Epidemic disease risks and implications for Veterinary Services.

Growth in the livestock sector is associated with heightened risk for epidemic diseases. The increasing spillover of new diseases from wildlife is being driven by wide-scale anthropogenic changes allowing for more frequent and closer wildlife-human and wildlife-livestock contacts. An increasing number of epidemics in livestock are associated with rapid transition of livestock systems from extensive to intensive, and local to global movement of livestock and their products through value chain networks with weak biosecurity. Major livestock epidemics in the past two decades have had substantial economic impacts, and the COVID-19 pandemic highlights the devastating socio-economic consequences that spillovers can have when not identified and controlled early in the process of emergence. This highlights the importance of Veterinary Services to integrated, whole-of-society efforts to control infectious diseases in animals. Emphasis within Veterinary Services must be placed on prevention and preparedness. The authors suggest four areas for continued improvement in Veterinary Services to meet this challenge. These are a) continued development of staff capacity for risk assessment and value chain analysis, together with improved policies and communication, b) appropriate adaptation of approaches to prevention and control in resource-poor settings, c) improved multi-sectoral and transboundary cooperation, which enables the sharing of resources and expertise, and d) systematic approaches that enable Veterinary Services to influence decisionmaking for trade, markets, business, public health, and livelihood development at the national and regional levels.

La croissance du secteur de l'élevage est associée à un risque accru de maladies épidémiques. Les changements anthropiques à grande échelle sont à l'origine du nombre croissant de maladies émergentes atteignant de nouvelles espèces réceptives (spillover) à partir de réservoirs sauvages, à la faveur de contacts plus fréquents et plus rapprochés entre la faune sauvage et les humains, d'une part, et entre la faune sauvage et les animaux domestiques, d'autre part. On considère qu'un nombre croissant d'épidémies affectant le bétail sont dues à la transition rapide des systèmes d'élevage extensif vers des systèmes intensifs, et aux mouvements du bétail et des produits de l'élevage de l'échelle locale à l'échelle mondiale par le biais de réseaux de chaînes de valeur dotés d'un faible niveau de biosécurité. Au cours des deux dernières décennies, d'importantes épidémies affectant le bétail ont eu un impact économique considérable ; en outre, la pandémie de COVID-19 a mis en évidence les conséquences socio-économiques dévastatrices des atteintes de nouvelles espèces réceptives par des agents pathogènes, lorsque ces maladies ne sont pas détectées et maîtrisées dès le processus d'émergence. Cela souligne l'importance cruciale des Services vétérinaires dans les efforts de lutte contre les maladies infectieuses chez les animaux, qui doivent être intégrés et mobiliser la société entière. Les Services vétérinaires doivent mettre un accent particulier sur la prévention et la préparation. Les auteurs proposent quatre aspects d'amélioration continue pour que les Services vétérinaires puissent relever ce défi. Il s'agit : a) du développement permanent des compétences des personnels vétérinaires en matière d'évaluation du risque et d'analyse des chaînes de valeur, et leur articulation avec de meilleures politiques et une communication plus performante ; b) une adaptation adéquate des méthodes de prévention et de contrôle dans les configurations faiblement dotées en ressources ; c) une meilleure coopération multisectorielle et transfrontalière afin de partager les ressources et les compétences ; d) des dispositifs systémiques permettant aux Services vétérinaires d'influencer les prises de décision en matière d'échanges internationaux, de marchés, de commerce, de santé publique et de développement des moyens de subsistance, à l'échelle nationale et régionale.

