Epidemiological Techniques Research Articles

Current trends in molecular epidemiology studies of Mycobacterium tuberculosis

Mycobacterium tuberculosis is one of the most harmful human pathogens worldwide, and there are mass efforts for controlling this pathogen. One of the powerful tools to find out and control this pathogen is molecular epidemiology techniques. Currently, wide ranges of techniques are available to type mycobacterium tuberculosis, and choosing the correct technique as a portable and standard method is difficult. IS6110 restriction fragment length polymorphism (RFLP) remains gold standard method on genotyping to date, but it is labor intensive and inefficient on samples which have fewer than six copy numbers of IS6110. In the recent years, some new methods have been introduced for genotyping of mycobacterium tuberculosis such as mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) and Spoligotyping. The present review tries to introduce new approaches in molecular techniques for epidemiological investigation of tuberculosis and to illustrate advantages and problems associated with them. Key words: Molecular epidemiology, Mycobacterium tuberculosis, fingerprinting, transmission, genotype.

Chronic myeloid leukemia in 2007

Chronic myeloid leukemia (CML), a hematopoietic stem cell cancer representing 15-20% of adult leukemias, is discussed. Epidemiology, staging biology, and monitoring techniques are reviewed. CML is a myeloproliferative disorder that affects all lineages of hematopoiesis. Final confirmation of CML comes with detection of the Philadelphia Chromosome (Ph) or BCR-ABL transcripts. The disease presents in one of three phases: chronic phase, accelerated phase, or blast crisis. Progression from chronic phase to accelerated phase usually involves the accumulation of additional cytogenetic aberrations and the arising of resistance to therapy. Although at one point mortality associated with CML was high, new kinase inhibitor therapies have markedly extended the life-span of these patients. These inhibitors were derived through the initial observation of the association of the Ph with CML and the eventual identification of the BCR-ABL oncogene which arises from this translocation. Analysis of the mechanism by which BCR-ABL transforms cells identified this protein as a tyrosine kinase and led to the targeting of this activity. The majority of patients present in chronic phase, which is where these kinase inhibitors have their greatest efficacy. Monitoring of disease progression is of critical importance as the prognosis drops significantly for patients with advanced disease. Blood counts, cytogenetics, and polymerase chain reaction (PCR) are currently used to assess disease. Blood counts are inexpensive but lack sensitivity. Cytogenetic karyotyping while requiring specialized training provides evidence of clonal evolution. Quantitative PCR is capable of tremendous sensitivity making it well suited for assessing response to therapy and the early detection of therapy failures. Our understanding of BCR-ABL has allowed the development of therapies, which may keep patients with CML in chronic phase indefinitely. This has created a situation in which patient monitoring is essential for detecting changes in the status of CML. The tests described here provide a comprehensive assessment of disease status allowing for effective patient management.

Effects of Low Doses of Radiation: Joint Statement from the Following Participants at the 15th Pacific Basin Nuclear Conference, Sessions Held in Sydney, Australia, Wednesday 18 October 2006

Effects of Low Doses of Radiation: Joint Statement from the Following Participants at the 15^th Pacific Basin Nuclear Conference, Sessions Held in Sydney, Australia, Wednesday 18 October 2006

Population-Based Analysis of Pathologic Data: A New Approach to the Investigation of Uterine Endometrial and Ovarian Endometrioid Carcinomas

Abstract Context.—Population-based analysis of the histopathology of endometrioid adenocarcinoma of the endometrium and ovary combined with epidemiologic techniques offer a new approach to exploring the relationship of tumors that share a similar range of morphologic phenotypes. Objective.—To evaluate the contribution of the Surveillance, Epidemiology, and End Results database to our understanding of gynecologic pathology. Specifically, to test and compare whether the etiology/pathogenesis of ovarian endometrioid cancer is as dependent upon the reproductive environment as uterine endometrial carcinoma. Design.—Graphic plots of the epidemiologic patterns were analyzed relating to incidence and age-specific rates of ovarian and uterine endometrioid carcinomas. The graphic analysis included evaluation of age frequency density plots and logarithmic plots (log-log) of age-specific incidence rates. Results.—At all ages, uterine endometrioid carcinomas have higher incidence rates than their ovarian homologues. U...

