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Full-Text Articles in Medicine and Health Sciences
Introduction Infectious Disease Modeling, Cristina Lanzas
Introduction Infectious Disease Modeling, Cristina Lanzas
Cristina Lanzas
No abstract provided.
Investigating Effects Of Between- And Within- Host Variability On Escherichia Coli O157 Shedding Pattern And Transmission, Shi Chen, Mike Sanderson, Cristina Lanzas
Investigating Effects Of Between- And Within- Host Variability On Escherichia Coli O157 Shedding Pattern And Transmission, Shi Chen, Mike Sanderson, Cristina Lanzas
Cristina Lanzas
Healthy cattle and their environment are the reservoir for the human pathogen Escherichia coli O157. In E. coli O157 epidemiology, supershedders have been loosely defined as cattle that shed high concentrations of E. coli O157 (≥104 colony-forming cells (CFU)/g of feces) at a single (or multiple) cross-section in time. Due to the variability in the pathogen shedding level among animals (between-host variability), as well as fluctuations in the level shed by a single animal (within-host variability), it is difficult to interpret fecal bacteria distributions, as well as to parse the relative contribution of between- and within-host variability to the observed …
Mathematical Modeling Of The Transmission And Control Of Foodborne Pathogens And Antimicrobial Resistance At Preharvest, Cristina Lanzas, Zhao Lu, Yrjo T. Grohn
Mathematical Modeling Of The Transmission And Control Of Foodborne Pathogens And Antimicrobial Resistance At Preharvest, Cristina Lanzas, Zhao Lu, Yrjo T. Grohn
Cristina Lanzas
Foodborne diseases are a significant health care and economical burden. Most foodborne pathogens are enteric pathogens harbored in the gastrointestinal tract of farm animals. Understanding the transmission of foodborne pathogens and dissemination of antimicrobial resistance at the farm level is necessary to design effective control strategies at preharvest. Mathematical models improve our understanding of pathogen dynamics by providing a theoretical framework in which factors affecting transmission and the control of the pathogens can be explicitly considered. In this review, we aim to present the principles underlying the mathematical modeling of foodborne pathogens and antimicrobial resistance at the farm level to …
Epidemiological Model For Clostridium Difficile Transmission In Healthcare Settings, Cristina Lanzas, Erik Dubberke, Zhao Lu, Kim Reske, Yrjo Grohn
Epidemiological Model For Clostridium Difficile Transmission In Healthcare Settings, Cristina Lanzas, Erik Dubberke, Zhao Lu, Kim Reske, Yrjo Grohn
Cristina Lanzas
Objective. Recent outbreaks of Clostridium difficile infection (CDI) have been difficult to control, and data indicate that the importance of different sources of transmission may have changed. Our objectives were to evaluate the contributions of asymptomatic and symptomatic C. difficile carriers to new colonizations and to determine the most important epidemiological factors influencing C. difficile transmission. Design, setting, and patients. Retrospective cohort study of all patients admitted to medical wards at a large tertiary care hospital in the United States in the calendar year 2008. Methods. Data from six medical wards and published literature were used to develop a compartmental …
Model Or Meal? Farm Animal Populations As Models For Infectious Diseases Of Humans, Cristina Lanzas, P Ayscue, R Ivanek, Y T. Grohn
Model Or Meal? Farm Animal Populations As Models For Infectious Diseases Of Humans, Cristina Lanzas, P Ayscue, R Ivanek, Y T. Grohn
Cristina Lanzas
In recent decades, theory addressing the processes that underlie the dynamics of infectious diseases has progressed considerably. Unfortunately, the availability of empirical data to evaluate these theories has not grown at the same pace. Although laboratory animals have been widely used as models at the organism level, they have been less appropriate for addressing issues at the population level. However, farm animal populations can provide empirical models to study infectious diseases at the population level.