El crecimiento del sector pecuario está condicionado por la existencia de un mayor riesgo de enfermedades epidémicas. La creciente diseminación de nuevas enfermedades a partir de animales silvestres es consecuencia de transformaciones antrópicas a gran escala que posibilitan un contacto más frecuente y estrecho de la fauna silvestre con el ser humano y el ganado. Cada vez son más las epidemias del ganado que tienen que ver con la rápida transición de los sistemas pecuarios de un régimen de producción extensiva a otro de producción intensiva y con el paso de la dimensión local a la mundial de la circulación de animales y sus derivados a través de redes de cadenas de valor que presentan una endeble seguridad biológica. En los últimos dos decenios ha habido grandes epidemias que han afectado al ganado y tenido importantes consecuencias económicas. La pandemia de COVID-19 es un elocuente ejemplo de los devastadores efectos socioeconómicos que puede tener la extensión de un patógeno cuando no se detecta y controla en un momento lo bastante precoz del proceso de emergencia. Ello pone de relieve la importancia que revisten los Servicios Veterinarios para que toda la sociedad pueda reaccionar de forma integrada a la hora de combatir las enfermedades infecciosas de los animales. Dentro de los Servicios Veterinarios, conviene poner el acento en la prevención y la preparación. Para lograr este objetivo los autores señalan cuatro ámbitos que exigen una constante mejora: a) el desarrollo continuo de la capacidad del personal en materia de determinación de riesgos y análisis de cadenas de valor, ligado a la mejora de las políticas y la comunicación; b) la adecuada adaptación de los métodos de prevención y control en contextos de escasos recursos; c) una mejor cooperación multisectorial y transfronteriza, que permita poner en común recursos y competencias técnicas; y d) enfoques sistemáticos que hagan posible que los Servicios Veterinarios influyan en los procesos decisorios relativos al desarrollo del comercio, los mercados, las empresas, la salud pública y los medios de sustento a escala tanto nacional como regional.

A large-scale study of a poultry trading network in Bangladesh: implications for control and surveillance of avian influenza viruses.

BACKGROUND: Since its first report in 2007, avian influenza (AI) has been endemic in Bangladesh. While live poultry marketing is widespread throughout the country and known to influence AI dissemination and persistence, trading patterns have not been described. The aim of this study is to assess poultry trading practices and features of the poultry trading networks which could promote AI spread, and their potential implications for disease control and surveillance. Data on poultry trading practices was collected from 849 poultry traders during a cross-sectional survey in 138 live bird markets (LBMs) across 17 different districts of Bangladesh. The quantity and origins of traded poultry were assessed for each poultry type in surveyed LBMs. The network of contacts between farms and LBMs resulting from commercial movements of live poultry was constructed to assess its connectivity and to identify the key premises influencing it. RESULTS: Poultry trading practices varied according to the size of the LBMs and to the type of poultry traded. Industrial broiler chickens, the most commonly traded poultry, were generally sold in LBMs close to their production areas, whereas ducks and backyard chickens were moved over longer distances, and their transport involved several intermediates. The poultry trading network composed of 445 nodes (73.2% were LBMs) was highly connected and disassortative. However, the removal of only 5.6% of the nodes (25 LBMs with the highest betweenness scores), reduced the network's connectedness, and the maximum size of output and input domains by more than 50%. CONCLUSIONS: Poultry types need to be discriminated in order to understand the way in which poultry trading networks are shaped, and the level of risk of disease spread that these networks may promote. Knowledge of the network structure could be used to target control and surveillance interventions to a small number of LBMs.

Active animal health surveillance in European Union Member States: gaps and opportunities.

Animal health surveillance enables the detection and control of animal diseases including zoonoses. Under the EU-FP7 project RISKSUR, a survey was conducted in 11 EU Member States and Switzerland to describe active surveillance components in 2011 managed by the public or private sector and identify gaps and opportunities. Information was collected about hazard, target population, geographical focus, legal obligation, management, surveillance design, risk-based sampling, and multi-hazard surveillance. Two countries were excluded due to incompleteness of data. Most of the 664 components targeted cattle (26·7%), pigs (17·5%) or poultry (16·0%). The most common surveillance objectives were demonstrating freedom from disease (43·8%) and case detection (26·8%). Over half of components applied risk-based sampling (57·1%), but mainly focused on a single population stratum (targeted risk-based) rather than differentiating between risk levels of different strata (stratified risk-based). About a third of components were multi-hazard (37·3%). Both risk-based sampling and multi-hazard surveillance were used more frequently in privately funded components. The study identified several gaps (e.g. lack of systematic documentation, inconsistent application of terminology) and opportunities (e.g. stratified risk-based sampling). The greater flexibility provided by the new EU Animal Health Law means that systematic evaluation of surveillance alternatives will be required to optimize cost-effectiveness.

[New and established aspects of cardiological diagnostics using TEE : Do we need 3D technology in clinical routine?] / Neues und Bewährtes in der kardiologischen Diagnostik mithilfe der TEE : Wird die 3­D-Technik in der klinischen Routine benötigt?

