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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.
Immune response to Sarcocystis neurona infection in naturally infected horses with equine protozoal myeloencephalitis. Equine protozoal myeloencephalitis (EPM) is one of the most common neurologic diseases of horses in the United States. The primary etiologic agent is Sarcocystis neurona. Currently, there is limited knowledge regarding the protective or pathophysiologic immune response to S. neurona infection or the subsequent development of EPM. The objectives of this study were to determine whether S. neurona infected horses with clinical signs of EPM had altered or suppressed immune responses compared to neurologically normal horses and if blood sample storage would influence these findings. Twenty clinical...
Endothelin receptor alterations in equine airway hyperreactivity. The purpose of this study was to evaluate the role of endothelin-1 (ET-1) and its receptors in the airway hyperreactivity of horses with obstructive pulmonary disease associated with summer pasture (SPAOPD). The right diaphragmatic lobe of the lung of 8 clinically healthy (unaffected) and 8 SPAOPD-affected horses was collected immediately after euthanasia. Bronchial rings (4 mm wide) were prepared and mounted in organ baths and attached to force transducers interfaced with a polygraph. Four rings were used to study each ET-1 receptor; 1 ring served as the control, and the other 3 were incubate...
Potential role of multiple rectal biopsies in the diagnosis of equine grass sickness. Two samples were taken postmortem from the rectum of each of 14 horses with grass sickness and 10 control horses, and four sections stained with haematoxylin and eosin were examined. By using as a criterion of grass sickness the presence of three chromatolytic neurons, 10 of the 14 cases were positive and none of the control horses was positive, giving a sensitivity of 71 per cent and a specificity of 100 per cent. No other histological features appeared to be of diagnostic value, and staining for Nissl substance in neurons with cresyl fast violet and methyl green-pyronin did not improve the s...
Cerebral listeriosis in an adult Freiberger gelding. Listeria monocytogenes infection, although rare in horses, can lead to septicaemia, gastroenteritis and abortion or stillborn foals. Equine cerebral listeriosis has been reported, but only in newborn animals. This report describes a Freiberger gelding with severe neuronal symptoms of sudden onset. The animal collapsed within 24 h and was humanely killed. Necropsy revealed multiple small brown to reddish foci within the brain stem and pons. Histopathology demonstrated multifocal suppurative meningoencephalitis with microabscesses and occasional intra-lesional, coccoid to rod-shaped, bacteria. T...
Severe pulmonary disease due to multisystemic eosinophilic epitheliotropic disease in a horse. Multisystemic eosinophilic epitheliotropic disease was diagnosed histologically in a 17-year-old Quarter Horse intact mare that was presented with a chronic history of respiratory distress. At necropsy, the lungs were poorly collapsed and the pulmonary parenchyma contained innumerable, discrete, spherical nodules in a miliary pattern. A few similar nodules were scattered in the liver and the renal lymph nodes. Histologically, these nodules consisted of fibrosing eosinophilic granulomas. Based on histologic findings and the absence of an etiologic agent, a diagnosis of multisystemic eosinophili...
Inflammatory aural polyp in a horse. An inflammatory aural polyp was identified in a 1-year-old standardbred filly, which presented with otorrhea and head rubbing. The polyp was removed by traction-avulsion, and the filly showed no subsequent signs of otorrhea. Aural polyps have not been reported in horses, but they are commonly seen in companion animals and humans. Un polype auditif inflammatoire a été identifié chez une pouliche Standardbred d’un an présentée pour otorrhée et frottage de tête. Le polype a été retiré par traction-avulsion et la pouliche n’a pas manifesté de signes subséquents d’otorrhée. Les ...
Lymphoscintigraphy of draught horses with chronic progressive lymphoedema. Early diagnosis of chronic progressive lymphoedema (CPL) may result in more effective interventions and provide a basis for further investigation of whether early diagnosis could be used as a means of eliminating potential genetic influences by cessation of breeding from affected individuals. Objective: Lymphoscintigraphy may be useful in draught horses to differentiate early lesions of CPL from other conditions in the pastern region. Methods: Forelimbs of 2 normal and 5 CPL-affected draught horses were evaluated with lymphoscintigraphy. Results: Lymphoscintigraphy showed clearly the presence ...
