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.
Derksen FJ, Scott JS, Slocombe RF, Robinson NE.We assessed the effect of aerosol Micropolyspora faeni challenge in two groups of ponies by measuring lung function, airway reactivity to aerosol histamine, and bronchoalveolar lavage fluid cytology. One group of ponies was sensitized by subcutaneous injection of M. faeni in complete Freund's adjuvant, and the other group served as control. In both groups of ponies, measurements were made at base line and 5 h after aerosol administration of 30 ml of saline or 30 ml of 1% wt/vol particulate M. faeni antigen in saline. Saline challenge had no effect on any of the measured variables. M. faeni cha...
Foil LD, Klei TR, Miller RI, Church GE, Foil CS, French DD, Smith JN.Seasonal changes in density and spatial distribution of Onchocerca cervicalis microfilariae were studied in ventral-midline skin of 15 infected pony mares in southern Louisiana. Triple running mean analysis of data over a 13-mo period indicated that a distinct pattern exists in total microfilariae population density and in microfilariae occurrence in different levels of the dermis. Microfilariae density reaches peak levels in the spring followed by a 58% decrease in the summer, a 19% increase in the fall, and a decrease to the lowest numbers in the winter. Microfilariae were found in all level...
Freestone JF, Hietala S, Moulton J, Vivrette S.A 7-year-old horse with no previous history of illness was determined to have a systemic infection of Rhodococcus equi. Rhodococcus equi was isolated from blood, tracheal fluid, and feces. Lymphopenia, failure to respond to concanavalin A and phytohemagglutinin lymphocyte stimulation testing, decreased concentrations of immunoglobulin (Ig)M, IgA, and IgG, low R equi antibody titer, histologic depletion of lymphoid tissue, and a failure to respond to antigenic stimulation led to the conclusion that both humoral and cell-mediated immunity were compromised. No cause for the acquired immunodeficie...
Matthews AG, Waitkins SA, Palmer MF.The prevalence of antibody titres to a range of 20 leptospira antigens in the serum of horses and ponies with no ophthalmic abnormalities and with ophthalmoscopic evidence of endogenous uveal inflammatory disease was determined using a microscopic agglutination technique. Titres against leptospira antigens were observed in 13 out of 138 (9.1 per cent) animals with no ophthalmic abnormalities, and in three out of 27 (11.1 per cent) animals with anterior uveitis. Serovar sejroe was common to all seropositive animals with anterior uveitis. The results show that leptospira infection is not a major...
Szymanski CM.Enlargement of the left eye, corneal opacification, and blindness were clinical signs of a teratoid medulloepithelioma in a 5-year-old Standardbred mare. Diagnosis was made on histologic examination of the enucleated eye. Medulloepitheliomas are congenital intraocular tumors arising from primitive ciliary body epithelium. Their development is rare in domestic animals.
De Cock AW, Mendoza L, Padhye AA, Ajello L, Kaufman L.Pythium insidiosum sp. nov., the etiologic agent of pythiosis, a cosmopolitan disease of horses, cattle, and dogs, is described and illustrated.
Ziemer EL, Parker HR, Carlson GP, Smith BP, Ishizaki G.An 11-year-old Quarter Horse mare and a 2-year-old Quarter Horse colt with clinical diagnoses of renal tubular acidosis (RTA) were donated to the University of California Veterinary Medical Teaching Hospital. A series of diagnostic tests was performed in an attempt to characterize the type and cause of RTA in these horses. Endogenous creatinine clearance and sodium sulfanilate clearance were within reference ranges; thus, no abnormality of glomerular function was detected. To assess renal tubular function in response to acid loading, each horse was given 0.1 g of NH4Cl/kg of body weight via na...