In comparison to transthoracic echocardiography (TTE) transesophageal echocardiography (TEE) enables an acquisition of images with better spatial resolution due to the use of higher ultrasound frequencies. Thus, the morphology and function of cardiac structures can principally be analyzed better and more accurately with TEE than with TTE. In addition, using three-dimensional (3D) TEE data sets standardized sectional planes can be constructed by post-processing, which enables quantitative assessment of the target structures. The size and function of the left ventricle can objectively and reproducibly be measured. End diastolic left ventricular volume and total stroke volume of the left ventricle can be accurately determined in patients with heart valve disease. Furthermore, particular cardiac structures that cannot be totally evaluated by two-dimensional (2D) echocardiography, can be completely analyzed by 3D TEE. In 2D images for example, only analyses of the right coronary cusp of the aortic valve are possible because only the center of the right coronary cusp can be visualized using conventional sectional level presentation. Using 3D TEE the non-coronary cusp and the left coronary cusp can also be visualized in the mid-sectional plane by post-processing of the 3D data set. Additional important structures of 3D TEE analysis are the left atrial auricle, the interatrial septum and the mitral valve. Planimetry of valvular and regurgitation orifices as well as the monitoring of interventions for treatment of structural heart diseases are further fields of application of clinically established 3D TEE diagnostics.

Quantitative Assessment of the Risk of Release of Foot-and-Mouth Disease Virus via Export of Bull Semen from Israel.

Various foot-and-mouth disease (FMD) virus strains circulate in the Middle East, causing frequent episodes of FMD outbreaks among Israeli livestock. Since the virus is highly resistant in semen, artificial insemination with contaminated bull semen may lead to the infection of the receiver cow. As a non-FMD-free country with vaccination, Israel is currently engaged in trading bull semen only with countries of the same status. The purpose of this study was to assess the risk of release of FMD virus through export of bull semen in order to estimate the risk for FMD-free countries considering purchasing Israeli bull semen. A stochastic risk assessment model was used to estimate this risk, defined as the annual likelihood of exporting at least one ejaculate of bull semen contaminated with viable FMD virus. A total of 45 scenarios were assessed to account for uncertainty and variability around specific parameter estimates and to evaluate the effect of various mitigation measures, such as performing a preexport test on semen ejaculates. Under the most plausible scenario, the annual likelihood of exporting bull semen contaminated with FMD virus had a median of 1.3 * 10-7 for an export of 100 ejaculates per year. This corresponds to one infected ejaculate exported every 7 million years. Under the worst-case scenario, the median of the risk rose to 7.9 * 10-5 , which is equivalent to the export of one infected ejaculate every 12,000 years. Sensitivity analysis indicated that the most influential parameter is the probability of viral excretion in infected bulls.

Experimental pig-to-pig transmission dynamics for African swine fever virus, Georgia 2007/1 strain.

African swine fever virus (ASFV) continues to cause outbreaks in domestic pigs and wild boar in Eastern European countries. To gain insights into its transmission dynamics, we estimated the pig-to-pig basic reproduction number (R 0) for the Georgia 2007/1 ASFV strain using a stochastic susceptible-exposed-infectious-recovered (SEIR) model with parameters estimated from transmission experiments. Models showed that R 0 is 2·8 [95% confidence interval (CI) 1·3-4·8] within a pen and 1·4 (95% CI 0·6-2·4) between pens. The results furthermore suggest that ASFV genome detection in oronasal samples is an effective diagnostic tool for early detection of infection. This study provides quantitative information on transmission parameters for ASFV in domestic pigs, which are required to more effectively assess the potential impact of strategies for the control of between-farm epidemic spread in European countries.

[Alcohol and arrhythmias]. / Alkohol und Rhythmusstörungen.

