A Bayesian Weibull survival model for time to infection data measured with delay

Parameter estimation of three-parameter Weibull probability model based on outlier detection

The Weibull probability model used in statistical analysis has become more popular in the inconsistency evaluation of used Li-ion batteries due to its flexibility in fitting asymmetrically distributed data. However, despite its better fitting of data with a non-zero minimum, the three-parameter Weibull model is less used because of its complicated calculation. Additionally, the Weibull family is likely to overfit and shows inference from outliers. Although conventional estimation methods for Weibull parameters based on dispersion and symmetry of the overall distribution lead to derivation from the actual data features, there is little research into methods to solve the contradiction between estimation accuracy and proper outlier detection. In this study, a Weibull parameter estimation method was proposed that features simplified computation and eliminates the interference from outliers. The outliers were identified based on the obtained Weibull parameters and excluded from the sample data. The method was implemented for fitting the capacity distribution of Li-ion batteries, which was verified by a chi-square test at a confidence of 95% and the Anderson-Darling test. It showed a higher goodness-of-fit and less error than the results of the maximum likelihood estimated Weibull model as well as the normal distribution. The optimal presetting of column number and peak reference point selection were determined by parameter discussion.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): paratuberculosis

Paratuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of paratuberculosis to be listed, Article 9 for the categorisation of paratuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to paratuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, paratuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria in Sections 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for paratuberculosis according to Article 8(3) criteria are several species of mammals and birds as susceptible species and some species of the families Bovidae, Cervidae and Leporidae as reservoirs.

Dam's infection progress and within-herd prevalence as predictors of Mycobacterium avium subsp. paratuberculosis ELISA response in Danish Holstein cattle

Understanding the primary routes of transmission of Mycobacterium avium subsp. paratuberculosis (MAP) is pivotal to manage the pathogen in cattle herds. MAP is transmitted both vertically and horizontally, and both the dam's stage of infection and the prevalence in the population are therefore potentially important for MAP transmission control. The objective of this study was therefore to assess the dam's infection progress and the within-herd test-prevalence as predictors of MAP infection in Danish dairy cattle. MAP specific antibody ELISA records from 95,025 dam-offspring pairs were combined with test-prevalence estimates from 939 Danish Holstein herds. The odds of testing ELISA-positive given the within-herd test-prevalence and the time-period a dam had had MAP specific antibodies were estimated for the offspring. Both dams and offspring were tested as adults, and parity-group was used to correct for the effect of age. The results showed that both the within-herd test-prevalence and the dam's infection progress were significant predictors, while the dams that had tested positive when giving birth and up to 0.7 years after were more likely to have offspring that would test positive. The odds of testing positive were about 1.5 to 2.5 times higher for these offspring, compared to offspring of dams that never tested positive. Furthermore, offspring born in high (>5% ELISA-positive) and medium (2.5 to 5% ELISA-positive) prevalence herds had 9 and 3, respectively, times higher odds of testing positive, compared to animals born in a low prevalence herd. The variance heterogeneity reduced 81% through the included predictors. The results of this study suggest that irrespective of the prevalence, offspring of dams with MAP specific antibodies should be considered as high-risk animals when managing the infection in cattle herds, but both the prevalence and the dam's infection status are important in MAP control.

Invited review: modeling within-herd transmission of Mycobacterium avium subspecies paratuberculosis in dairy cattle: a review

Epidemiological models have been developed to test hypotheses on Mycobacterium avium ssp. paratuberculosis (Map) transmission in a herd, and to compare different paratuberculosis control strategies and alternatives for certification-and-surveillance schemes. The models are simplified representations of existing biological processes tailored to the questions they are intended to answer. Such models depend on available knowledge about the underlying processes, notably in relation to pathogen transmission. All decisions relating to integration of specific aspects of the herd structure and transmission mechanisms as well as modeling objective will influence model behavior and simulation results. This paper examines assumptions on pathogen transmission and risk mitigation represented in 8 epidemiological models of within-herd Map transmission in dairy cattle. We describe available models' structure and examine them in the context of current knowledge about host infection and pathogen transmission pathways. We investigate how population structure and herd management are modeled with regard to their influence on contact structure and pathogen transmission. We show that assumptions about routes of transmission and their contribution within a herd vary greatly among models. Gaps of knowledge that are pivotal to defining transmission equations and parameters, such as variation of susceptibility with age and variability of pattern of shedding, are identified. Quantitative estimates of this incomplete information should be targeted by future research. Existing models could be improved by considering indirect transmission via the environment taking account of Map survival and contact structure between animals in a herd, and by including calf-to-calf transmission, which has recently been proven as being important.