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.
Weld JM, Kamerling SG, Combie JD, Nugent TE, Woods WE, Oeltgen P, Tobin T.The effects of naloxone on the cardiovascular, hematologic and metabolic derangements associated with endotoxic and hemorrhagic shock were studied in unanesthetized horses. In the first of 3 experiments blood glucose and lactate levels, hematocrit, white, red and differential white cell counts, rectal temperature and clinical signs were obtained before and after endotoxin (10 micrograms/Kg) administration in 5 horses. In the second experiment, two groups of 3 horses received either intravenous naloxone (0.04 mg/Kg) or saline, 7 minutes prior to endotoxin. In a third experiment two groups of 4 ...
Lindberg R.A morphological study on equine granulomatous enteritis (EGE) in 13 horses is presented. All horses were young (1 to 5 years old) standardbreds. Based on gross pathology, cases were classified into those with diffuse (11 cases) and those with localized (2 cases) small bowel lesions. The granulomatous reaction in the gut was marked by diffuse and patchy infiltrates and distinct granulomas, composed of epithelioid cells, macrophages and lymphoid cells, and was devoid of necrosis. Salient accompanying features of the small bowel included lymphoid hyperplasia, peri-lymphatic and transmural inflamm...
Valberg SJ, McKinnon AO.Five horses with fatal clostridial cellulitis are described. The characteristic findings were the rapid development of a crepitant swelling with an associated toxemia, which in four cases followed intramuscular injections. The clinical features, diagnostic techniques and pathogenesis are discussed. The importance of an early diagnosis is emphasized.
Asbury AC, Gorman NT, Foster GW.The addition of serum to uterine secretions was shown to opsonize Streptococcus zooepidemicus and significantly enhance bacterial phagocytosis by equine neutrophils. Treatment of serum by heat inactivation at 56 degrees C, EDTA treatment, and C3 consumption reduced phagocytosis and therefore demonstrated that the process was complement-dependent. The amount of C3 present in uterine secretions was measured in a series of 14 mares infected with Streptococcus zooepidemicus . Ten of the 14 mares had detectable amounts of C3; however, the C3 had been cleaved and rendered nonfunctional. The importan...
Pomorski Z, Pinkiewicz E, Grzebuła S.In the studies attempts were to demonstrate the occurrence of immunological reactivity against antigens of the lens and tunica vascularis of the eye in periodical inflammation of eyes in horses. For this purpose antigens from the lens and tunica vascularis of the eye, prepared in our laboratory, were used in the experiments. The reactivity of horses with monthly symptoms of blindness against the above antigens was determined in vivo (skin tests and PCA) and in vitro (ID reaction). The results obtained mainly in skin tests account for its occurrence in some percentage of diseased animals, becau...
Srivastava SK, Barnum DA.Streptococcus equi was found to adhere to tongue, cheek and nasal epithelial cells of ponies, in vitro. Maximum adherence was observed at pH 7.5 after one hour of incubation of bacteria with epithelial cells. This adherence was more on epithelial cells from adult animals than from foals. Streptococci exposed to heat (60 degrees C for 10 min) or treated with pepsin or trypsin showed a reduced adherence, whereas an increase occurred on treatment with hyaluronidase. Antibodies against whole S. equi cells or M-like protein blocked the adherence, whereas antibodies against group-specific carbohydra...
Blythe LL, Cardinet GH, Meagher DM, Brown MP, Wheat JD.The histologic and histochemical features of palatine muscles from 53 horses were studied; 25 of the horses were racehorses that had upper airway obstruction associated with dorsal displacement of the soft palate and 28 of the horses did not have any respiratory disorders and served as controls. Pathologic features observed included myonecrosis, phagocytosis, mononuclear cell infiltration of perimysial connective tissue, alkaline phosphatase-positive myofibers, and myofibers with cytoarchitectural changes that included irregular staining of the intermyofibrillar sarcoplasm and sarcoplasmic mas...
Herd RP, Donham JC.Forty horses having microfilariae of Onchocerca cervicalis in association with dermatitis, alopecia, and pruritus on the ventral midline were given a single IM injection of 0.2 mg of ivermectin/kg of body weight (June to August 1981). Microfilarial counts in the 40 horses ranged from 18 to 42,446 microfilariae/skin snip on the day of treatment, and histopathologic examination of these skin sections indicated a chronic eosinophilic dermatitis. Numerous microfilariae were in the dermis, but there was no consistent relationship between the presence of microfilariae and the severity of the inflamm...