Larval cyathostominosis in horses in Ontario: an emerging disease? From 1991 to 2003, 24 cases of larval cyathostominosis were diagnosed at postmortem in equids, 15 (63%) from 2001 to 2003. Cases occurred from September to May, the majority from October to December. Median age was 12 mo. Diarrhea, colic, and weight loss were common clinical signs. Hypoalbuminemia and microcytosis were consistent findings. Cyathostominose larvaire chez des chevaux en Ontario: une maladie émergente? De 1991 à 2003, 24 cas de cyathostominose larvaire ont été diagnostiqués à l’examen post mortem chez des équidés dont 15 (63 %) entre 2001 et 2003. Les cas étaient rappor...
Noninfected tenosynovitis of the digital flexor tendon sheath: a retrospective analysis of 76 cases. Until recently, the pathogenesis of noninfected tenosynovitis of the digital flexor tendon sheath (DFTS) has been considered obscure. With the advent of tenoscopy some inciting causes have been described, but to date few cases with a precise diagnosis have been reported. Objective: Tenoscopic surgery enables accurate diagnosis and facilitates treatment of noninfected tenosynovitis of the DFTS. Methods: The case records of all horses with noninfected tenosynovitis of the DFTS admitted to a referral clinic over a 7-year period were evaluated retrospectively. Follow-up information was obtained by...
Clinical findings, diagnosis, prevalence and predisposing factors for lameness localised to the middle carpal joint in young Standardbred racehorses. Lameness related to the middle carpal joint (MCJ) occurs in up to 30% of young Standardbred horses in race training and the incidence increase with radiographic severity of third carpal bone (C3) sclerosis on DPr-DDIO (skyline) view of the carpus. Factors predisposing horses to carpal injury have not been well investigated. Objective: To determine the importance of MCJ lameness as a cause of wastage in young Standardbred racehorses, stage of training at which it occurs and predisposing factors, and to describe clinical findings and diagnosis. Methods: Standardbred horses (n = 114) entering the...
Investigation of equine influenza cases exhibiting neurological disease: coincidence or association? Equine influenza is usually a transient and self-limiting disease. However, during an outbreak of equine influenza in the UK in 2003 there were reports of unusually severe clinical signs among unvaccinated animals. Two influenza-infected horses developed neurological signs, and one was subjected to euthanasia. Post-mortem examination of the brain revealed viral-type non-suppurative encephalitis, and influenza virus antigen was demonstrated by immunolabelling of sections of nasal mucosa. A syndrome known as influenza-associated encephalopathy has been described in man. Although not proved, the ...
The Fell pony immunodeficiency syndrome also occurs in the Netherlands: a review and six cases. Over the last ten years a fatal syndrome associated with immunodeficiency and severe anaemia has been reported in young Fell pony foals in the UK. Affected foals are usually normal at birth but from the age of 2-4 weeks they progressively lose condition and become severely anaemic. Signs of immunodeficiency become apparent at around 3-4 weeks of age. Morbidity is low but mortality is 100% despite intensive treatment. Affected foals die or are euthanized usually before they reach the age of 3 months. A single autosomal recessive gene is suggested to be on the basis of the syndrome. Recently, af...
Penetration of equine leukocytes by merozoites of Sarcocystis neurona. Horses are considered accidental hosts for Sarcocystis neurona and they often develop severe neurological disease when infected with this parasite. Schizont stages develop in the central nervous system (CNS) and cause the neurological lesions associated with equine protozoal myeloencephalitis. The present study was done to examine the ability of S. neurona merozoites to penetrate and develop in equine peripheral blood leukocytes. These infected host cells might serve as a possible transport mechanism into the CNS. S. neurona merozoites penetrated equine leukocytes within 5 min of co-culture. I...
