Topic:Pathogenesis
Pathogenesis in horses refers to the biological mechanisms that lead to the development and progression of diseases within equine species. This process involves a complex interaction between the horse's immune system, genetic predispositions, environmental factors, and infectious agents such as bacteria, viruses, or parasites. Understanding pathogenesis is essential for identifying how diseases manifest and progress in horses, which can inform diagnostic and therapeutic strategies. Research in this area often focuses on specific diseases, examining factors such as pathogen entry, immune response, tissue damage, and recovery processes. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of pathogenesis in equine health.
Equine arteritis virus is not a togavirus but belongs to the coronaviruslike superfamily. The nucleotide sequence of the genome of equine arteritis virus (EAV) was determined from a set of overlapping cDNA clones and was found to contain eight open reading frames (ORFs). ORFs 2 through 7 are expressed from six 3'-coterminal subgenomic mRNAs, which are transcribed from the 3'-terminal quarter of the viral genome. A number of these ORFs are predicted to encode structural EAV proteins. The organization and expression of the 3' part of the EAV genome are remarkably similar to those of coronaviruses and toroviruses. The 5'-terminal three-quarters of the genome contain the putative EAV p...
Endotoxemia in horses. A review of cellular and humoral mediators involved in its pathogenesis. Endotoxemia remains the leading cause of death in horses, being intimately involved in the pathogenesis of gastrointestinal disorders that cause colic and neonatal foal septicemia. Endotoxins, normally present within the bowel, gain access to the blood across damaged intestinal mucosa, or endotoxemia occurs when gram negative organisms proliferate in tissues. Endotoxins are removed from the circulation by the mononuclear phagocyte system, and the response of mononuclear phagocytes to these lipopolysaccharides (LPS) play an important role in determining the severity of clinical disease. Macroph...
The role of endothelial cell infection in the endometrium, placenta and foetus of equid herpesvirus 1 (EHV-1) abortions. One of three mares in the last trimester of pregnancy became paraplegic 7 days after experimental infection with EHV-1 and was killed 10 days after infection (d.p.i.). The other two mares aborted foetuses at 12 and 14 d.p.i. In the first mare, virus was detected by immunofluorescence (IIF) and immunoperoxidase (IP) staining in endothelial cells of the endometrium, placenta and umbilical vein, but not in any other foetal tissues. In the experimentally aborted foetuses, and in two other independent field cases of abortions, endothelial cell infection was also detected in the foetuses, both in ma...
Chronic obstructive pulmonary disease. COPD continues to be a severe condition in horses. Despite increased understanding of its pathogenesis, there is relatively little information on effective treatment regimens. Management and prevention are critical, and more emphasis should be placed on improved housing, bedding, and feeding. More sophisticated accurate methods also are required for identifying specific causative allergens.
Osteochondrosis and juvenile spavin in equids. Thirty-six of 50 young equids examined at necropsy for gross pathologic and histopathologic evidence of osteochondrosis were determined to have lesions characteristic of this disorder in the distal joints of the tarsus. Abnormalities ranged from retained endochondral cores underlying undisturbed articular cartilage surfaces to clefts, subchondral osseous cyst-like lesions, and cartilage ulceration. Our findings supported the conclusion that osteochondrosis may cause spavin in the juvenile equid.
Exercise-induced pulmonary hemorrhage. This article addresses many aspects of exercise-induced pulmonary hemorrhage (EIPH). Reports of the prevalence, effect on performance, and the clinical signs and means of diagnosis of EIPH are included. Radiologic and scintigraphic findings in horses with EIPH are reported. Pathogenesis and treatment are discussed.
Black walnut (Juglans nigra) toxicosis: a model for equine laminitis. Twelve light horse geldings developed laminitis within 8 to 12 h of being dosed by nasogastric tube with an aqueous extract of black walnut (Juglans nigra). Four of the 12 horses developed the severe signs of grade 3 laminitis (lame at a walk, refused to lift feet). Laminitis was accompanied by mild depression and limb oedema. There was no evidence of shock or colic. The horses developed neutropenia by 4 h after dosing with the extract, which shifted to a relative neutrophilia by 8 to 12 h. Minimal increases in plasma epinephrine and cortisol concentrations were suggested in severely affected ...
