What Is Anthrax?

Anthrax has been feared for its high mortality in animals and humans for centuries. The etiologic agent is considered a potentially devastating bioweapon, and since 1876-when Robert Koch demonstrated that Bacillus anthracis caused anthrax-it has been considered the sole cause of the disease. Anthrax is, however, a toxin-mediated disease. The toxins edema toxin and lethal toxin are formed from protein components encoded for by the pXO1 virulence plasmid present in pathogenic B. anthracis strains. However, other members of the Bacillus cereus group, to which B. anthracis belongs, have recently been shown to harbor the pXO1 plasmid and produce anthrax toxins. Infection with these Bacillus cereus group organisms produces a disease clinically similar to anthrax. This suggests that anthrax should be defined by the exotoxins encoded for by the pXO1 plasmid rather than the bacterial species it has historically been associated with, and that the definition of anthrax should be expanded to include disease caused by any member of the B. cereus group containing the toxin-producing pXO1 plasmid or anthrax toxin genes specifically.

Modelling the ecological niche of naturally occurring anthrax at global and circumpolar extents using an ensemble modelling framework.

Bacillus anthracis, the causative agent of anthrax, is a spore-forming bacterium that primarily affects herbivorous livestock, wildlife and humans exposed to direct contact with infected animal carcasses or products. To date, there are a limited number of studies that have delineated the potential global distribution of anthrax, despite the importance of the disease from both an economic and public health standpoint. This study compiled occurrence data (n = 874) of confirmed human and animal cases from 1954 to 2021 in 94 countries. Using an ensemble ecological niche model framework, we developed updated maps of the global predicted ecological suitability of anthrax to measure relative risk at multiple scales of analysis, including a model for circumpolar regions. Additionally, we produced maps quantifying the disease transmission risk associated with anthrax to cattle, sheep and goat populations. Environmental suitability for B. anthracis globally is concentred throughout Eurasia, sub-Saharan Africa, the Americas, Southeast Asia, Australia and Oceania. Suitable environments for B. anthracis at the circumpolar scale extend above the Arctic Circle into portions of Russia, Canada, Alaska and northern Scandinavia. Environmental factors driving B. anthracis suitability globally include vegetation, land surface temperature, soil characteristics, primary climate conditions and topography. At the circumpolar scale, suitability is influenced by soil factors, topography and the derived climate characteristics. The greatest risk to livestock is concentrated within the Indian subcontinent, Australia, Anatolia, the Caucasus region, Central Asia, the European Union, Argentina, Uruguay, China, the United States, Canada and East Africa. This study expands on previous work by providing enhanced knowledge of the potential spatial distribution of anthrax in the Southern Hemisphere, sub-Saharan Africa, Asia and circumpolar regions of the Northern Hemisphere. We conclude that these updated maps will provide pertinent information to guide disease control programs, inform policymakers and raise awareness at the global level to lessen morbidity and mortality among animals and humans located in environmentally suitable areas.

A generalizable one health framework for the control of zoonotic diseases.

Effectively preventing and controlling zoonotic diseases requires a One Health approach that involves collaboration across sectors responsible for human health, animal health (both domestic and wildlife), and the environment, as well as other partners. Here we describe the Generalizable One Health Framework (GOHF), a five-step framework that provides structure for using a One Health approach in zoonotic disease programs being implemented at the local, sub-national, national, regional, or international level. Part of the framework is a toolkit that compiles existing resources and presents them following a stepwise schematic, allowing users to identify relevant resources as they are required. Coupled with recommendations for implementing a One Health approach for zoonotic disease prevention and control in technical domains including laboratory, surveillance, preparedness and response, this framework can mobilize One Health and thereby enhance and guide capacity building to combat zoonotic disease threats at the human-animal-environment interface.

Potential distributions of Bacillus anthracis and Bacillus cereus biovar anthracis causing anthrax in Africa.

