Applying population-genetic models in theoretical evolutionary epidemiology

Much of the existing theory for the evolutionary biology of infectious diseases uses an invasion analysis approach. In this Ideas and Perspectives article, we suggest that techniques from theoretical population genetics can also be profitably used to study the evolutionary epidemiology of infectious diseases. We highlight four ways in which population-genetic models provide benefits beyond those provided by most invasion analyses: (i) they can make predictions about the rate of pathogen evolution; (ii) they explicitly draw out the mechanistic way in which the epidemiological dynamics feed into evolutionary change, and thereby provide new insights into pathogen evolution; (iii) they can make predictions about the evolutionary consequences of non-equilibrium epidemiological dynamics; (iv) they can readily incorporate the effects of multiple host dynamics, and thereby account for phenomena such as immunological history and/or host co-evolution.     

The epidemiology of heartwater: Establishment and maintenance of endemic stability

Although heartwater (Cowdria ruminantium infection) is one of the most economically important tick-borne diseases of sub-Saharan Africa, its epidemiology he's remained poorly understood until recently. New data, suggesting that heartwater is present in an endemically stable state in much of sub-Saharan Africa and demonstrating vertical transmission of Cowdria ruminantium in the field, have altered previously accepted views on heartwater epidemiology. In this paper, Sharon Deem and colleagues present an overview of the epidemiology of heartwater based on recent studies, discuss the factors that make endemic stability possible, make recommendations for future directions in research, and provide a foundation for the development of epidemiological models.     

Dry root rot (Rhizoctonia bataticola (Taub.) Butler): an emerging disease of chickpea – where do we stand?

Dry root rot caused by Rhizoctonia bataticola (Macrophomina phaseolina) of chickpea (Cicer arietinum L.) is gaining importance in the changed scenario of climate when growing crop is predisposed to high temperature and moisture stress. Being mainly a soil-inhabiting pathogen, many environmental and soil factors are responsible for the development of disease. No systematic research related to the biology, ecology and epidemiology of dry root rot in chickpea has been conducted so far. Research is needed to improve the identification and characterisation of variability within its epidemiological and pathological niches. Limited literature available on host plant resistance for dry root rot indicated lack of resistant sources for this disease. The present article discusses current status of the disease in the context of climate change and possible management options to alleviate the problem.     

Impact of dry mouth conditions on oral health-related quality of life in older people

Objective: The aim of the present study was to evaluate the impact of dry mouth conditions on oral health‐related quality of life in frail old people, residents at community care centers. Further, reliability and validity of a visual analogue scale (VAS) for dry mouth symptoms were determined within the study cohort. Background: In old people functional, social and psychological impacts of oral conditions are associated with an overall sense of well being and general health. Subjective dry mouth and reduced saliva flow are common disorders in old people caused by disease and medication. Thus, dry mouth conditions may be determinants for compromised oral health‐related quality of life in old people. Method: In total, 50 old people living at service homes for the old people were asked to answer questionnaires on subjective dry mouth (VAS) and Oral Health Impact Profile (OHIP14) for oral health‐related quality of life. Saliva flow was estimated by absorbing saliva into a pre‐weighed cotton roll. Results: The final study cohort comprised 41 old people (aged 83–91 years). Significant associations were identified between both objective and subjective dry mouth and overall or specific aspects of oral health‐related quality of life. Conclusion: Dry mouth (objective and subjective) is significantly associated with oral health‐related quality of life strengthening the value of monitoring dry mouth conditions in the care of frail old people.     

From hierarchy to network: a richer view of evidence for evidence-based medicine

Evidence-based medicine (EBM) advocates the improvement of patient care through the use of current best research evidence in medical decision making. In practice, "best evidence" generally refers to where a study fits on a hierarchy of evidence, which places randomized controlled trials (RCTs) and other population-level research above laboratory research. Because population research is concerned primarily with average results obtained from large groups of people, ranking evidence on the basis of its place in the hierarchy is shortsighted and ultimately limits the ability of research results to inform the care of individual patients. The history and methodology of epidemiology reveals a close relationship between population-level and laboratory research; both types of research are necessary if we are to understand the causes of a disease. What EBM does not take into account in its hierarchy of evidence is that the same thing is true for research on the safety and efficacy of medical interventions. To maximize the information that clinical research can provide for clinical care, RCTs should be designed to elucidate within-group variability. This can only be done if the hierarchy of evidence is replaced by a network that takes into account the relationship between epidemiological and laboratory research.     