Clinical, viral, and genetic evaluation of equine degenerative myeloencephalopathy in a family of Appaloosas. A clinical, viral, hematologic , and genetic study was conducted over a 4-year period on a family of Appaloosas with high incidence of clinical ataxia and pathologic features of equine degenerative myeloencephalopathy. Marginal to deficient serum vitamin E (alpha-tocopherol) and blood selenium values were the only other consistent antemortem abnormalities in the affected horses. Members of this family were all descendants of a clinically normal mare and were raised in 3 separate environments with variable quality of feed. All horses had access to pasture grasses. Normal chromosomal karyotypes ...
Equine herpesvirus 1 sequence near the left terminus codes for two open reading frames. We have previously reported the sequence of the equine herpesvirus one genomic termini that are homologous to the genomic termini of other herpesviruses. In this paper, we present the nucleotide sequence adjacent to the left terminus sequence (map units 0.0087 to 0.0237). This sequence codes for two open reading frames (ORF) which are homologous to ORF2 and ORF3 of the varicella-zoster virus genome and are located at colinear positions. The L region sequence presented here also contains a segment that is involved in the generation of the genome of EHV-1 DI particles through recombination with ...
Preferential denervation of the adductor muscles of the equine larynx. I: Muscle pathology. The laryngeal muscles of 18 horses were examined histologically. The neurogenic changes found in each muscle were scored by four reviewers and the results evaluated statistically. Fifteen of these horses had endoscopic evidence of abnormal laryngeal function, three of which were defined as having adductor paralysis. Measurement of muscle fibre area in two horses with idiopathic laryngeal hemiplegia (ILH) was performed. In the quantitative study of neurogenic change, the adductor muscles were more significantly affected than the abductor muscle. This was also true in the clinical cases of ILH w...
[Papillomatosis of cattle and its relationship to equine sarcoid]. The aetiology and the pathogenesis of equine sarcoids are described. Aspects of therapy are discussed.
[A case of diprosopus in a foal]. A case of diprosopus in a foal is described. This is only the second report of such a deformity in the equine species. Hereditary pathology and pathogenesis are discussed.
The action of low dose endotoxin on equine bowel motility. Post operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1 micrograms/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestin...
Rhodococcus equi: an animal and human pathogen. Recent isolations of Rhodococcus equi from cavitatory pulmonary disease in patients with AIDS have aroused interest among medical microbiologists in this unusual organism. Earlier isolations from humans had also been in immunosuppressed patients following hemolymphatic tumors or renal transplantation. This organism has been recognized for many years as a cause of a serious pyogranulomatous pneumonia of young foals and is occasionally isolated from granulomatous lesions in several other species, in some cases following immunosuppression. The last decade has seen many advances in understanding o...
[Spavin in horses]. The pathogenesis of bone spavin and its implications for diagnosis and therapy are reviewed. The pathogenesis of spavin can be divided into three phases, which are characterised by fibrillation of cartilage, osteolysis and ankylosis respectively. It will depend on the degree of osteolysis whether diagnostic anaesthesia should be added to standard clinical and radiological examinations. Satisfactory results of treatment in the group of patients with severe osteolysis can only be obtained by arthrodesis of the distal tarsal joints. It is expected that biomechanical investigations will provide a ...
[Chronic disease of the two sesamoid bones of the lower foot of the horse]. The aetiology and pathogenesis of navicular bone disease and sesamoidosis are discussed on the basis of findings reported in the literature and research. A marked similarity is found to be present between the clinical presentation, aetiology and pathogenesis of these two diseases. In addition, the intra and juxta-articular signs of degeneration as seen in these diseases are similar to those seen in various forms of arthrosis. Circulatory disturbances resulting from partial or complete arterial occlusion, caused by arteriosclerosis, are likely to play an important role in the cause of degenerat...
Epizootiological and virological studies of foal diarrhea associated with serotype 3 rotavirus. Epizootiological and virological studies were conducted on foal diarrhea occurring in 3 foal-raising locations in a light horse farm from March to July, 1987. At the first location, although 27 (75%) of 36 foals had developed diarrhea, the isolation rate of rotavirus (RV) was low (5/14 feces, 36%). Many of the foals had the disease as early as 23 days after birth. At the second and third locations, 21 (27%) of 78 foals and 41 (76%) of 54 foals were affected with diarrhea. Isolation rates of RV were 90% (20/22 feces) and 100% (26/26 feces), respectively. The diseased cases were observed through...