BACKGROUND: Bacillus cereus biovar anthracis (Bcbva) is an emergent bacterium closely related to Bacillus anthracis, the etiological agent of anthrax. The latter has a worldwide distribution and usually causes infectious disease in mammals associated with savanna ecosystems. Bcbva was identified in humid tropical forests of Côte d'Ivoire in 2001. Here, we characterize the potential geographic distributions of Bcbva in West Africa and B. anthracis in sub-Saharan Africa using an ecological niche modeling approach. METHODOLOGY/PRINCIPAL FINDINGS: Georeferenced occurrence data for B. anthracis and Bcbva were obtained from public data repositories and the scientific literature. Combinations of temperature, humidity, vegetation greenness, and soils values served as environmental variables in model calibrations. To predict the potential distribution of suitable environments for each pathogen across the study region, parameter values derived from the median of 10 replicates of the best-performing model for each pathogen were used. We found suitable environments predicted for B. anthracis across areas of confirmed and suspected anthrax activity in sub-Saharan Africa, including an east-west corridor from Ethiopia to Sierra Leone in the Sahel region and multiple areas in eastern, central, and southern Africa. The study area for Bcbva was restricted to West and Central Africa to reflect areas that have likely been accessible to Bcbva by dispersal. Model predicted values indicated potential suitable environments within humid forested environments. Background similarity tests in geographic space indicated statistical support to reject the null hypothesis of similarity when comparing environments associated with B. anthracis to those of Bcbva and when comparing humidity values and soils values individually. We failed to reject the null hypothesis of similarity when comparing environments associated with Bcbva to those of B. anthracis, suggesting that additional investigation is needed to provide a more robust characterization of the Bcbva niche. CONCLUSIONS/SIGNIFICANCE: This study represents the first time that the environmental and geographic distribution of Bcbva has been mapped. We document likely differences in ecological niche-and consequently in geographic distribution-between Bcbva and typical B. anthracis, and areas of possible co-occurrence between the two. We provide information crucial to guiding and improving monitoring efforts focused on these pathogens.

Anthrax Epizootic in Wildlife, Bwabwata National Park, Namibia, 2017.

In late September 2017, Bwabwata National Park in Namibia experienced a sudden die-off of hippopotamuses and Cape buffalo. A multiorganizational response was initiated, involving several ministries within Namibia and the US Centers for Disease Control and Prevention. Rapid interventions resulted in zero human or livestock cases associated with this epizootic.

Prevention and Control of Youth Camp-Associated Acute Gastroenteritis Outbreaks.

BACKGROUND: Approximately 14 million children attend more than 14000 US camps every year. Shared accommodations and activities can facilitate acute gastroenteritis (AGE) outbreaks. METHODS: We analyzed data from the National Outbreak Reporting System on US youth camp-associated AGE outbreaks that occurred between 2009 and 2016. We also conducted a systematic literature search of youth camp-associated AGE outbreaks that have occurred around the world and a gray literature search for existing recommendations on outbreak prevention and control at camps worldwide. RESULTS: Thirty-nine US jurisdictions reported a total of 229 youth camp-associated AGE outbreaks to the National Outbreak Reporting System. Of the 226 outbreaks included in our analyses, 120 (53%) were reported to have resulted from person-to-person transmission, 42 (19%) from an unknown transmission mode, 38 (17%) from foodborne transmission, 19 (8%) from waterborne transmission, 5 (2%) from animal contact, and 2 (<1%) from environmental contamination. Among 170 (75%) outbreaks with a single suspected or confirmed etiology, norovirus (107 [63%] outbreaks), Salmonella spp (16 [9%]), and Shiga-toxin producing Escherichia coli (12 [7%]) were implicated most frequently. We identified 43 additional youth camp-associated AGE outbreaks in the literature that occurred in various countries between 1938 and 2014. Control measures identified through the literature search included camp closure, separation of ill campers, environmental disinfection, and education on food preparation and hand hygiene. CONCLUSIONS: Youth camp-associated AGE outbreaks are caused by numerous pathogens every year. These outbreaks are facilitated by factors that include improper food preparation, inadequate cleaning and disinfection, shared accommodations, and contact with animals. Health education focused on proper hygiene and preventing disease transmission could help control or prevent these outbreaks.

Enhancing Surveillance and Diagnostics in Anthrax-Endemic Countries.