Seroprevalences of Toxoplasma gondii and Neospora sp. infections in Swedish horses. Sera from 414 Swedish horses were investigated for the presence of antibodies to Toxoplasma gondii and Neospora sp. by the T. gondii direct agglutination test (DAT), and an Neospora caninum iscom-ELISA. Five sera (1%) had a titre >1:40 in DAT, but when analysed by immunoblotting against T. gondii antigens only two of them were positive, giving a seroprevalence of 0.5%. Since the Neospora iscom ELISA had not been validated for equine sera it was used for an initial screening, and all sera with an optical density exceeding 0.200 absorbance units were selected for further investigation by immu...
Molecular characterization of Clostridium difficile isolates from horses in an intensive care unit and association of disease severity with strain type. To determine molecular characteristics, antimicrobial susceptibility, and toxigenicity of Clostridium difficile isolates from horses in an intensive care unit and evaluate associations among severity of clinical disease with specific strains of C difficile. Methods: Prospective study. Methods: 130 horses. Methods: Feces were collected from horses admitted for acute gastrointestinal tract disease with loose feces and submitted for microbial culture and immunoassay for toxin production. Polymerase chain reaction assays were performed on isolates for toxins A and B genes and strain identification...
Characterization of experimentally induced post-traumatic osteoarthritis in the medial femorotibial joint of horses. To study osteoarthritis in the equine medial femorotibial (MFT) joint after a single traumatic injury. Methods: 10 mature horses. Methods: In vitro explant cultures were used to determine injury threshold for stifle joint cartilage. Contusive impacts were applied to the medial femoral condyle (MFC), and horses were followed for 84 (n = 5) and 180 days (5). Synovial fluid samples were collected every 14 days for determination of sulphated glycosaminoglycan (sGAG) concentrations. Radiographic and lameness evaluations were performed. Gross and histologic descriptions, and immunohistochemistry, ca...
[Halicephalobus gingivalis infection in a 5-year-old Tinker gelding]. A 5-year old Tinker gelding was referred to the Department of Equine Sciences with a left eye uveitis and fever. At presentation the horse showed a mild lethargy, fever and decreased vision of the left eye. Rectal examination revealed an enlarged left kidney, with a hard and an irregular surface. The cranial mesentery artery had an enlarged and irregular aspect. Blood analysis showed anaemia, leucocytosis, increased blood urea nitrogen and creatinine and a hyperproteinemia. Urine analysis repeatedly showed a marked proteinuria and an increased gammaGT/creatinine ratio. The amount of abdominal ...
The S2 accessory gene of equine infectious anemia virus is essential for expression of disease in ponies. Equine infectious anemia virus (EIAV) is a macrophage-tropic lentivirus that persistently infects horses and causes a disease that is characterized by periodic episodes of fever, thrombocytopenia, and viremia. EIAV encodes only four regulatory/accessory genes, (tat, rev, ttm, and S2) and is the least genetically complex of all known lentiviruses. We sought to determine the role of the EIAV S2 accessory gene of EIAV by introducing mutations that would prevent S2 expression on the p19/wenv17 infectious molecular clone. Virus derived from the p19/wenv17 molecular clone is highly virulent and rout...
Combined amino acid mutations occurring in the envelope closely correlate with pathogenicity of EIAV. The Chinese equine infectious anemia virus (EIAV) donkey-leukocyte attenuated vaccine (DLV) provides a unique natural model system to study the attenuation mechanism and immunological control of lentivirus replication. Critical consensus mutations were identified between virulent Chinese EIAV strains and vaccine strains. Based on a full-length infectious clone of EIAV vaccine strain pLGFD3, two molecular clones, mFD5-4-7 and mFD7-2-11, were successfully constructed, in which 4 and 6 critical consensus mutations in the env gene of the vaccine strain were point-mutated to the wild-type sequence,...