Development Of A Mechanistic Model To Represent The Dynamics Of Particle Flow Out Of The Rumen And To Predict Rate Of Passage Of Forage Particles In Dairy Cattle., S Seo, Cristina Lanzas, L O. Tedeschi, A Pell, D G. Fox
Development Of A Mechanistic Model To Represent The Dynamics Of Particle Flow Out Of The Rumen And To Predict Rate Of Passage Of Forage Particles In Dairy Cattle., S Seo, Cristina Lanzas, L O. Tedeschi, A Pell, D G. Fox
Cristina Lanzas
A mechanistic and dynamic model was developed to represent physiological aspects of particle dynamics in the reticulo-rumen (RR) and to predict rate of passage out of the RR (Kp) of forage particles quantitatively. The model consists of 2 conceptual pools with 3 spatial compartments of particles; the compartment the particle enters is based on functional specific gravity (FSG). The model assumes 2 major pressure gradient-driven flows of particles out of the RR through the reticulo-omasal orifice between 2 consecutive primary reticular contractions. One is associated with the second phase of primary reticular contraction and involves propulsion of particles in the …
Modeling On-Farm Escherichia Coli O157:H7 Population Dynamics, P Ayscue, Cristina Lanzas, R Ivanek, Y T. Grohn
Modeling On-Farm Escherichia Coli O157:H7 Population Dynamics, P Ayscue, Cristina Lanzas, R Ivanek, Y T. Grohn
Cristina Lanzas
Escherichia coli O157:H7 is a potentially fatal foodborne pathogen with a putative reservoir for human infection in feedlot cattle. In order to more effectively identify targets for intervention strategies, we aimed to (1) assess the role of various feedlot habitats in E. coli O157:H7 propagation and (2) provide a framework for examining the relative contributions of animals and the surrounding environment to observed pathogen dynamics. To meet these goals we developed a mathematical model based on an ecological metapopulation framework to track bacterial population dynamics inside and outside the host. We used E. coli O157:H7 microbiological and epidemiological literature to …
Improved Feed Protein Fractionation Schemes For Formulating Rations With The Cornell Net Carbohydrate And Protein System, Cristina Lanzas, G A. Broderick, D G. Fox
Improved Feed Protein Fractionation Schemes For Formulating Rations With The Cornell Net Carbohydrate And Protein System, Cristina Lanzas, G A. Broderick, D G. Fox
Cristina Lanzas
Adequate predictions of rumen-degradable protein (RDP) and rumen-undegradable protein (RUP) supplies are necessary to optimize performance while minimizing losses of excess nitrogen (N). The objectives of this study were to evaluate the original Cornell Net Carbohydrate Protein System (CNCPS) protein fractionation scheme and to develop and evaluate alternatives designed to improve its adequacy in predicting RDP and RUP. The CNCPS version 5 fractionates CP into 5 fractions based on solubility in protein precipitant agents, buffers, and detergent solutions: A represents the soluble nonprotein N, B1 is the soluble true protein, B2 represents protein with intermediate rates of degradation, B3 is …
The Effect Of Heterogeneous Infectious Period And Contagiousness On The Dynamics Of Salmonella Transmission In Dairy Cattle, Cristina Lanzas, S Brien, R Ivanek, Y Lo, P P. Chapagain, K A. Ray, P Ayscue, L D. Warnick, Y T. Grohn
The Effect Of Heterogeneous Infectious Period And Contagiousness On The Dynamics Of Salmonella Transmission In Dairy Cattle, Cristina Lanzas, S Brien, R Ivanek, Y Lo, P P. Chapagain, K A. Ray, P Ayscue, L D. Warnick, Y T. Grohn
Cristina Lanzas
The objective of this study was to address the impact of heterogeneity of infectious period and contagiousness on Salmonella transmission dynamics in dairy cattle populations. We developed three deterministic SIR-type models with two basic infected stages (clinically and subclinically infected). In addition, model 2 included long-term shedders, which were defined as individuals with low contagiousness but long infectious period, and model 3 included super-shedders (individuals with high contagiousness and long infectious period). The simulated dynamics, basic reproduction number (R0) and critical vaccination threshold were studied. Clinically infected individuals were the main force of infection transmission for models 1 and 2. …
The Risk And Control Of Salmonella Outbreaks In Calf-Raising Operations: A Mathematical Modeling Approach, Cristina Lanzas, L D. Warnick, R Ivanek, P Ayscue, D V. Nydam, Y T. Grohn
The Risk And Control Of Salmonella Outbreaks In Calf-Raising Operations: A Mathematical Modeling Approach, Cristina Lanzas, L D. Warnick, R Ivanek, P Ayscue, D V. Nydam, Y T. Grohn