Naturally occurring anthrax disproportionately affects the health and economic welfare of poor, rural communities in anthrax-endemic countries. However, many of these countries have limited anthrax prevention and control programs. Effective prevention of anthrax outbreaks among humans is accomplished through routine livestock vaccination programs and prompt response to animal outbreaks. The Centers for Disease Control and Prevention uses a 2-phase framework when providing technical assistance to partners in anthrax-endemic countries. The first phase assesses and identifies areas for improvement in existing human and animal surveillance, laboratory diagnostics, and outbreak response. The second phase provides steps to implement improvements to these areas. We describe examples of implementing this framework in anthrax-endemic countries. These activities are at varying stages of completion; however, the public health impact of these initiatives has been encouraging. The anthrax framework can be extended to other zoonotic diseases to build on these efforts, improve human and animal health, and enhance global health security.

Foodborne Disease Outbreaks in Correctional Institutions-United States, 1998-2014.

OBJECTIVES: To present the first update on the epidemiology of US foodborne correctional institution outbreaks in 20 years. METHODS: We analyzed data from the Centers for Disease Control and Prevention's Foodborne Disease Outbreak Surveillance System to describe correctional institution outbreaks from 1998 to 2014 and compare them with other foodborne outbreaks. RESULTS: Two hundred foodborne outbreaks in correctional institutions were reported, resulting in 20 625 illnesses, 204 hospitalizations, and 5 deaths. Median number of outbreak-associated illnesses per 100 000 population per year was 45 (range = 11-141) compared with 7 (range = 4-10) for other outbreaks. These outbreaks accounted for 6% (20 625 of 358 330) of outbreak-associated foodborne illnesses. Thirty-seven states reported at least 1 outbreak in a correctional institution. Clostridium perfringens (28%; 36 of 128) was the most frequently reported single etiology. The most frequently reported contributing factor was food remaining at room temperature (37%; 28 of 76). CONCLUSIONS: Incarcerated persons suffer a disproportionate number of outbreak-associated foodborne illnesses. Better food safety oversight and regulation in correctional food services could decrease outbreaks. Public Health Implications. Public health officials, correctional officials, and food suppliers can work together for food safety. Clearer jurisdiction over regulation of correctional food services is needed.

Vital Signs: Multistate Foodborne Outbreaks - United States, 2010-2014.

INTRODUCTION: Millions of U.S. residents become ill from foodborne pathogens each year. Most foodborne outbreaks occur among small groups of persons in a localized area. However, because many foods are distributed widely and rapidly, and because detection methods have improved, outbreaks that occur in multiple states and that even span the entire country are being recognized with increasing frequency. METHODS: This report analyzes data from CDC's Foodborne Disease Outbreak Surveillance System to describe multistate foodborne outbreaks that occurred in the United States during 2010-2014. RESULTS: During this 5-year period, 120 multistate foodborne disease outbreaks (with identified pathogen and food or common setting) were reported to CDC. These multistate outbreaks accounted for 3% (120 of 4,163) of all reported foodborne outbreaks, but were responsible for 11% (7,929 of 71,747) of illnesses, 34% (1,460 of 4,247) of hospitalizations, and 56% (66 of 118) of deaths associated with foodborne outbreaks. Salmonella (63 outbreaks), Shiga toxin-producing E. coli (34), and Listeria monocytogenes (12) were the leading pathogens. Fruits (17), vegetable row crops (15), beef (13), sprouts (10), and seeded vegetables (nine) were the most commonly implicated foods. Traceback investigations to identify the food origin were conducted for 87 outbreaks, of which 55 led to a product recall. Imported foods were linked to 18 multistate outbreaks. CONCLUSIONS: Multistate foodborne disease outbreaks account for a disproportionate number of outbreak-associated illnesses, hospitalizations, and deaths relative to their occurrence. Working together, food industries and public health departments and agencies can develop and implement more effective ways to identify and to trace contaminated foods linked to multistate outbreaks. Lessons learned during outbreak investigations can help improve food safety practices and regulations, and might prevent future outbreaks.

Source attribution of human salmonellosis: an overview of methods and estimates.

Reducing the burden of foodborne salmonellosis is challenging. It requires identification of the most important food sources causing disease and prioritization of effective intervention strategies. For this purpose, a variety of methods to estimate the relative contribution of different sources of Salmonella infections have been applied worldwide. Each has strengths and limitations, and the usefulness of each depends on the public health questions being addressed. In this study, we reviewed the source attribution methods and outcomes of several studies developed in different countries and settings, comparing approaches and regional differences in attribution estimates. Reviewed results suggest that illnesses and outbreaks are most commonly attributed to exposure to contaminated food, and that eggs, broiler chickens, and pigs are among the top sources. Although most source attribution studies do not attribute salmonellosis to produce, outbreak data in several countries suggest that exposure to raw vegetables is also an important source. International travel was also a consistently important exposure in several studies. Still, the relative contribution of specific sources to human salmonellosis varied substantially between studies. Although differences in data inputs, methods, and the point in the food system where attribution was estimated contribute to variability between studies, observed differences also suggest regional differences in the epidemiology of salmonellosis.