Population-Based Analysis of Pathologic Data: A New Approach to the Investigation of Uterine Endometrial and Ovarian Endometrioid Carcinomas

Population-based analysis of the histopathology of endometrioid adenocarcinoma of the endometrium and ovary combined with epidemiologic techniques offer a new approach to exploring the relationship of tumors that share a similar range of morphologic phenotypes. To evaluate the contribution of the Surveillance, Epidemiology, and End Results database to our understanding of gynecologic pathology. Specifically, to test and compare whether the etiology/pathogenesis of ovarian endometrioid cancer is as dependent upon the reproductive environment as uterine endometrial carcinoma. Graphic plots of the epidemiologic patterns were analyzed relating to incidence and age-specific rates of ovarian and uterine endometrioid carcinomas. The graphic analysis included evaluation of age frequency density plots and logarithmic plots (log-log) of age-specific incidence rates. At all ages, uterine endometrioid carcinomas have higher incidence rates than their ovarian homologues. Up to the age of 50 years, the log-log plots of age-specific incidence rates for each of these tumors remain essentially parallel. In contrast, after age 50 (menopause), the incidence rates begin to diverge: the rates for uterine endometrial carcinomas continue to rise, whereas the rates for ovarian endometrioid carcinomas plateau. This divergence persists even when the age-specific incidence is stratified according to histologic grade. Interestingly, endometrial stromal sarcomas follow an incidence rate pattern nearly identical to that of ovarian endometrioid carcinomas. The continuum of cellular and molecular events predisposing to gynecologic cancers of endometrioid phenotype apparently cease to operate in the ovary after menopause, but additional cellular and molecular events appear to occur in the ageing uterine endometrium.

Space–Time Patterns of Risk: A Cross National Assessment of Residential Burglary Victimization

Using epidemiological techniques for testing disease contagion, it has recently been found that in the wake of a residential burglary, the risk to nearby homes is tem- porarily elevated. This paper demonstrates the ubiquity of this phenomenon by analyzing space-time patterns of burglary in 10 areas, located in five different countries. While the precise patterns vary, for all areas, houses within 200 m of a burgled home were at an elevated risk of burglary for a period of at least two weeks. For three of the five countries, differences in these patterns may partly be explained by simple differences in target density. The findings inform theories of crime concentration and offender targeting strategies, and have implications for crime forecasting and crime reduction more generally.

Investigation of an outbreak of Legionnaires’ disease: Hereford, UK 2003

This report describes the investigation and control of a community outbreak of Legionnaires' disease in Hereford, UK, in November 2003. Outbreak investigation consisted of epidemiological survey, identification and environmental investigation of potential sources, microbiological analysis of clinical and environmental samples and mapping the location of potential sources and the movement and residence of cases. Each identified source was allocated a 'composite score' based on different zones of exposure and wind direction. Altogether, 28 cases were identified, with an overall case fatality rate of 7%. All cases had epidemiological links to Hereford city centre. The 'composite score' identified a cluster of cooling towers as being the most likely source of the outbreak. Environmental samples from one of the cooling towers in the cluster and clinical samples from two patients were positive for Legionella pneumophilia serogroup 1 and were indistinguishable by molecular sub-typing. In this outbreak, the use of microbiological, environmental and epidemiological techniques facilitated the rapid identification of a cooling tower as the source of this outbreak. This study illustrates the continuing importance of cooling towers as a source of Legionnaires' disease and the utility of obtaining and comparing both clinical and environmental samples.

Patient‐to‐Patient Transmission of Hepatitis B Virus Associated with Oral Surgery

We used molecular epidemiologic techniques to document patient-to-patient transmission of hepatitis B virus (HBV) between 2 outpatient oral surgery patients operated on 161 min apart. Serological testing of 25 (93%) of 27 patients operated on after the source patient revealed that 19 (76%) of 25 were previously immune to HBV; no additional cases were identified. We found no deficiencies in infection control practices. Transmission may have been limited by the high prevalence (64%) of patients vaccinated against HBV. To our knowledge, this is the first documented case of patient-to-patient transmission of a bloodborne pathogen in a dental setting in the United States.

