Download or read book Modelling the Transmission of and Effectiveness of Control Measures for Mycobacterium Avium Subsp Paratuberculosis in Dairy Herds written by Clara Marcé and published by . This book was released on 2010 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paratuberculosis is a worldwide incurable disease of ruminants resulting in a decrease in milk production and slaughter value. The aim of this thesis was to evaluate the epidemiological and economic effectiveness of selected control programmes in infected dairy herds. A stochastic simulation model has been developed to represent both the population dynamics within a dairy herd and the transmission of Mycobacterium avium subsp. paratuberculosis (Map). It has been coupled to an existing bioeconomic model. The spontaneous within-herd progression of Map infection after the introduction of one infected cattle in an initially susceptible herd was studied in the absence of control measure. The effect of within-herd contacts on Map spread in a persistently infected herd was investigated. The cost-effectiveness of test-and-cull strategies to control Map infection in dairy herds was assessed. Simulation outcomes put forward that, even when no control measure is implemented, fadeout can occur if less than two clinically affected animals are present. In persistently infected herds, the two main transmission routes are transmission via the environment of the farm and in utero transmission. Isolating calves from their herd mates during the first weeks of age has no significant impact on Map transmission. Limiting or delaying calf exposure to adult faeces and early culling of clinically affected adults are thus recommended to decrease Map prevalence in infected dairy herds. Systematic test-and-cull appears cost-effective if implemented from the day one infected cattle is introduced. The tool designed here is flexible and enables studying other control options within a dairy herd.

Download or read book Statistical Modeling of Longitudinal Data from Dairy Herds written by Rebecca Lee Smith and published by . This book was released on 2011 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mycobacterium avium subsp. paratuberculosis (MAP) causes infections in ruminants characterized by long latent periods, imperfect diagnostic tests, and production effects sufficient to result in early culling. In order to optimize control of this pathogen, the exact effects of both the infection and the control strategies must be understood. The goal of this dissertation is to statistically analyze various aspects of MAP in dairy herds, including the production effects of infection, its distribution in the dairy herd environment, and the transmission rates of animals shedding MAP. For this purpose, longitudinal data sets from commercial dairy herds have been analyzed, allowing for a more thorough understanding of MAP in typical farms. Cows in the high-shedding category (>30 cfu/g of MAP in feces) were found to produce approximately 4 kg less milk per day, on average, and to have higher culling rates and lower calving rates than non-shedding cows. In addition, the number of high-shedding animals in a pen was positively correlated with the amount of MAP cultured from the environment in that pen. In contrast, low-shedding cows were found to have higher culling rates than nonshedding cows, but no significant difference in calving rates or milk production. The average amount of fecal shedding in the herd was found to be predictive of both the odds of MAP being found in environmental samples and the amount of MAP in those samples, but environmental sampling was not found to be a sensitive herd-level diagnostic test. These results will enable optimization of economic models for MAP control by providing quantitative estimates of the effect of MAP on commercial dairy farms. In addition, it was found that reversible-jump Markov Chain Monte Carlo models are unable to estimate transmission rates for MAP using current longitudinal data sets, due to the large amount of missing data.

