Disease In Human Populations Research Articles

Industrial Food Animal Production and Global Health Risks: Exploring the Ecosystems and Economics of Avian Influenza

Many emerging infectious diseases in human populations are associated with zoonotic origins. Attention has often focused on wild animal reservoirs, but most zoonotic pathogens of recent concern to human health either originate in, or are transferred to, human populations from domesticated animals raised for human consumption. Thus, the ecological context of emerging infectious disease comprises two overlapping ecosystems: the natural habitats and populations of wild animals, and the anthropogenically controlled habitats and populations of domesticated species. Intensive food animal production systems and their associated value chains dominate in developed countries and are increasingly important in developing countries. These systems are characterized by large numbers of animals being raised in confinement with high throughput and rapid turnover. Although not typically recognized as such, industrial food animal production generates unique ecosystems—environments that may facilitate the evolution of zoonotic pathogens and their transmission to human populations. It is often assumed that confined food animal production reduces risks of emerging zoonotic diseases. This article provides evidence suggesting that these industrial systems may increase animal and public health risks unless there is recognition of the specific biosecurity and biocontainment challenges of the industrial model. Moreover, the economic drivers and constraints faced by the industry and its participants must be fully understood in order to inform preventative policy. In order to more effectively reduce zoonotic disease risk from industrial food animal production, private incentives for the implementation of biosecurity must align with public health interests.

Genome-wide association studies are coming for human infectious diseases

A genetic contribution to infectious disease in human populations has long been suspected and is now supported by more than 50 years of epidemiological evidence showing, for example, infection rates to be much higher than disease rates. In successful family studies of high-penetrance effects, single gene mutations have been identified that reveal a molecular mechanism leading to increased risk of a specific infectious disease. However, in population-based studies, genetic variants conferring host susceptibility to various infectious diseases have been difficult to uncover. Although mutations such as that in the CCR5 gene, which confers protection against HIV infection, have been reliably discovered, polymorphisms affecting larger proportions of a population have been hard to prove definitively. The recent arrival of the genome-wide association study format, currently being applied to Kawasaki disease, tuberculosis, malaria, HIV, dengue and others, gives us hope that these challenges can finally be met, with implications for population-based treatment and prognosis strategies.

Antifungal Drug Resistance - Concerns for Veterinarians

In the 1990s, there were increased incidences of fungal infectious diseases in human population which might be due to increase in immunosuppressive diseases. But the major concern was increase in prevalence of resistance to antifungal drugs which were reported both in the fungal isolates of human beings and that of animal origin. In both animals and human beings, resistance to antimicrobial agents has important implications for morbidity, mortality and health care costs, because resistant strains are responsible for bulk of infection in animals and human beings, and large number of antimicrobial classes offers more diverse range of resistance mechanisms to study and resistance determinants move into standard well-characterized strains that facilitates the detailed study of molecular mechanisms of resistance in microorganisms. Studies on resistance to antifungal agents has been lagging behind that of antibacterial resistance for several reasons, the foremost reason might be fungal agents were not recognized as important animal and human pathogens, until relatively in recent past. But the initial studies of antifungal drug resistance in the early 1980s, have accumulated a wealth of knowledge concerning the clinical, biochemical, and genetic aspects of this phenomenon. Presently, exploration of the molecular aspects for antifungal drug resistance has been undertaken. Recently, the focus was on several points like developing a more detailed understanding of the mechanisms of antimicrobial resistance, improved methods to detect resistance when it occurs, methods to prevent the emergence and spread of resistance and new antimicrobial options for the treatment of infections caused by resistant organisms.

Epidemiological studies in incidence, prevalence, mortality, and comorbidity of the rheumatic diseases.