GI Epidemiology: infection epidemiology and acute gastrointestinal infections

Gastrointestinal infection is a major cause of morbidity and mortality worldwide. The World Health Organisation estimated that in 2001 diarrheal disease was the third most common cause of mortality from infectious diseases worldwide, accounting for some 1.9 million deaths. Gastrointestinal infection is also linked to chronic diseases, for example Helicobacter pylori infection and gastric cancer. To introduce the features of infection epidemiology that differentiates it from disease epidemiology in general. The epidemiologic study of infection is essential for disease control. Infection epidemiology requires consideration of micro-organisms (the infection process and transmission pathways) as well as the host (clinical presentation, behavior and immune status). Although infection epidemiologists often draw on methods used in chronic disease epidemiology there are some special features of infection epidemiology that require additional investigative approaches. We have highlighted these unique features and described some of the special methods available to track infection to its source. * The epidemiologic approach to the investigation of gastrointestinal infection is influenced by the interaction between micro-organisms and the host. * The infection epidemiologist can draw on "standard" epidemiologic techniques and on special methods. * Collaboration with microbiologists is essential for studying infection epidemiology. The purpose of this chapter is to introduce the features of infection epidemiology that differentiate it from disease epidemiology in general. Epidemiologic concepts covered in other chapters will not be repeated here, but readers should bear in mind that those methods are also available to use in the study of infection.

Relative contribution of hookworm and <i>Ascaris lumbricoides</i> to iron deficiency anemia among school pupils in Nasarawa area, Nigeria

Stool and blood specimens of 418 school pupils were examined for intestinal parasites and iron deficiency anemia respectively, using rapid field epidemiological techniques. 156 (37.3%) of the pupils were infected with different species of intestinal parasites. More than forty-six percent (46.8%) of the infected individuals were anemic. Hookworm (28.8%) and Ascaris lumbricoides (16.7%) were the dominant helminthes encountered. Cases of mixed infection with these dominant species and other intestinal parasites were also documented. The overall prevalence of anemia (38.8%) in this community was high. Pupils with cases of mixed infection (hookworm and A. lumbricoides) were more anemic than those with single infections of hookworm and A. lumbricoides. Both hookworm and A. lumbricoides proved to contribute significantly to anemia in the area. A linear relationship was observed between parasite infection, anemia and weight of the pupils, but this was not statistically significant. Keywords: Hookworm; Ascaris; anemia; school pupils; NigeriaInternational Journal of Natural and Applied Sciences Vol. 2 (3) 2006: pp 205-209

Serratia marcescens bacteremia – an indicator for outbreak management and heightened surveillance

Colonization of neonatal intensive care units by Serratia marcescens is associated with clinical outbreaks. We report the management of an outbreak in a newborn services unit (NBS), in 2004, of a strain of S. marcescens that was present in the unit from 1994. Over the 10-year period, increases in clinical isolates demonstrated three epidemic curves, each spanning 3-4 years and each involving positive blood cultures. In 2004, clinical isolates of S. marcescens bacteremia prompted an investigation. Control measures including screening, creation of a separate unit, use of contact precautions, education, environmental sampling, strategies to reduce overcrowding, surveillance and molecular epidemiological techniques were implemented. In total, 99 babies were either colonized or infected with S. marcescens between December 2003 and December 2005. Isolates were tested with ribotyping identifying one main endemic strain. No environmental source was found, however, the outbreak terminated following adherence to infection control principles. Epidemiological information, structural and practice changes were used to prevent transmission and control the outbreak.