Download or read book Epidemiological Tools for Cost effective Detection and Control of Paratuberculosis in Dairy Herds written by Saraya Tavornpanich and published by . This book was released on 2005 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of Mycobacterium Avium Subsp Paratuberculosis in Dairy Herds written by Annabelle Beaver and published by . This book was released on 2017 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Johne’s disease, a severe granulomatous enteritis of ruminant animals, is caused by Mycobacterium avium subsp. paratuberculosis (MAP). MAP infections have detrimental consequences for animal health and reduce dairy-herd productivity. Bacterial fastidiousness and slow generation time encumber diagnostic testing strategies. MAP is also a potential etiologic agent of human Crohn’s disease, with the bulk-milk supply serving as a possible transmission vector. The objective of this dissertation is to explore MAP infection dynamics on dairy farms, with an emphasis on the routes of bulk-milk contamination, transmission risk across production type, and the interplay between diagnostic testing outcomes. Accordingly, we have applied statistical and mathematical approaches to both cross-sectional and longitudinal datasets. Using questionnaire data from 292 U.S. dairies, we conducted a comparative risk assessment of organic vs. conventional management and determined that organic herds were at higher risk for new MAP infections. We concluded, empirically, that organic farms were more susceptible to a synergism of risk factors within the maternity pen and should improve calving-area hygiene if electing to permit cow-calf contact. Bulk-milk testing was also conducted for these herds. Most high ELISA tanks were PCR negative, implying that ELISA is not a perfect predictor of bulk-milk MAP status; for accurate risk assessment, bulk-milk ELISA should be used in tandem with PCR. A combination of ELISA and PCR may also aid in determining the specific route of bulk-milk contamination (either environmental or direct shedding). To extend the investigation to individual animals, longitudinal data were obtained from 14 MAP-positive cows in 2 low-prevalence herds. Robust relationships between culture, fecal qPCR, and milk ELISA were revealed, using mixed linear modeling to adjust for cow characteristics. We explored temporal relationships and observed that spikes in fecal shedding were predictive of subsequent high milk ELISA results. We also noted that disease “Progressors,” (infected animals with increasing fecal MAP CFU over time) had higher antibody titers overall. Interestingly, the paucity of positive milk samples, from both individual and bulk- tank sources, suggests that milk contamination is not a chief concern in low-prevalence herds. Armed with insights from these studies, in addition to published literature, we developed a mathematical model to explore the interaction between categories of infection, environmental MAP burden, and bulk-tank contamination. Direct shedding into milk accounted for

Download or read book Modeling Disease Spread and Control written by Tariq Halasa and published by Frontiers Media SA. This book was released on 2018-01-18 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mathematical models are useful tools to understand the epidemiology and agent-host interaction of diseases. They are developed and applied since over a century, but with increasing computer capacity, they become increasingly prominent as part of evidence based decision making. Mathematical models are frequently used to construct preparedness and contingency plans for highly contagious diseases such as foot-and-mouth disease. This allows proposing effective strategies to control the spread of the disease in case of an incursion, and avails useful tools to support decision making during an outbreak. They are also used to monitor, prevent and control endemic diseases within populations or farms. In addition, mathematical models improve our understanding of the contact structure between farms, pointing out risky elements in the contact network for disease introduction or further spread within the population. This Research Topic presents valuable studies presenting different aspects and implementations of mathematical modeling for disease spread and control in the veterinary field. The areas covered include model construction, network analysis, tools for decision makers, and costeffective control of endemic diseases.

Download or read book Shedding of Mycobacterium Avium Subsp Paratuberculosis in Naturally Exposed Dairy Calves and Associated Risk Factors written by Michael William Bolton and published by . This book was released on 2009 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diagnosis and Control of Johne s Disease written by National Research Council and published by National Academies Press. This book was released on 2003-08-13 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Johne's Disease is a chronic, progressive intestinal disease caused by infection with Mycobacterium avium subspecies paratuberculosis (Map) that affects primarily ruminant animals. In recent decades there has been growing concern over the lack of effective control of this disease and questions have arisen regarding the possibility that Map infection could be a cause of some cases of Crohn's disease in humans. This report presents a broad outline of the steps that should be taken to control Johne's disease, reduce the spread of Map, and minimize effects of the disease in animals. The report also describes the weaknesses of our current research agenda and provides recommendations for a new research strategy to resolve the question of whether there is a link between Johne's and Crohn's diseases.

