Serological Comparison of Native Antigen ELISAs with Rapid ICT Test Kits for the Diagnosis of Human Alveolar and Cystic Echinococcosis in China.

BACKGROUND: The aim of this study was to compare the diagnostic performance of native antigen ELISAs and ADAMU-AE/CE commercial ICT test kits in subjects either exposed to Echinococcus infection or with clinically diagnosed alveolar (AE) or cystic (CE) echinococcosis. METHODS: A total of 370 subjects with a previous clinical confirmation of CE or AE from northwestern China were recruited. Serum samples were also obtained from 3923 children/teenagers during a community survey. All sera were tested using native antigen ELISAs. The ADAMU-AE/CE test kits were subsequently used for the serology of the 370 clinically confirmed individuals and of 251 children/teenagers that were ELISA antibody-positive for both Echinococcus species but ultrasound-negative during baseline survey. An analysis of the association between the serological tests and ultrasound classification was carried out amongst 89 AE and 164 CE cases. A Kappa consistency analysis was undertaken to compare the diagnostic performance of the native antigen ELISAs and the ADAMU kits and the ultrasound imaging results. The χ² test was also used for a comparison of the different seropositivity rates between the groups. FINDINGS: There was poor consistency (Kappa = 0.26 and 0.28 for AE and CE respectively) between the native antigen ELISAs and the ADAMU kits for the diagnosis of AE and CE among the cases and the surveyed children/teenagers, but a relatively good consistency (Kappa = 0.63) between the ADAMU-AE kit and ultrasound observations for the AE cases. Additionally, of the 251 teenagers co-positive for both AE and CE antibodies by the native antigen ELISAs, only one was found positive by the ADAMU-AE kit, verified as a new AE case on subsequent ultrasound follow-up. The remainder (N = 250) were negative by serology using the ADAMU-AE/CE kits and by ultrasound examination. The two native antigen ELISAs did not discriminate well between cases of clinically diagnosed AE and CE. In contrast, ADAMU-AE and ADAMU-CE commercial ICT test kits readily differentiated cases of AE from CE with specificities of 99% for AE and 100% for CE. CONCLUSIONS: The ADAMU-AE/CE kits proved reliable, accurate, and amenable diagnostic tools in the clinical setting for confirmation of suspected AE/CE cases. The native antigen ELISAs tests can provide useful information on the level of human exposure to Echinococcus infection.

Using Regional Sero-Epidemiology SARS-CoV-2 Anti-S Antibodies in the Dominican Republic to Inform Targeted Public Health Response.

Incidence of COVID-19 has been associated with sociodemographic factors. We investigated variations in SARS-CoV-2 seroprevalence at sub-national levels in the Dominican Republic and assessed potential factors influencing variation in regional-level seroprevalence. Data were collected in a three-stage cross-sectional national serosurvey from June to October 2021. Seroprevalence of antibodies against the SARS-CoV-2 spike protein (anti-S) was estimated and adjusted for selection probability, age, and sex. Multilevel logistic regression was used to estimate the effect of covariates on seropositivity for anti-S and correlates of 80% protection (PT80) against symptomatic infection for the ancestral and Delta strains. A total of 6683 participants from 134 clusters in all 10 regions were enrolled. Anti-S, PT80 for the ancestral and Delta strains odds ratio varied across regions, Enriquillo presented significant higher odds for all outcomes compared with Yuma. Compared to being unvaccinated, receiving ≥2 doses of COVID-19 vaccine was associated with a significantly higher odds of anti-S positivity (OR 85.94, [10.95-674.33]) and PT80 for the ancestral (OR 4.78, [2.15-10.62]) and Delta strains (OR 3.08, [1.57-9.65]) nationally and also for each region. Our results can help inform regional-level public health response, such as strategies to increase vaccination coverage in areas with low population immunity against currently circulating strains.

Spatial predictive risk mapping of lymphatic filariasis residual hotspots in American Samoa using demographic and environmental factors.