Salmonella enterica serotype Infantis in southern Italy from 2000-2005: molecular typing of isolates from human and non human sources

Serotype Infantis ranks within the top-five Salmonella serotypes in many European countries. An association between this serotype and the poultry ecosystem is apparent in some geographic areas and could account for its persistent or emergent role as causative agent of human salmonellosis. Recently, in southern Italy isolation from eggs and poultry has become increasingly frequent, and in one case the egg yolk also cultured positive. Molecular typing was performed to assess the possible relationship among isolates from human, food and animal sources. Isolates of serotype Infantis identified in southern Italy between 2000 and 2005 rom various sources were submitted to pulsed field gel electrophoresis (PFGE) by a CHEF-Mapper apparatus fter endonuclease digestion of DNA by XbaI. PFGE patterns of isolates from swine and poultry reservoirs showed distinctive PFGE profiles and human solates shared pulsotypes with isolates from both sources. Moreover, egg isolates from different farms ppeared very similar to each other. Epidemiological investigation and risk assessment can obtain reliable and useful pointers from he pplication of molecular epidemiology techniques.

Health screening for a translocation of captive-reared tuatara (Sphenodon punctatus) to an island refuge

AIMS: To screen tuatara undergoing translocation from a captive crèche to an island refuge for evidence of health and known diseases, and apply basic epidemiological techniques to assess the significance of disease test results. METHODS: Tuatara (n=353) were physically examined and samples were taken from a random selection (n=30) for estimated white cell counts, screening for haemoparasites, and culture for Salmonella, Yersinia, Aeromonas and Campylobacter spp. Direct faecal smears were carried out on-site, and faecal floats were later performed to assess levels of endoparasitism with helminths and protozoa (n=69). Modified Ziehl-Neelsen staining was used to screen faecal smears, and positive specimens were further screened using an immunofluorescence antibody (IFA) test for Cryptosporidium oocysts. RESULTS: There was no evidence of external parasites on any of the animals examined and only one animal had a gross abnormality. All estimated white cell counts were in the range 2.8– 17.5 × 109/L. No haemoparasites were observed. There were no enteric pathogens cultured, indicating the intestinal carriage of these bacteria in the tuatara was 9.4%. Of the 69 individual faecal samples examined, 12 (17%) had unidentified coccidial oocysts, 21 (30%) had nematode ova of various kinds, and 12 (17%) had intestinal carriage of motile protozoa consistent with Trichomonas spp and another unidentified organism. Nineteen (28%) tuatara had acid-fast oocysts present; however, IFA staining failed to detect any Cryptosporidium oocysts. CONCLUSIONS: Our understanding of the diversity of gastrointestinal endoparasites affecting tuatara is inadequate as many of the parasite ova seen could not be identified. This is the first record of tuatara as a host for Trichomonas spp of protozoa in the gastrointestinal tract.

Dryland Salinity and Human Health Outcomes

P-527 Large tracts of the Western Australian agricultural zone have become saline due to extensive land clearing for agriculture. Native perennial vegetation is replaced with shallow rooted crops and pastures resulting in rising water tables which dissolve salt in the soil layer and bring it to the surface. Currently it is calculated that approximately 5.7 million hectares are at risk or are affected by dryland salinity and models predict the situation worsening in the next 50 years. This environmental degradation has profound ecological impacts through the reduction of an already depleted biodiversity. Such ecosystem disruption has many adverse outcomes including an increased health risk among the resident human population. The current study takes an interdisciplinary, tiered approach using both epidemiological and ecological techniques. Environmental data was examined with human health data from Western Australia's Data Linkage Unit using spatial Bayesian modelling to determine if any associations exist between environmental degradation and the health of the human population. Mosquito-borne disease was chosen as a case study to investigate in detail as this has a complex disease ecology that is strongly influenced by environmental factors. Notifications of the primary mosquito-borne disease of concern in southern Australia, Ross River virus (RRV), were combined with environmental data, field sampling of mosquito populations and investigations of underlying trophic processes that regulate the ecology of the disease (such as predator-prey relationships between aquatic invertebrates and mosquitoes). This multi-disciplinary approach was used to investigate the impact of dryland salinity on mosquito-borne disease risk. The Bayesian modelling of ecosystem and human health found that increased rates of asthma, depression, suicide and ischemic heart disease were all positively associated with areas of increased dryland salinity. In the mosquito-borne disease case study, preliminary results indicate that dryland salinity has impacts on disease ecology and creates the potential for increased health risk. Populations of the main vector species of RRV in Australia were significantly higher in saline affected areas. For larval mosquitoes this relationship with salinity also correlated with a reduction in aquatic predators. This study represents the first attempt to investigate the impact between dryland salinity, the primary cause of ecosystem disruption in Australia, and human health outcomes. The findings clearly underline the link between environmental degradation and adverse human health outcomes; which may be further enhanced in the future given the predicted increase in extent and severity of dryland salinity over the next 50 years.