Epidemiology is the study of the distribution and determinants of disease in human populations. Over the past decade there has been considerable progress in our understanding of the fundamental descriptive epidemiology (levels of disease frequency: incidence and prevalence, comorbidity, mortality, trends over time, geographic distributions, and clinical characteristics) of the rheumatic diseases. This progress is reviewed for the following major rheumatic diseases: rheumatoid arthritis (RA), juvenile rheumatoid arthritis, psoriatic arthritis, osteoarthritis, systemic lupus erythematosus, giant cell arteritis, polymyalgia rheumatica, gout, Sjögren's syndrome, and ankylosing spondylitis. These findings demonstrate the dynamic nature of the incidence and prevalence of these conditions – a reflection of the impact of genetic and environmental factors. The past decade has also brought new insights regarding the comorbidity associated with rheumatic diseases. Strong evidence now shows that persons with RA are at a high risk for developing several comorbid disorders, that these conditions may have atypical features and thus may be difficult to diagnose, and that persons with RA experience poorer outcomes after comorbidity compared with the general population. Taken together, these findings underscore the complexity of the rheumatic diseases and highlight the key role of epidemiological research in understanding these intriguing conditions.

Anemia como problema de saúde pública: uma realidade atual

In 1990, the United Nations held a World Summit in New York, in which goals for the upcoming decade were established. One of these goals was a one-third reduction in the prevalence of anemia among women at childbearing age. Despite this modest percentage, epidemiological indicators point to the opposite direction, indicating an increasing occurrence of anemia in different regions of the world, including in Brazil. These data show that anemia has continued since the antiquity to be one of the most prevalent and widespread diseases in human populations. Thus, a number of questions without answers arise regarding the actual prevalence and etiopathogenesis of the problem as well as with respect to the degree of implantation and the effectiveness of control measures.

Angling for Thyroid Answers: Study Links PBDEs to Hormone Disruption in Male Sport-Fish Consumers

Levels of polybrominated diphenyl ethers (PBDEs) measured in human samples have increased in recent years, but the health effects of these compounds are not well studied. A group of persistent pollutants similar in structure to polychlorinated biphenyls (PCBs), PBDEs are thought to affect endocrine function, but this relationship has only been examined in several small studies. A new study significantly expands this knowledge base by analyzing PBDE exposure among a large cohort of male sport-fish consumers and concluding that these exposures are associated with increased thyroglobulin antibodies and increased thyroxine (T4) in adult males independent of PCB exposure [EHP 116:1635–1641; Turyk et al.]. The study examined 405 adult males who consumed sport fish from the Great Lakes during the early 1990s. Researchers gathered data on the subjects’ levels of fish consumption, medical diseases, and use of medications, and took serum samples that were tested for PBDEs, PCBs, and DDE, a metabolite of DDT that may affect thyroid hormones. Total and free T4 and triiodothyronine (T3) were measured in serum and urine. PBDE concentrations were positively associated with increased T4 and reverse T3, and inversely correlated with total T3 and thyroid-stimulating hormone (TSH). In addition, PBDEs were positively related to the percentage of T4 bound to albumin, a carrier protein. An observed increase in thyroglobulin antibodies in men with the highest PBDE exposures may indicate an increased susceptibility to autoimmune thyroiditis among people who have been exposed to PBDEs, according to the authors. The findings of a positive association of PBDEs with T4 are not consistent with results of animal studies that have shown decreased T4 in rats and mice exposed to PBDE. However, the results do align with those of several smaller human studies. The authors speculate the disparity may be attributable to the fact that, while thyroid hormone regulation is similar among vertebrates, some functions differ by species. A major strength of the study is the measurement of the effects of PBDEs on multiple hormones and the consideration of other environmental exposures that can affect thyroid hormones. The authors point out that their findings provide a rationale for future mechanistic studies related to PBDE exposure, including how those exposures may be linked to changes in thyroid hormone metabolism and binding of T4 to serum-binding proteins. Also needed, they write, are larger studies to determine whether PBDE exposure is related to thyroid disease in human populations.

