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Topic:Disease Etiology
Disease etiology in horses refers to the study of the causes and development of diseases within equine populations. It encompasses various factors, including genetic predisposition, environmental influences, infectious agents, and nutritional imbalances, that contribute to the onset and progression of diseases in horses. Understanding disease etiology is essential for identifying risk factors and implementing preventative measures in equine health management. This topic includes research on pathogen-host interactions, the impact of management practices on disease incidence, and the role of genetic and environmental factors in disease susceptibility. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of disease etiology in horses.
Identification of lipoprotein homologues of pneumococcal PsaA in the equine pathogens Streptococcus equi and Streptococcus zooepidemicus. Streptococcus equi and Streptococcus zooepidemicus are major etiological agents of upper and lower airway disease in horses. Despite the considerable animal suffering and economic burden associated with these diseases, the factors that contribute to the virulence of these equine pathogens have not been extensively investigated. Here we demonstrate the presence of a homologue of the Streptococcus pneumoniae PsaA protein in both of these equine pathogens. Inhibition of signal peptide processing by the antibiotic globomycin confirmed the lipoprotein nature of the mature proteins, and surface expo...
Animal models of asthma: potential usefulness for studying health effects of inhaled particles. Asthma is now recognized to be a chronic inflammatory disease that affects the whole lung. Incidence appears to be increasing despite improved treatment regimens. There is substantial epidemiological evidence suggesting a relationship between the incidence and severity of asthma (e.g., hospitalizations) and exposure to increased levels of air pollution, especially fine and ultrafine particulate material, in susceptible individuals. There have been a few studies in animal models that support this concept, but additional animal studies to test this hypothesis are needed. However, such studies mu...
Bacterial infection of the lower respiratory tract in 34 horses. To investigate associations between the bacteriology and aspects of history, clinical presentation, outcome and pathology of lower respiratory tract disease of 34 horses. Methods: Detailed aerobic and anaerobic bacteriological investigations were performed on clinical specimens from horses with pneumonia, lung abscessation and necrotic pneumonia with or without pleurisy in an attempt to identify those bacteria that might contribute to the initiation and progression of infection. Results: Bacteria were cultured from 33 of the 34 horses. In ten cases, only aerobic/facultatively anaerobic isolate...
Miscellaneous. This section includes clinical conditions which have unique characteristics which make them unsuitable for inclusion in the first six sections. The clinical description, aetiology and histopathologic findings of the unusual ear lesion, aural plaques, are described. Dermatoses complicated by, or caused by, photosensitivity are discussed in regards to their aetiology and pathogenesis as well as clinical features. The suggestion that photosensitization plays a role in the development of the lesions seen in pastern leukocytoclastic vasculitis is made. This section ends with an in depth discussion ...
Immunologic diseases. Selected equine cutaneous diseases for which there is strong evidence of an immunological aetiology are discussed in this section. The reactive disorders of urticaria, Culicoides hypersensitivity, erythema multiforme, drug eruptions and systemic granulomatous disease are included. The autoimmune diseases of the horse with cutaneous manifestations (pemphigus foliaceus, pemphigus vulgaris, bullous pemphigoid and cutaneous lupus erythematosus) are discussed. The clinical signs and diagnostic features of these immunologically induced equine dermatoses are defined, and the challenges in making a de...
Nodular diseases. The development of a nodule is a fairly common reaction pattern in the skin and subcutaneous tissues of the horse. In many such nodules, the inciting aetiologic agent or antigen is unknown, but in some equine cases there is significant evidence for insect bite origin. The pathogenesis of some equine nodular diseases appears to involve marked collagen degeneration which varies from hyalinization to lysis and can become mineralized. The exact role the lytic collagen has in the pathogenesis of these lesions is still unknown. Vascular changes may be present in some entities. Other nodules may be c...
Genomic variability of equine herpesvirus-5. Seventeen New Zealand isolates of equine herpesvirus 5 (EHV-5) were compared to the Australian prototype strain. PCR primers were designed to amplify EHV-5 glycoprotein B (gB) gene, and Restriction Fragment Length Polymorphism (RFLP) was used to detect differences between cloned PCR products. EHV-5 isolates from different horses showed a high degree of heterogeneity. However, EHV-5 isolates from individual horses remained homogeneous when examined over a period of time or isolated from different sites. A single EHV-5 gB RFLP profile was detected in isolates from each individual horse but one. ...