Svalastoga E.Microangiographical investigations of the navicular bone in horses with navicular disease show, compared to similar investigations of normal navicular bones, that, in general, the vascular pattern is preserved but the vessels are dilated with "pooling" of the contrast medium subchondrally under facies flexoria. Similar changes may be observed in cases of human arthrosis. The present investigation therefore supports the view that navicular disease is a disease which resembles arthrosis.
Turk MA, Breeze RG, Gallina AM.The pathologic features of bronchiolitis were studied in horses and ponies from 30 minutes to 27 days after an oral dose of 3-methylindole (3MI). From 30 minutes to 3 hours, lesions were limited to nonciliated bronchiolar epithelial (Clara) cells, which lost apical caps and cytoplasmic granules and had dilated smooth endoplasmic reticulum (SER). At 12 hours, necrotic Clara cells were exfoliated; degeneration and necrosis were evident, in bronchiolar ciliated cells. Rare epithelial cells with hyperplastic SER appeared on the denuded basal lamina at 24 hours. Inflammatory cells, epithelia, fibro...
Camp CJ, Leid HW.Extracts of Onchocerca cervicalis, an equine parasite, were incubated with radiolabeled equine neutrophils and neutrophil migration was assessed for factors derived from the parasite itself or for host-derived factors after incubation of these same parasite extracts with equine serum. No stimulus for cell migration was observed in saline extracts of adult worms, uterine microfilariae, or skin microfilariae at any dosage tested. However, after incubation of saline extracts with fresh normal equine sera a marked stimulus for neutrophil migration was observed. Ablation of this biologic activity w...
Campbell TM, Studdert MJ, Blackney MH.Some kinetic data on the inactivation of equine herpesvirus type 1 (EHV1) and equine rhinovirus type 1 (ERhV1) by betapropiolactone (BPL) and ultraviolet (UV) irradiation are reported. 0.25% BPL at 37 degrees C for 1 h reduced the titre of EHV1 by greater than 10(3 . 4) and of ERhV1 by greater than 10(4 . 1) TCID50/ml. UV irradiation (334 microW/cm2) produced similar reductions in titre after 2 min. These data were used as a basis for inactivating EHV1 and ERhV1 by the combined action of BPL and UV irradiation. Viruses were exposed to 0.1% BPL for 1 h at 4 degrees C with constant stirring, fol...
Derksen FJ, Robinson NE, Slocombe RF.In awake sensitized ponies, we studied the effect of aerosol ovalbumin challenge on ventilation, pulmonary mechanics, lung volume, and gas exchange before and after vagal blockade. We also challenged the left lung and measured respiratory rate (f) and right and left respiratory system resistance (RrsR, RrsL) before and after both left and bilateral vagal section. Bilateral ovalbumin aerosol challenge increased f, minute ventilation (VE), total respiratory system resistance (Rrs), and minimal volume, decreased dynamic compliance, total lung capacity, and arterial oxygen tension, and was without...
Clarke LL, Garner HE, Hatfield D.Acute laminitis-hypertension was produced by carbohydrate overloading of the gastrointestinal tract in 12 adult horses. Obel grade 3 (OG3) lameness developed 40 hours (+/- 3.5, SEM) after overfeeding. At OG3 lameness, mean plasma volume was significantly decreased (P less than 0.005) when compared with base-line values. Before OG3 lameness, transient decreases in serum phosphorus and calcium were recorded. Mild hyponatremia also developed before OG3 lameness and persisted. After establishment of OG3 lameness, persistent hypokalemia and increased plasma aldosterone concentration occurred coinci...
Fricker C, Riek W, Hugelshofer J.The digital arteries of 10 horses suffering from navicular disease, and 7 horses from a control group, were examined angiographically. The horses from the disease group showed complete or partial occlusion of the digital arteries in all cases. In the control group of 7 healthy horses, isolated vessel obstructions were also found but these were limited to narrowing of part of an artery only. Histological investigations showed that total occlusion of a vessel involved an organised thrombus but that partial occlusion generally involved changes to the vascular wall, similar to those caused by enda...
