (along with an opportunity to present at the conference). Students are encouraged to submit essays on geospatial issues as well as technical research papers, relating to any field geospatial field. Students should display original thought and creativity in the development of the papers.

POSTERS – Community College and GIS Certificate students are specifically invited to submit posters for the competition. The posters will undergo a review process under the direction of an esteemed panel of academic and practitioner members of URISA. The top ten posters will receive an award of a one-year membership in URISA.

For details and submission guidelines, visit http://www.urisa.org/student_competition

[Source: URISA press release]

The Effects of City Streets on an Urban Disease Vector

/ Matt Artz / 2 Comments

PLoS Comput Biol PLOS Computational Biology, 17 January 2013

Corentin M. Barbu, Andrew Hong, Jennifer M. Manne, Dylan S. Small, Javier E. Quintanilla Calderón, Karthik Sethuraman, Víctor Quispe-Machaca, Jenny Ancca-Juárez, Juan G. Cornejo del Carpio, Fernando S. Málaga Chavez, César Náquira, and Michael Z. Levy

“With increasing urbanization vector-borne diseases are quickly developing in cities, and urban control strategies are needed. If streets are shown to be barriers to disease vectors, city blocks could be used as a convenient and relevant spatial unit of study and control. Unfortunately, existing spatial analysis tools do not allow for assessment of the impact of an urban grid on the presence of disease agents. Here, we first propose a method to test for the significance of the impact of streets on vector infestation based on a decomposition of Moran’s spatial autocorrelation index; and second, develop a Gaussian Field Latent Class model to finely describe the effect of streets while controlling for cofactors and imperfect detection of vectors. We apply these methods to cross-sectional data of infestation by the Chagas disease vector Triatoma infestans in the city of Arequipa, Peru.

Spatial distribution of Triatoma infestans presence in households of Paucarpata, Arequipa, Peru.

Spatial distribution of Triatoma infestans presence in households of Paucarpata, Arequipa, Peru. Map of the study area. Black indicates infested households, white non-infested households, and grey non-inspected households. The area encircled by dashes was used to fit the Gaussian Field Latent Class model; the remaining area was used as a validation dataset. The close-up shows the urban grid underneath and the aggregation of vectors within city blocks.

“Our Moran’s decomposition test reveals that the distribution of T. infestans in this urban environment is significantly constrained by streets (p<0.05). With the Gaussian Field Latent Class model we confirm that streets provide a barrier against infestation and further show that greater than 90% of the spatial component of the probability of vector presence is explained by the correlation among houses within city blocks. The city block is thus likely to be an appropriate spatial unit to describe and control T. infestans in an urban context. Characteristics of the urban grid can influence the spatial dynamics of vector borne disease and should be considered when designing public health policies.”