The effects of alcohol on induction of arrhythmias is dose-dependent, independent of preexisting cardiovascular diseases or heart failure and can affect otherwise healthy subjects. While the probability of atrial fibrillation increases with the alcohol dosage, events of sudden cardiac death are less frequent with low and moderate consumption but occur more often in heavy drinkers with alcoholic cardiomyopathy. Men are first affected at higher dosages of alcohol but women can suffer from arrhythmias at lower dosages. Thromboembolisms and ischemic stroke can occur less often at lower dosages of alcohol; however, hemorrhagic stroke and subarachnoid hemorrhage are increased with higher alcohol dosages. Recognizable protective mechanisms of alcohol with respect to cardiovascular diseases only occur with lower amounts of alcohol of less than 10 g per day. Underlying mechanisms explain these controversial effects. Specific therapeutic options for alcohol-related arrhythmias apart from abstinence from alcohol consumption are not known.

Systematic review of surveillance systems and methods for early detection of exotic, new and re-emerging diseases in animal populations.

In this globalized world, the spread of new, exotic and re-emerging diseases has become one of the most important threats to animal production and public health. This systematic review analyses conventional and novel early detection methods applied to surveillance. In all, 125 scientific documents were considered for this study. Exotic (n = 49) and re-emerging (n = 27) diseases constituted the most frequently represented health threats. In addition, the majority of studies were related to zoonoses (n = 66). The approaches found in the review could be divided in surveillance modalities, both active (n = 23) and passive (n = 5); and tools and methodologies that support surveillance activities (n = 57). Combinations of surveillance modalities and tools (n = 40) were also found. Risk-based approaches were very common (n = 60), especially in the papers describing tools and methodologies (n = 50). The main applications, benefits and limitations of each approach were extracted from the papers. This information will be very useful for informing the development of tools to facilitate the design of cost-effective surveillance strategies. Thus, the current literature review provides key information about the advantages, disadvantages, limitations and potential application of methodologies for the early detection of new, exotic and re-emerging diseases.

Seasonality and Distribution Pattern of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) in Virginia Vineyards.

Brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a highly polyphagous invasive insect pest from eastern Asia that feeds on numerous fruit, vegetable, and field crops. Four commercial vineyards in Virginia were sampled in 2012 and 2013 to study the basic biology, seasonality, and distribution pattern of H. halys in vineyards. At each vineyard, two blocks were selected. Weekly 3-min timed count visual samplings were performed in border and interior sections from late May until mid-September. Overwintering adult bugs were first detected in vineyards in May; however, the timing of first detection differed among vineyards. Egg masses were found primarily in June and July, and were usually found on the lower surface of grape leaves, although they were occasionally on the upper leaf surface, on the berry, or on the rachis. All developmental stages of H. halys were found in vineyards, suggesting that grape can serve as a reproductive host for H. halys. Substantial variation in H. halys densities was found among vineyards and throughout the growing season. The first instars were found on egg masses and after molting, dispersed throughout the grape vines. The date on which the first egg mass was collected was considered as a biofix. Based on a degree-day model, there were sufficient degree-days for completion of a generation in Virginia vineyards. Significantly higher numbers of H. halys were collected in border sections compared with interior sections. These results are discussed in relation to the potential pest status of H. halys in vineyards and implications for possible control strategies.

Invasive cardiac aspergillosis after orthotopic liver transplantation.

Invasive aspergillus infection occurs in 5 - 42 % of liver-transplanted recipients and is a dangerous complication, associated with high mortality if untreated. However, the early diagnosis of invasive aspergillosis can be elusive, as clinical signs are unspecific and the pathogenic agent is difficult to demonstrate. We here report about a 58-year-old man with acute liver failure caused by newly diagnosed chronic hepatitis B infection who underwent liver transplantation. The postoperative course was uneventful, and the patient was discharged after 30 days. After 105 days the patient was readmitted because of fever, recurrent chest and abdominal pain. Computed tomography revealed a cardiac lesion; other diagnostic steps including bone-marrow and endomycordial biopsy, virological and microbiological investigations gave no clear findings. To exclude a malignant process, thoracotomy with mass and simultaneous lower left lobe resection were performed. Histopathological findings revealed an invasive perimyocardial aspergillosis. Immediate intravenous therapy with voriconazole and caspofungin was initiated and monitoring of the mass was performed with transesophageal echocardiography and Cardio-MRI. Due to slightly increase of the lesion, medication was switched to posaconazole and caspofungin. Under this dual fungal treatment the lesion regressed and the patient could be discharged after two months in good clinical condition. Frequent Cardio-MRI scan after discharge showed further mass-regression. Therefore antifungal treatment was switched to oral posaconazole mono-therapy. After one year, complete reduction of the mass was achieved and antifungal therapy was discontinued. Recent diagnostic imaging follow-up showed no pathological finding.