Diversity and origin of hepatitis C virus infection among unpaid blood donors in the Netherlands

To improve transfusion policy and to increase understanding of the spread of hepatitis C virus (HCV) in the general population, HCV infections among voluntary Dutch blood donors were examined with molecular epidemiologic techniques. During 6 years, 1997 through 2002, confirmed anti-HCV-positive donors were interviewed on HCV-associated risk behavior with a standardized questionnaire. Additionally, HCV isolates were genotyped, partially sequenced, and compared to sequences obtained from Dutch injecting drug users (IDUs). HCV prevalence and incidence rates among Dutch donors were extremely low; the residual risk of transmitting HCV was calculated to be 1 in 30 million donations. Former IDUs (21%), transfusion recipients (30%), and immigrants (>12%) were identified as major HCV risk groups. Cryptogenic transmission caused 18 percent of infections among new donors and all infections among repeat donors. Compared to IDUs, genotype distribution among donors was highly diverse; major subtypes were 3a (27%), 1a (24%), 1b (24%), 2a/b (10%), and 4 (9%). Half of the donors were infected with IDU-related subtypes 1a and 3a, whereas subtype 1b mainly spread via blood transfusion and various other nosocomial modes of transmission in the past. HCV infections acquired in endemic countries could be clearly identified based on genotype. Different modes of transmission are linked to infections with certain HCV subtypes, suggesting separate HCV epidemics, but spillover between different risk groups underlines the value of molecular epidemiologic techniques to gain insight into the origin and dynamics of HCV infections on a population level.

Mycobacterium bovisInfection in Animals and Humans, 2nd Edition

The stated purpose of the second edition of Mycobacterium bovis Infection in Animals and Humans is to provide medical professionals, allied health scientists, research workers, and graduate students with current information on the significance of M. bovis in the control and eradication of tuberculosis in animals and humans. This newest edition deals with topics such as the public health significance of M. bovis, pathogenesis of M. bovis, epidemiology of M. bovis (with an entire chapter on molecular epidemiologic techniques), PCR detection of M. bovis with formalin-fixed tissues, and DNA vaccines. As with the first edition, the second edition delivers several updates from various countries on the status of M. bovis infection in animals and humans. Little accessible published information has been available on this topic, which makes the book especially useful. The second edition also deals with several areas not covered in the first edition, including molecular epidemiology, evolution of the M. tuberculosis complex, tuberculosis caused by M. pinnipedii in fur seals and sea lions, the economics of bovine tuberculosis, and cost-benefit analysis of disease eradication programs. Several chapters deal with timely issues related to tuberculosis in wildlife. In spite of its strengths, the second edition adds little additional information to material provided in the first edition on the topics of pathogenesis or diagnosis of bovine tuberculosis. In addition, although most of the photomicrographs are adequate, several are of such poor quality that they are of little use. Also, as with any multiauthored volume, some repetition occurs on general topics. The book achieves its stated purposes, however, and will be especially useful as a reference for researchers, regulatory agencies, and graduate students. It will be less informative for those interested in detailed discussions on research in the field of pathogenesis or diagnosis of M. bovis infection.

Évaluation de la pertinence du cours international sur les trypanosomoses humaines africaines

The goal of this study was to evaluate the adequacy and relevance of a training course on Human African Trypanosomiasis, targeted to reach support and coordination staff in charge of activities being carried out in related prevention and control programmes. A questionnaire was emailed to the four course organisers and the 65 participants. The response rate among the participants was 41%. The training needs expressed covered issues such as treatment, diagnostic and epidemiological techniques, improved knowledge of the disease, and control planning. The lectures given were adapted for participants' professional activities. At the time of the evaluation (one to three years after the course) 67% of the participants had begun implementing the knowledge they had acquired and applying it to their practice, particularly in the area of programme planning. The analysis of the questionnaire's results pointed to the sections of the course that would benefit from modifications, such as the need for the development of lessons and modules in the areas of patient management and planning for future training sessions.