Tolliver SC, Lyons ET, Drudge JH.The prevalence and number of naturally acquired gastrointestinal parasites were compiled for horses used in critical tests of activity of parasiticides over a 28-year period (1956-1983). Data are presented as follows: n = number of horses examined; % = mean prevalence; number in parentheses after % = aggregate mean number of parasites in infected horses. Parasites found were: bots (n = 513) - Gasterophilus intestinalis, 2nd instar, 61%(58); 3rd instar, 94%(168); G. nasalis, 2nd instar, 36%(28); 3rd instar, 81%(51); stomach worms (n = 200) - Habronema muscae, 65%(179); Draschia megastoma, 29%(9...
White NA, Tyler DE, Blackwell RB, Allen D.Records of 20 horses with small intestinal disease causing acute colic and affecting the proximal portion of the small intestine were examined retrospectively. The disease was characterized by severe to moderate pain, which was replaced by depression, fever, gastric reflux, slight distention of the affected small intestine, leukocytosis, and high concentrations of total protein in the peritoneal fluid. Grossly, the affected intestines were hemorrhagic and had yellow discoloration. Histopathologic findings included submucosal edema, neutrophilic infiltration of the submucosal and laminal propri...
Critchley KL.A 6 month Welsh pony filly with an interventricular septal defect in conjunction with a pulmonary stenosis due to a bicuspid pulmonary valve is described. The animal had poor exercise tolerance, a loud pansystolic murmur and a precordial thrill. Blood pressure and oxygen tension values obtained during cardiac catheterization suggested the diagnosis which was confirmed at autopsy.
Simonin EM, Babasyan S, Tarsillo J, Wagner B.IgE+ plasmablasts develop following allergen exposure and B cell activation. They secrete IgE and therefore are directly linked to maintain the mechanisms of IgE-mediated allergies. Here, we show that the presence of IgE+ plasmablasts in peripheral blood not only coincides with clinical allergy, but also predicts the upcoming development of clinical disease. Using an equine model of naturally occurring allergy, we compared the timing of allergen exposure, arrival of IgE+ plasmablasts in peripheral blood, and onset of clinical disease. We found that IgE+ plasmablasts predict the development of ...
Huskamp B, Scheidemann W.Ninety-six horses with chronic recurrent caecal impaction associated with hypertrophy of muscle layers in the caecal base or in the whole caecum were examined from 1990 to 1996. Enlargement of the caecocolic orifice was completed surgically in 58 horses. Of those horses having surgery, 50 were discharged from the hospital while 8 were subjected to euthanasia at the hospital due to complications. Twenty-seven of the 50 horses discharged were normal at follow-up while 23 died or were subjected to euthanasia due to acute or recurrent colic, recurrent impaction in the ascending or descending colon...
Bauer BS.Although not comprehensive of all ocular conditions in the equine species, this article concentrates on various ophthalmic conditions observed in the horse where laboratory diagnostics are recommended. The importance of laboratory diagnostic testing cannot be underestimated with equine ophthalmic disease. In many cases, laboratory diagnostics can aid in obtaining an early diagnosis and determining appropriate therapy, which in turn, can provide a better prognosis. In unfortunate cases where ocular disease results in a blind, painful eye necessitating enucleation, light microscopic evaluation i...
Mair TS, Osborn RS.X-ray diffraction crystallography was used to determine the crystalline composition of 18 equine urinary calculi, including stones originating in the kidney, bladder and urethra. Calcium carbonate in the form of calcite was found to be the major component in all calculi examined. Other components commonly found included weddellite and substituted vaterite. Urine deposits from a number of normal horses were also examined. The significance of these findings, as well as those from a number of previous reports, are discussed in relation to the possible aetiology of urolithiasis in the horse.
Slone DE, Humburg JM, Jagar JE, Powers RD.Rectal tears were detected in three horses treated for colic. Based on historical, clinical, and postmortem findings, the tears could not be attributed to the attending veterinarian and were therefore not iatrogenic (physician induced). One tear was attributable to an infarction that presumably resulted from thromboembolism; 1 tear occurred without any evidence of external cause and resulted in such severe peritonitis that the cause and resulted in such severe peritonitis that the cause could not be determined, and 1 tear occurred during rectal palpation by the owner, before he called the vete...
