Identifying residual foci of Plasmodium falciparum infections for malaria elimination: the urban context of Khartoum, Sudan

Background

Identifying the location and size of residual foci of infections is critical where malaria elimination is the primary goal. Here the spatial heterogeneity of Plasmodium falciparum infections within the urban extent of Khartoum state in Sudan is investigated using data from cross-sectional surveys undertaken from 1999 to 2008 to inform the Khartoum Malaria Free Initiative (KMFI).

Methods

From 1999–2008 the KMFI undertook cross-sectional surveys of 256 clusters across 203 random samples of residential blocks in the urban Khartoum state in September of each year. Within sampled blocks, at least five persons, including at least one child under the age of five years, were selected from each household. Blood smears were collected from the sampled individuals to examine the presence of P. falciparum parasites. Residential blocks were mapped. Data were analysed for spatial clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic.

Results

A total of 128,510 malaria slide examinations were undertaken during the study period. In 1999, overall prevalence was 2.5%, rising to 3.2% in 2000 and consistently staying below 1% in subsequent years. From 2006, over 90% of all surveyed clusters reported no infections. Spatial clustering of infections was present in each year but not statistically significant in the years 2001, 2002, 2004 and 2008. Spatial clusters of high infection were often located at the junction of the Blue and White Niles.

Conclusion

Persisting foci of malaria infection in Khartoum are likely to distort wide area assessments and disproportionately affect future transmission within the city limits. Improved investments in surveillance that combines both passive and active case detection linked to a geographic information system and a more detailed analysis of the location and stability of foci should be undertaken to facilitate and track malaria elimination in the state of Khartoum.     

Assessment of the national schistosomiasis control program in a typical region along the Yangtze River,China

Schistosomiasis remains a major public health problem in eastern China, particularly along the Yangtze River Basin. The latest national schistosomiasis control program (NSCP) was implemented in 2005 with the main goal of reducing the rate of infection to less than 5% by 2008 and 1% by 2015. To assess the progress, we applied a Bayesian spatio-temporal model to describe dynamics of schistosomiasis in Guichi, Anhui Province, China, using annual parasitological and environmental data collected within 41 sample villages for the period 2005–2011. Predictive maps of schistosomiasis showed that the disease prevalence remains constant and low. Results of uncertainty analysis, in the form of probability contour maps (PCMs), indicated that the first goal of “infection rate less than 5% by 2008” was fully achieved in the study area. More longitudinal data for schistosomiasis are needed for the assessment of the second goal of “infection rate less than 1% by 2015”. Compared with the traditional way of mapping uncertainty (e.g., variance or mean-square error), our PCMs provide more realistic information for schistosomiasis control.     

Trends in the postfortification prevalence of spina bifida and anencephaly in the United States

BACKGROUND: The prevalence of NTDs in the US declined significantly after mandatory folic acid fortification; however, it is not known if the prevalence of NTDs has continued to decrease in recent years relative to the period immediately following the fortification mandate. METHODS: Population‐based data from 21 birth defects surveillance systems were used to examine trends in the birth prevalence of spina bifida and anencephaly during 1999–2000, 2001–2002, and 2003–2004. Prevalence data were stratified by non‐Hispanic White, non‐Hispanic Black, and Hispanic race or ethnicity. Prevalence ratios were calculated by dividing the birth prevalences during the later time periods (2001–2002 and 2003–2004) by the birth prevalences during 1999–2000. RESULTS: During 1999–2004, 3,311 cases of spina bifida and 2,116 cases of anencephaly were reported. Hispanic infants had the highest prevalences of NTDs for all years. For all infants, the combined birth prevalences of spina bifida and anencephaly decreased 10% from the 1999–2000 period to the 2003–2004 period. The decline in spina bifida (3%) was not significant; however the decline in anencephaly (20%) was statistically significant. CONCLUSIONS: While the prevalences of spina bifida and anencephaly in the United States have declined since folic acid fortification in the food supply began, these data suggest that reductions in the prevalence of anencephaly continued during 2001–2004 and that racial and ethnic and other disparities remain. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.     

