Current research and theories on the pathogenesis of acute laminitis in the horse

A large number of studies have been undertaken in recent years aimed at furthering our understanding of the complex mechanisms underlying the common and debilitating condition of acute laminitis in the horse. Many of these studies have either reinforced or cast doubt on previously held theories on the pathogenesis of this disease, while others have suggested new mechanisms which may play a key role in its development. This review seeks to put the current hypotheses into the context of this recent body of evidence. While a unifying theory may not yet seem to be achievable, this review demonstrates that most of the current theories are not mutually exclusive. Studies utilising in vitro and in vivo models of the disease, particularly addressing the areas of inflammation, haemodynamic disturbances and enzyme activation in the hoof, as well as the preceding events occurring in the hindgut, have helped to explain many clinical observations of the disease and may possibly lead to more effective therapies and means of prevention in the future.     

Cellular pathogenesis in prion diseases

Prion diseases are characterised by neuronal loss, vacuolation (spongiosis), reactive astrocytosis, microgliosis and in most cases by the accumulation in the central nervous system of the abnormal prion protein, named PrP(Sc). In this review on the "cellular pathogenesis in prion diseases", we have chosen to highlight the main mechanisms underlying the impact of PrP(C)/PrP(Sc) on neurons: the neuronal dysfunction, the neuronal cell death and its relation with PrP(Sc) accumulation, as well as the role of PrP(Sc) in the microglial and astrocytic reaction.     

朊病毒致病机理的研究进展

就细胞型朊蛋白PrP^c的分子生物学特性、朊蛋白的生理功能、致病性朊蛋白PrP^sc对免疫系统的影响、朊病毒的外周致病机理以及相关细胞因子、化学因子与朊病毒神经侵袭之间的关系、朊病毒从外周到中枢的转运机制、入侵门户、血液传播及朊病的其他病理标志和检测方法的研究做一综述。     

TSE pathogenesis in cattle and sheep

Many studies have been undertaken in rodents to study the pathogenesis of transmissible spongiform encephalopathies (TSE). Only a few studies have focused on the pathogenesis of bovine spongiform encephalopathy (BSE) and scrapie in their natural hosts. In this review, we summarize the most recent insights into the pathogenesis of BSE and scrapie starting from the initial uptake of TSE agents and crossing of the gut epithelium. Following replication in the gut-associated lymphoid tissues (GALT), TSE agents spread to the enteric nervous system (ENS) of the gut. Infection is then carried through the efferent fibers of the post-ganglionic neurons of the parasympathetic and sympathetic nervous system to the pre-ganglionic neurons in the medulla oblongata of the brain and the thoracic segments of the spinal cord. The differences between the pathogenesis of BSE in cattle and scrapie in sheep are discussed as well as the possible existence of additional pathogenetic routes.     

Cytokines in the pathogenesis of influenza

Uncomplicated influenza in humans, horses or swine is characterized by massive virus replication in respiratory epithelial cells, inflammation and an abrupt onset of general and respiratory disease. There is now growing evidence that the so-called early cytokines produced at the site of infection mediate many of the clinical and pathological manifestations. Among these cytokines are interferon-alpha (IFN-alpha), tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) alpha and beta, interleukin-6 (IL-6), interleukin-8 (IL-8) and monocyte-attracting chemokines. This paper reviews: (1) in vivo examinations of the cytokine profiles during influenza in mice, humans or swine; (2) in vivo data on the probable role of these cytokines; and (3) selected in vitro data on cytokine induction by the influenza virus. Examination of respiratory secretions of experimentally infected humans or animals revealed a brisk and concurrent rise in several of the cytokines mentioned. Moreover, peak cytokine levels directly correlated with virus replication and disease. In the mouse model, specific anti-cytokine strategies have further confirmed the role of cytokines in body temperature changes, anorexia and lung inflammation. However, cytokines were clearly not the only factor contributing to disease, and they seemed to be essential for resolution of the infection. Though influenza virus was shown to induce cytokines in cell culture, in vitro experiments have also revealed conflicting data. Furthermore, the viral genes or products that are responsible for cytokine induction are unknown. Exactly this information would make important contributions to our understanding of the genetic basis of viral virulence.     

Relevance versus dissemination of primary information in animal science

As a follow-up to an inventory of media containing primary information in animal science, a series of interviews was held to quantify the international relevance of animal-science literature. It appears that there are major discrepancies between the dissemination which many primary contributions receive and the geographical distribution of their potential readership. More frequent use of letters publishing might help to reduce such deficiencies.     