Epidemiological reflections of the contribution of anthropology to public health policy and practice

Academic disciplines like anthropology and epidemiology provide a niche for researchers to speak the same language, and to interrogate the assumptions that they use to investigate problems. How anthropological and epidemiological methods communicate and relate to each other affects the way public health policy is created but the philosophical underpinnings of each discipline makes this difficult. Anthropology is reflective, subjective and investigates complexity and the individual; epidemiology, in contrast, is objective and studies populations. Within epidemiological methods there is the utilitarian concept of potentially sacrificing the interests of the individual for the benefits of maximizing population welfare, whereas in anthropology the individual is always included. Other strengths of anthropology in the creation of public health policy include: its attention to complexity, questioning the familiar; helping with language and translation; reconfiguring boundaries to create novel frameworks; and being reflective. Public health requires research that is multi-, inter- and trans-disciplinary. To do this, there is a need for each discipline to respect the 'dignity of difference' between disciplines in order to help create appropriate and effective public health policy.     

The interface between epidemiology and population genetics

Modern biology increasingly integrates disparate disciplines. Here, Steve Paterson and Mark Viney examine the interface between epidemiology and population genetics. They argue that infection and inheritance can be considered as analogous processes, and that epidemiology and population genetics share many common features. They consider the potential for existing population genetic theory to dissect epidemiological patterns in field studies and they consider other relationships between genetics and epidemiology that provide a research challenge for the future.     

The Epidemiologist's Dilemma: A Position Paper on the Role of Epidemiology in Canadian Research

Canadian epidemiology is currently in transition from being primarily interested in infectious disease to becoming active in investigating causes of non-infectious disease. Generally, epidemiologists limit their work to “field”, “basic”, or “theoretical” epidemiology. In all three fields there appears to be a shortage of qualified personnel which is likely to become even more acute because of new roles that epidemiologists will probably play in the future. A minimum of 40 full-time epidemiologists is currently required in Canada.Departments other than departments of preventive medicine at medical schools and teaching hospitals are currently spending 79.5% of all funds allocated for non-microbiological epidemiological research in Canada. Since epidemiology is by its very nature population orientated, rather than clinically orientated, clinicians require consultative advice from epidemiologists at many stages of their research. Epidemiological facilities in departments of preventive medicine should therefore be strengthened in order to provide research training and didactic courses needed as the numbers of physicians, nurses and paramedical persons are increased.     

Elucidating relationships between P.falciparum prevalence and measures of genetic diversity with a combined genetic-epidemiological model of malaria

There is an abundance of malaria genetic data being collected from the field, yet using these data to understand the drivers of regional epidemiology remains a challenge. A key issue is the lack of models that relate parasite genetic diversity to epidemiological parameters. Classical models in population genetics characterize changes in genetic diversity in relation to demographic parameters, but fail to account for the unique features of the malaria life cycle. In contrast, epidemiological models, such as the Ross-Macdonald model, capture malaria transmission dynamics but do not consider genetics. Here, we have developed an integrated model encompassing both parasite evolution and regional epidemiology. We achieve this by combining the Ross-Macdonald model with an intra-host continuous-time Moran model, thus explicitly representing the evolution of individual parasite genomes in a traditional epidemiological framework. Implemented as a stochastic simulation, we use the model to explore relationships between measures of parasite genetic diversity and parasite prevalence, a widely-used metric of transmission intensity. First, we explore how varying parasite prevalence influences genetic diversity at equilibrium. We find that multiple genetic diversity statistics are correlated with prevalence, but the strength of the relationships depends on whether variation in prevalence is driven by host- or vector-related factors. Next, we assess the responsiveness of a variety of statistics to malaria control interventions, finding that those related to mixed infections respond quickly (∼months) whereas other statistics, such as nucleotide diversity, may take decades to respond. These findings provide insights into the opportunities and challenges associated with using genetic data to monitor malaria epidemiology.     