Miller RI, Campbell RS.During a clinical study of equine phycomycosis in tropical northern Australia 3 specific forms of phycomycosis were identified. Of 266 cases diagnosed in 5 different laboratories, hyphomycosis caused by Hyphomyces destruens was responsible for 76.7%, basidiobolomycosis caused by Basidiobolus haptosporus for 18.0%, and entomophthoramycosis caused by Conidiobolus coronatus for 5.3%. Most cases of hyphomycosis were observed between March and July, that is after the monsoonal wet summer, but were calculated from clinical histories to originate in the wet season between November and May. Basidiobol...
Shively MA, Banks KL, Greenlee A, Klevjer-Anderson P.Equine infectious anemia is a chronic disease of horses caused by a nononcogenic retrovirus. Studies were undertaken to determine the types of cells involved in the in vitro lymphoproliferative response to viral antigens and the dynamics of this reaction. It was observed that reactive lymphocytes were present at unpredictable times in the peripheral blood of infected horses. This reaction was shown to be specific for the interaction of equine infectious anemia virus and T lymphocytes. Enriched B-lymphocyte populations did not divide when exposed to equine infectious anemia virus. Macrophages w...
Moore JN, Mcilwraith CW.Two cases of osteochondrosis are presented. Lesions involving the lateral trochlear ridge of the femur are demonstrated on conventional radiographs and double-contrast arthrograms. A radiographic suggestion of osteochondrosis lesions in the patella is noted. Post mortem examination of one case confirmed the presence of partially free cartilaginous flaps. Reference is made to familial tendency to osteochondrosis in man, dog, pig and horse. The significance of rapid growth rate in the pathogenesis of the condition is also discussed.
van Nie CJ, van der Kamp JS.A case of tricuspid atresia in a premature foal associated with large atrial septal and ventricular septal defects is reported. This anomaly is compared with other cases in horses as reported in the literature. As tricuspid atresia in horses is usually not diagnosed so that relatively few cases have been reported, a classification similar to that of human anomalies is not possible. It is suggested that the present malformation is due to abnormal development of the atrioventricular canal. The factors involved in the pathogenesis of this abnormal development are obscure.
Pycock JF, Allen WE.The neutrophil is involved in the defence of the mare's uterus against micro-organisms. The ability of Streptococcus zooepidemicus and its growth products to induce shape changes or directional locomotion (chemotaxis) of equine neutrophils was investigated; no effect was found.
Breaud TP, Steelman CD, Roth EE, Adams WV.A tissue culture of Culex pipiens quinquefasciatus Say ovarian cells appeared to support the growth of equine infectious anemia (EIA) virus. Shetland ponies inoculated with 2nd, 7th, 9th, and 11th passages of mediums harvested from infected tissue culture had clinical signs of the disease and became EIA positive on 11, 19, 23, and 43 days after inoculation, respectively.
Liu IK, Cheung AT, Walsh EM, Ayin S.The functional competence of uterine-derived polymorphonuclear neutrophils (PMNs) from 28 mares was measured for migration responsiveness by use of a chamber (filter) assay. Uterine infection was induced with Streptococcus zooepidemicus in mares considered resistant to chronic uterine infection (Grade I). In sequential analysis of uterine flushings obtained from these mares 5, 12, 15, 20, and 25 h after infection was induced, PMNs showed an initial rise at 12 h (from 5), then a general decline in migration response and in concentration of cells per ml from 12 through 25 h post-inoculation. In ...
Stadler P.The anterior enteritis syndrome in the horse is reviewed with reference to the aetiology, pathogenesis, clinical findings, laboratory findings, diagnosis, treatment, prognosis and post mortem findings.
Dart AJ, Pascoe RR.A 12-year-old Quarterhorse stallion was presented with a severe lameness in the left forefoot. There was a 3 cm diameter cavity in the sole that extended to the solar surface of the distal phalanx. Radiographs revealed an osteomyelitis and a sequestrum which probably developed following the prolonged topical application of 10 percent formalin. The sequestrum was removed and the infected bone curetted under general anaesthesia. The horse was shod with heart bar shoes on both front feet 7 days after the surgery. Eight months later, radiographs showed marked rotation of the distal phalanx despite...
Pye J, Spriet M, Dow P, Katzman S, Murphy BG.To describe clinical, imaging, gross, and histopathological abnormalities associated with osteochondral necrosis of the femoral condyles in foals and identify features suggestive of a common pathogenesis. 8 Thoroughbred foals euthanized with a presumptive diagnosis of necrosis of the femoral condyles. Postmortem CT was performed on all distal femoral epiphyseal samples. The articular epiphyseal cartilage complex (AECC) of affected distal femurs was examined grossly and histologically, focusing on lesions of interest identified on CT images. 7 foals were between 9 and 23 days old at the time of...