Evidence for predatory control of the invasive round goby

We coupled bioenergetics modeling with bottom trawl survey results to evaluate the capacity of piscivorous fish in eastern Lake Erie to exert predatory control of the invading population of round goby Neogobius melanostomus. In the offshore (>20 m deep) waters of eastern Lake Erie, burbot Lota lota is a native top predator, feeding on a suite of prey fishes. The round goby invaded eastern Lake Erie during the late 1990s, and round goby population size increased dramatically during 1999–2004. According to annual bottom trawl survey results, round goby abundance in offshore waters peaked in 2004, but then declined during 2004–2008. Coincidentally, round goby became an important component of burbot diet beginning in 2003. Using bottom trawling and gill netting, we estimated adult burbot abundance and age structure in eastern Lake Erie during 2007. Diet composition and energy density of eastern Lake Erie burbot were also determined during 2007. This information, along with estimates of burbot growth, burbot mortality, burbot water temperature regime, and energy densities of prey fish from the literature, were incorporated into a bioenergetics model application to estimate annual consumption of round goby by the adult burbot population. Results indicated that the adult burbot population in eastern Lake Erie annually consumed 1,361 metric tons of round goby. Based on the results of bottom trawling, we estimated the biomass of yearling and older round goby in offshore waters eastern Lake Erie during 2007–2008 to be 2,232 metric tons. Thus, the adult burbot population was feeding on round goby at an annual rate equal to 61% of the estimated round goby standing stock. We concluded that the burbot population had high potential to exert predatory control on round goby in offshore waters of eastern Lake Erie.     

Analysis of gene origin in the first adult returns to the Cultus sockeye salmon captive breeding program

Rigorous evaluation of the utility of captive breeding for the restoration of depleted wild salmonid fish populations has not been undertaken. In particular, little is known about the reproductive success of captively-bred individuals that are released back into an extant population and their capacity to assist in long-term population persistence. For the endangered Cultus Lake sockeye salmon population, we examined the potential genetic contribution of the first juvenile fish released from a captive breeding program upon their maturity in the natural Cultus Lake environment. Genetic analysis of 792 Cultus sockeye salmon that were spawned in captivity in 2004 and their adult progeny of 2007 and 2008 revealed a genetic bottleneck originating from 20 wild sockeye salmon hatchery-spawned at Cultus Lake in the previous generation. Pedigree analysis revealed that six of the 20 sockeye salmon spawned in 2001 (grandparents) gave rise to a majority of the hatchery spawners in 2004 (parents) and provided more than 30% of the genes in the progeny that survived to maturity in the wild. Allele frequencies and genetic diversity of the age three progeny that returned to Cultus Lake from their marine migration in 2007 reflected the bottleneck, but its genetic signature was faint among the more genetically diverse age four fish that returned in 2008. Two-generation analysis of gene origin among fish resulting from 2004 hatchery production indicated that they contained the genetic diversity expected from 36 effective ancestors.     

Ubiquitous variability in the prevalence of Trichobilharzia stagnicolae (Schistosomatidae) infecting Stagnicola emarginata in three northern Michigan lakes

During 4 consecutive collecting seasons from 1998 through 2001, 77,326 common beach snails (Stagnicola emarginata, Lymnaeidae) were examined for infections by Trichobilharzia stagnicolae from multiple sites on Walloon Lake, Higgins Lake, and Lake Leelanau, located in the northern region of the lower peninsula of Michigan. Snails were examined for infections using the light-box technique (exposure to bright fluorescent light). The prevalence of infected snails varied significantly among lakes within a year, between years in a lake, at a site from year to year, and at a site over a collecting season. Overall annual prevalence ranged from 0.54% (1999) to 1.32% (2001) on Walloon Lake, from 0.56% (2001) to 1.06% (1998) on Higgins Lake, and 0.30% (2001) to 0.89% (2000) on Lake Leelanau. Generally, the peak in prevalence coincided in July on the lakes. Prevalence was found to increase with snail length in all lakes. A comparison of the light-box technique and crushing snails demonstrated that prevalence varied in magnitude by technique as much as 1.2 and 5.7 times.     