Download or read book Economic Consequences of Paratuberculosis Control in Dairy Cattle Herds written by Anne Braad Kudahl and published by . This book was released on 2005 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Diagnostic Tests for Detection of Mycobacterium Avium Subsp Paratuberculosis MAP at the Herd level and Cow level written by Carrie J. Lavers and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this research was to evaluate herd and cow-level Mycobacterium avium subspecies paratuberculosis (MAP) diagnostic tests within non-infected and low to moderate within-herd prevalence MAP-infected herds. Specific objectives were to estimate herd-level sensitivity and specificity of environmental culture and milk ELISA, determine predictors influencing herd test characteristics, evaluate cow-level test characteristics and between-test agreement of commercial milk ELISAs, and quantify additional diagnostic information gained from repeating a milk ELISA test. A longitudinal study was conducted between May 2009 and February 2011 on 34 dairy herds from Prince Edward Island, Nova Scotia, and New Brunswick. Environmental manure samples were collected every 3 mo, and cow manure and milk samples were collected from all lactating cows in the herd every 6 mo. Pooled fecal culture was used to establish MAP herd status. Individual fecal culture from cows within positive fecal culture pools was used to determine apparent within-herd MAP prevalence. Cow and environmental manure samples were cultured in a broth system, with confirmatory PCR targeting the hspX gene. Milk samples were analyzed using 3 commercial milk ELISAs. For herd-level statistical analyses, pseudogold standard methods were applied (herd reference: repeated pooled fecal culture). For cow-level test characteristics, pseudogold standard methods (reference: fecal culture) and latent class analyses were performed. Generalized estimating equation models accounted for repeated measures. Herd sensitivity of environmental culture was 71%, and specificity was 99%. Herd sensitivity of 3 milk ELISAs ranged from 56 - 63%, and herd specificity from 80 - 96%. Herd sensitivity of both environmental culture and milk ELISA improved as within-herd MAP prevalence increased. However, environmental culture sensitivity was higher at lower within-herd prevalence than herd milk ELISA tests, indicating environmental culture is a more appropriate test to detect low-prevalence herds. The proportion of positive samples within an environmental culture set was positively associated with within-herd MAP prevalence, establishing that environmental culture provides an estimation of within-herd prevalence for further risk management decisions. Evaluation of cow-level milk ELISA results revealed between-test agreement was low for positive ELISA tests. Cow-level milk ELISA sensitivities ranged from 28 - 35%, and specificities from 99 - 100%, and were not different for pseudogold standard methods or latent class models. Likelihood ratios indicated that cows with ELISA results in the uppermost quantitative category had a greater likelihood of MAP fecal shedding, necessitating specific management strategies for these cows. When a milk ELISA test was repeated 12 mo later, sensitivity increased from 26% for the initial test only, to 45% for the combined tests, while specificity decreased minimally. A repeated milk ELISA test substantially improves the probability to detect a MAP-infected cow, and should be considered for a herd control program. Development of effective herd and cow-level paratuberculosis testing programs is essential for the implementation of a successful MAP control program. Our herd-level analyses provide an estimation of the impact of within-herd prevalence on herd test characteristics, which will assist in selection of appropriate herd tests. Our cow-level ELISA analyses provide test characteristics of commercially available ELISAs, and extend the use of ELISA results beyond a single dichotomous outcome. Consideration of our quantitative ELISA results and interpretation of repeat ELISA tests will further improve management recommendations for the development of successful MAP control programs.