BACKGROUND: American Samoa successfully completed seven rounds of mass drug administration (MDA) for lymphatic filariasis (LF) from 2000-2006. The territory passed the school-based transmission assessment surveys in 2011 and 2015 but failed in 2016. One of the key challenges after the implementation of MDA is the identification of any residual hotspots of transmission. METHOD: Based on data collected in a 2016 community survey in persons aged ≥8 years, Bayesian geostatistical models were developed for LF antigen (Ag), and Wb123, Bm14, Bm33 antibodies (Abs) to predict spatial variation in infection markers using demographic and environmental factors (including land cover, elevation, rainfall, distance to the coastline and distance to streams). RESULTS: In the Ag model, females had a 26.8% (95% CrI: 11.0-39.8%) lower risk of being Ag-positive than males. There was a 2.4% (95% CrI: 1.8-3.0%) increase in the odds of Ag positivity for every year of age. Also, the odds of Ag-positivity increased by 0.4% (95% CrI: 0.1-0.7%) for each 1% increase in tree cover. The models for Wb123, Bm14 and Bm33 Abs showed similar significant associations as the Ag model for sex, age and tree coverage. After accounting for the effect of covariates, the radii of the clusters were larger for Bm14 and Bm33 Abs compared to Ag and Wb123 Ab. The predictive maps showed that Ab-positivity was more widespread across the territory, while Ag-positivity was more confined to villages in the north-west of the main island. CONCLUSION: The findings may facilitate more specific targeting of post-MDA surveillance activities by prioritising those areas at higher risk of ongoing transmission.

Incidence and predictors of Escherichia coli producing extended-spectrum beta-lactamase (ESBL-Ec) in Queensland, Australia from 2010 to 2019: a population-based spatial analysis.

The dissemination of Escherichia coli producing extended-spectrum beta-lactamase (ESBL-Ec) is evident in the community. A population-based spatial analysis is necessary to investigate community risk factors for ESBL-Ec occurrence. The study population was defined as individuals with ESBL-Ec isolated in Queensland, Australia, from 2010 to 2019. Choropleth maps, global Moran's index and Getis-Ord Gi* were used to describe ESBL-Ec distribution and identify hot spots. Multivariable Poisson regression models with or without spatially structured random effects were performed. A total of 12 786 individuals with ESBL-Ec isolate were identified. The crude incidence rate increased annually from 9.1 per 100 000 residents in 2010 to 49.8 per 100 000 residents in 2019. The geographical distribution of ESBL-Ec changed from random to clustered after 2014, suggesting presence of community-specific factors that can enhance occurrence. Hot spots were more frequently identified in Outback and Far North Queensland, future public health measures to reduce transmission should prioritise these communities. Communities with higher socioeconomic status (RR = 0.66, 95% CI 0.55-0.79, per 100 units increase) and higher proportion of residents employed in the agricultural industry (RR = 0.79, 95% CI 0.67-0.95, per 10% increase) had lower ESBL-Ec incidence. Risk factors for occurrence appear differential between remote and city settings and this should be further investigated.

Spatially Explicit Environmental Factors Associated with Lymphatic Filariasis Infection in American Samoa.

Under the Global Program to Eliminate Lymphatic Filariasis (LF) American Samoa conducted seven rounds of mass drug administration (MDA) between 2000 and 2006. Subsequently, the territory passed the WHO recommended school-based transmission assessment survey (TAS) in 2011/2012 (TAS-1) and 2015 (TAS-2) but failed in 2016, when both TAS-3 and a community survey found LF antigen prevalence above what it had been in previous surveys. This study aimed to identify potential environmental drivers of LF to refine future surveillance efforts to detect re-emergence and recurrence. Data on five LF infection markers: antigen, Wb123, Bm14 and Bm33 antibodies and microfilaraemia, were obtained from a population-wide serosurvey conducted in American Samoa in 2016. Spatially explicit data on environmental factors were derived from freely available sources. Separate multivariable Poisson regression models were developed for each infection marker to assess and quantify the associations between LF infection markers and environmental variables. Rangeland, tree cover and urban cover were consistently associated with a higher seroprevalence of LF-infection markers, but to varying magnitudes between landcover classes. High slope gradient, population density and crop cover had a negative association with the seroprevalence of LF infection markers. No association between rainfall and LF infection markers was detected, potentially due to the limited variation in rainfall across the island. This study demonstrated that seroprevalence of LF infection markers were more consistently associated with topographical environmental variables, such as gradient of the slope, rather than climatic variables, such as rainfall. These results provide the initial groundwork to support the detection of areas where LF transmission is more likely to occur, and inform LF elimination efforts through better understanding of the environmental drivers.