Of Horses and Men: Urticaria. Abstract- Urticarial eruptions, with or without pruritus, are common lesions in horses. The pathogenesis of these lesions can include immunological and other mechanisms. Research in the human field suggests that the mast cell co-ordinates the urticarial response by releasing a complex array of inflammatory mediators. Other cells, including the neutrophil, the eosinophil and the macrophage, may also play a role in the development of wheals. Elucidation of the role of many of these cells and mediators in the evolution of urticaria is only just beginning. Successful treatment of this dermatologic...
Distribution of labelled cysteine and methionine in the matrix of the stratum medium of the wall and in the laminar layer of the equine hoof. The distribution of 35-S-labelled cysteine and methionine in the epidermis of the equine hoof following 2 hours of intra-arterial injection was studied by microautoradiography. Material for autoradiography was obtained by biopsy about 1 hour after termination of the intra-arterial injection and also 10 and 40 days later. In the specimens obtained one hour after the injection of labelled cysteine and methionine, the amount of radioactivity in the matrix and in the most proximal part of the laminar layer was very high. There was a clear difference between the distribution of the two labelled ami...
Fatigue fractures in thoroughbred racehorses: relationships with age, peak bone strain, and training. The North American Thoroughbred racehorse was chosen as a model to study the pathogenesis of fatigue failure of bone. This species has a high incidence of spontaneous fatigue failure of bone (bucked shins) during its early training. In vivo strain gauge studies of the third metacarpal bone of four young racehorses running at racing speeds showed high principal compressive strains [-4,841 +/- 572 (SD) microstrain] while two older horses had lower principal compressive strains (-3,317 microstrain measured at racing speed, -3,250 microstrain extrapolated from a slower speed run). Previously repor...
Immunoreactive prostaglandin production by equine monocytes and alveolar macrophages and concentrations of PGE2 and PGF in bronchoalveolar lavage fluid. Because of their capacity to produce prostanoids, alveolar macrophages may play a part in the pathogenesis of chronic obstructive pulmonary disease (COPD). Cultured equine alveolar macrophages and peripheral blood monocytes synthesised mainly prostaglandin (PG)F and PGE2. They also synthesised smaller quantities of PGI2, measured as the stable metabolite 6-keto-PGF1 alpha, and thromboxane B2. Concentrations of immunoreactive PGF and PGE2 were measured in bronchoalveolar lavage fluid collected from clinically normal horses (n = 3) and horses with COPD (n = 3). None of the normal horses had dete...
Effects of allopurinol on endotoxin-induced increase in serum xanthine oxidase in the horse. Using a modified bovine milk enzyme kinetic assay, xanthine oxidase activity of serum collected from 34 adult, healthy horses of both sexes was determined. Enzyme activity varied from 0 to 126 mU litre-1 with a mean of 44.95 +/- 21.05 mU litre-1. The optimal pH and temperature for maximal activity were 7.8 and 28 degrees C, respectively. Freezing the serum for four days at -70 degrees C did not destroy the enzyme activity. Various doses (25, 50 and 75 micrograms kg-1, intraperitoneally) of endotoxin (lipopolysaccharide D1 Escherichia coli O26:B6) previously known to have caused moderate to sev...
In vitro antimicrobial activity of defensins against ocular pathogens. New approaches to antimicrobial therapy for ocular pathogens must overcome organisms that are resistant to current therapeutic modalities. This investigation examined the antimicrobial activity of novel antimicrobial neutrophil peptides (defensins NP-1 and NP-5) against isolates from clinical ocular microbial infections in humans and horses. The test panel of human clinical isolates included Candida albicans, an alpha-hemolytic Streptococcus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Morganella morganii. The test panel of equine pathogens included three clinical isolates of P aerug...
Evaluation of a bronchoalveolar lavage technique. The bronchoalveolar lavage (BAL) technique described produced no detectable gross or histopathological lesions. Airway fluid accumulation was observed for up to 4 h post lavage. There was good qualitative correlation between BAL cytopathological and diffuse pulmonary pathological changes. The technique provided an accurate assessment of the presence and extent of exercise induced pulmonary haemorrhage.
Histopathological development of equine cutaneous papillomas. The histopathological development of equine cutaneous papillomas was studied in 78 warts naturally occurring in 50 one to 3-year-old Thoroughbred or Arab horses and in 54 warts experimentally induced in three 2-year-old Thoroughbreds. Lesions in the natural cases were categorized into three phases, growth, development and regression. Main lesions of the growing phase were marked hyperplasia of the basal cells and mild to moderate acanthosis, hyper- and parakeratosis with a few intranuclear inclusion bodies (IIB) which were positive with anti-bovine papillomavirus serum. In the developing phase...