Spatial Epidemiology and GIS in Marine Mammal Conservation Medicine and Disease Research

The use of spatial epidemiology and geographical information systems (GIS) facilitates the incorporation of spatial relationships into epidemiological investigations of marine mammal diseases and conservation medicine. Spatial epidemiology is the study of the spatial variation in disease risk or incidence and explicitly addresses spatial structures and functions that factor into disease. The GIS consists of input, management, analysis, and presentation of spatial disease data and can act as an integrative tool so that a range of varied data sources can be combined to describe different environmental aspects of wild animals and their diseases. The use of modern spatial analyses and GIS is becoming well developed in the field of marine mammal ecology and biology, but has just recently started to gain more use in disease research. The use of GIS methodology and spatial analysis in nondisease marine mammal studies is briefly discussed, while examples of the specific uses of these tools in mapping, surveillance and monitoring, disease cluster detection, identification of environmental predictors of disease in wildlife populations, risk assessment, and modeling of diseases, is presented. Marine mammal disease investigations present challenges, such as less consistent access to animals for sampling, fewer baseline data on diseases in wild populations, and less robust epidemiologic study designs, but several recommendations for future research are suggested. Since location is an integral part of investigating disease, spatial epidemiology and GIS should be incorporated as a data management and analysis tool in the study of marine mammal diseases and conservation medicine.     

Characterization of an outbreak of hand, foot, and mouth disease in Nanchang, China in 2010

Recent outbreaks of human enterovirus 71 (EV71) infection and EV71-associated hand, foot, and mouth disease (HFMD) in China have affected millions and potentially lead to life-threatening complications in newborns. Furthermore, these outbreaks represent a significant global public health issue in the world. Understanding the epidemiology of HFMD and EV71 infection and their transmission patterns in China is essential for controlling outbreaks. However, no studies on the outbreaks of HFMD and EV71 infection in China during 2010 have been reported. In this report, we carried out an epidemiological analysis to study an outbreak of HFMD and EV71 infection in 2010 in the city of Nanchang in the Jiangxi province of People's Republic of China. From April 7 to May 11, 2010, a total of 109 HFMD cases were reported, and in this report the HFMD cases were studied by both epidemiological and laboratory analyses. The epidemiological study indicates that children aged younger than 8 years old represented more than 90% of the reported cases, with the age group of 1-3 years containing the highest number of cases. Laboratory studies detected a high prevalence of EV71 amongst the cases in our study, suggesting EV71 as a common enterovirus found in HFMD cases in Nanchang. Phylogenetic analysis of the sequence of the VP1 region of four EV71 isolates indicated that the Nanchang strains belong to the C4 subgenotype commonly found in China during outbreaks in 2008 but contain distinct variations from these strains. Our study for the first time characterizes the epidemiology of HFMD and EV71 infection in China in 2010 and furthermore, provides the first direct evidence of the genotype of EV71 circulating in Nanchang, China. Our study should facilitate the development of public health measures for the control and prevention of HFMD and EV71 infection in at-risk individuals in China.     

Epidemiological studies on radiation carcinogenesis in human populations following acute exposure: nuclear explosions and medical radiation.

The present review provides an understanding of our current knowledge of the carcinogenic effect of low-dose radiation in man, and surveys the epidemiological studies of human populations exposed to nuclear explosions and medical radiation. Discussion centers on the contributions of quantitative epidemiology to present knowledge, the reliability of the dose-incidence data, and those relevant epidemiological studies that provide the most useful information for risk estimation of cancer induction in man. Reference is made to dose-incidence relationships from laboratory animal experiments where they may obtain, for problems and difficulties in extrapolation from data obtained at high doses to low doses, and from animal data to the human situation. The paper describes the methods of application of such epidemiological data for estimation of excess risk of radiation-induced cancer in exposed human populations and discusses the strengths and limitations of epidemiology in guiding radiation protection philosophy and public health policy.     