Potential use of antibodies to provide an earlier indication of lymphatic filariasis resurgence in post-mass drug ad ministration surveillance in American Samoa.

BACKGROUND: Under the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted 7 rounds of mass drug administration (MDA) between 2000 and 2006. The territory passed transmission assessment surveys (TASs) in 2011 (TAS-1) and 2015 (TAS-2). In 2016, the territory failed TAS-3, indicating resurgence. This study aims to determine if antibodies (Abs) may have provided a timelier indication of LF resurgence in American Samoa. METHODS: We examined school-level antigen (Ag) and Ab status (presence/absence of Ag- and Ab-positive children) and prevalence of single and combined Ab responses to Wb123, Bm14, and Bm33 Ags at each TAS. Pearson chi-square test and logistic regression were used to examine associations between school-level Ab prevalence in TAS-1 and TAS-2 and school-level Ag status in TAS-3. RESULTS: Schools with higher prevalence of Wb123 Ab in TAS-2 had higher odds of being Ag-positive in TAS-3 (odds ratio [OR] 24.5, 95% confidence interval [CI] 1.2-512.7). Schools that were Ab-positive for WB123 plus Bm14, Bm33, or both Bm14 and Bm33 in TAS-2 had higher odds of being Ag-positive in TAS-3 (OR 16.0-24.5). CONCLUSION: Abs could provide earlier signals of resurgence and enable a timelier response. The promising role of Abs in surveillance after MDA and decision making should be further investigated in other settings.

Implications of a travel connectivity-based approach for infectious disease transmission risks in Oceania.

INTRODUCTION: The increase in international travel brought about by globalisation has enabled the rapid spread of emerging pathogens with epidemic and pandemic potential. While travel connectivity-based assessments may help understand patterns of travel network-mediated epidemics, such approaches are rarely carried out in sufficient detail for Oceania where air travel is the dominant method of transportation between countries. DESIGN: Travel data from the Australian Bureau of Statistics, Stats NZ and the United Nations World Tourism Organization websites were used to calculate travel volumes in 2018 within Oceania and between Oceania and the rest of the world. The Infectious Disease Vulnerability Index (IDVI) was incorporated into the analysis as an indicator of each country's capacity to contain an outbreak. Travel networks were developed to assess the spread of infectious diseases (1) into and from Oceania, (2) within Oceania and (3) between each of the Pacific Island Countries and Territories (PICTs) and their most connected countries. RESULTS: Oceania was highly connected to countries in Asia, Europe and North America. Australia, New Zealand and several PICTs were highly connected to the USA and the UK (least vulnerable countries for outbreaks based on the IDVI), and to China (intermediate low vulnerable country). High variability was also observed between the PICTs in the geographical distribution of their international connections. The PICTs with the highest number of international connections were Fiji, French Polynesia, Guam and Papua New Guinea. CONCLUSION: Travel connectivity assessments may help to accurately stratify the risk of infectious disease importation and outbreaks in countries depending on disease transmission in other parts of the world. This information is essential to track future requirements for scaling up and targeting outbreak surveillance and control strategies in Oceania.

Estimating the prevalence of Echinococcus in domestic dogs in highly endemic for echinococcosis.