Functional morphology of the equine pelvic flexure and its role in disease. A review. The hindgut is the major site in the horse for nutrient digestion and absorption. Most of this activity occurs in the large intestinal compartments, i.e., cecum, right and left ventral colon and left and right dorsal colon. The colonic pelvic flexure is a short and narrow loop connecting the left ventral and left dorsal colon. It is not significant directly in digestive and absorptive processes but plays an important functional role in regulating colonic aboral and retropropulsive transit of digesta through its motility pacemaker activity. The pelvic flexure also contributes to the pathophysio...
Closure of the abdominal wall at the umbilicus and the development of umbilical hernias in a group of foals from birth to 11 months of age. The closure of the body wall defect at the umbilicus was studied in relation to the development of umbilical hernias in a group of 44 normal foals, 25 of which were followed from birth until five months of age, and 19 from birth until 11 months of age. At birth, 19 of the foals had a defect in the body wall at the umbilicus that was termed a 'palpable umbilical ring'. In 18 of them this defect disappeared within four days, but in the other the ring did not close and a hernial sac with abdominal contents was palpable. This foal was considered to be the only foal to have a truly congenital umbil...
In vitro evaluation of intraluminal factors that may alter intestinal permeability in ponies with carbohydrate-induced laminitis. To study the in vitro effects of cecal contents incubated with corn starch on colonic permeability in horses. Methods: 4 healthy adult ponies. Methods: Mucosal specimens were obtained from the right ventral colon and mounted in Ussing chambers. Changes in short circuit current, conductance, and large-molecule permeability in response to addition of cecal contents and cecal contents incubated with corn starch were evaluated for 120 minutes. Results: Incubation of cecal contents with corn starch for 8 hours resulted in a decrease in cecal content pH and an increase in lactic acid concentration. ...
Alterations in cartilage type-II procollagen and aggrecan contents in synovial fluid in equine osteochondrosis. The etiology and pathophysiology of osteochondrosis remain poorly understood because it is difficult to obtain material from lesions in the early stage of this disease and because there is no satisfactory experimental animal model. We wished to determine whether there are changes in articular cartilage turnover in equine osteochondrosis, which closely resembles the human disease, by assaying cartilage matrix molecules in synovial fluids. We used immunoassays that measure a keratan sulfate epitope and the epitope 846 on the cartilage proteoglycan aggrecan and the C-propeptide of cartilage type-...
An outbreak of type C botulism in 12 horses and a mule. A USDA Early Response Team investigated deaths of several horses and a mule in northern Arizona at the request of local animal health officials. Thirteen animals (12 horses and 1 mule) housed at 5 facilities in a 7.4 square mile area died between August 1998 and January 1999. Clinical signs consisted of muscular weakness that rapidly progressed to lateral recumbency. Ten animals had paresis of the tongue, throat, or lips. Affected animals appeared alert and were interested in eating and drinking, even while recumbent. All 13 animals were euthanatized. Clostridium botulinum type C was isolated ...
[Occurrence of various immunoglobulin isotopes in horses with equine recurrent uveitis (ERU)]. We investigated 30 healthy eyes and 41 eyes with ERU from 57 horses. The total immunoglobulin titers and titers of IgGa, IgGb, IgM were measured in aqueous humour, vitreous and serum using different ELISA techniques. Every sample investigated contained detectable amounts of immunoglobulins. Compared to control eyes significantly increased titers were found in the aqueous humour and vitreous of the ERU eyes for all immunoglobulin isotypes studied (p < or = 0.01). While IgM was detected in only 2 out of thirty aqueous humour and in none of the thirty vitreous samples of healthy eyes, 79.6% of sa...
[The “problem” mare part 3: veterinary supervision at the stud and during early pregnancy]. In this last article the veterinary supervision of problem mares at the stud is reviewed. Treatment possibilities are evaluated. The usefulness of treatment with progestagens in order to sustain pregnancy or to prevent embryonic death is discussed.
Age-related effects of TGF-beta on proteoglycan synthesis in equine articular cartilage. The synthesis of proteoglycans was measured in normal equine articular cartilage of ages 9 months to 20 years and the effect of TGF-beta1 on this activity was investigated. The rate of incorporation of [(35)S]Na(2)SO(4) decreased with age as did the responsiveness of the tissue to the growth factor. The enhanced synthesis of proteoglycan induced at all ages by TGF-beta1 was down-regulated by IL-1 beta and retinoic acid. The expression of mRNA for TGF-beta1, 2, and 3 was also measured, and although the level of TGF-beta1 was highest at all ages, the expression of each growth factor decreased wi...
