Pathophysiology in horses involves the study of functional changes that occur in the body as a result of disease or injury. This field examines the mechanisms through which diseases develop and progress, as well as how they affect the body's normal physiological processes. In equine research, pathophysiology encompasses a wide range of conditions, including respiratory disorders, musculoskeletal injuries, gastrointestinal diseases, and metabolic syndromes. Understanding these processes helps in identifying potential therapeutic targets and developing effective treatment strategies. This page collects peer-reviewed research studies and scholarly articles that explore the underlying mechanisms, clinical manifestations, and implications of various pathophysiological conditions in equine health.
Glazier DB, Farrelly BT, O'Connor J.A congenital heart defect characterised by persistent patency (open-ness) of the ventricular septum, permitting flow of blood directly between ventricles, bypassing the pulmonary circulation and resulting in various degrees of cyanosis (blue discolouration of the skin) due to oxygen deficiency. Clinical signs include systolic murmur and a palpable thrill on both sides of the chest, dyspnoea and poor tolerance of exercise.
Roberts MC, Pinsent PJ.Three horses suffering from malabsorption were shown to have alimentary lymphosarcoma predominantly affecting the small intestine and the associated lymph nodes. The diffuse cellular infiltration in two of the case produced marked changes in the villous architecture reducing the available mucosal surface area, and, with lowered or barely detectable disaccharidase activities, contributed to the impairment of digestive-absorptive processes. One of the horses maintained a voracious appetite and was not diarrhoeic, but failed to gain weight, indicating differences in the production and utilisation...
Baker JR, Leyland A.In a histological survey of 244 tumerous growths from 155 horses, the tumours commonly found were fibromas, squamous cell carcinomas, sarcoids and papillomas, most frequently affecting the skin, external genitalia, eye and orbit. The histological features that differentiate fibroblastic citaneous growths are detailed so that the clinical behaviour of these distinct neoplasms can be studied.
Muir WW, Moore CA, Hamlin RL.The influence of various concentrations of CO2 and O2 in the inspired gases on minute volume (V), tidal volume (VT), and respiratory rate (breaths per min; BPM) was examined in nonanesthetized, nonsedated normal horses. The VT and BPM increased linearly in response to increases in inspired CO2 concentration and curvilinearly in response to decreases in inspired Os concentration. The V increased curvilinearly in response to both increases in inspired CO2 concentration and decreases in inspired O2 concentration.
Wensing T, van Gent DM, Schotman AJ, Kroneman J.(I) The lipid and lipoprotein concentrations in sera of 4 healthy and 9 hyperlipaemic patients were determined. From the results of the analyses, it is suggested that three types of hyperlipoproteinaemia can be distinguished in ponies: (a) Type 1, characterised by a very pronounced increase in only the very low density lipoproteins (VLDL); (b) Type 2, in which there is a pronounced increase in the chylomicrons (Chylo) and the very low density lipoproteins (VLDL); (c) Type 3, which can be the result of fasting and is characterised by a moderate increase in the concentration of chylomicrons and ...
Bisgard GE, Orr JA, Will JA.Hemodynamic measurements were made in 6 ponies at low altitude (Madison, WI, altitude, 250 m) and after 1, 2, 4, and 6 weeks at high altitude (Climax, CO, altitude, 3,400 m). The salient findings were that ponies maintain an increased heart rate and cardiac output and develop significant pulmonary hypertension at high altitude. The average control resting mean pulmonary artery pressure (BPpul) was 25.1 mm of Hg at 250 m; this value increased to 56.3 mm of Hg after 6 weeks at 3,400 m. An additional finding was that the pulmonary vascular response to acute hypoxia seemed to increase with time at...