Cristina Lanzas
Salmonellosis in calves has economic and welfare implications, and serves as a potential source of human infections. Our objectives were to assess the risk of Salmonella spread following its introduction into a herd of pre-weaned calves and to evaluate the efficacy of control strategies to prevent and control outbreaks. To meet these objectives, we developed a model of Salmonella transmission within a pre-weaned group of calves based on a well documented outbreak of salmonellosis in a calf-raising operation and other literature. Intervention scenarios were evaluated in both deterministic and stochastic versions of the model. While the basic reproduction number (R0) …
Development Of A Mechanistic Model To Represent The Dynamics Of Liquid Flow Out Of The Rumen And To Predict The Rate Of Passage Of Liquid In Dairy Cattle, S Seo, Cristina Lanzas, L O. Tedeschi, D G. Fox
Development Of A Mechanistic Model To Represent The Dynamics Of Liquid Flow Out Of The Rumen And To Predict The Rate Of Passage Of Liquid In Dairy Cattle, S Seo, Cristina Lanzas, L O. Tedeschi, D G. Fox
Cristina Lanzas
A mechanistic and dynamic model was developed to represent the physiological aspects of liquid dynamics in the rumen and to quantitatively predict liquid flow out of the reticulorumen (RR). The model is composed of 2 inflows (water consumption and salivary secretion), one outflow (liquid flow through the reticulo-omasal orifice (ROO), and one in-and-out flow (liquid flux through the rumen wall). We assumed that liquid flow through the ROO was coordinated with the primary reticular contraction, which is characterized by its frequency, duration, and amplitude during eating, ruminating, and resting. A database was developed to predict each component of the model. …
Evaluation Of Protein Fractionation Systems Used In Formulating Rations For Dairy Cattle, Cristina Lanzas, S Seo, L O. Tedeschi, D G. Fox
Evaluation Of Protein Fractionation Systems Used In Formulating Rations For Dairy Cattle, Cristina Lanzas, S Seo, L O. Tedeschi, D G. Fox
Cristina Lanzas
Production efficiency decreases when diets are not properly balanced for protein. Sensitivity analyses of the protein fractionation schemes used by the National Research Council Nutrient Requirement of Dairy Cattle (NRC) and the Cornell Net Carbohydrate and Protein System (CNCPS) were conducted to assess the influence of the uncertainty in feed inputs and the assumptions underlying the CNCPS scheme on metabolizable protein and amino acid predictions. Monte Carlo techniques were used. Two lactating dairy cow diets with low and high protein content were developed for the analysis. A feed database provided by a commercial laboratory and published sources were used to …
Digestion Kinetics Of Dried Cereal Grains, Cristina Lanzas, A N. Pell, D G. Fox
Digestion Kinetics Of Dried Cereal Grains, Cristina Lanzas, A N. Pell, D G. Fox
Cristina Lanzas
Grain fermentability largely determines the feed value of grains for ruminants. Our objective was to evaluate the variation in kinetics of gas production of cereal grains and the relationship among gas production, chemical composition and feed value. Eighteen barley, 99 corn, 23 sorghum, and 57 wheat samples were fermented in vitro for 48 h. Gas production was measured with a computerized system and an exponential model was fitted to the data. The impact of the variation in composition and kinetics on the feed value of grains in feedlot rations was assessed with the Cornell Net Carbohydrate and Protein System (CNCPS). …
A Revised Cncps Feed Carbohydrate Fractionation Scheme For Formulating Rations For Ruminants, Cristina Lanzas, C J. Sniffen, S Seo, L O. Tedeschi, D G. Fox
A Revised Cncps Feed Carbohydrate Fractionation Scheme For Formulating Rations For Ruminants, Cristina Lanzas, C J. Sniffen, S Seo, L O. Tedeschi, D G. Fox
Cristina Lanzas
Balancing ruminant diets for appropriate levels and types of dietary carbohydrates (CHO) is necessary to maximize production while assuring the health of the animals. Several feed fractions (i.e., volatile fatty acids (VFA), lactate, sugars, starch) are now being measured in some commercial feed laboratories and this information may assist in better formulating diets. A CHO fractionation scheme based on ruminal degradation characteristics needed for nutritional models is described and its impact on predictions with the Cornell Net Carbohydrate and Protein System (CNCPS) is assessed. Dietary CHO are divided into eight fractions: the CA1 is volatile fatty acids (VFA), CA2 is …