Quinolone-resistant Salmonella enterica serotype Enteritidis infections associated with international travel.

We found a strong association between nalidixic acid-resistant Salmonella enterica serotype Enteritidis infections in the United States and recent international travel by linking Salmonella Enteritidis data from the National Antimicrobial Resistance Monitoring System and the Foodborne Diseases Active Surveillance Network.

Surveillance for foodborne disease outbreaks - United States, 1998-2008.

PROBLEM/CONDITION: Foodborne diseases cause an estimated 48 million illnesses each year in the United States, including 9.4 million caused by known pathogens. Foodborne disease outbreak surveillance provides valuable insights into the agents and foods that cause illness and the settings in which transmission occurs. CDC maintains a surveillance program for collection and periodic reporting of data on the occurrence and causes of foodborne disease outbreaks in the United States. This surveillance system is the primary source of national data describing the numbers of illnesses, hospitalizations, and deaths; etiologic agents; implicated foods; contributing factors; and settings of food preparation and consumption associated with recognized foodborne disease outbreaks in the United States. REPORTING PERIOD: 1998-2008. DESCRIPTION OF THE SYSTEM: The Foodborne Disease Outbreak Surveillance System collects data on foodborne disease outbreaks, defined as the occurrence of two or more cases of a similar illness resulting from the ingestion of a common food. Public health agencies in all 50 states, the District of Columbia, U.S. territories, and Freely Associated States have primary responsibility for identifying and investigating outbreaks and use a standard form to report outbreaks voluntarily to CDC. During 1998-2008, reporting was made through the electronic Foodborne Outbreak Reporting System (eFORS). RESULTS: During 1998-2008, CDC received reports of 13,405 foodborne disease outbreaks, which resulted in 273,120 reported cases of illness, 9,109 hospitalizations, and 200 deaths. Of the 7,998 outbreaks with a known etiology, 3,633 (45%) were caused by viruses, 3,613 (45%) were caused by bacteria, 685 (5%) were caused by chemical and toxic agents, and 67 (1%) were caused by parasites. Among the 7,724 (58%) outbreaks with an implicated food or contaminated ingredient reported, 3,264 (42%) could be assigned to one of 17 predefined commodity categories: fish, crustaceans, mollusks, dairy, eggs, beef, game, pork, poultry, grains/beans, oils/sugars, fruits/nuts, fungi, leafy vegetables, root vegetables, sprouts, and vegetables from a vine or stalk. The commodities implicated most commonly were poultry (18.9%; 95% confidence interval [CI] = 17.4-20.3) and fish (18.6%; CI = 17.2-20), followed by beef (11.9%; CI = 10.8-13.1). The pathogen-commodity pairs most commonly responsible for outbreaks were scombroid toxin/histamine and fish (317 outbreaks), ciguatoxin and fish (172 outbreaks), Salmonella and poultry (145 outbreaks), and norovirus and leafy vegetables (141 outbreaks). The pathogen-commodity pairs most commonly responsible for outbreak-related illnesses were norovirus and leafy vegetables (4,011 illnesses), Clostridium perfringens and poultry (3,452 illnesses), Salmonella and vine-stalk vegetables (3,216 illnesses), and Clostridium perfringens and beef (2,963 illnesses). Compared with the first 2 years of the study (1998-1999), the percentage of outbreaks associated with leafy vegetables and dairy increased substantially during 2006-2008, while the percentage of outbreaks associated with eggs decreased. INTERPRETATION: Outbreak reporting rates and implicated foods varied by state and year, respectively; analysis of surveillance data for this 11-year period provides important information regarding changes in sources of illness over time. A substantial percentage of foodborne disease outbreaks were associated with poultry, fish, and beef, whereas many outbreak-related illnesses were associated with poultry, leafy vegetables, beef, and fruits/nuts. The percentage of outbreaks associated with leafy vegetables and dairy increased during the surveillance period, while the percentage associated with eggs decreased. PUBLIC HEALTH ACTIONS: Outbreak surveillance data highlight the etiologic agents, foods, and settings involved most often in foodborne disease outbreaks and can help to identify food commodities and preparation settings in which interventions might be most effective. Analysis of data collected over several years of surveillance provides a means to assess changes in the food commodities associated most frequently with outbreaks that might occur following improvements in food safety or changes in consumption patterns or food preparation practices. Prevention of foodborne disease depends on targeted interventions at appropriate points from food production to food preparation. Efforts to reduce foodborne illness should focus on the pathogens and food commodities causing the most outbreaks and outbreak-associated illnesses, including beef, poultry, fish, and produce.