Jackson DS.This paper reviews some of the biochemical modifications involved in fibrous tissue formation and discusses possible ways of controlling fibrosis in clinical conditions. The lathyritic agents, beta-aminoproprionitrile (BAPN) and penicillamine, appear in certain situations to be able to control fibrosis by blocking the biosynthesis of collagen. There are no compounds that are yet known which are capable of reversing pre-existing fibrosis and future research may perhaps be more profitably directed towards the stimulation of collagen catabolism rather than the inhibition of its synthesis.
Young KM, Lunn DP.Technologic advances in immunodiagnostic testing have enhanced our understanding of the pathogenesis of a broad array of diseases, including infectious diseases, immunodeficiency disorders, and immune-mediated disorders. If applied rationally, with an understanding of the questions the tests answer as well as the limitations that constrain their use, these tests can serve as valuable aids in the diagnosis and management of equine diseases.
Fatemi-Nainie S, Anderson LW, Cheevers WP.MC-1 is an equine sarcoid-derived cell line which spontaneously releases a retrovirus possessing genomic sequence homology with an inducible endogenous retrovirus of normal equine cells. A complete characterization of MC-1 tumor cells was undertaken, including morphology, growth kinetics, and saturation density, selective growth in semisolid media, uptake of 2-deoxyglucose, and tumorigenicity in athymic nude mice. MC-1 cells, in contrast to normal equine dermal fibroblasts, exhibit all of the characteristics of malignantly transformed cells.
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 ...
Gothe R.This paper gives a survey on biology and ecology of equine tapeworms as well as on pathogenesis, clinics, diagnosis, therapy, and prophylaxis of tapeworm infections.
Stitz L, Richt JA, Rott R.An overview of the pathogenesis of Borna disease (BD) in rats as a model for the naturally occurring infection in horses and sheep is presented. Our findings revealed a virus infection in which a virus-specific T cell-mediated immune response leads to disease. The immune cells capable of mediating this immunopathological reaction were defined as helper/inducer T cells. In all, the described observations indicate that CD4+ T cells and macrophages trigger a delayed-type hypersensitivity reaction and cause BD together with other cells of the immune system.
Mele M, Ramseyer A, Burger D, Leeb T, Gerber V.Overall, monogenetic hereditary diseases are less important for the breeding industry than polygenetic diseases because they are relatively rare. For the individual animal, however, these diseases have often a dramatic outcome and many of these diseases presently known are lethal. For several of them the exact pathogenesis is known and DNA-tests are available to confirm the exact diagnosis.
Jaeschke G, Rudolph R.Clinicopathological aspects of equine leukosis are discussed in a review. Among various other findings, only hypercalcaemia accompanied by paraneoplastic syndrome in the course of equine leukosis, increased values of alkaline phosphatase as usual in tumorous diseases, and hypalbuminaemia and hypergammaglobulinaemia in mesentric and intestinal forms of equine leukosis seem to have some diagnostic and pathogenetic significance. Changed values of further parameters are more or less non-specific concomitant signs, indicating that other organs or organ systems have been affected. However, in case o...
Svalastoga E.Microangiographical investigations of the navicular bone in horses with navicular disease show, compared to similar investigations of normal navicular bones, that, in general, the vascular pattern is preserved but the vessels are dilated with "pooling" of the contrast medium subchondrally under facies flexoria. Similar changes may be observed in cases of human arthrosis. The present investigation therefore supports the view that navicular disease is a disease which resembles arthrosis.
Iqbal J, Purewal AS, Edington N.The aim of this study was to investigate the role of immediate early gene (gene63) in the pathogenesis of equine herpesvirus 1 (EHV-1) acute and latent infections in equine and murine models. EHV-1 gene63 mutant virus (g63mut) along with EHV-1 (Ab4) was used for intracerebral and intranasal infection of 3 and 17-day-old mice. Both viruses were recovered at the same frequency from tissues after infection. Two Welsh ponies were infected via the intranasal route with each of the viruses. Acute infection was monitored by virus isolation from nasal swabs and peripheral blood leukocytes. Six weeks p...