Scott-Orr H.The challenges faced in demonstrating Australia's freedom from equine influenza following the outbreak in 2007-08 and the responding strategy developed by the Proof of Freedom Working Group are presented.
Galosi CM, Norimine J, Echeverría MG, Oliva GA, Nosetto EO, Etcheverrigaray ME, Tohya Y, Mikami T.The genomes of 10 equine herpesvirus 1 (EHV-1) strains isolated in Argentina from 1979 to 1991, and a Japanese HH1 reference strain were compared by restriction endonuclease analysis. Two restriction enzymes, BamHI and BglII, were used and analysis of the electropherotypes did not show significant differences among isolates obtained from horses with different clinical signs. This suggests that the EHV-1 isolates studied, which circulated in Argentina for more than 10 years, belong to a single genotype.
Science (New York, N.Y.)July 19, 1946
Volume 104, Issue 2690 53-54 doi: 10.1126/science.104.2690.53
Sulkin SE, Goth A, Zarafonetis C.Anesthesia, by ether, is effective in the treatment of western equine encephalomyelitis in mice. Of mice treated with deep ether anesthesia soon after the intracerebral injection of western equine virus, only 58 per cent developed the disease as compared with 92.4 per cent of control animals. When anesthesia was delayed the approximate length of the incubation period, 60 per cent of the animals developed the disease as compared with 92.4 per cent of the controls. In addition, ether anesthesia delays the development of central nervous system symptoms not only when administered soon after the in...
Gelberg HB, Smetzer DL, Foreman JH.Four young horses of various breeds and suffering from atrial fibrillation died of heart failure. All had markedly high pulmonary arterial pressure, right-sided cardiomegaly, and lack of histologic lesions in the right atrium or pulmonary parenchyma. Three horses had hypertrophy and/or necrosis of the tunica media of the pulmonary vasculature. Clinical signs of disease, physiologic data, and pathologic findings indicated that these horses had primary pulmonary hypertension with secondary right-sided cardiac ventricular hypertrophy and dilatation, atrial fibrillation, and heart failure.
Platt H.Many infections of the equine placenta and fetus result from ascending spread along the cervical canal. Most abortions due to infection occur during the later stages of pregnancy and the possible effects of intrauterine infection on the developing fetus and young foal are discussed.
Sellon DC.FPT of immunoglobulin in foals is the commonest form of acquired immunodeficiency in horses. FPT predisposes foals to bacterial infections and septicemia and easily is preventable and treatable if breeding farms and veterinarians are attentive to optimum foaling management practices. Other forms of acquired immunodeficiencies are uncommon in horses, although immune function may be transiently suppressed by a wide variety of drugs, infections, or other conditions. As immunologic testing becomes more sophisticated and more readily available to equine practitioners, acquired immunodeficiencies ar...
Firth EC, Alley MR, Hodge H.Two cases of Rhodococcus equi infection in foals are described, in which osteomyelitis was a feature. Because rhodococcal infection is usually low grade and chronic, and because the signs of early metaphysitis can be subtle, any articular or periarticular swelling in a foal from a farm with a history of rhodococcosis should be strongly suspected to be associated with R equi until proven otherwise.
Recent outbreaks of equine infectious anaemia and equine viral arteritis in the UK. Update on the equine infectious anaemia situation in Europe. West Nile virus reported in several Mediterranean countries. Current and future approaches to equine viral arteritis control in the UK. These are among matters discussed in the quarterly equine disease surveillance report for April to June 2010, prepared by Defra, the Animal Health Trust and the British Equine Veterinary Association.
