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Wilschut L.I.,University Utrecht | Addink E.A.,University Utrecht | Heesterbeek J.A.P.,University Utrecht | Dubyanskiy V.M.,Stavropol Plague Control Research Institute | And 7 more authors.
International Journal of Applied Earth Observation and Geoinformation

Plague is a zoonotic infectious disease present in great gerbil populations in Kazakhstan. Infectious disease dynamics are influenced by the spatial distribution of the carriers (hosts) of the disease. The great gerbil,the main host in our study area, lives in burrows, which can be recognized on high resolution satellite imagery.In this study, using earth observation data at various spatial scales, we map the spatial distribution of burrows in a semi-desert landscape. The study area consists of various landscape types. To evaluate whether identification of burrows by classification is possible in these landscape types, the study area was subdivided into eightlandscape units, on the basis of Landsat 7 ETM+ derived Tasselled Cap Greenness and Brightness, and SRTM derivedstandard deviation in elevation. In the field, 904 burrows were mapped. Using two segmented 2.5 m resolution SPOT-5 XS satellite scenes, reference object sets were created. Random Forests were built for both SPOT scenes and used to classify the images. Additionally, a stratified classification was carried out, by building separate Random Forests per landscape unit. Burrows were successfully classified in all landscape units. In the 'steppe on floodplain' areas, classification worked best: producer's and user's accuracy in those areas reached 88% and 100%, respectively. In the 'floodplain' areas with a more heterogeneous vegetation cover, classification worked least well; there, accuracies were 86 and 58% respectively. Stratified classification improved the results in all landscape units where comparison was possible (four), increasing kappa coefficients by 13, 10, 9 and 1%, respectively. In this study, an innovative stratification method using high- and medium resolution imagery was applied inorder to map host distribution on a large spatial scale. The burrow maps we developed will help to detect changes in the distribution of great gerbil populations and, moreover, serve as a unique empirical data set which can be used as input for epidemiological plague models. This is an important step in understanding the dynamics of plague. © 2012 Elsevier B.V. Source

Wilschut L.I.,University Utrecht | Addink E.A.,University Utrecht | Heesterbeek H.,University Utrecht | Heier L.,University of Oslo | And 8 more authors.
International Journal of Health Geographics

Background: Plague (Yersinia pestis infection) is a vector-borne disease which caused millions of human deaths in the Middle Ages. The hosts of plague are mostly rodents, and the disease is spread by the fleas that feed on them. Currently, the disease still circulates amongst sylvatic rodent populations all over the world, including great gerbil (Rhombomys opimus) populations in Central Asia. Great gerbils are social desert rodents that live in family groups in burrows, which are visible on satellite images. In great gerbil populations an abundance threshold exists, above which plague can spread causing epizootics. The spatial distribution of the host species is thought to influence the plague dynamics, such as the direction of plague spread, however no detailed analysis exists on the possible functional or structural corridors and barriers that are present in this population and landscape. This study aims to fill that gap.Methods: Three 20 by 20 km areas with known great gerbil burrow distributions were used to analyse the spatial distribution of the burrows. Object-based image analysis was used to map the landscape at several scales, and was linked to the burrow maps. A novel object-based method was developed - the mean neighbour absolute burrow density difference (MNABDD) - to identify the optimal scale and evaluate the efficacy of using landscape objects as opposed to square cells. Multiple regression using raster maps was used to identify the landscape-ecological variables that explain burrow density best. Functional corridors and barriers were mapped using burrow density thresholds. Cumulative resistance of the burrow distribution to potential disease spread was evaluated using cost distance analysis. A 46-year plague surveillance dataset was used to evaluate whether plague spread was radially symmetric.Results: The burrow distribution was found to be non-random and negatively correlated with Greenness, especially in the floodplain areas. Corridors and barriers showed a mostly NWSE alignment, suggesting easier spreading along this axis. This was confirmed by the analysis of the plague data.Conclusions: Plague spread had a predominantly NWSE direction, which is likely due to the NWSE alignment of corridors and barriers in the burrow distribution and the landscape. This finding may improve predictions of plague in the future and emphasizes the importance of including landscape analysis in wildlife disease studies. © 2013 Wilschut et al.; licensee BioMed Central Ltd. Source