Chaos induced by breakup of waves in a spatial epidemic model with nonlinear incidencerate

Spatial epidemiology is the study of spatial variation in disease risk or incidence, includingthe spatial patterns of the population. The spread of diseases in human populations canexhibit large scale patterns, underlining the need for spatially explicit approaches. In thispaper, the spatiotemporal complexity of a spatial epidemic model with nonlinear incidencerate, which includes the behavioral changes and crowding effect of the infective individuals,is investigated. Based on both theoretical analysis and computer simulations, we find outwhen, under the parameters which can guarantee a stable limit cycle in the non-spatialmodel, spiral and target waves can emerge. Moreover, two different kinds of breakup ofwaves are shown. Specifically, the breakup of spiral waves is from the core and thebreakup of target waves is from the far-field, and both kinds of waves becomeirregular patterns at last. Our results reveal that the spatiotemporal chaos isinduced by the breakup of waves. The results obtained confirm that diffusioncan form spiral waves, target waves or spatial chaos of high population density,which enrich the findings of spatiotemporal dynamics in the epidemic model.

Nonstandard numerical methods for a mathematical model for influenza disease

In this paper we construct and develop two competitive implicit finite difference scheme for a deterministic mathematical model associated with the evolution of influenza A disease in human population. Qualitative dynamics of the model is determined by the basic reproduction number, R 0 . Numerical schemes developed here are based on nonstandard finite difference methods. Our aim is to transfer essential properties of the continuous model to the discrete schemes and to obtain unconditional stable schemes. The proposed numerical schemes have two fixed points which are identical to the critical points of the continuous model and it is shown that they have the same stability properties. Numerical simulations with different initial conditions, parameters values and time step sizes are developed for different values of parameter R 0 , convergence to the disease free equilibrium point when R 0 < 1 and to the endemic equilibrium point when R 0 > 1 are obtained independent of the time step size. These numerical integration schemes are useful since can reproduce the dynamics of original differential equations.

Role of stearoyl-CoA desaturase in human metabolic disease

Stearoyl-CoA desaturase (SCD) is a highly conserved Δ-9 desaturase that converts saturated fatty acids into monounsaturated fatty acids. Mice lacking the Scd1 gene are characterized by decreased adiposity and increased lipid oxidation and insulin sensitivity in liver and skeletal muscle. Two isoforms of SCD have also been identified in humans, and there appears to be an association between SCD expression and adiposity. This review will provide a brief update of recent progress in understanding the role of SCD in mediating the progression of disease in human populations, with a special emphasis on metabolic disease.

Systematic quantitative function annotation of mouse genes

Several years after sequencing human and mouse genomes, much remains to be discovered about the functions of most genes. Computational prediction of gene function promises to help focus limited experimental resources on the most likely hypotheses. In this study, a standardized collection of mouse functional genomic data was assembled, and nine bioinformatics teams used this dataset to independently train classifiers and generate predictions of function for 21,603 mouse genes. We compared the performance of function prediction algorithms and identified strengths and weaknesses of current functional genomic datasets. Quantitative function predictions may be useful, e.g., in the study of complex disease in human populations.

Genomic approaches to bone and joint diseases. Statistics in genetic epidemiology

There is a tremendous amount of study on common diseases or complex diseases to detect multiple genes and environmental factors or interactive effects to play a role in the development of those diseases. Genetic Epidemiology is a field of research, which focuses on the role of genetic factors and their interaction with environmental factors in the occurrence of disease in human populations. In this article, I overviewed the basics of probability theory and statistical inference based on likelihood function that we need in genetic study.

Recent Developments in Patents Targeting Toll-Like Receptor Genes

Toll-like receptors (TLRs) are members of pattern recognition receptor family involved in sensing and eliciting responses against many pathogens based primarily on their molecular patterns. TLRs are major markers of innate host defence and are evolutionarily conserved across various species from insects to humans. These type I transmembrane proteins expressed by innate immune cells (dendritic cells, macrophages, NK cells), cells of the adaptive immunity (T and B lymphocytes) and non-immune cells (epithelial, endothelial cells and fibroblasts) orchestrate the adaptive immunity to combat the infections. Thirteen TLRs have been identified in mammals and the overlap between them allows recognition of a diverse range of pathogens. Recent research reviewed here is focused on modulating the innate immunity in mammals through use of TLR agonists in combating infections. Single nucleotide polymorphisms (SNPs) of TLR genes associated with incidence and course of infectious diseases and inherited diseases in human population are also reviewed.