BACKGROUND: Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are highly endemic in Xiji County of Ningxia Hui Autonomous Region (NHAR) in China where the control campaign based on dog de-worming with praziquantel has been undertaken over preceding decades. This study is to determine the current prevalence of Echinococcus granulosus and E. multilocularis in domestic dogs and monitor the echinococcosis transmission dynamics. METHODS: Study villages were selected using landscape patterns (Geographic Information System, GIS) for Echinococcus transmission "hot spots", combined with hospital records identifying risk areas for AE and CE. A survey of 750 domestic dogs, including copro-sampling and owner questionnaires, from 25 selected villages, was undertaken in 2012. A copro-multiplex PCR assay was used for the specific diagnosis of E. granulosus and E. multilocularis in the dogs. Data analysis, using IBM SPSS Statistics, was undertaken, to compare the prevalence of the two Echinococcus spp. in dogs between four geographical areas of Xiji by the χ2 test. Univariate analysis of the combinations of outcomes from the questionnaire and copro-PCR assay data was carried out to determine the significant risk factors for dog infection. RESULTS: The highest de-worming rate of 84.0% was found in the northwest area of Xiji County, and significant differences (P <  0.05) in the de-worming rates among dogs from the four geographical areas of Xiji were detected. The highest prevalence (19.7%, 59/300) of E. multilocularis occurred in northwest Xiji, though the highest prevalence (18.1%, 38/210) of E. granulosus occurred in southwest Xiji. There was no significant difference (P >  0.05) in the prevalence of E. granulosus in dogs from the northwest, southwest, northeast, and southeast of Xiji, but there were significant differences (P <  0.05) between dogs infected with E. multilocularis from the four areas. None of the other independent variables was statistically significant. CONCLUSIONS: The results from this study indicate a high prevalence of both E. granulosus and E. muiltilocularis in dogs in Xiji County, NHAR. Transmission of E. multilocularis was more impacted by geographical risk-factors in Xiji County than that of E. granulosus. Dogs have the potential to maintain the transmission of both species of Echinococcus within local Xiji communities, and the current praziquantel dosing of dogs appears to be ineffective or poorly implemented in this area.

Spatial prediction of the risk of exposure to Echinococcus spp. among schoolchildren and dogs in Ningxia Hui Autonomous Region, People's Republic of China.

The geographical distribution of Echinococcus spp. infections in Ningxia Hui Autonomous Region (NHAR) has been reported to be expanding in response to environmental change. The aim of the present study was to predict and compare the spatial distribution of human seropositivity for Echinococcus granulosus and Echinococcus multilocularis and infections with these parasites in dogs in four counties in the south of NHAR to identify communities where targeted prevention and control efforts are required. Predicted seroprevalence of E. granulosus in schoolchildren and E. granulosus infections in dogs concurred spatially, whereas predicted seroprevalence of E. multilocularis in schoolchildren and E. multilocularis infections in dogs differed spatially. Enhanced vegetation index was significantly associated with E. multilocularis seropositivity among schoolchildren, and infections with E. granulosus and E. multilocularis in dogs. A positive association was also found between dog infection with E. granulosus and cultivated land, and a negative association between human seropositivity for E. granulosus and bare-land/artificial surfaces. The findings of this study support the importance of land cover and climatic variables in determining habitat suitability for Echinococcus spp. infections, and suggest that definitive hosts other than dogs (e.g. foxes) are important in defining the geographical risk of human seropositivity for E. multilocularis in NHAR.

Environmental risk factors and changing spatial patterns of human seropositivity for Echinococcus spp. in Xiji County, Ningxia Hui Autonomous Region, China.

BACKGROUND: Human echinococcoses are parasitic helminth infections that constitute a serious public health concern in several regions across the world. Cystic (CE) and alveolar echinococcosis (AE) in China represent a high proportion of the total global burden of these infections. This study was conducted to predict the spatial distribution of human seropositivity for Echinococcus species in Xiji County, Ningxia Hui Autonomous Region (NHAR), with the aim of identifying communities where targeted prevention and control efforts are required. METHODS: Bayesian geostatistical models with environmental and demographic covariates were developed to predict spatial variation in the risk of human seropositivity for Echinococcus granulosus (the cause of CE) and E. multilocularis (the cause of AE). Data were collected from three cross-sectional surveys of school children conducted in Xiji County in 2002-2003, 2006-2007 and 2012-2013. Environmental data were derived from high-resolution satellite images and meteorological data. RESULTS: The overall seroprevalence of E. granulosus and E. multilocularis was 33.4 and 12.2%, respectively, across the three surveys. Seropositivity for E. granulosus was significantly associated with summer and winter precipitation, landscape fragmentation variables and the extent of areas covered by forest, shrubland, water and bareland/artificial surfaces. Seropositivity for E. multilocularis was significantly associated with summer and winter precipitations, landscape fragmentation variables and the extent of shrubland and water bodies. Spatial correlation occurred over greater distances for E. granulosus than for E. multilocularis. The predictive maps showed that the risk of seropositivity for E. granulosus expanded across Xiji during the three surveys, while the risk of seropositivity for E. multilocularis became more confined in communities located in the south. CONCLUSIONS: The identification of high-risk areas for seropositivity for these parasites, and a better understanding of the role of the environment in determining the transmission dynamics of Echinococcus spp. may help to guide and monitor improvements in human echinococcosis control strategies by allowing targeted allocation of resources.

