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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.
Small intestinal adenomatous polyposis resulting in protein-losing enteropathy in a horse. A 4-year-old Quarter Horse gelding was presented with a history of weight loss of 6 months duration, along with extensive ventral subcutaneous edema. Clinicopathologic findings included a markedly low serum total protein (2.9 g/dl) and a low packed cell volume (24%). The mucosal surface of the distal jejunum and entire ileum were carpeted with numerous polypoid, papillary, and glandular masses comprised of pseudostratified tall columnar cells and large numbers of interspersed goblet cells. Neoplastic change was diffuse throughout the mucosa of each mass, but abrupt demarcation occurred between...
Analyses of TCRB rearrangements substantiate a profound deficit in recombination signal sequence joining in SCID foals: implications for the role of DNA-dependent protein kinase in V(D)J recombination. We reported previously that the genetic SCID disease observed in Arabian foals is explained by a defect in V(D)J recombination that profoundly affects both coding and signal end joining. As in C.B-17 SCID mice, the molecular defect in SCID foals is in the catalytic subunit of the DNA-dependent protein kinase (DNA-PKCS); however, in SCID mice, signal end resolution remains relatively intact. Moreover, recent reports indicate that mice that completely lack DNA-PKCS also generate signal joints at levels that are indistinguishable from those observed in C.B-17 SCID mice, eliminating the possibilit...
Evaluation of nitric oxide as an inhibitory neurotransmitter in the equine ventral colon. To determine the role of nitric oxide and an apamin-sensitive nonadrenergic noncholingeric inhibitory transmitter on contractility of the ventral colon of horses. Methods: Strips of the circular and longitudinal muscle layers and taenia of the ventral colon from 14 horses. Methods: Muscle strips were suspended in tissue baths and attached to force transducers. Contractile activity of circular, longitudinal, and taenia muscle strips in response to electrical field stimulation was measured after addition of apamin and a nitric oxide inhibitor, N-nitro-L-arginine methyl ester (L-NAME). Results: E...
Equid herpesvirus-induced immunosuppression is associated with lymphoid cells and not soluble circulating factors. A paresis isolate of equid herpesvirus 1 (EHV1, Ab4/8) and a plaque-purified virus derived from it (EHV1, Ab4/13), induced long-term suppression of both mitogenic and antigen-specific lymphocyte proliferations in adult outbred ponies. Peripheral blood mononuclear cells (PBMC) taken from a pony after EHV1 infection suppressed the in vitro function of normal cells but serum did not. This showed that the observed immune suppression was associated with circulating PBMC and/or their products rather than circulating soluble factors such as antigen or immune complexes. The results suggested that prod...
Gangrene in the distal extremity of all 4 limbs of a 2-week-old foal. Wet gangrene developed in all 4 limbs following repair of a rupture in the lower urinary tract in a 2-week-old foal. Dehydration and hypoxemia are suspected as the inciting causes of the necrosis.
Kinetics of equine neutrophil elastase release and superoxide anion generation following secretagogue activation: a potential mechanism for antiproteinase inactivation. Man and horses both suffer from neutrophil mediated pulmonary diseases however there are striking species differences in the underlying pathology. In particular while pulmonary emphysema is a common pathological sequel to human respiratory disease it is not a major feature of the common equine neutrophil mediated condition, chronic obstructive pulmonary disease (COPD). The proposed reason for this difference is that equine neutrophils contain less elastase than equivalent human cells and therefore there is a reduced risk of excess and/or uninhibited elastase activity, which is considered the m...
Treatment of granular cell tumor via complete right lung resection in a horse. A 7-year-old warmblood mare was referred because of a respiratory tract disorder; pulmonary granular cell tumor was diagnosed. Pulmonary granular cell tumor is a locally invasive but rare type of tumor with low metastatic potential. The entire right lung was resected to ensure removal of all neoplastic tissue. The horse recovered well and has minimal difficulties functioning with one lung. Most of these tumors are diagnosed during postmortem examination. To our knowledge, this is the first report of pulmonary granular cell tumor treated by complete lung resection in a horse.
Role of dendritic cell targeting in Venezuelan equine encephalitis virus pathogenesis. The initial steps of Venezuelan equine encephalitis virus (VEE) spread from inoculation in the skin to the draining lymph node have been characterized. By using green fluorescent protein and immunocytochemistry, dendritic cells in the draining lymph node were determined to be the primary target of VEE infection in the first 48 h following inoculation. VEE viral replicon particles, which can undergo only one round of infection, identified Langerhans cells to be the initial set of cells infected by VEE directly following inoculation. These cells are resident dendritic cells in the skin, which mi...