Download or read book Epidemiology Detection and Milk Production Effects of Mycobacterium Avium Subspecies Paratuberculosis on California Dairies written by Sharif Shafik Aly and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Johne's disease is a granulomatous enteritis of cattle caused by Mycobacterium avium subsp. paratuberculosis (MAP). Interest in Johne's is promoted by reports of decreased milk production, however, most publications were cross-sectional. The longitudinal studies available lack an assessment of confounding and model the standard lactation curve rather than that expressed by each cow. For the first study, mixed models based on causal diagrams were used to estimate the association between MAP and milk production, using cow-specific splines. Compared to test-negative cows, MAP seropositive and shedding cows produced 2.5 and 2.2 Kg less of milk per day, respectively. Environmental sampling and pooled fecal culture were used to identify super-shedders, cows that shed MAP in tens of thousands per gram of feces. The objective was to estimate the cost-effectiveness of diagnostic strategies to identify super-shedders such as ranking pens on a dairy by MAP bioburden using environmental samples. Subsequently, cows in high MAP bioburden pens would be tested. Results of the second study found that the reliability of environmental sampling across collectors and over 5 days was excellent (81%) and good (67%), respectively. Due to routine moving of cows between pens for management purposes, pen rankings must be available within 2-3 days. The availability of quantitative real-time PCR (qrt-PCR) made it possible to quantify MAP in samples within days compared to weeks using culture. Results of the third study found good correlation between assays for pooled and environmental samples ( -0.66 and -0.76, respectively) and a non-linear association between results of both assays that differed in magnitude between fresh and thawed samples. A whole herd test was conducted including combinations of serum or milk ELISA, qrt-PCR or culture of environmental, individual or pooled fecal samples. Results of all the tests were used to simulate 15 diagnostic strategies to detect super-shedders on a large dairy and estimate their cost-effectiveness. A whole herd qrt-PCR survey sample was the most sensitive (80%) of all 15 strategies. The most cost-effective strategy was to rank milking pens by MAP bioburden, ELISA test milk of cows in high MAP bioburden pens, followed by qrt-PCR testing of ELISA positive cows.

Download or read book Epidemiologic Investigations of Mycobacterium Avium Subspecies Paratuberculosis Infections in Ohio Dairy Herds written by Alecia Larew Naugle and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The development of effective control programs for Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne's disease, requires a complete understanding of the epidemiology of this agent in animal populations. The research described herein addresses several aspects of the epidemiology of this infection in dairy cattle. Fecal culture and ELISA results collected from nine Ohio dairy herds involved in Johne's disease testing programs are described, and likelihood ratios for multiple levels of ELISA S/P ratios are calculated using these test records. The likelihood ratios calculated here suggest that the quantitative use of ELISA S/P ratios to predict the infection status of an individual cow from a MAP-infected dairy herd provides the most confidence when S/P ratios are considerably higher than the manufacturer's recommended cut-off value. A prospective study of 55 Ohio dairy herds evaluated the relationships between farm management practices, milk production parameters and fecal cortisol levels. The influence of herd MAP-infection status on fecal cortisol levels was also assessed. Herd, management groups within herds and time of sample collection appear to significantly influence fecal cortisol levels; however, few specific management practices or milk production parameters that consistently influence these values were identified. Production data for individual dairy cows were matched with results for MAP tests in order to compare testday production parameters between cows that were test-positive relative to those that were test-negative for both the ELISA and fecal culture. On a given testday, significant losses in milk production were identified for both fecal culture and ELISA-positive cows relative to test-negative cows. These observations provide additional information for dairy producers to consider as they make culling decisions regarding MAP test-positive cows. Finally, a mail survey comparing the adoption of management practices recommended for Johne's disease control between Ohio dairy herds involved in testing programs relative to those herds that were not testing is described. Results of this survey demonstrate that, even if a producer believed his/her herd was not infected, participation in a testing program was associated with the adoption of management practices recommended for Johne's disease control.

Download or read book Transmission Dynamics Of Mycobacterium Avium Subspecies Paratuberculosis In Closed Dairy Herds In The Us written by Rebecca M. Mitchell and published by . This book was released on 2011 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we present work focused on within farm dynamics of Mycobacterium avium subsp paratuberculosis (MAP) infection on commercial US dairies. We focused on using deterministic mathematical models informed by molecular epidemiology and analysis of longitudinal data to evaluate current assumptions of MAP transmission. In vitro analysis of bovine-specific MAP strains revealed a difference in survival of bovine-specific MAP strains but no difference in monocyte-derived macrophages from shedding and non-shedding exposed animals. Molecular analysis of strains of MAP in dam-daughter pairs in a seven-year longitudinal dataset showed that vertical transmission plays a small but identifiable role in MAP transmission. In a metaanalysis of experimental infections of cows with MAP, most calves shed MAP within 12 months of infection. Duration of early shedding and time to late shedding were both dependent on age at exposure, while dose delivered played a role in duration of early shedding only. We integrated early shedding into on-farm models and it played an important role in MAP persistence in herds undergoing intervention attempts. Adding age- and dose-dependent early shedding created a forward feedback loop in which MAP can persist in populations which would not support introduction.