Fell Pony syndrome in a pony in North America. A 5-week-old Fell Pony colt was examined for fever, lethargy, and anemia. The colt had been lethargic for 1 week before examination, had continued to nurse, had a temperature of 104°F (40°C), and was treated with ceftiofur (5 mg/kg IM q12h). Approximately 36 hours before examination, the colt developed watery diarrhea. Blood work performed by the referring veterinarian on the day of admission revealed a PCV of 10%.
Real-time polymerase chain reaction: a novel molecular diagnostic tool for equine infectious diseases. The focus of rapid diagnosis of infectious disease of horses in the last decade has shifted from the conventional laboratory techniques of antigen detection, microscopy, and culture to molecular diagnosis of infectious agents. Equine practitioners must be able to interpret the use, limitations, and results of molecular diagnostic techniques, as they are increasingly integrated into routine microbiology laboratory protocols. Polymerase chain reaction (PCR) is the best-known and most successfully implemented diagnostic molecular technology to date. It can detect slow-growing, difficult-to-cultiv...
Persistent mucus accumulation: a consequence of delayed bronchial mucous cell apoptosis in RAO-affected horses? This study examined the contribution of delayed apoptosis of bronchial mucous cells to mucus accumulation in equine recurrent airway obstruction (RAO). In pilot studies, Bcl-2, an apoptosis inhibitor, was detected in airway mucous cells of RAO-affected horses in remission and during acute disease, when most mucus was secreted. To study whether delayed apoptosis results in an increase in the number of mucous cells during disease recovery, six RAO-affected and six control horses were fed hay for 5 days to induce inflammation and then pellets for 7 days to partially resolve RAO before euthanasia....
Construction and validation of a risk-screening questionnaire for the investigation of recurrent airway obstruction in epidemiological studies of horse populations in Great Britain. Recurrent airway obstruction (RAO) is an environmental respiratory disease affecting horses. A risk-screening questionnaire (RSQ) for RAO would provide a useful tool to investigate the epidemiology of the disease in horses; our aim in this study was to construct and validate such an instrument. Guidance for what questions to include in the RSQ came from three processes: a review of the scientific literature, a survey of equine practitioners in the UK and a consultation with 19 experts using a modified Delphi technique. The latter consultation consisted of two rounds; agreement amongst the expe...
Horse madness (hippomania) and hippophobia. Anthropophagic horses have been described in classical mythology. From a current perspective, two such instances are worth mentioning and describing: Glaucus of Potniae, King of Efyra, and Diomedes, King of Thrace, who were both devoured by their horses. In both cases, the horses' extreme aggression and their subsequent anthropophagic behaviour were attributed to their madness (hippomania) induced by the custom of feeding them with flesh. The current problem of 'mad cow' disease (bovine spongiform encephalopathy) is apparently related to a similar feed pattern. Aggressive behaviour in horses c...
Kinetics of amyloid aggregation of mammal apomyoglobins and correlation with their amino acid sequences. In protein deposition disorders, a normally soluble protein is deposited as insoluble aggregates, referred to as amyloid. The intrinsic effects of specific mutations on the rates of protein aggregation and amyloid formation of unfolded polypeptide chains can be correlated with changes in hydrophobicity, propensity to convert alpha-helical to beta sheet conformation and charge. In this paper, we report the aggregation rates of buffalo, horse and bovine apomyoglobins. The experimental values were compared with the theoretical ones evaluated considering the amino acid differences among the sequen...
Systemic Cryptococcus albidus infection in a Doberman Pinscher. Cryptococcus albidus is a saprophytic, encapsulated yeast usually found in air, both outdoor and indoor, and sometimes on human skin. It is not usually considered to be a primary pathogen. Most cryptococcal infections of humans and animals are caused by Cryptococcus neoformans. Several cases of C. albidus infection have been reported in humans over the past 20 years. In the veterinary literature, 2 equine cases have been described: genital infection and mycotic keratitis. The present report is the first documented case of C. albidus systemic infection in a dog. Veterinarians and diagnosticians...