Krook L, Whalen JP, Lesser GV, Berens DL.Nutritional secondary hyperparathyroidism (NSH) defines a spontaneous and experimental disease in most domesticated and in some wild animals, caused by dietary calcium deficiency and/or phosphorus excess. Calcium deficiency results directly in hypocalcemia, and phosphorus excess induces hyperphosphatemia which causes hypocalcemia. Secondary hyperparathyroidism thus results and the plasma parameters return to normal and are maintained but only at the expense of progressive bone loss. The bone loss is generalized but the bones are not uniformly affected. The hierarchy of bone loss is, in decreas...
Ackerman N, Garner HE, Coffman JR, Clement JW.The angiographic appearance of the normal equine foot was compared with the appearance of equine feet affected with chronic laminitis. The normal foot was characterized by complete filling of the terminal arch, 8 to 10 main branches between 0.1 and 0.2 cm in diameter, a symmetrical netlike vascular pattern in the corium of the hoof, and numerous fine vessels in the corium of the coronary band. The feet affected with chronic laminitis were characterized by poor filling of the terminal arch, larger and less numerous primary branches, an irregular vascular pattern in the corium of the hoof, areas...
Williams MR.Rats were injected intradermally with rabbit anti-ovalbumin serum and 3 hours later were challenged intravenously with ovalbumin and Evans Blue dye. Inflammatory lesions were produced within 20 minutes and their size was markedly dose-dependent. Attempts were made to interfere with this passive cutaneous anaphylaxis (PCA) by admixture of normal IgG with the rabbit anti-ovalbumin to measure the relative tissue binding affinities of IgG from various species. It was found that normal IgG from any of the species tested had an enhancing effect on PCA in rats. These immunoglobulins serially arranged...
Vitums A, Grant BD, Stone EC, Spencer GR.ABSTRACT Transposition of the aorta to the right ventricle with atresia of the pulmonary trunk was described in a 2 year old horse. Clinical and physiological examinations were performed and data recorded. Teratogenesis of the present anomaly was discussed and the literature reviewed. The probable course of circulation during the fetal life and after birth of this animal was suggested. An extensive col-lateral circulation was developed to the lungs, which might explain how the animal could live so long.
Ackerman N, Garner HE, Coffman JR, Clement JW.The angiographic appearance of the normal equine foot was compared with the appearance of equine feet affected with chronic laminitis. The normal foot was characterized by complete filling of the terminal arch, 8 to 10 main branches between 0.1 and 0.2 cm in diameter, a symmetrical netlike vascular pattern in the corium of the hoof, and numerous fine vessels in the corium of the coronary band. The feet affected with chronic laminitis were characterized by poor filling of the terminal arch, larger and less numerous primary branches, an irregular vascular pattern in the corium of the hoof, areas...
Dubuc V, Laverty S, Richard H, Doré M, Theoret C.There is a growing interest in the scientific community to use computer-based software programs for the quantification of cells during physiological and pathophysiological processes. Drawbacks of computer-based methods currently used to quantify immunohistochemical staining are the complexity of use, expense of software and overly-simplified descriptions of protocol thereby limiting reproducibility. The precise role of mast cells in equine cutaneous wound healing is unknown. Given the contribution of mast cells to the chronic inflammation observed in human keloid, a pathology similar to exuber...
Mills PC, Higgins AJ.The athletic ability of the horse is facilitated by vital physiological adaptations to high-intensity exercise, including a thin (but strong) pulmonary blood-gas barrier, a large pulmonary functional reserve capacity and a consequent maximum oxygen uptake (VO2max) far higher than in other species. A high pulmonary artery pressure also serves to enhance pulmonary function, although stress failure of lung capillaries at high pulmonary transmural pressures, and the contribution of other factors which act in the exercising horse to increase pulmonary vascular tone, may lead to pathological or path...
Kinsella HM, Hostnik LD, Toribio RE.Most homeostatic systems in the equine neonate should be functional during the transition from intra- to extrauterine life to ensure survival during this critical period. Endocrine maturation in the equine fetus occurs at different stages, with a majority taking place a few days prior to parturition and continuing after birth. Cortisol and thyroid hormones are good examples of endocrine and tissue interdependency. Cortisol promotes skeletal, respiratory, cardiovascular, thyroid gland, adrenomedullary, and pancreatic differentiation. Thyroid hormones are essential for cardiovascular, respirator...