Treatment, outcome and quality of life after Fournier's gangrene: a multicentre study.

AIM: The object of this study was to describe the course of Fournier's gangrene and assess quality of life in a group of affected patients. METHOD: We evaluated patients who received inpatient treatment for Fournier's gangrene at five hospitals in northern Germany from 1995 to 2010. Surviving patients were asked to take part in a clinical follow-up and complete the Short-Form 36 (SF-36) quality-of-life questionnaire and a disease-specific questionnaire including a physical examination. RESULTS: Of the 86 patients, 72 (83.7%) were men. The mean age of the patients was 57.9 ± 13.9 (25-89) years. The mean length of hospital stay was 52.0 ± 54.0 (1-329) days. Fourteen (16.3%) patients (eight men) died primarily from Fournier's gangrene. The most common aetiological event was anogenital abscess formation (n = 24; 27.9%). Seventy-one (82.5%) patients had a mixed polymicrobial infection. SF-36 physical role functioning (P = 0.010), physical functioning (P = 0.008), general health (P = 0.010) and physical health summary (P = 0.006) scores were significantly lower than those of the normal population. Deterioration in sexual function was reported by 65% of the patients. CONCLUSION: Patients with Fournier's gangrene experience persistent physical and mental health problems for a long period of time following their primary hospital stay and must receive long-term care from a variety of specialists, otherwise the disease leads to an increase in the duration of morbidity and a decrease in quality of life.

The impact of foreshortening on regional strain--a comparison of regional strain evaluation between speckle tracking and tissue velocity imaging.

PURPOSE: The conventional parameter of systolic function is global left ventricular (LV) ejection fraction (EF), but this parameter will be replaced by global strain because it seems to be more robust. However, regional strain differences can have a significant impact on global strain. Thus, the aim of the present study was to evaluate the effect of non-standardized scanning on regional strain values determined by 2D speckle tracking and tissue velocity imaging (TVI). Regional longitudinal peak systolic strain (PSS) was measured in standardized data sets of the apical 4-chamber view (ChV) and in a standardized oblique foreshortened view in patients with normal wall motion patterns. MATERIALS AND METHODS: A standardized 4ChV and a foreshortened 4ChV - defined by distinct cardiac structures - were acquired using a Vivid E9 system in 54 patients. All regional PSS values measured in monoplane 2D loops in lateral and septal regions were analyzed to detect the differences between regional strain measured in the standard and the foreshortened view. RESULTS: Significant PSS differences due to FS were detected in patients using 2D speckle tracking for the basal septal regions (p < 0.001). No significant differences due to FS were detected in patients during the analysis of TVI-based strain values (p > 0.05, paired sample T-test). CONCLUSION: To our knowledge this is the first study focusing on methodological aspects - especially standardization - using speckle tracking and TVI. Due to the lower accuracy of strain calculation based on TVI in basal regions, foreshortening has no significant impact on quantitative parameters of TVI-derived strain values in normal contracting hearts. Using speckle tracking, however, foreshortening induces significant differences of basal septal strain in normal contracting hearts. In the presence of regional wall motion defects, a lack of standardization of the views will cause inhomogeneous patterns of regional strain depending on the scan planes through the center of the infarction or its penumbra. Thus, non-standardization will have a significant impact on deformation parameters in 2D echocardiography.

H9N2 avian influenza virus dispersal along Bangladeshi poultry trading networks.

Avian influenza virus subtype H9N2 is endemic in Bangladesh's poultry population. The subtype affects poultry production and poses a potential zoonotic risk. Insufficient understanding of how the poultry trading network shapes the dissemination of avian influenza viruses has hindered the design of targeted interventions to reduce their spread. Here, we use phylodynamic analyses of haemagglutinin sequences to investigate the spatial spread and dispersal patterns of H9N2 viruses in Bangladesh's poultry population, focusing on its two largest cities (Dhaka and Chattogram) and their poultry production and distribution networks. Our analyses suggest that H9N2 subtype avian influenza virus lineage movement occurs relatively less frequently between Bangladesh's two largest cities than within each city. H9N2 viruses detected in single markets are often more closely related to viruses from other markets in the same city than to each other, consistent with close epidemiological connectivity between markets. Our analyses also suggest that H9N2 viruses may spread more frequently between chickens of the three most commonly sold types (sunali-a cross-bred of Fayoumi hen and Rhode Island Red cock, deshi-local indigenous, and exotic broiler) in Dhaka than in Chattogram. Overall, this study improves our understanding of how Bangladesh's poultry trading system impacts avian influenza virus spread and should contribute to the design of tailored surveillance that accommodates local heterogeneity in virus dispersal patterns.