Tuberculosis: evolution in millennia and minutes

Tuberculosis remains a global public health threat: the causative organism, Mycobacterium tuberculosis, was once thought to show little genetic variation, but research in the last 10 years has demonstrated an ability to change in a series of different time frames. Related species of mycobacteria have undergone evolution by deletion of segments of DNA, allowing Mycobacterium bovis and other species to emerge from the M. tuberculosis complex, disproving the previously accepted theories. Deletions also affect the pathogenic potential of different lineages of M. tuberculosis. Over shorter time periods genetic variation is achieved by the movement of insertion sequences such as IS6110. Some lineages identified by this means are over-represented in patient populations, suggesting a genetic advantage, although the mechanism for this is not yet apparent. M. tuberculosis must also adapt to host and antibiotic selection pressure, and this is achieved by point mutations. Almost all antibiotic resistance emerges in this way, and data from clinical and in vitro studies indicate that M. tuberculosis exists with pre-existent mutants that remain as a small proportion of the population because of fitness deficits. Under certain physiological conditions, these rarer mutants may be favoured and, when antibiotic selection pressure is applied, will rise to dominate the bacterial population. M. tuberculosis is a highly effective pathogen that has caused disease in human populations for millennia. We are now starting to understand some of the genetic mechanisms behind this phenomenon.

Evolving genomic approaches to the study of complex cardiovascular diseases in human populations: genetic and genomic epidemiology

Evolving genomic approaches to the study of complex cardiovascular diseases in human populations: genetic and genomic epidemiology

Cryptosporidium oocysts and Balantidium coli Cysts in Pigs Reared Semi-intensively in Zuru, Nigeria

A cross-sectional study was conducted on the presence of Cryptosporidium oocysts and Balantidium coli cysts in fecal samples from semi-intensively managed pigs in Zuru Local Government Area of Kebbi State, Nigeria between November 2005 and July, 2006. A total of 632 households with human population of 5905 were identified in seven pig- rearing locations in the study area while 105 (16.6%) of these households with human population of 1105 (18.7%) reared a total number of 3895 pigs. Physical randomization was used to select 50% representative samples of pig-rearing households and pigs for this study. Out of the 402 pigs from 55 households, 207 (51.5%) pigs were positive for Balantidium coli cysts, 56 (13.9%) for Cryptosporidium oocysts while mixed infection was observed in 29 (7.2%). There is significance difference in the distribution of the two parasites in the pigs surveyed (p < 0.05). Young pigs were most affected with infection rates of 33 (58.9%) Cryptosporidium oocysts, 113 (54.6%) Balantidium coli cysts and 17(58.6%) mix infection. Human fecal samples collected from 53 individuals revealed 3 (5.7%) positive cases of Cryptosporidium oocysts all in young ones while a positive case of Balantidium coli cyst infection was found in an adult female. Water and soil samples from two areas were also found to contain both organisms. The semi-intensive system of pig rearing which allowed pigs to scavenge and defecate about, defective personal and environmental hygiene couple with the usage of untreated pig feaces as manure on vegetable farms in the study area can enhance the spread of these zoonotic diseases in human population.

Recognition of the epidemiological significance of Neisseria meningitidis capsular serogroup W135 in the Rio de Janeiro region, Brazil

Neisseria meningitidis retains its ability to cause endemic and hiperendemic disease in human population living in any environment, as well as localized outbreaks and massive epidemics in civilians and military personnel. In Rio de Janeiro it has been reported in the 1990s as prolonged outbreak of serogroup B and at least one epidemic of serogroup C was well defined, both demanding quick action by the Public Health authorities. We report here the emergence of serogroup W135 meningococcal disease causing endemic and case cluster in Rio de Janeiro during the first years of this new century.