Epidemiologic analysis of factors influencing exertional rhabdomyolysis in Thoroughbreds. To determine incidence, effect on performance, and management practices associated with exertional rhabdomyolysis (ER) in Thoroughbreds. Methods: Medical records for 984 Thoroughbreds and a survey of trainers of horses with and without ER. Methods: Medical records for 984 Thoroughbreds stabled at a midwestern racetrack were examined to determine the incidence of ER during the 1995 racing season. A retrospective questionnaire was administered to trainers to determine management practices associated with ER in 59 Thoroughbreds with ER and 47 control Thoroughbreds in training. Multiple logistic r...
Equine trophoblast as an immunological target. A cytotoxic T-lymphocyte assay was used to determine whether equine chorionic girdle cells are susceptible to lysis by CD8+ cytotoxic T cells primed in vitro against allogeneic lymphocytes. Classical cytotoxic T-lymphocyte activity against fresh or cultured trophoblast targets was demonstrated using peripheral blood lymphocytes from nonpregnant mares. Lysis of allogeneic (horse) and xenogeneic (donkey) lymphocyte targets was used as a control for trophoblast lysis. The major histocompatibility complex (MHC) class I specificity of the cytotoxic T-lymphocyte reactions was determined using panels...
Hydrocoele of the vaginal cavity of stallions. The aim of the present study was to analyse the effect of hydrocoele of the vaginal cavity of stallions on semen characteristics, libido and fertility, and to contribute to the understanding of the aetiopathology of this condition in stallions. Hydrocoele did not substantially affect either the libido or semen characteristics of affected stallions compared with a control group, and had no effect on fertility. However, the protein content of hydrocoelic fluid was significantly higher than that of peritoneal fluid and was lower than the protein content of blood serum. Electrophoretic profiles of...
Inhibin localization in equine granulosa-theca cell tumours and inhibin forms in tumour fluid. The aim of this study was to examine inhibin production in granulosa-theca cell tumours (GTCT). The experimental aims were: (i) to determine GTCT cell types that produce inhibin alpha- and betaA-subunits; (ii) to determine whether alpha- and betaA-subunit forms differ in GTCT fluid and normal equine follicular fluid (eFF); and (iii) to determine whether dimeric inhibin (alpha betaA) is present in GTCT plasma and tumour fluid. Plasma, tumour fluid and tumour tissue were collected from mares (n=6) with GTCT. Plasma and eFF were collected during the follicular phase from mares (n=4) undergoing no...
Immunolocalization of a novel protein (P19) in the endometrium of fertile and subfertile mares. One of the major progesterone-dependent endometrial proteins in the mare is a novel 19 kDa lipocalin (P19). This protein is secreted by the endometrial glands and is readily detectable in uterine secretions during the luteal phase of the oestrous cycle and early pregnancy. The function of P19 is unknown, but since most lipocalins act as carriers of small hydrophobic molecules, it probably transports a maternal factor to the conceptus during pregnancy. In this study, a high titre antiserum raised against recombinant-derived P19 was used to detect by immunohistochemistry the protein in endometri...
Functional disturbances in the endometrium of barren mares: a histological and immunohistological study. Different types of endometrial maldifferentiation were investigated by histopathological (haematoxylin-eosin (HE), periodic acid Schiff-alcian blue and picro-sirius red staining) and immunohistological (oestrogen and progesterone receptors, Ki-67 antigen, intermediate filaments and laminin) analysis of endometrial biopsy specimens from mares (n=34), most of which had been barren for at least 1 year. Two major features were observed: (i) unequal differentiation, in which two functional stages are visible within a single biopsy sample: areas which are differentiated in accordance with the stage ...
Oxytocin and PGF2alpha release in mares resistant and susceptible to persistent mating-induced endometritis. Mares resistant (n=7) and susceptible (n=9) to persistent mating-induced endometritis were artificially inseminated (AI) during oestrus with chilled extended semen. Blood samples were collected from 30 min before AI, for 2 h after AI and again between 16 and 18 h after AI. Samples were assayed for oxytocin and the PGF2alpha metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM). AI caused a significant increase in oxytocin concentrations in both the resistant and susceptible mares and there was no significant difference in oxytocin release between the two groups of mares. Mean PGFM concentrations w...
Possible role of autoimmunity to spermatozoa in idiopathic infertility of stallions. Testicular degeneration is a major cause of subfertility in stallions, although an aetiological diagnosis cannot be made in most cases. In the present study, autoimmune testicular degeneration was induced and evaluated in stallions by immunizing stallions with their own spermatozoa mixed with an adjuvant. The factors evaluated included changes in semen quality and testicular histology. A large decrease in sperm number and quality was observed in response to sperm autoantigens. An ELISA test specific for antisperm antibodies was developed which enabled antibody titres in serum, seminal plasma a...