糖尿病流行病学研究策略及分子遗传学研究进展

流行病学是现代医学的一门重要的基础学科,也是一门应用广泛的应用学科。流行病学作为方法学在复杂疾病研究中有不可替代的作用。糖尿病具有复杂疾病属性,应该以系统的多层次的流行病学方法为研究策略。本文从流行病学与临床医学、遗传学及分子生物学交叉所形成的分支学科--临床流行病学、遗传流行病学及分子流行病学三个方面对糖尿病的研究进展作一综述,并从分子遗传学角度列举了部分糖尿病的候选基因。提出糖尿病的研究应该从宏观流行病学(如社会环境等因素的影响)和微观流行病学(如分子遗传等)结合系统地进行研究。     

Evaluation of the clinical efficacy of a mouthwash and oral gel containing the antimicrobial proteins lactoperoxidase, lysozyme and lactoferrin in elderly patients with dry mouth--a pilot study

Objectives: To evaluate the clinical efficacy of a mouthwash and oral gel containing the antimicrobial proteins lactoperoxidase, lactoferrin and lysozyme, in a sample of elderly individuals with dry mouth. Material and methods: Twenty elderly institutionalised subjects with dry mouth and with a certain degree of independence for daily life activities were included in this pilot study. A randomised, double blind and cross‐over design was used. The study variables comprised subjective dry mouth sensation, the severity of discomfort assessed by means of a visual analogical scale (VAS), the Oral Health Impact Profile (OHIP), the presence of signs and symptoms of dry mouth, sialometry and Candida albicans culture. All the variables were recorded before and after each of the two periods of the study. Results: The 20 selected subjects we made up of 16 women and four men, with a mean age of 81.3 years. Improvement was observed on analysing the data between the first and second intervention period in terms of the OHIP values, the presence of dry mouth, and the need to drink fluids to swallow. However, the improvement in certain variables before and after treatment did not take a positive course in all cases, and some subjects even improved with placebo. Conclusions: The evaluated mouthwash and oral gel improved some subjective and clinical aspects in elderly individuals with dry mouth, though a placebo effect cannot be entirely discarded.     

Epidemiological Trends of Dengue Disease in Colombia (2000-2011): A Systematic Review

A systematic literature review was conducted to describe the epidemiology of dengue disease in Colombia. Searches of published literature in epidemiological studies of dengue disease encompassing the terms “dengue”, “epidemiology,” and “Colombia” were conducted. Studies in English or Spanish published between 1 January 2000 and 23 February 2012 were included. The searches identified 225 relevant citations, 30 of which fulfilled the inclusion criteria defined in the review protocol. The epidemiology of dengue disease in Colombia was characterized by a stable “baseline” annual number of dengue fever cases, with major outbreaks in 2001–2003 and 2010. The geographical spread of dengue disease cases showed a steady increase, with most of the country affected by the 2010 outbreak. The majority of dengue disease recorded during the review period was among those <15 years of age. Gaps identified in epidemiological knowledge regarding dengue disease in Colombia may provide several avenues for future research, namely studies of asymptomatic dengue virus infection, primary versus secondary infections, and under-reporting of the disease. Improved understanding of the factors that determine disease expression and enable improvement in disease control and management is also important.     

Unmanned Aircraft Systems for Studying Spatial Abundance of Ungulates: Relevance to Spatial Epidemiology

Complex ecological and epidemiological systems require multidisciplinary and innovative research. Low cost unmanned aircraft systems (UAS) can provide information on the spatial pattern of hosts’ distribution and abundance, which is crucial as regards modelling the determinants of disease transmission and persistence on a fine spatial scale. In this context we have studied the spatial epidemiology of tuberculosis (TB) in the ungulate community of Doñana National Park (South-western Spain) by modelling species host (red deer, fallow deer and cattle) abundance at fine spatial scale. The use of UAS high-resolution images has allowed us to collect data to model the environmental determinants of host abundance, and in a further step to evaluate their relationships with the spatial risk of TB throughout the ungulate community. We discuss the ecological, epidemiological and logistic conditions under which UAS may contribute to study the wildlife/livestock sanitary interface, where the spatial aggregation of hosts becomes crucial. These findings are relevant for planning and implementing research, fundamentally when managing disease in multi-host systems, and focusing on risky areas. Therefore, managers should prioritize the implementation of control strategies to reduce disease of conservation, economic and social relevance.     

Validity of Epidemiological Data in Risk Assessment Applications

Data from epidemiological studies might be seen as superior to data from animal bioassays for risk assessment purposes. Because humans are the population of interest, use of epidemiological data avoids interspecies extrapolation. However, one must not assume that an epidemiological study is necessarily valid at face value. We describe issues of validity that arise in the conduct and interpretation of epidemiological research and that affect the utility of epidemiological data in risk assessment. These issues include choice of study design, size and representativeness of the study sample, measurement of exposures and outcomes, control of confounding and specification of statistical model for analysis of data, all of which affect the accuracy and validity of study results.     