Download or read book A Hybrid Modeling Approach to Assess the Efficacy of Control Measures on Paratuberculosis on U S Dairy Farms written by Malinee Konboon and published by . This book was released on 2016 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paratuberculosis, also known as Johne's disease or JD, is a chronic contagious infection, caused by Mycobaterium avium paratuberculosis (MAP). This fatal disease is incurable and causes considerable economic losses to the industry. Each year, the U.S. dairy industry loses over 200 million dollars due to the infection. Using the cattle movement data of six California dairy farms and Johne's disease transmission data, a mathematical model was developed to determine control policies that can minimize the likelihood of outbreaks and the incidence and prevalence of the infection in dairy farms. In particular, we have implemented a hybrid modeling approach that combines the between-pen cattle movements with progression of the infection in each pen to study the effect of cattle movement patterns on the spread of disease. Using the basic reproduction number, the infection risk in cattle in each pen and the entire farm was calculated. It is shown that the overall infection risk is substantially reduced when the average residence time and the population size in high risk pens are minimized. Using numerical simulations, spread of epidemic waves in dairy farms and impacts of control measures are numerically explored. It is shown that a single control measure is insufficient to prevent outbreaks. Whereas a combination of control measures such as test and cull, and intensive pen cleaning may lead to a disease-free environment in the dairy farms.

Download or read book Observed Management Practices in Relation to the Risk of Infection with Paratuberculosis and to the Spread of Mycobacterium Avium Subsp Paratuberculosis in Swiss Dairy and Beef Herds written by Rahel Künzler and published by . This book was released on 2014 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Control Strategies for Johne s Disease in Dairy Cattle written by Roxanne Bee Pillars and published by . This book was released on 2008 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Impact of a New Method for the Detection of Mycobacterium Avium Subspecies Paratuberculosis on the Control of Johne s Disease in Dairy Cattle written by Zara Elizabeth Gerrard and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Seasonal Heat Stress on the Diagnosis of Mycobacterium Avium Subsp Paratuberculosis in Texas Dairy Cattle written by Summer Joy Strickland and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The validity of Johne's disease herd status programs and on-farm disease control programs that rely on established 'cutpoints' (e.g., S/P ratios) for ELISA serological tests such as the HerdChek® (IDEXX Laboratories Inc., Westbrook, Maine) may be susceptible to varied seasonal test accuracy. An observed depression in the proportion of a large central Texas dairy herd classified as "positive" during the months of July and August led to our investigation. We hypothesized that there exists a seasonal variability in serological response to Mycobacterium avium subsp. paratuberculosis that is directly related to heat stress. We further hypothesized that a reciprocal response may occur during periods of heat stress that results in a greater risk of fecal shedding in subclinically-infected animals. Starting in October 2002, we invoked a testing regime that included multiple testing of 720 individual adult cows over each of four seasons including spring, summer, fall, and winter. We collected serum on a cyclic, monthly basis from three random groupings of cows, and, based on the ELISA results, collected fecal samples from the 20% of cows with the highest S/P ratios. We continued to sample in this manner for the period of one year and at the end of that period, analyzed the serum en masse. The ELISA outcome values were treated both as categorical and continuous variables (e.g., S/P ratio). The potential lagged effects of heat stress on S/P ratio, as well as the potential for a change in test result (negative to positive or vice versa) due to heat stress were assessed. The results for fecal culture were analyzed on a categorical scale and were compared to the ELISA results to explore the possibility of a reciprocal response. In the present study, we did not observe any of the significant seasonal effects of heat stress on S/P ratios and proportion seropositive to MAP that were observed in the historical (and less valid) cross-sectional time-series data conducted in 2001. In addition, we found no evidence to support a hypothesis linking seasonal heat stress to the risk of fecal culture positivity for the causative bacterium for Johne's disease.