Recognition of the epidemiological significance of Neisseria meningitidis capsular serogroup W135 in the Rio de Janeiro region, Brazil

Neisseria meningitidis retains its ability to cause endemic and hiperendemic disease in human population living in any environment, as well as localized outbreaks and massive epidemics in civilians and military personnel. In Rio de Janeiro it has been reported in the 1990s as prolonged outbreak of serogroup B and at least one epidemic of serogroup C was well defined, both demanding quick action by the Public Health authorities. We report here the emergence of serogroup W135 meningococcal disease causing endemic and case cluster in Rio de Janeiro during the first years of this new century.

Cigarette smoke and adverse health effects: An overview of research trends and future needs

A large volume of data has accumulated on the issues of tobacco and health worldwide. The relationship between tobacco use and health stems initially from clinical observations about lung cancer, the first disease definitively linked to tobacco use. Almost 35 years ago, the Office of the Surgeon General of the United States Health Service reviewed over 7000 research papers on the topic of smoking and health, and publicly recognized the role of smoking in various diseases, including lung cancer. Since then, numerous studies have been published that substantiate the strong association of tobacco use with a variety of adverse human health effects, most prominently with cancer and cardiovascular diseases. Cigarette smoking is regarded as a major risk factor in the development of lung cancer, which is the main cause of cancer deaths in men and women in the United States and the world. Major advances have been made by applying modern genetic technologies to examine the relationship between exposure to tobacco smoke and the development of diseases in human populations. The present review summarizes the major research areas of the past decade, important advances, future research needs and federal funding trends.

Cigarette Smoking and Incident Chronic Kidney Disease: A Systematic Review

Background: Several studies have examined the role of cigarette smoking in the development of renal disease in human populations. However, there have been no systematic reviews on the evidence linking smoking with incident renal disease. Methods: We performed an evidence-based evaluation of peer-reviewed research published during 1966–2005, from a search of five databases, including Ovid MEDLINE and EMBASE. Results: Of the 28 studies that were reviewed, 11 were excluded from the final analysis due to poor methodological quality (n = 6), no reported risk estimate for the association between smoking and kidney disease (n = 3), inability to find a Japanese translator (n = 1), and duplicate cohort (n = 1). Seventeen studies were included in the final analysis; seven studies found an overall significant association between smoking and incident chronic kidney disease, and three studies found a significantly increased risk of chronic kidney disease in current smokers that was gender and/or dose related. An increased risk of developing chronic kidney disease among smokers was significantly associated with male gender (relative risk 2.4, 95% confidence interval 1.2–4.5), >20 cigarettes smoked/day (odds ratio 1.51, 95% confidence interval 1.06–2.15, and relative risk 2.3, 95% confidence interval 1.2–4.3), and smoking >40 years (odds ratio 1.45, 95% confidence interval 1.00–2.09). A pooled estimate of the relative risk (meta-analysis) was deemed inappropriate due to the heterogeneity in methodologies utilized by the different studies. Conclusions: This comprehensive review reveals overall evidence for current cigarette smoking as a risk factor for incident chronic kidney disease. Further investigation is needed to more carefully examine the strength of the association between cigarette smoking and incident kidney disease.

The perpetuation and epidemic recurrence of communicable diseases in human populations

Recurrence of communicable diseases is a looming threat for human populations. Factors explaining the recurrences are partially known, involving demographics, biology, and complex relationships with the environment, but no comprehensive theory exists today. Here, we review some recent results obtained in modelling studies with a view to understanding better the mechanisms of perpetuation. Factors intrinsic to the interaction of pathogen and host have regained interest in this respect, especially with multiple pathogen and multiple population interactions. Extrinsic factors, including pure demography and environmental forcing are also strong predictors. With increasingly detailed data available, large-scale integrated models will help sorting out the multiple influences on recurrence. To cite this article: P.-Y. Boëlle, C. R. Biologies 330 (2007).