Attributing human foodborne illness to food sources and water in Latin America and the Caribbean using data from outbreak investigations.

Foodborne pathogens are responsible for an increasing burden of disease worldwide. Knowledge on the contribution of different food sources and water for disease is essential to prioritize food safety interventions and implement appropriate control measures. Source attribution using outbreak data utilizes readily available data from outbreak surveillance to estimate the contribution of different sources to human disease. We developed a probabilistic model based on outbreak data that attributes human foodborne disease by various bacterial pathogens to sources in Latin America and the Caribbean (LA&C). Foods implicated in outbreaks were classified by their ingredients as simple foods (i.e. belonging to one single food category), or complex foods (i.e. belonging to multiple food categories). For each agent, the data from simple-food outbreaks were summarized, and the proportion of outbreaks caused by each category was used to define the probability that an outbreak was caused by a source. For the calculation of the number of outbreaks attributed to each source, simple-food outbreaks were attributed to the single food category in question, and complex-food outbreaks were partitioned to each category proportionally to the estimated probability. We analysed all bacterial pathogens together, focused on important bacterial pathogens separately, and, when data were sufficient, performed analyses by country, decade and location. Between 1993 and 2010, 6313 bacterial outbreaks were reported by 20 countries. In general, the most important sources of bacterial disease were meat, dairy products, water and vegetables in the 1990s, and eggs, vegetables, and grains and beans in the 2000s. We observed fluctuations of the most important sources of disease for each pathogen between decades and countries, which may be a consequence of changes in the control of zoonotic disease over the years, of changes in food consumption habits, or of changes in public health focus and availability of data of different pathogens. This study identified data gaps in the region and highlighted the importance of effective surveillance systems to identify sources of disease. Still, the application of this method for source attribution in the LA&C region was successful, and we concluded that this approach can be used to attribute disease to food sources and water in other regions, including developing regions with limited data on the public health impact of foodborne diseases.

Association between antimicrobial resistance in Escherichia coli isolates from food animals and blood stream isolates from humans in Europe: an ecological study.

BACKGROUND: In addition to medical antimicrobial usage, the use of antimicrobials in food animals contributes to the occurrence of resistance among some bacterial species isolated from infections in humans. Recently, several studies have indicated that a large proportion of Escherichia coli causing infections in humans, especially those resistant to antimicrobials, have an animal origin. METHODS: We analyzed the correlation between the prevalence of antimicrobial resistance in E. coli isolates from blood stream infections in humans and in E. coli isolates from poultry, pigs, and cattle between 2005 and 2008 for 11 countries, using available surveillance data. We also assessed the correlation between human antimicrobial usage and the occurrence of resistance in E. coli isolates from blood stream infections. RESULTS: Strong and significant correlations between prevalences of resistance to ampicillin (r=0.94), aminoglycosides (r=0.72), third-generation cephalosporins (r=0.76), and fluoroquinolones (r=0.68) were observed for human and poultry E. coli isolates. Similar significant correlations were observed for ampicillin (r=0.91), aminoglycosides (r=0.73), and fluoroquinolone resistance (r=0.74) in pig and human isolates. In cattle isolates, only ampicillin resistance (r=0.72) was significantly correlated to human isolates. When usage of antimicrobials in humans was analyzed with antimicrobial resistance among human isolates, only correlations between fluoroquinolones (r=0.90) and third-generation cephalosporins (r=0.75) were significant. CONCLUSIONS: Resistance in E. coli isolates from food animals (especially poultry and pigs) was highly correlated with resistance in isolates from humans. This supports the hypothesis that a large proportion of resistant E. coli isolates causing blood stream infections in people may be derived from food sources.