The ecology of Biomphalaria sudanica in Lake Ziway, Ethiopia

A longitudinal study was made over a period of 24 months from January 2001 to December 2002 in Lake Ziway, Ethiopia, to elucidate factors influencing changes in the population density of Biomphalaria sudanica and to identify seasons of peak transmission of Schistosoma mansoni. Between January 2001 and December 2002, bimonthly visits were made to the lake to collect data on snail population density and schistosome infection in snails, vegetation and lake water level. Water samples were collected during the dry and rainy seasons and chemical analyses were made for major cations, anions, electrical conductivity, total hardness and pH using standard methods for the examination of water and wastewater. The seasonal fluctuation in the population density of B. sudanica was found to be highly associated with rainfall, water level of the lake and vegetation availability and abundance. Water chemical analysis showed that major cations and anions were all within the range reported for other African freshwaters. Both malacological and meteorological data show that snail population density in Lake Ziway peaks at the end of the long rainy season (June–August), coinciding with a seasonal transmission peak of schistosomiasis.     

Nest success and hatchling survival of American alligators within inland wetlands of east Texas

Because of liberalization of American alligator (Alligator mississippiensis) harvest management in Texas, estimates of nest success and hatchling survival for inland populations are essential for long-term, sustainable population and harvest management. To date, few studies have examined American alligator nest success and hatchling survival. We initiated a 3-year study from 2006 to 2008 to document alligator nest success and hatchling survival within several wetlands in east Texas. From June 2006 to August 2008, we located 30 nests from 3 wetlands within east Texas, where overall nest success was 44.2% (95% CI = 25.1–63.1%), irrespective of year. Nest circumference and day during the nesting season exerted the greatest influence on nest success. Additionally, from August 2006 to August 2008 we captured, marked, and released 271 hatchling alligators at Little Sandy National Wildlife Refuge, and recaptured an additional 192 hatchling alligators during this time. We estimated yearly apparent survival at 6.0% (95% CI = 2.0–14.6%) for hatchling alligators born in 2006 and 43.0% (95% CI = 28.4–57.8%) for those hatched in 2007. Variation in nest success and hatchling survival was likely attributed to fluctuating water levels and habitat management practices. Alligator harvest regulations need to account for variability in nest success and hatchling survival by including site-specific estimates of these metrics into harvest models. Failing to account for spatial and temporal variation in nest success and hatchling survival may result in unsustainable harvest and/or overharvest. © 2012 The Wildlife Society.     

Analysis of risk factors and changing trends the infection rate of intestinal schistosomiasis caused by S. japonicum from 2005 to 2014 in Lushan city

Intestinal schistosomiasis caused by S. japonicum has long been a threat to the health of residents within endemic areas, especially along the mid-tier of the Yangtze River basin as well as the Dongting and Poyang lakes. Therefore, we collected monitoring data from 2005 to 2014 in Lushan City, Jiujiang City, Jiangxi Province, which is located downstream of Poyang Lake. We conducted a logistic regression analysis in 2005 and in 2008 and then conducted a time series analysis from 2005 to 2014 in Lushan city. The results of the logistic regression analysis showed that after integrated measures were implemented in Lushan city in 2004, the infection rate of intestinal schistosomiasis decreased sharply in different populations, but fishermen had a greater risk of contracting intestinal schistosomiasis in both 2005 and 2008. From the time series analysis, we found that the infection rate decreased sharply from 2005 to 2009 and then increased slowly from 2009 to 2011 before finally becoming relatively stable and the predicated infection rates in HES, SM2, and SM3 are ?1.14%, 0.35%, 0.29%, respectively, compared with 0.41% of schistosomiasis infection in 2014, showing a downward trend. Our study indicated that the integrated measures initiated in 2004 in Lushan city had a positive effect on controlling intestinal schistosomiasis, but we should still emphasize special treatment of particular populations, such as fishermen, and should consider environmental changes, such as changes in the water level of Poyang Lake, in the future.     