LeBlanc PH, Broadstone RV, Derksen FJ, Robinson NE.Distal airway segments (ID, 3 to 4 mm; length, 5 mm) from 2 groups of horses were isolated and suspended in tissue baths filled with Krebs solution, aerated with 5% CO2 in oxygen and maintained at 37 degrees C. Responses to exogenous acetylcholine, isoproterenol, or electrical field stimulation were compared. Control horses (n = 30) had no history of recurrent airway obstruction, whereas principal horses (n = 15) had recurrent airway obstruction and were studied during an acute episode of airway obstruction. Although the distal airways contracted in response to the cumulative half-logarithmic ...
Williams MR.Rats were injected intradermally with rabbit anti-ovalbumin serum and 3 hours later were challenged intravenously with ovalbumin and Evans Blue dye. Inflammatory lesions were produced within 20 minutes and their size was markedly dose-dependent. Attempts were made to interfere with this passive cutaneous anaphylaxis (PCA) by admixture of normal IgG with the rabbit anti-ovalbumin to measure the relative tissue binding affinities of IgG from various species. It was found that normal IgG from any of the species tested had an enhancing effect on PCA in rats. These immunoglobulins serially arranged...
Mouithys-Mickalad A, Storms N, Franck T, Ceusters J, de la Rebière de Pouyade G, Deby-Dupont G, Serteyn D.Experimental laminitis, characterized by a failure of the dermal-epidermal interface of the foot, can be induced in horses by the oral administration of a black walnut extract (BWE). In the early phase of this severe and painful disease, an activation of neutrophil occurs, with the release of myeloperoxidase (MPO), a pro-oxidant enzyme of neutrophils, in plasma, skin, and laminar tissue. Juglone, a naphthoquinone derivative endowed with redox properties, is found in walnuts and has been incriminated in this neutrophil activation. We report for the first time the inhibitory activity of juglone ...
Littlejohn A.Twenty cases of chronic cough originating in the lung and associated with loss of performance were clinically examined. The physical signs observed were compared with those observed in a control series of 38 clinically normal horses. Reduced work tolerance, coughing for more than 3 months and abnormal pulmonary sounds (râles) were primary signs of chronic obstructive pulmonary disease (COPD). Forced abdominal expiratory efforts and pumping of the anus were regarded as confirmatory signs. Neither nasal discharge nor increased marginal distance was found to be a reliable sign of COPD. The mean ...
Kurz JP, Schoenhals KE, Hullinger GA, Van Wettere AJ.Syringomyelia is a form of myelodysplasia defined by the formation of one or more fluid-filled cavities within the spinal cord that do not communicate with the central canal. The defect may be congenital or acquired. Clinical signs correlate to the segment of spinal cord affected and include pain, paresis, proprioceptive deficits, alterations in sensation, scoliosis, and autonomic dysfunction. This report describes the clinical and pathologic changes in a case of acquired syringomyelia in a 10-year-old American Paint Horse mare. The horse had a six-week history of progressive proprioceptive de...
Roy MF.Sepsis develops in horses when the host response to the invading pathogens is not properly balanced according to the severity of the insult. Several clinical conditions frequently encountered in equine practice may be associated with the development of sepsis and have the potential to progress to more severe forms, such as severe sepsis, MODS, and septic shock. Consequently, it is important for equine practitioners to be aware of the manifestations,pathophysiology, and treatment of sepsis. Although enormous progress has been made in recent years in our understanding of the pathophysiology of s...