Global monitoring of Salmonella serovar distribution from the World Health Organization Global Foodborne Infections Network Country Data Bank: results of quality assured laboratories from 2001 to 2007.

Salmonella enterica is commonly acquired from contaminated food and is an important cause of illness worldwide. Interventions are needed to control Salmonella; subtyping Salmonella by serotyping is useful for targeting such interventions. We, therefore, analyzed the global distribution of the 15 most frequently identified serovars of Salmonella isolated from humans from 2001 to 2007 in laboratories from 37 countries that participated in World Health Organization Global Foodborne Infections Network and demonstrated serotyping proficiency in the Global Foodborne Infections Network External Quality Assurance System. In all regions throughout the study period, with the exception of the Oceania and North American regions, Salmonella serovars Enteritidis and Typhimurium ranked as the most common and second most common serovar, respectively. In the North American and Oceania (Australia and New Zealand) regions, Salmonella serovar Typhimurium was the most common serovar reported, and Salmonella serovar Enteritidis was the second most common serovar. During the study period, the proportion of Salmonella isolates reported from humans that were Salmonella serovar Enteritidis was 43.5% (range: 40.6% [2007] to 44.9% [2003]), and Salmonella serovar Typhimurium was 17.1% (range: 15% [2007] to 18.9% [2001]). Salmonella serovars Newport (mainly observed in Latin and North American and European countries), Infantis (dominating in all regions), Virchow (mainly observed in Asian, European, and Oceanic countries), Hadar (profound in European countries), and Agona (intense in Latin and North American and European countries) were also frequently isolated with an overall proportion of 3.5%, 1.8%, 1.5%, 1.5%, and 0.8%, respectively. There were large differences in the most commonly isolated serovars between regions, but lesser differences between countries within the same region. The results also highlight the complexity of the global epidemiology of Salmonella and the need and importance for improving monitoring data of those serovars of highest epidemiologic importance.

Prevalence of tetracycline resistance and genotypic analysis of populations of Escherichia coli from animals, carcasses and cuts processed at a pig slaughterhouse.

A Danish pig slaughterhouse was visited in this study to investigate the impact of carcass processing on prevalence of tetracycline-resistant Escherichia coli, and to identify the origins of carcass contaminations with E. coli by assessing genetic diversity of E. coli populations on carcasses. A total of 105 carcasses were sampled at five sequential stages: after stunning, after scalding, after splitting, after cooling and after cutting. Total and tetracycline-resistant E. coli were counted for each sample and tetracycline resistance prevalence per sample was calculated by the fraction of tetracycline-resistant E. coli out of total E. coli. From 15 repeatedly sampled carcasses, 422 E. coli isolates from faeces, stunned carcasses, split carcasses and chilled carcasses were examined by pulse-field gel electrophoresis (PFGE) and tested for antimicrobial susceptibility. The results showed that E. coli counts and the prevalence of tetracycline-resistant E. coli per sample were both progressively reduced after each sampling stage. PFGE analysis showed that E. coli populations from stunned carcasses were highly genetically diverse, compared with those from split carcasses and faeces. Thirteen carcasses (87%) were contaminated with E. coli that were also isolated from faeces of either the same or other pigs slaughtered on the same day; and 80% of stunned carcasses shared the same E. coli PFGE subtypes. The results suggest that some carcass processing steps in the slaughterhouse were effective in reducing both E. coli numbers and the tetracycline resistance prevalence in E. coli on carcasses. Faeces from the same or other pigs slaughtered on the same day were likely to be an important source of E. coli carcass contamination. Combined data from E. coli enumeration, PFGE typing and antimicrobial susceptibility testing suggest that tetracycline-susceptible E. coli probably persisted better compared to resistant ones during the carcass processing.

WHO Global Salm-Surv external quality assurance system for serotyping of Salmonella isolates from 2000 to 2007.