Post-mortem findings of gastric ulcers in Swedish horses up to one year of age: a retrospective study 1924-1996. Necropsy records from 702 horses, less than one year old, that were subjected to necropsy between 1924 and 1996 were used to estimate the prevalence of gastric ulceration in younger horses and to evaluate some potential risk factors that may contribute to the development of gastric ulceration. Information concerning breed, gender, age, season of death, clinical signs of colic, medical treatment, parasitism and documentation of diseases in different organs were recorded, as well as size, number and anatomical distribution of ulcers. Gastric ulcers were found in 96 of 702 young horses (14%) and ...
A survey of white line disease in Japanese racehorses. A survey was carried out into white line disease in 1781 Thoroughbred racehorses kept in stables at the Japan Racing Association (JRA) Miho Training Center (MTC) September-October 1996. The survey was conducted while horses were being shod by farriers. The horses that still exhibited damaged white lines after regular trimming were diagnosed as having white line disease. The factors recorded were age, sex, number of diseased horses, number of diseased hooves, number of lesions by region over the bearing border of the hoof and the classified length of such lesions. The percentage of total diseas...
[35 leptospira isolated from the vitreous body of 32 horses with recurrent uveitis (ERU)]. 130 vitreous samples, systematically collected in 1998 from 117 horses during vitrectomy, were cultured for the presence of leptospires. All horses suffered from equine recurrent uveitis (ERU), also known as periodic ophthalmia or moon blindness, and were treated surgically to combat painful attacks, and to preserve vision. In 35 out of 130 vitreous samples (35/130 = 26.9%), leptospires could be isolated. These isolates belong to the grippotyphosa serogroup (n = 31) and to the australis serogroup (n = 4). So, for the first time, leptospires were recovered from eyes in vivo in a large number of...
The association of Clostridium botulinum type C with equine grass sickness: a toxicoinfection? The cause of grass sickness, an equine dysautonomia, is unknown. The disease usually results in death. Gastrointestinal (GI) dysfunction is a common clinical manifestation in all forms of the disease. It is generally thought that equine grass sickness (EGS) is caused by an ingested or enterically produced neurotoxin which is absorbed through the GI tract. Clostridium botulinum was first implicated as a causative agent when it was isolated from the GI tract of a horse with EGS in 1919. The aim of the present study was to investigate the hypothesis that EGS results from toxicoinfection with C. b...
[Rhinopneumonia or mycotoxin intoxication? Neurologic phenomena in horses from a riding school]. In the course of several days most of the 40 riding-school horses turned out in paddocks developed ataxia of variable severity. Five of these horses showed severe ataxia and tremors, became paralyzed and were euthanized. Eleven privately-owned horses which were stabled on the same premises showed no clinical signs. The most likely diagnosis seemed to be the 'neurological form of EHV1', although the signs were not entirely typical. A few weeks later a second outbreak occurred among the riding-school horses and one of the privately-owned horses also showed signs of ataxia. In the meantime it had...
Management factors affecting the risk for vesicular stomatitis in livestock operations in the western United States. To identify management factors affecting the risk of animals developing vesicular stomatitis (VS). Methods: Case-control study. Methods: Horses, cattle, and sheep with suspected vesicular stomatitis on 395 premises in Colorado, New Mexico, Utah, and Arizona. Methods: Data were collected during the VS outbreak of 1997. Diagnosticians interviewed livestock owners and completed a supplemental questionnaire. Cases were defined as those premises that had a completed questionnaire and had > or = 1 animal positive for VS. Control premises were all premises investigated that had a completed questionna...
An apparently gluten-induced photosensitivity in horses. Primary photosensitization was observed in 3 Appaloosa mares. The skin lesions were diffuse erythema followed by edema and subsequently weeping and finally dry gangrene and ulceration. The severe photosensitivity dermatitis was apparently induced by gluten ingestion. Resolution of lesions occurred after withdrawal of the suspected dairy concentrate feed and prevention of exposure to sunlight. Neither the ponies nor donkey, which were not fed with the suspected concentrate, exhibited similar skin lesions or other clinical abnormalities. Gluten metabolites may contain photodynamic agents that ca...
Monensin poisoning in Brazilian horses. Three outbreaks of monensin poisoning caused 12 deaths in 16 horses. The illnesses were associated with the ingestion of the same batch of a commercial ration labeled for feeder calves which contained 180 +/- 20 ppm sodium monensin. The morbidity rate was 100% and lethality was 60%, 75%, and 100%. Clinical signs were tachycardia and cardiac arrythmia, groaning, incoordination, sudoresis, recumbency, and paddling movements with the limbs before death. Two horses had dark discolored urine (myoglobinuria). Serum levels of creatine phosphokinase activity were increased. Main necropsy findings were...