Brice AG, Forster HV, Pan LG, Lowry TF, Murphy CL, Mead J.We studied the changes in breathing and respiratory muscle electromyograms (EMG) during passively induced increases in end-expiratory lung volume (EELV) in awake normal (N), hilar nerve-denervated (HND), carotid body-denervated (CBD), and HND + CBD ponies. EELV was increased by applying continuous negative pressure (-10 and -20 cmH2O) around the torso of the standing pony. In all groups, negative pressure produced sustained increases in EELV that were linearly related to the degree of negative pressure. Elevated EELV decreased breathing frequency (f) in N and CBD ponies but increased f in HND ...
de Rebière de Pouyade G, Salciccia A, Ceusters J, Deby-Dupont G, Serteyn D, Mouithys-Mickalad A.The endothelium plays an active role in ischemia/reperfusion injuries. Herein, we report the effect of a single or successive cycles of anoxia/reoxygenation (A/R) on the mitochondrial respiratory function of equine endothelial cells (cultured from carotids) monitored by high resolution oxymetry, and on their production of reactive oxygen species (ROS). ROS were measured by electron paramagnetic resonance (ESR) using POBN and DMPO spin traps, and by gas chromatography (GC) of ethylene released by ROS-induced α-keto-γ-(methylthio)butyric acid (KMB) oxidation. The oxygen consumption significant...
Meyers K, Reed S, Keck M, Clem M, Bayly W.Twenty-three horses with clinical signs of gastrointestinal disease were evaluated once or serially during the course of the disease for the presence or absence of circulating endotoxin-like substances (ET+ or ET-) and whether the horses were negative, positive, or very positive for serum fibrin/fibrinogen degradation products (FDP-, FDP+, or FDP++). In addition, platelet count, activated partial thromboplastin time (APTT), and 1-stage prothrombin time (OSPT) were measured. When examined initially, 5 horses were ET-/FDP-, 8 were ET-/FDP+, 7 were ET+/FDP-, 3 were ET+/FDP+, and none was ET+/FDP+...
Hesselkilde EZ, Carstensen H, Flethøj M, Fenner M, Kruse DD, Sattler SM, Tfelt-Hansen J, Pehrson S, Braunstein TH, Carlson J, Platonov PG....Large animal models are important in atrial fibrillation (AF) research, as they can be used to study the pathophysiology of AF and new therapeutic approaches. Unlike other animal models, horses spontaneously develop AF and could therefore serve as a bona fide model in AF research. We therefore aimed to study the electrical, functional and structural remodelling caused by chronic AF in a horse model. Nine female horses were included in the study, with six horses tachypaced into self-sustained AF and three that served as a time-matched sham-operated control group. Acceleration in atrial fibrilla...
Shaba JJ, Behan Braman A, Robinson NE.In many inflammatory diseases plasma cortisol concentration (CORT) increases at the onset of acute inflammation, but the situation in recurrent airway obstruction (RAO) of horses is unknown. Methods: Split-plot repeated measures design with one grouping factor (disease) and two repeated factors (day and 3-hour intervals). Objective: To test the hypothesis that CORT increases as acute exacerbations of RAO develop. Methods: Four RAO-susceptible and 4 control horses were placed in a low dust environment (LDEnv) for 2 days followed by 2 days in a high dust environment (HDEnv). Exacerbations of RAO...
Woodie JB, Ducharme NG, Hackett RP, Erb HN, Mitchell LM, Soderholm LV.Dorsal displacement of the soft palate (DDSP) is a common condition in racehorses for which various surgical treatments are often performed. In light of recent findings that suggested the position of the larynx may influence the occurrence of DDSP, we investigated whether a noninvasive mean of affecting the position of the larynx could be effective in the management of DDSP. Objective: An external device (laryngohyoid support; LHS) positioning the larynx in a more rostral and dorsal location and preventing caudal displacement of the basihyoid bone would be effective in preventing DDSP during s...
Sander K, Deegen E, Ohnesorge B.In a placebo-controlled drug study data were collected about flow, volume and expiratory CO2-concentration in 13 horses with chronic obstructive pulmonary disease before and until 2.5 h after intravenous injection of clenbuterol. An ultrasonic flow measuring unit and an infrared-CO2-analyser (Spiroson Scientific) were used. functional deadspace and expiratory mixed volume were calculated. In addition the effect on the partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood was tested and the alveolo-arterial oxygen difference (AaDO2) determined. The volume of the functio...