Common bottlenose dolphin (Tursiops truncatus) social structure and distribution changes following the 2008 Unusual Mortality Event in the Indian River Lagoon,Florida

In animal societies with fission-fusion dynamics, demographic disturbances can influence the social and spatial structure of the population. Within the Indian River Lagoon (IRL), Florida, common bottlenose dolphins (Tursiops truncatus) have experienced recurrent unusual mortality events (UMEs) providing an opportunity to examine postdisturbance population and social cluster restructuring. This study investigates the impact of the potentially nonepizootic 2008 UME on the IRL dolphin population. Photo-identification surveys conducted from August 2006 to May 2010 were stratified into pre- (August 2006–April 2008) and post-UME (September 2008–May 2010) time periods. Social network and spatial (univariate kernel density) analyses were limited to individuals sighted 5+ times per period (pre-UME = 183, post-UME = 134), and indicated a change from 11 to ten social clusters, although individuals did not always reassociate with pre-UME cluster associates. Despite the social and spatial disconnect between IRL proper and Mosquito Lagoon clusters, both network density and core area spatial overlap increased post-UME allowing for increased intercluster interactions. However, intracluster associations increased as well, allowing the population to maintain multiple social clusters within a loosely connected network. This study shows the important role sociality may play in the adaptability of cetaceans to environmental and demographic changes.     

Epidemiology of Schistosoma japonicum in China: morbidity and strategies for control in the Dongting Lake region

Dongting Lake, covering a very large surface water area of 2691km(2), is located in Hunan Province in the southern part of the People's Republic of China. It is the second-largest freshwater lake in China and plays an important role in regulating the amount of water in the Yangtze River, China's longest river. The annual water level of the lake changes by as much as 15m, rising in summer and falling in winter. Asian schistosomiasis has been endemic in the Dongting Lake region for centuries and it has had a devastating effect on the public health of the local people. After a difficult struggle for more than four decades, a concerted programme, supported by the World Bank Loan and instigated in 1992, has resulted in remarkable progress in the control of the disease in many endemic areas of the region. However, the great challenge remains to consolidate and maintain the achievements made to date. The Schistosoma japonicum intermediate host (Oncomelania hupensis hupensis) snail habitats are huge, estimated at 1768km(2) in 1996; these are increasing at a rate of 34.7km(2) annually due to high silt deposition from the Yangtze River itself and from the connecting rivers in Hunan province, and construction of embankments in the Dongting Lake region. It is anticipated that the construction of the Three Gorges Super Dam, the largest engineering project ever undertaken, will substantially extend the range of the snail habitats and increase the number of new schistosomiasis cases. In many areas, human re-infections with S. japonicum after drug (praziquantel) treatment remain unacceptably high (up to 20% of those treated are re-infected annually) due to occupational (mainly fishing) water contact. This paper reviews the history and the current status of schistosomiasis control in the lake region, it explores the epidemiological factors which influence the prevalence of the infection and the disease it causes, and it provides insight into future approaches to control which might finally eradicate the infection.     

Juvenile habitat partitioning and relative productivity in allochronically isolated sockeye salmon (Oncorhynchus nerka)

Allochronic divergence, like spatial isolation, may contribute to population diversity and adaptation, however the challenges for tracking habitat utilization in shared environments are far greater. Adult Klukshu River (Yukon, Canada) sockeye salmon, Oncorhynchus nerka, return as genetically distinct "early" and "late" runs. Early and late adult spawning populations (1999 and 2000) and their subsequent fry (sampled at 7 sites in 2000 and at 8 sites in 2001 throughout Klukshu Lake and River) were genotyped at eight microsatellite loci. Bayesian assignment was used to determine the spatial distribution of early versus late fry; although intermixed, the distribution of fry significantly differed in Klukshu Lake and in the Klukshu River in 2001, based on crosstab analyses. Late-run fry predominated in Klukshu Lake at all sites, while early-run fry were most common in the north and south of Klukshu Lake and in Klukshu River. Early-run spawners had significantly higher relative productivity (early life survival) than late-run fish (2.9 times more fry produced per early-run adult in 2000, and 9.2 times more in 2001). This study demonstrates spatial habitat partitioning and differences in the contribution of allochronically isolated populations to fry abundance, and highlights annual variability that likely contributes to recruitment variation.     