Prevalence of and risk factors for MRSA carriage in companion animals: a survey of dogs, cats and horses.

We investigated the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage in a convenience sample of purposely selected populations of dogs, cats and horses in the Greater London area. Swabs from carriage sites were pooled, enriched and processed by standard bacteriological methods. The presence of nuc and mecA was confirmed for MRSA. Risk factors were investigated among veterinary treatment group animals using exact logistic regression analysis. Twenty-six (1.53%) MRSA carriers were identified in the 1692 animals (15/704 dogs, 8/540 cats, 3/152 horses). Animals presenting for veterinary treatment more frequently carried MRSA than healthy animals (OR 7.27, 95% CI 2.18-24.31, P<0.001). Concurrent carriage of non-MRSA coagulase-positive staphylococci was associated with MRSA carriage (OR 0.088, 95% CI 0.016-0.31, P<0.001); none of the other 13 putative risk factors was significant. MRSA carriage was rare in the selected companion animal populations. The absence of typical risk factors indicates that companion animals act as contaminated vectors rather than as true reservoirs.

Herd contact structure based on shared use of water points and grazing points in the Highlands of Ethiopia.

The use of shared common water points (WPs) and grazing points (GPs) at two different levels of administrative aggregation (village and kebelle) in a region of the Highlands of Ethiopia was explored by means of a questionnaire survey and social network analysis. Despite GPs being more abundant than WPs (208 and 154, respectively), individual GPs provide more contact opportunities for animals. There was great variability in the contact structure of the selected villages within kebelles for both networks, with this variability being higher in the GP networks for each kebelle. Contrary to the commonly held view that WPs are critical for the potential transmission of infectious diseases, intervention at GPs in the Ethiopian Highlands may have greater impact on contacts and thereby opportunities for transmission of infectious diseases between flocks. Some villages appear naturally at much lower risk of introducing disease. These findings could help the design of surveillance and control activities for directly transmitted infectious diseases.

An assessment of the feasibility of a poultry tracing scheme for smallholders in Vietnam.

Tracing movements could assist the implementation of bio-containment measures during a disease outbreak. To evaluate the potential for implementing a tracing system for a poultry supply chain in northern Vietnam, a four-month longitudinal study was conducted to identify marketing practices associated with poultry traceability. Poultry sold in batches were traced between farms and markets, and their traceability was assessed upon market arrival. A total of 315 batches were released from the farms; 37% arrived at a market, from which 57.3% were 'traceable'. The results of the multivariable analysis showed that traceability was associated with farms operating through no more than two traders (Odds ratio [OR] = 5.97, 95% CI 1.15-30.92) and batches brought to the market on the day of purchase (OR = 4.05, 95% CI 1.23-13.27). No specific incentives were provided to farmers or traders. Results suggest that there is potential for implementing a poultry traceability scheme, although the tracing methodology should be refined.

Integration of participatory approaches into surveillance systems.

Animal health surveillance is essential for protecting public health, enhancing access to international markets for animals and their products, and improving animal health, production and welfare. It is of vital importance for protecting and improving the livelihoods of diverse groups of livestock keepers and stakeholders in livestock value chains. Surveillance systems consist of sets of complementary components which generate information to inform risk assessment, decision-making and policy formulation for both national programmes and international trade. Participatory approaches have the potential to add value to surveillance systems by enhancing their performance, especially their sensitivity and timeliness, and encouraging the inclusion of marginalised groups. This paper summarises key considerations in the assessment and design of animal health surveillance and discusses how participatory approaches can be integrated into comprehensive surveillance systems, leading to a more effective overall outcome for both domestic and international purposes.

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.