O'Rielly JL, Beard WL, Renn TN, Padden AJ, Hinchcliff KW.To investigate the effect of combined staphylectomy and laryngotomy on upper airway mechanics in clinically normal horses running on a treadmill. Methods: 6 Standardbreds. Methods: Upper airway mechanics were measured with horses trotting or pacing on a treadmill at 5, 8, and 10 m/s before and 6 weeks after combined staphylectomy and laryngotomy. Pharyngeal and tracheal inspiratory and expiratory pressure were measured by use of transnasal tracheal and pharyngeal side hole catheters connected to differential pressure transducers. A pneumotachograph mounted on the rostral end of an airtight fac...
Landoni MF, Foot R, Frean S, Lees P.The objective of this study was to analyse the effects of 4 nonsteroidal anti-inflammatory drugs (NSAIDs) on the production of beta-glucuronidase (beta-glu), tumour necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), interleukin-1 (IL-1) and prostaglandin E2 (PGE2) by lipopolysaccharide (LPS)-stimulated equine synoviocytes. The agents studied were flunixin, tolfenamic acid, S(+)ketoprofen (KTP) and R(-)ketoprofen. LPS-induced release of beta-glu from synoviocytes was inhibited in a concentration dependent manner by all 4 compounds, tolfenamic acid being the most potent. Of the 2 KTP enant...
Aleman M, Puchalski SM, Williams DC, Kass PH, Holliday TA.Facial and vestibulocochlear nerve dysfunction occurs commonly in horses with temporohyoid osteoarthropathy (THO); however, auditory dysfunction has not been thoroughly assessed. Objective: To determine if auditory abnormalities occur in horses with THO. Methods: Eleven diseased and 8 control horses. Methods: This is a prospective study in which brainstem auditory-evoked responses (BAER) were recorded in 11 horses diagnosed with THO through neurologic, endoscopic, radiographic, or computed tomographic examinations. BAER findings were compared with those recorded from 8 adult control horses. Re...
Medina-Torres CE, Underwood C, Pollitt CC, Castro-Olivera EM, Hodson MP, Richardson DW, van Eps AW.Failure of lamellar energy metabolism, with or without ischaemia, may be important in the pathophysiology of sepsis-associated laminitis. Objective: To examine lamellar perfusion and energy balance during laminitis development in the oligofructose model using tissue microdialysis. Methods: In vivo experiment. Methods: Six Standardbred horses underwent laminitis induction using the oligofructose model (OFT group) and 6 horses were untreated controls (CON group). Microdialysis probes were placed in the lamellar tissue of one forelimb (all horses) as well as the skin dermis of the tail in OFT hor...
Tadros EM, Frank N, Newkirk KM, Donnell RL, Horohov DW.The role of endotoxemia in the development of laminitis remains unclear. Although systemic inflammation is a risk factor for laminitis in hospitalized horses, experimental endotoxin administration fails to induce the disease. While not sufficient to cause laminitis by itself, endotoxemia might predispose laminar tissue to damage from other mediators during systemic inflammation. In "two-hit" models of organ damage, sequential exposure to inflammatory stimuli primes the immune system and causes exaggerated inflammatory responses during sepsis. Acute laminitis shares many characteristics with se...
Cochrane CA, Freeman KL, Knottenbelt DC.Wound healing in equidae is delayed and more complicated than in other species. These complications arise from a condition known as exuberant granulation tissue formation. The lower limb of the horse is frequently slower to heal than other parts of the body and has a particular tendency to produce excess (exuberant) granulation tissue. Sarcoids are tumor-like lesions of the skin which often appear at the site of wounds. This study compared the growth characteristics of the sarcoid and granulation tissue-derived cells with normal dermal fibroblasts grown from primary cell cultures. All three ce...