Spatial Analysis of Schistosomiasis in Hubei Province,China: A GIS-Based Analysis of Schistosomiasis from 2009 to 2013

Background

Schistosomiasis remains a major public health problem in China. The major endemic areas are located in the lake and marshland regions of southern China, particularly in areas along the middle and low reach of the Yangtze River. Spatial analytical techniques are often used in epidemiology to identify spatial clusters in disease regions. This study assesses the spatial distribution of schistosomiasis and explores high-risk regions in Hubei Province, China to provide guidance on schistosomiasis control in marshland regions.

Methods

In this study, spatial autocorrelation methodologies, including global Moran’s I and local Getis–Ord statistics, were utilized to describe and map spatial clusters and areas where human Schistosoma japonicum infection is prevalent at the county level in Hubei province. In addition, linear logistic regression model was used to determine the characteristics of spatial autocorrelation with time.

Results

The infection rates of S. japonicum decreased from 2009 to 2013. The global autocorrelation analysis results on the infection rate of S. japonicum for five years showed statistical significance (Moran’s I > 0, P < 0.01), which suggested that spatial clusters were present in the distribution of S. japonicum infection from 2009 to 2013. Local autocorrelation analysis results showed that the number of highly aggregated areas ranged from eight to eleven within the five-year analysis period. The highly aggregated areas were mainly distributed in eight counties.

Conclusions

The spatial distribution of human S. japonicum infections did not exhibit a temporal change at the county level in Hubei Province. The risk factors that influence human S. japonicum transmission may not have changed after achieving the national criterion of infection control. The findings indicated that spatial–temporal surveillance of S. japonicum transmission plays a significant role on schistosomiasis control. Timely and integrated prevention should be continued, especially in the Yangtze River Basin of Jianghan Plain area.     

Spatiotemporal Cluster Patterns of Hand,Foot, and Mouth Disease at the County Level in Mainland China, 2008-2012

Background

Hand, foot, and mouth disease (HFMD) is known to be a highly contagious childhood illness. In recent years, the number of reported cases of HFMD has significantly increased in mainland China. This study aims at the epidemiological features, spatiotemporal patterns of HMFD at the county/district level in mainland China.

Methods

Data on reported HFMD cases for each county from 1 January 2008 to 31 December 2012 were obtained from the Chinese Center for Disease Control and Prevention. Cluster analysis, spatial autocorrelation, and retrospective scan methods were used to explore the spatiotemporal patterns of the disease.

Results

The annual incidences varied greatly among the counties, ranging from 0 to 74.31‰ with the median of 5.42‰ (interquartile range: 1.54‰–13.55‰) during 2008–2012 in mainland China. Counties close to provincial capital cities generally had higher incidences than rural counties. A seasonal distribution was observed between the northern and southern China, of which dual epidemic were shown in southern China and usually only one in northern China. Based on the global and local spatial autocorrelation analysis, we found that the spatial distribution of HFMD was presented a significant clustering pattern for each year (P<0.001), and hotspots of the disease were mostly distributed in coastal provinces of China. The retrospective scan statistic further identified the dynamics of spatiotemporal clustering areas of the disease, which were mainly distributed in the counties of eastern and southern China, as well as provincial capitals and their surrounding counties.

Conclusions

The spatiotemporal clustering areas of the disease identified in this way were relatively stable, and imminent public health planning and resource allocation should be focused within those areas.     