An international external quality assurance system (EQAS) for the serotyping of Salmonella species was initiated in 2000 by WHO Global Salm-Surv to enhance the capacity of national reference laboratories to obtain reliable data for surveillance purposes worldwide. Seven EQAS iterations were conducted between 2000 and 2007. In each iteration, participating laboratories submitted serotyping results for eight Salmonella isolates. A total of 249 laboratories in 96 countries participated in at least one EQAS iteration. A total of 756 reports were received from the participating laboratories during the seven EQAS iterations. Cumulatively, 76% of participating laboratories submitted data for all eight strains, and 82% of strains were correctly serotyped. In each iteration, 84% to 96% of the laboratories correctly serotyped the Salmonella enterica serovar Enteritidis isolate that was included as an internal quality control strain. Regional differences in performance were observed, with laboratories in Central Asia and the Middle East performing less well overall than those in other regions. Errors that resulted in incorrect serovar identification were typically caused by difficulties in the detection of the phase two flagellar antigen or in differentiation within antigen complexes; some of these errors are likely related to the quality of the antisera available. The results from the WHO Global Salm-Surv EQAS, the largest of its kind in the world, show that most laboratories worldwide are capable of correctly serotyping Salmonella species. However, this study also indicates a continuing need for improvement. Future training efforts should be aimed at enhancing the ability to detect the phase two flagellar antigen and at disseminating information on where to purchase high-quality antisera.

Human contacts and potential pathways of disease introduction on Georgia poultry farms.

As highly pathogenic avian influenza H5N1 virus continues to circulate in the world, poultry farm biosecurity and timely reporting of morbidity and mortality among commercial poultry farms in the United States are major concerns. To assess the vulnerability of poultry farms to the introduction and spread of a highly infectious pathogen, such as the currently circulating H5N1 influenza virus, a survey was administered to growers in two counties in Georgia representing areas of low and high poultry densities. Survey questions regarding horizontal contacts and management were sent to commercial broiler and breeder-layer chicken producers. Responses were used to estimate and compare contact rates and patterns between the two regions. The distribution of high-risk visitors (i.e., those going inside the poultry houses) to poultry farms did not vary significantly between growers in counties with high and low poultry densities or between breeder-layer and broiler growers. Compared with broiler producers in the county with high poultry density, broiler growers in the county with low poultry density were more likely to hire non-family employees to help with poultry management (62% vs. 17%; P = 0.001) and assist other growers with their poultry (31% vs. 6%; P = 0.025). Use of contracted litter services was significantly higher (P = 0.019) among broiler growers in the poultry-dense county (40%) compared with the low-density county (6%). Compared with broiler growers, breeder-layer producers also were significantly more likely to hire non-family employees to help on the farm (53% vs. 17%; P = 0.008). Poultry growers in the highly poultry-dense county were more likely to have a public road or field receiving poultry litter within a quarter mile of their poultry houses, compared with those in the lower density county. Data obtained in this study support the observations of published poultry disease outbreak investigations and highlight the differences in farm vulnerability to disease introduction within areas of different poultry densities and management practices.

Shigella from humans in Thailand during 1993 to 2006: spatial-time trends in species and serotype distribution.

In Thailand during 1993-2006, a total of 9063 Shigella isolates from different medical centers were serotyped and trends over time and spatial clustering analyzed. Of 3583 cases with age information, 1315 (37%) cases were from children between 0 and 4 years and 684 (19%) from children between 5 and 8 years. Most infections were recorded during 1993-1994 (> 1500 per year), decreasing to < 200 in 2006. The relative species distribution also changed. During 1993-1994, Shigella flexneri accounted for 2241 (65%) of 3474 isolations. This proportion decreased to 64 (36%) of 176 infections in 2006. Most infections occurred during July and August, and fewest in December. S. flexneri clustered around Bangkok, and Shigella sonnei in southern Thailand. Most S. flexneri infections were caused by serotype 2a (1590 of 4035) followed by serotype var X (1249). For both serotypes, a pronounced decrease in the number of isolates occurred over time. A much smaller decrease was observed for serotype 3a isolates. Phase I S. sonnei was initially most common, but shifted gradually over phase I, II, to only phase II. No differences in spatial distribution were found. The three most common S. flexneri serotypes all clustered in, around, and west of Bangkok. Serotypes 2a and 3a also clustered in southern Thailand, whereas var X clustered north and northeast of Bangkok. In conclusion, looking at Shigella species, Thailand changed from being a developing country to a developed country between 1995 and 1996. In addition, major shifts in the types of S. sonnei were observed as were differences in spatial clustering of S. flexneri and S. sonnei and S. flexneri serotypes.