Diagnosis and management of abnormal embryonic development characterized by formation of an embryonic vesicle without an embryo in mares. To determine the incidence, ultrasonographic characteristics, and risk factors associated with embryonic development characterized by formation of an embryonic vesicle without an embryo in mares. Methods: Prevalence survey. Methods: 159 pregnant mares. Methods: From 1994 to 1998, mares between 11 and 40 days after ovulation with normal and abnormal embryonic development were examined ultrasonographically, and characteristics of each conceptus were recorded. Results: The incidence of abnormal embryonic development in mares characterized by formation of an embryonic vesicle without an embryo was...
Changes in liver copper concentration of thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams. To monitor the change in liver copper concentration of Thoroughbred foals from birth to 160 days of age and to determine the effects of supplementation by two injections of copper edetate given to dams in late gestation on the liver copper concentration of their foals at birth. Methods: Ten mares pregnant to the same stallion were randomised into two groups on the basis of age, liver copper concentration and expected foaling date. The treatment group mares were given 100 mg and 250 mg copper edetate intramuscularly during the ninth and tenth months of gestation respectively. Foals had liver bi...
The kinetics of Langerhans cells in equine insect hypersensitivity “Kasen”. An immunohistochemical study was carried out on the kinetics of Langerhans cells (LCs) at various pathological stages of "Kasen". Skin lesions of "Kasen" that were collected by biopsy from May to October were classified histopathologically into three stages: initial (Group I, 31 cases), developing (Group II, 50 cases) and regressing (Group III, 13 cases). LCs showed a positive reaction with anti-equine thymocytes (EqT6) monoclonal antibody (MoAb) and anti-major histocompatibility complex (MHC) class II MoAb by immunohistochemical staining. The anti-EqT6 MoAb was intensely positive along the cy...
Towards an understanding of equine pleuropneumonia: factors relevant for control. To review relevant literature on factors associated with the development of equine pleuropneumonia. Methods: A review of the literature using a range of databases including Current Contents, Medline, ChemAbstracts, Biological Abstracts and CAB and a comprehensive search strategy which involved use of keywords, author and subject category searches. Additional sources included review of articles cited by key accumulated references. Results: Since the early years of this century, many of the "gaps" in our knowledge of the pathogenesis of this disease have been filled. We now know that equine pleu...
Equine viral arteritis. Equine viral arteritis (EVA) can cause prominent economic losses for the equine industry. The purpose of this review is to provide the pathologist some familiarity with the clinical history, lesions, pathogenesis, and diagnosis of EVA. EVA is caused by an arterivirus (equine arteritis virus, EAV), and the vascular system is the principal but not unique viral target. EVA has variable presentations, including interstitial pneumonia, panvasculitis with edema, thrombosis and hemorrhage, lymphoid necrosis, renal tubular necrosis, abortion, and inflammation of male accessory genital glands. EAV anti...
Evaluation of diet as a cause of gastric ulcers in horses. To measure pH, volatile fatty acid (VFA) concentrations, and lactate concentrations in stomach contents and determine number and severity of gastric lesions in horses fed bromegrass hay and alfalfa hay-grain diets. Methods: Six 7-year-old horses. Methods: A gastric cannula was inserted in each horse. Horses were fed each diet, using a randomized crossover design. Stomach contents were collected immediately after feeding and 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, and 24 hours after feeding on day 14. The pH and VFA and lactate concentrations were measured in gastric juice Number and severity of gastri...
Establishment and characterization of equine autonomic ganglion cell lines to enable direct testing of candidate toxins involved in equine dysautonomia (grass sickness). To enable direct testing of a range of potential toxins or pathogens that might be involved in grass sickness, equine thoracic sympathetic chain ganglion cell lines were established from primary cell cultures by retroviral-mediated transduction of the temperature-sensitive mutant of the establishment oncogene encoding SV40 large T antigen. Morphological and behavioral features, temperature dependence, and immunocytochemical characteristics of the cell lines were investigated. The majority of cells were noradrenergic neurons in which dopamine-beta-hydroxylase, the enzyme that catalyzes norepine...