Wilschut L.I.,University Utrecht | Laudisoit A.,University of Liverpool | Hughes N.K.,University of Antwerp | Addink E.A.,University Utrecht | And 6 more authors.
Journal of Biogeography

Aim: The spatial structure of a population can strongly influence the dynamics of infectious diseases, yet rarely is the underlying structure quantified. A case in point is plague, an infectious zoonotic disease caused by the bacterium Yersinia pestis. Plague dynamics within the Central Asian desert plague focus have been extensively modelled in recent years, but always with strong uniformity assumptions about the distribution of its primary reservoir host, the great gerbil (Rhombomys opimus). Yet, while clustering of this species' burrows due to social or ecological processes could have potentially significant effects on model outcomes, there is currently nothing known about the spatial distribution of inhabited burrows. Here, we address this knowledge gap by describing key aspects of the spatial patterns of great gerbil burrows in Kazakhstan. Location: Kazakhstan. Methods: Burrows were classified as either occupied or empty in 98 squares of four different sizes: 200 m (side length), 250 m, 500 m and 590-1020 m. We used Ripley's K statistic to determine whether and at what scale there was clustering of occupied burrows, and semi-variograms to quantify spatial patterns in occupied burrows at scales of 250 m to 9 km. Results: Significant spatial clustering of occupied burrows occurred in 25% and 75% of squares of 500 m and 590-1020 m, respectively, but not in smaller squares. In clustered squares, the clustering criterion peaked around 250 m. Semi-variograms showed that burrow density was auto-correlated up to a distance of 7 km and occupied density up to 2.5 km. Main conclusions: These results demonstrate that there is statistically significant spatial clustering of occupied burrows and that the uniformity assumptions of previous plague models should be reconsidered to assess its significance for plague transmission. This field evidence will allow for more realistic approaches to disease ecology models for both this system and for other structured host populations. © 2015 The Authors. Source

Popova A.Yu.,Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing | Gus'kov A.S.,Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing | Ivanov G.E.,Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing | Chikina L.V.,Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing | And 4 more authors.
Voprosy Pitaniia

The problems of catering control various client groups during the XXII Olympic Winter Games and XI Paralympic Winter Games of 2014 in Sochi is one of the priorities of the sanitary and epidemiological welfare of the population during mass events. The data on the order of nutrition of guests and participants of the games, control of food items, sanitary and microbiological monitoring of drinking water, food raw materials and products are presented. It is noted that the ongoing supervisory activities contributed to the sanitary and epidemiological well-being during the Games. The purpose of this study was to lighting modern achievements in the field of nutrition and food microbiology in the period of the Olympic Games and the determination of their value to the further improvement and use at when conducting mass gatherings. Source

Eremenko E.I.,Stavropol Plague Control Research Institute | Ryazanova A.G.,Stavropol Plague Control Research Institute | Tsygankova O.I.,Stavropol Plague Control Research Institute | Tsygankova E.A.,Stavropol Plague Control Research Institute | And 2 more authors.
Molecular Genetics, Microbiology and Virology

A study of the genotypes of Bacillus anthracis strains isolated from the Caucasus region was per- formed using multiple-locus variable-number tandem repeat analysis (MLVA). Among 149 strains, 32 dis- tinctive MLVA-8 genotypes belonging to the A1a, A3a, A4, and B1 molecular diversity groups were identified. Nine genotypes were not described previously; six genotypes were not found in other geographic regions and can be considered endemic for the Caucasus. The majority of the identified genotypes are widespread not only in the Caucasus, but also throughout Eurasia, Africa, and America. The molecular diversity of Cauca- sian isolates is comparable to the global diversity. This represents the historical character of this region, prox- imity to ancient trade routes, and intensity of the anthrax epizootic in Caucasus. The obtained results are of interest from the theoretical point of view, as well as for application in epidemiological research on anthrax outbreaks. © Allerton Press, Inc., 2012. Source

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