Experience in organizing primary specialization in epidemiology

Experience in the organization of the primary stage of specialization in epidemiology is described. In the process of this specialization the students study the subject and the methods of an epidemiologist's work, practice their skills in epidemiological analysis, acquire experience and skills necessary for work with scientific literature and in research. Grounds for the necessity of summarizing the working experience of different chairs in the form of methodological recommendations to be universally used through the country are given.     

Plant virus ecology and epidemiology: historical perspectives,recent progress and future prospects

After clarifying the relationship between the closely related concepts of ecology and epidemiology as they are used in plant virology, this article provides a historical perspective on the subject before discussing recent progress and future prospects. Ecology focuses on virus populations interacting with host populations within a variable environment, while epidemiology focuses on the complex association between virus and host plant, and factors that influence spread. The evolution and growth of plant virus ecology and epidemiology since its inception to the present day, and the major milestones in its development, are illustrated by examples from influential historical reviews published in the Annals of Applied Biology over the last 100 years. Original research papers published in the journal are used to illustrate important ecological and epidemiological principles and new developments in both fields. Both areas are multifaceted with many factors influencing host plants, and virus and vector behaviour. The highly diverse scenarios that arise from this process influence the virus population and the spatiotemporal dynamics of virus distribution and spread. The review then describes exciting progress in research in the areas of molecular epidemiology and ecology, and understanding virus–vector interactions. Application of new molecular techniques has greatly accelerated the rate of progress in understanding virus populations and the way changes in these populations influence epidemics. Viruses cause direct and plant‐mediated indirect effects on insect vectors by modifying their life cycles, fitness and behaviour, and one of the most fascinating recent fields of research concerns plant‐mediated indirect virus manipulation of insect vector behaviour that encourages virus spread. Next, the review describes the current state of knowledge about spread of plant viruses at the critical agro‐ecological interface between managed and natural vegetation. There is an urgent need to understand how viruses move in both directions between the two and be able to anticipate these kinds of events. To obtain an understanding of, and ability to foresee, such events will require a major research effort into the future. The review finishes by discussing the implications of climate change and rapid technological innovation for the types of research needed to avoid virus threats to future world food supplies and plant biodiversity. There has been lamentably little focus on research to determine the magnitude of the threat from diseases caused in diverse plant virus pathosystems under different climate change scenarios. Increasing technological innovation offers many opportunities to help ensure this situation is addressed, and provide plant virus ecology and epidemiology with a very exciting future.     

Epidemiology in protection and prevention against environmental mutagens/carcinogens Examples from occupational medicine

Subjects occupationally exposed to potential mutagens/carcinogens represent the most suitable groups for epidemiological studies aimed at assessing the risk for the individual or the offspring. Several cancer risks to humans have been detected by epidemiological studies performed in occupational settings. Cancer epidemiology studies have been able (a) to identify specific occupations or agents associated with the risk; (b) to verify the results of experimental studies; (c) to test the effectiveness of changes in production or preventive measures in decreasing risks. Reproductive epidemiology has suggested a risk of spontaneous abortions or of malformation in the offspring of workers exposed to some chemicals or occupations, but data are often conflicting due to methodological problems. With the aim of early assessment of risk in mind, the epidemiological use of indicators of exposure or of the early effect of exposure to genotoxic agents is increasingly applied to occupational groups. Cytological monitoring of subjects at risk of occupational cancer of lung or bladder is carried out mainly to diagnose precancerous lesions of target tissues. Cytogenetic methods (chromosome aberrations, SCE, micronuclei) in somatic cells provide a means for detecting early effects of occupational exposure to known or potential mutagens/carcinogens in selected groups of individuals, but their significance is widely debated. Monitoring of urinary mutagenicity, as applied in nurses handling cytostatic drugs, is an example of how an indicator of exposure to genotoxins can be used to evaluate the impact of preventive measures. Among the perspectives, biochemical epidemiology seems to be promising in detecting individuals genetically susceptible to cancer.