Don-van't Slot HP, van der Kolk JH.Severe-Combined-Immunodeficiency-Disease (SCID) is discussed with special reference to its pathogenesis, clinical symptoms, pathology, and diagnosis. The disorder has been observed in the USA, Canada, Great Britain, and Australia and is characterized by an autosomal recessive mode of inheritance. The clinical features of the disease seen in Arab foals under 46 days of age are intermittent fever, (adenoviral) pneumonia, and weight loss sometimes associated with diarrhoea. From 1998 on, the SCID gene can be detected in the Netherlands by means of DNA analysis.
Rosser EJ.Although there are numerous dermatoses in the horse in which the formation of crusts occurs, there are two relatively common and important infectious crusting dermatoses, namely, dermatophytosis and dermatophilosis. This article reviews the current concepts regarding the etiology and pathogenesis of each disease, as well as the more common clinical presentations, methods of diagnosis, and treatment.
Allen AL.Postmortem radiography can be a valuable supplement to traditional necropsy. This article provides examples where postmortem radiographs have been useful in diagnosing and documenting lesions in animals, and have helped demonstrate important principles of the pathology and the pathogenesis of lesions identified at necropsy. This article also discusses additional circumstances where the application of postmortem radiography might be worthwhile.
Marr KA, Lees P, Page CP, Cunningham FM.The leukotrienes (LT) LTD4 and LTB4 have been shown to cause bronchoconstriction and neutrophil accumulation, respectively, in horse lungs. Such changes are characteristic of the equine allergic respiratory disease, chronic obstructive pulmonary disease (COPD). To further investigate the role of these putative mediators in the pathogenesis of equine COPD the effect of a 5-lipoxygenase inhibitor, fenleuton, on antigen-induced changes in horses with this condition has been examined. Six horses with COPD underwent a series of four antigen challenges, one month apart, with placebo pre-treatment on...
Szczerba-Turek A, Siemionek J, Wasowicz K, Szweda W, Raś A, Platt-Samoraj A.BPV-1 is now recognized as a main etiological agent of equine sarcoids. The etiopathogenesis of the equine sarcoids is equivocal and is not yet fully understood. The aim of the present study was to analyse a partial sequence of the L1 gene of BPV associated with equine sarcoids in Polish horses. After clinical diagnosis, 40 skin lesions obtained from 29 horses were collected. The amplicons of a fragment of BPV L1 DNA were detected using PCR with MY09/MY11 primers in 31 specimens. All of them were recognized as BPV-1. Phylogenetic analysis has allowed the amplicons of partial L1 gene to be divi...
Mair TS, Pearson GR.A 3 1/2-year-old bay gelding of the cob type showed nervous signs and coughing associated with breaking-in and exercise. At post-mortem examination, heavy melanin pigmentation of the meninges of the hind brain and the medulla was identified and, on histological examination, melanin-containing cells were found within connective tissue extending into the medulla. The lesion was considered to be a melanotic hamartoma.
Holbrook TC, Gilliam LL, Stein FP, Morgan SE, Avery AL, Confer AW, Panciera RJ.Caley Pea (Lathyrus hirsutus) is potentially toxic to horses, but large case series are not reported. Objective: To describe the clinical signs of horses intoxicated with Lathyrus hirsutus and speculate on the neuroanatomical lesion localization and pathogenesis based upon the observed clinical signs. Methods: Twenty-two of 25 horses ranging in age from 6 to 34 months were affected. Five affected horses were presented to the OSUCHVS for evaluation and treatment after having been attended at the ranch by a local veterinarian (ALA). An additional horse that had been euthanized was also presented...
Karamendin K, Abishov A, Kydyrmanov A, Akhmetzhanova M.In 2011, there was an outbreak of a disease with mass abortions among horses in southeastern Kazakhstan. The AK-2011 strain was isolated from an aborted fetus and subsequently identified as equid alphaherpesvirus 1. Here, we describe the nearly complete genome sequence of the AK-2011 strain, attenuated for vaccine development.
Malekinejad H, Alizadeh-Tabrizi N, Ostadi A, Fink-Gremmels J.The pathogenesis of equine grass sickness (EGS) has not fully understood. A better understanding of the exact pathogenesis of diseases can help to make an accurate diagnosis. Previous studies reported some pathological damage of neuronal cells in EGS patients. In this study, primarily cytotoxicity of serum from three clinically EGS-diagnosed horses on PC12 Tet-off (PTO) cells was assessed. Subsequently, the apoptotic tests including cytochrome C release, caspase-3/7 activity measurement and DNA fragmentation assay were conducted to clarify the apoptotic effect of serum from EGS patients. Addit...