Reijerkerk EP, Veldhuis Kroeze EJ, Sloet van Oldruitenborgh-Oosterbaan MM.Equine sarcoidosis is a rare disorder usually characterized by exfoliative dermatitis, moderate to severe wasting, and sarcoidal granulomatous inflammation of multiple organ systems. It has an unknown aetiopathogenesis. The condition is not related to equine sarcoid. This case report describes generalized cutaneous and systemic sarcoidosis in an 11-year-old Trakehner mare (case A) and in a 7-year-old Dutch Warmblood gelding (case B). Case A was presented with cutaneous sarcoidosis on the head and body and was diagnosed on the basis of histological examination of skin. Case B presented with mul...
Brosnahan MM, Silvela EJ, Crumb J, Miller DC, Erb HN, Antczak DF.Invasive trophoblast from Day 34 horse conceptuses survives in extrauterine sites in allogeneic recipients that are immunologically naive to donor major histocompatibility complex class I antigens. The ectopic trophoblast retains its in utero characteristics, including similar lifespan, physiologic effect of its secreted product (equine chorionic gonadotropin) upon the recipient's ovaries, and induction of host immune responses. Immunologic memory has not been considered previously in this experimental system. We hypothesized that primary exposure to ectopic trophoblast would affect the recipi...
Gaughan EM, Hackett RP.Over a 10-year period, cecocolic intussusception was diagnosed in 11 of 842 horses undergoing surgical treatment for colic at the New York State College of Veterinary Medicine. Eight horses died or were euthanatized because of poor prognosis determined at surgery or because of postoperative complications. Three horses recovered without complication after manual reduction of the intussusception and partial typhlectomy, using an intestinal stapling device.
Berhane Y, Bailey SR, Harris PA, Griffiths MJ, Elliott J.Elevated plasma homocysteine (HCy) concentration is a risk factor for cardiovascular diseases associated with endothelial dysfunction, including the human digital ischaemic disease, Raynaud's phenomenon. Objective: HCy causes dysfunction of equine vascular endothelium and elevated plasma concentrations predispose to laminitis. Objective: To determine 1) the concentration of HCy in vitro, which inhibits equine vascular endothelial cell function and 2) any association between risk of laminitis and plasma HCy concentration. Methods: Endothelial function was studied by measuring endothelium-depend...
Chua MM, Morgan DO, Karush F.The immune response to a bacterial vaccine of Streptococcus faecalis (strain N) was characterized in all of the seven horses studied by the sustained production of about 90% IgM anti-lactose antibody over a period of 44 weeks with maximum values of the total antibody ranging from 4 mg/ml of serum to 12 mg/ml of serum. With respect to the binding of a lactose-containing ligand the association constants of the antibodies purified from sera obtained between 5 and 44 weeks fell in the range of 1 times 10-5 M-1 to 2 times 10-5 M-1. Not only was there no significant indication of maturation of a-fin...
Scheffer CJ, Blaauw G, Dik KJ, Sloet van Oldruitenborgh-Oosterbaan MM.A mini-Shetland stallion was referred with bilateral pruritus localized to the anterior neck. More detailed clinical examination also revealed ataxia, and diagnostic imaging, including pre- and post-contrast computed tomography, revealed an old fracture of C2. Spinal cord compression was diagnosed. The probable causal relation between the fracture, the ataxia, and the localized pruritus seems comparable to the 'contusio cervicalis posterior' in humans, in which spinal cord trauma may cause pruritus in the associated dermatome.
Barrell EA, Kamm JL, Hendrickson DA.A 7-year-old mixed-breed stallion was admitted because of colic. Results: Entrapment of the left colon in the renosplenic space was diagnosed via rectal palpation and ultrasonographic examination, despite a renosplenic space ablation 6.5 years earlier. Results: The renosplenic entrapment was corrected with a combination of phenylephrine administration, rolling, and ballottement of the horse's abdomen during general anesthesia. The following week, left flank laparoscopic renosplenic space ablation was performed with the horse standing. On examination of the previous surgical site, only 4 bands ...