Guthrie AJ, Killeen VM, Mülders MS, Grosskopf JF.The ratio of the cardiopulmonary blood volume to stroke volume is called the cardiopulmonary flow index (CPFI). The CPFI can be determined indirectly from the simultaneous recording of a radiocardiogram and an electrocardiogram. The CPFI and cardiac output were measured simultaneously in horses (n = 10) that were diagnosed as having cardiac disease. The diseased subjects were probably all exposed to feed contaminated with the ionophore, salinomycin, and all showed clinical signs indicative of chronic toxic myocarditis. The results obtained from these subjects were compared with those from cont...
Roberts MC, Seawright AA.Colic was induced in horses and ponies following topical or intravenous (iv) administration of amitraz, a formamidine acaricide. The condition was characterised by rapid cessation of intestinal sounds, stasis, extensive impaction and tympany throughout the large colon. Three animals that were necropsied had a faecalith obstructing the proximal small colon aboral to marked colonic impaction. A reproducible and reversible impaction colic syndrome could be induced by an iv injection of 1 mg amitraz/kg body weight in solvent. There were immediate central nervous system and intestinal signs. Large ...
Han Y, Tang C, Liao Q, Li Z, Deng L.Serum and plasma are commonly used in clinical practice considering the widely accepted fact that the "normal" protein expression pattern of a healthy animal changes under disease conditions. We herein used a label-free mass spectrometry-based quantitative proteomics approach to characterize the serum proteome of donkeys. A total of 277 unique proteins were identified from 2,388 unique peptides. Gene ontology analyses showed that the most frequent processes were related to metabolic activities and biological regulation, response to stimulus, and immune system processes. The main annotated area...
Lowry TF, Forster HV, Forster MA, Murphy CL, Brice AG, Pan LG.The objective of the present study was to determine the effect of elevated inspired CO2 on respiratory dead space (VD) of 12 normal, 8 carotid body-denervated (CBD), 7 hilar nerve-denervated (HND), and 6 CBD+HND ponies. The Fowler technique was used to determine VD on a breath-by-breath basis while the ponies breathed room air and inspired CO2 at 3 and 6%. During room air breathing, tidal volume (VT) and VD were greater in HND ponies than in normal and CBD ponies (P less than 0.05), and VT was less and VD/VT was greater after CBD than before CBD. For all groups. VD, VT, and breathing frequency...
Robertson TP, Bailey SR, Peroni JF.Equine laminitis is a crippling condition that continues to defy repeated efforts to delineate the precise mechanisms involved and develop effective therapeutic strategies for use in the clinic. In this article, the possible role of dysfunction of the laminar vasculature is discussed, with particular emphasis on the venous side of the laminar microvasculature and the possible role(s) that metabolic syndrome and thrombosis may play in the dysfunction observed in the laminar microvasculature during the development of laminitis.
Malalana F, Stylianides A, McGowan C.Equine recurrent uveitis (ERU) is a spontaneous disease characterised by repeated episodes of intraocular inflammation. The epidemiology of ERU has not been fully elucidated, but the condition appears to be much more common in horses than is recurrent uveitis in humans, especially in certain breeds and geographical regions. Both humans and horses show a similarly altered immune response and a marked autoimmune response as the primary disease pathophysiology. However, an inciting cause is not always clear. Potential inciting factors in horses include microbial agents such as Leptospira spp. Mic...
Godber LM, Brown CM, Mullaney TP.A 13-year-old American Saddlebred mare was presented with a 4-day history of anorexia. Physical examination revealed increased inspiratory effort and bony enlargement of the distal limbs. Radiographs indicated a thoracic mass and periosteal proliferations on the distal limbs consistent with hypertrophic osteopathy. Gastric endoscopy revealed distal esophageal and gastric ulceration, and functional pyloric stenosis. Abdominal ultrasonographic examination revealed multiple large, cystic structures associated with the liver. A percutaneous biopsy indicated the thoracic mass to be a granular cell ...