Spatiotemporal patterns and environmental drivers of human echinococcoses over a twenty-year period in Ningxia Hui Autonomous Region, China.

BACKGROUND: Human cystic (CE) and alveolar (AE) echinococcoses are zoonotic parasitic diseases that can be influenced by environmental variability and change through effects on the parasites, animal intermediate and definitive hosts, and human populations. We aimed to assess and quantify the spatiotemporal patterns of human echinococcoses in Ningxia Hui Autonomous Region (NHAR), China between January 1994 and December 2013, and examine associations between these infections and indicators of environmental variability and change, including large-scale landscape regeneration undertaken by the Chinese authorities. METHODS: Data on the number of human echinococcosis cases were obtained from a hospital-based retrospective survey conducted in NHAR for the period 1 January 1994 through 31 December 2013. High-resolution imagery from Landsat 4/5-TM and 8-OLI was used to create single date land cover maps. Meteorological data were also collected for the period January 1980 to December 2013 to derive time series of bioclimatic variables. A Bayesian spatio-temporal conditional autoregressive model was used to quantify the relationship between annual cases of CE and AE and environmental variables. RESULTS: Annual CE incidence demonstrated a negative temporal trend and was positively associated with winter mean temperature at a 10-year lag. There was also a significant, nonlinear effect of annual mean temperature at 13-year lag. The findings also revealed a negative association between AE incidence with temporal moving averages of bareland/artificial surface coverage and annual mean temperature calculated for the period 11-15 years before diagnosis and winter mean temperature for the period 0-4 years. Unlike CE risk, the selected environmental covariates accounted for some of the spatial variation in the risk of AE. CONCLUSIONS: The present study contributes towards efforts to understand the role of environmental factors in determining the spatial heterogeneity of human echinococcoses. The identification of areas with high incidence of CE and AE may assist in the development and refinement of interventions for these diseases, and enhanced environmental change risk assessment.

Land cover change during a period of extensive landscape restoration in Ningxia Hui Autonomous Region, China.

Environmental change has been a topic of great interest over the last century due to its potential impact on ecosystem services that are fundamental for sustainable development and human well-being. Here, we assess and quantify the spatial and temporal variation in land cover in Ningxia Hui Autonomous Region (NHAR), China. With high-resolution (30m) imagery from Landsat 4/5-TM and 8-OLI for the entire region, land cover maps of the region were created to explore local land cover changes in a spatially explicit way. The results suggest that land cover changes observed in NHAR from 1991 to 2015 reflect the main goals of a national policy implemented there to recover degraded landscapes. Forest, herbaceous vegetation and cultivated land increased by approximately 410,200ha, 708,600ha and 164,300ha, respectively. The largest relative land cover change over the entire study period was the increase in forestland. Forest growth resulted mainly from the conversion of herbaceous vegetation (53.8%) and cultivated land (30.8%). Accurate information on the local patterns of land cover in NHAR may contribute to the future establishment of better landscape policies for ecosystem management and protection. Spatially explicit information on land cover change may also help decision makers to understand and respond appropriately to emerging environmental risks for the local population.

The landscape epidemiology of echinococcoses.

Echinococcoses are parasitic diseases of major public health importance globally. Human infection results in chronic disease with poor prognosis and serious medical, social and economic consequences for vulnerable populations. According to recent estimates, the geographical distribution of Echinococcus spp. infections is expanding and becoming an emerging and re-emerging problem in several regions of the world. Echinococcosis endemicity is geographically heterogeneous and over time it may be affected by global environmental change. Therefore, landscape epidemiology offers a unique opportunity to quantify and predict the ecological risk of infection at multiple spatial and temporal scales. Here, we review the most relevant environmental sources of spatial variation in human echinococcosis risk, and describe the potential applications of landscape epidemiological studies to characterise the current patterns of parasite transmission across natural and human-altered landscapes. We advocate future work promoting the use of this approach as a support tool for decision-making that facilitates the design, implementation and monitoring of spatially targeted interventions to reduce the burden of human echinococcoses in disease-endemic areas.