Accuracy assessment of supervised classification of submersed macrophytes: the case of the Gavaraget region of Lake Sevan,Armenia

The necessity of assessing the accuracy of spatial data derived from remote sensing methods and used in geographic information system (GIS) analyses has been regarded as a critical component of many projects. In this article, supervised classified QuickBird satellite imageries of submersed macrophytes of the Gavaraget region of Lake Sevan (Armenia) during 2006–2008 are validated in a GIS environment. The results of this assessment are represented by error matrices presenting the overall accuracy, the user and producer accuracies in each category, as well as the kappa coefficients. The assessments were done at three levels: the vegetation types, the growth (vertical) type, and the species levels. At the vegetation level, an overall accuracy of more than 86% was achieved in 2006 and 2007, while that in 2008 was about 72%. Substantial agreements were achieved between the classified remote sensing data and the reference (groundtruth) data for both 2006 and 2007. Only a fair agreement was attained in 2008. The kappa coefficients ranged from 0.39 to 0.89. At the growth type level, only the 2006 classification attained a substantial agreement, with an overall accuracy of 80%. The 2007 and 2008 classifications had above average and average overall accuracies of 72 and 64%, respectively. The kappa coefficient had a lowest value of 0.35 and a highest value of 0.70 at the growth type level. At the species level, Chara spp. or Zannichellia palustris and Potamogeton pectinatus had high user accuracies of more than 90% and a high overall accuracy of 82% in 2006. High user accuracies (>80%) occurred for P. pectinatus (for 2007 and 2008) and No Vegetation (for 2007). The remaining species, however, had low user and producer accuracies of less than 64%. The kappa coefficients ranged between 0.36 and 0.73 at the species level.     

Suitability and limitations of portion-specific abattoir data as part of an early warning system for emerging diseases of swine in Ontario

Background  

Abattoir data have the potential to provide information for geospatial disease surveillance applications, but the quality of the data and utility for detecting disease outbreaks is not well understood. The objectives of this study were to 1) identify non-disease factors that may bias these data for disease surveillance and 2) determine if major disease events that took place during the study period would be captured using multi-level modelling and scan statistics. We analyzed data collected at all provincially-inspected abattoirs in Ontario, Canada during 2001-2007. During these years there were outbreaks of porcine circovirus-associated disease (PCVAD), porcine reproductive and respiratory syndrome (PRRS) and swine influenza that produced widespread disease within the province. Negative binomial models with random intercepts for abattoir, to account for repeated measurements within abattoirs, were created. The relationships between partial carcass condemnation rates for pneumonia and nephritis with year, season, agricultural region, stock price, and abattoir processing capacity were explored. The utility of the spatial scan statistic for detecting clusters of high partial carcass condemnation rates in space, time, and space-time was investigated.     

Trends in Animal Rabies Surveillance in the Endemic State of Minas Gerais,Brazil

Rabies is a viral zoonosis affecting mammal species and causes large economic losses. Included among the neglected diseases, it is still insufficiently addressed by governments and the international community, despite formal surveillance and control programs. This study used a dataset of 10,112 rabies diagnoses in animals provided by the Brazilian passive surveillance system from 2001 to 2012. The positivity rate of the tested samples was 26.4%, and a reduction in the total samples sent during the last six years was observed. The kernel density map indicated case concentration in the south region and a decrease in density of rabies cases in the second period studied (2007 to 2012). The directional trend of positive rabies diagnoses remained in the south region, as shown by the standard deviational ellipse. The spatial scan statistic identified three large clusters of positive diagnoses, one in the first period (2001-2006) and two in the second period (2007-2012), indicating an expansion of risk areas. The decrease in rabies cases from 2006 to 2012 does not necessarily reflect lower viral circulation or improvement in actions by epidemiological surveillance; this decrease could indicate a deficiency in epidemiological surveillance during the observation period due to the increase in the silent areas. Surveillance should maintain an increasing or constant number of tests during the years in addition to a reduction in the number of outbreaks of rabies, which would indicate a lower positivity rate. The findings in this study indicate deterioration in the effectiveness of the passive surveillance for rabies. The number of rabies cases, total number of tests performed and positivity rate are good indicators for evaluating passive surveillance. This paper can function as a guide for the assessment and improvement of the actions in passive surveillance of rabies.     

Mapping the spatial distribution of the biomass and filter‐feeding effect of invasive dreissenid mussels on the winter‐spring phytoplankton bloom in Lake Michigan

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