The pathogenesis of heartwater

Hypotheses on the pathogenesis of heartwater, which have been published so far, are briefly reviewed. Attempts were made at counteracting the effects of vaso-active substances released by mast cells by treating mice infected with Cowdria ruminantium with antagonists to histamin and serotonin on one hand, and with mast cell stabilizers on the other, but were not successful. Preliminary findings suggest that a hypersensitive type of reaction, triggered by the release of pharmacologically active substances, may possibly be basic to the pathogenesis of heartwater. Complement, and the products of arachidonic acid metabolism, possibly play a role in the release of the vaso-active substances.     

The pathogenesis of dermatophilosis

Tropical Animal Health and Production - Pathogen, host and environmental factors must be considered in order to understand the pathogenesis of dermatophilosis. A frequently cited sequence of events...     

Host and bacterial factors in listeriosis pathogenesis

Members of the Genus Listeria are ubiquitous environmental saprophytic microorganisms. If ingested they can cause a severe disseminated disease (listeriosis) that has a high mortality rate, the highest of any food-borne pathogen, even with antibiotic therapy. Central to the high mortality rate is the hallmark characteristic of the microorganism to grow intracellularly. The presence of listeriae in food processing plants has resulted in many outbreaks of human disease and large scale recalls of processed foods. Despite the ubiquity of the microorganism, the actual disease rate (those animals showing disease signs over those exposed) is quite low and disease is almost always associated with an underlying predisposition (pregnancy being the most common in otherwise normal individuals). There are many features of the pathogenesis of listeriosis that have remained mysterious despite the extensive use of the microorganism in the study of cell-mediated immunity and intracellular growth. Informational advances such as the sequence of the mouse and listerial genomes, and technical advances such as the discovery of listeria-susceptible mouse strains, may renew interest in the study of the natural pathogenesis of the disease. This may be further facilitated by studies that employ the natural inoculation route and mimic common predisposing conditions witnessed in victims of natural outbreaks.     

Relevance of the variability of kidding day in Creole goats in Guadeloupe

The results of 5732 records of kids born between 1985 and 1996 at Gardel Agricultural Experiment Station (INRA) in Guadeloupe, were used in order to estimate the effect of kidding day (KD) on individual preweaning growth performances, total productivity of Creole goats and litter size. The flock was subjected to a restricted mating season for a long time, by using male effect. The results of the fixed linear model showed a highly significant (P<0.001) effect of KD on growth rate and total productivity of does. Live weights of kids born around the 21st day of the kidding period (KP) was 4% to 7% higher than those of kids born the first day of the KP. For total productivity of does, this ratio did not reached more than 4%. The optimum at 70 days of age occurred around 14th day of the KD with 3% of improvement of total productivity. No effect was observed upon litter size. The genetic (co)variance components were estimated by six different Individual Animal Models. The heritability (h²) estimated from the best model, was h_D²=0.25±0.05 for genetic direct effect; h_M²=0.09±0.04 for genetic maternal effect and the genetic correlation between direct and maternal effects was −0.86±0.12. The use of KD could be highly recommended in a breeding program in this population of Creole meat goats, since it is quite easy to record under commercial conditions as a character related to reproductive performance.     

The pathogenesis of Rhodococcus equi pneumonia in foals

The pathogenesis of Rhodococcus equi pneumonia in foals is reviewed. The main routes of infection are respiratory and alimentary. The latter is probably the chief route of exposure in all foals and probably leads to development of specific immunity. Susceptible foals, those whose maternal immunity wanes before generation of their own immune response, readily develop disease if exposed aerogenously to sufficient numbers of R. equi. Management and environmental circumstances have a major role to play in determining the magnitude of this challenge and, therefore, in the prevalence of the disease. Infection of a naive foal leads to severe, suppurative bronchopneumonia with suppurative lymphadenitis of regional nodes and, in approximately 50% of animals, to necrotizing enterocolitis. The foal is uniquely susceptible to R. equi pneumonia; comparable experimental infections do not produce progressive destructive pulmonary lesions in other animal species. In the naive foal lung, R. equi behaves as a facultative intracellular pathogen, avoiding destruction within the alveolar macrophage by inhibiting phagolysosome fusion and possibly by causing lysosomal degranulation. The role of putative virulence factors, such as equi factor, remains to be elucidated.     

Mechanisms of pathogenesis in herpetic immunoinflammatory ocular lesions

This article reviews possible mechanisms by which ocular infections with herpes simplex virus result in a blinding immunoinflammatory lesion in the cornea. We conclude that this immunoinflammatory response involves multiple immune mechanisms including autoimmunity.