Hall RF, Pursell AR, Cole JR, Youmans BC.An epizootic of equine infectious anemia (EIA) involved 35 horses on a farm in south Georgia. During a 126-day period, 21 of these horses became seropositive for EIA. After the initial diagnosis in July, the horses were tested every 7 to 10 days. At least one additional horse was found to be seropositive on each testing day. As soon as they were determined to be seropositive, the horses were removed from the herd and sent to slaughter. The removal of the seropositive horses, however, did not stop the epizootic. We believe the initial infection was from a 7-year-old stallion that recently had b...
Dorr TE, Higgins RJ, Dangler CA, Madigan JE, Witham CL.Three cases of equine protozoal myeloencephalitis were diagnosed over a 12-month period in horses that had never left the state of California. These cases suggest that the disease is enzootic in California.
Ford TS, Vaala WE, Sweeney CR, Skand D, Saik JE.A 15-year-old Quarter Horse gelding was examined because of chronic intermittent colic of 40 days' duration. The clinical signs included acute onset of depression, ptyalism, abdominal splinting, and rolling within an hour of eating. An intramural mass of the esophagus was identified during esophagoscopy. A large soft-tissue density surrounding the distal portion of the esophagus, creating a stricture, was identified on an esophagogram. With the horse slightly sedated, pleuroscopy was performed, allowing direct visualization and biopsy of the mass. The histopathologic diagnosis was squamous cel...
Hughes K.Cases of Hendra virus infection in horses in Australia have been seen regularly since the virus was first isolated in 1994. Kristopher Hughes, associate professor of equine medicine at Charles Sturt University in Australia, gives an overview of how knowledge of the virus has developed in the past 20 years.
Lopes MS, Diesterbeck U, da Câmara Machado A, Distl O.Navicular disease or podotrochlosis is one of the main causes of progressive forelimb lameness in warmblood horses. The objective of this study was to refine a quantitative trait locus on horse chromosome 2 for radiological alterations in the contour of the navicular bone (RAC) in Hanoverian warmblood horses. Genotyping was performed in 192 Hanoverian warmblood horses from 17 paternal half-sib groups. The marker set was extended to 58 informative microsatellites including nine newly developed microsatellites. QTL for RAC could be delineated at 32.50-43.13 Mb and a further new QTL for RAC could...
Dicht S, Del Chicca F, Fürst A.Ectopic teeth occur because of failure of the first branchial cleft to close during development and are found mostly in young horses. Such dentigerous cysts are often located at the base of the ear, forming a notable swelling with a fistula, as it was the case with the two year old Iceland mare «Runa». In order to confirm the diagnosis, x-ray images were taken, which is also necessary to locate the ectopic tooth correctly. While operating, the whole cystic membrane should be removed and it is important to prevent adjacent nerves and blood vessels from damage. Prognosis for complete healing a...
Cohen ND, Honnas CM.To determine the incidence of the risk factors for developing diarrhea in horses after celiotomy for colic. Methods: Retrospective cohort study. Methods: 357 adult horses that had celiotomy for colic at the teaching hospital between Jan 1, 1990 and Sep 1, 1994. Methods: Medical records of horses that had celiotomy for colic were reviewed to abstract information regarding development of diarrhea, signalment, history, and treatment. Results: In horses that had celiotomy for colic, the incidence of diarrhea was 53.2% (190/357). Using multiple logistic regression, horses with a disorder of the lar...
Jeffcott LB, Kold SE, Melsen F.The gross and histological appearance of subchondral bone cysts in six Thoroughbred or partbred horses is described. The lesions were all situated in the centre of the medial femoral condyle and were not associated with any other damage to the articular surface of the femorotibial or femoropatellar joints. In three cases the cysts were unilateral but had an early non-cystic lesion present in the opposite stifle. All the cysts had a narrow channel at their distal extremity which communicated with the femorotibial joint. The more recently developed ones were fluid filled and contained fibrous st...