Molecular Epidemiology of Pleural and Other Extrapulmonary Tuberculosis: A Maryland State Review

Limited information exists about the current epidemiological characteristics of extrapulmonary tuberculosis. However, pleural tuberculosis is usually considered to be a manifestation of primary tuberculosis. Our objective was to use molecular epidemiological techniques to describe the occurrence of pleural and other extrapulmonary tuberculosis in Maryland, a state with moderate tuberculosis incidence. We surveyed tuberculosis cases reported with a single site of disease in Maryland from 1996 through 2001. Genotyping of Mycobacterium tuberculosis isolates was performed with an IS6110-based restriction fragment-length polymorphism analysis. DNA clustering of strains with >5 IS6110 bands, with supporting epidemiologic information on patients, served as a proxy for recent transmission. A total of 1811 patients with tuberculosis were reported (incidence, 5.9 cases per 100,000 population). Of 1411 patients (77.9%) with cultures positive for M. tuberculosis, 1246 (88.3%) had a single site of disease, with 934 (75.0%) of these isolates having >5 IS6110 bands. Of the 934 patients included in the analyses, 729 (78.0%) had pulmonary tuberculosis, and 205 (22.0%) had extrapulmonary tuberculosis; of the latter group, 46 patients had pleural disease, and 159 patients had nonrespiratory disease. In multivariate analyses, patients with pleural tuberculosis were not significantly associated with clustered strains, compared with patients with nonrespiratory or pulmonary tuberculosis disease. Having a DNA-clustered strain was negatively associated with nonrespiratory tuberculosis, compared with pulmonary disease (adjusted odds ratio, 0.48; P = .003). Nonrespiratory extrapulmonary tuberculosis is less likely than pulmonary tuberculosis to be a result of recent infection. Pleural tuberculosis is not an appropriate indicator for recent transmission among our population.

Management of Distal Biceps and Triceps Ruptures

The management of distal biceps and triceps ruptures is reviewed. Epidemiology, clinical presentation, evaluation, surgical management, nonoperative management, and rehabilitation rationale and techniques are presented. Although various surgical repair techniques are used, none has been shown to produce superior clinical outcomes. The literature is lacking information to provide evidence-based decisions regarding rehabilitation strategies. Prospective studies comparing types and timing of repairs and timing and techniques for a postoperative program are needed. As that information is not yet available, the rehabilitation plan outlined in this article is based on timetables for healing tissue, strength of repair, prevention of complications, consideration of patient's medical history and injury history, and review of the literature. Familiarity with the different treatment options assists the surgeon and therapist tailor a therapy program that is optimal for each individual patient.

Recurrent candidaemia in a neonate with Hirschsprung's disease: fluconazole resistance and genetic relatedness of eight Candida tropicalis isolates

The incidence of candidaemia among immunocompromised patients in Malaysia is increasing at an alarming rate. Isolation of clinical strains that are resistant to fluconazole has also risen markedly. We report here the repeated isolation of Candida tropicalis from the blood of a neonatal patient with Hirschsprung's disease. In vitro fluconazole susceptibility tests of the eight isolates obtained at different time points showed that seven of the isolates were resistant and one isolate was scored as susceptible dose-dependent. Random amplification of polymorphic DNA fingerprinting of the isolates using three primers and subsequent phylogenetic analysis revealed that these isolates were highly similar strains having minor genetic divergence, with a mean pairwise similarity coefficient of 0.893+/-0.041. The source of the infectious agent was thought to be the central venous catheter, as culture of its tip produced fluconazole-resistant C. tropicalis. This study demonstrates the utility of applying molecular epidemiology techniques to complement traditional mycological culture and drug susceptibility tests for accurate and appropriate management of recurrent candidaemia and highlights the need for newer antifungals that can combat the emergence of fluconazole-resistant C. tropicalis strains.