The study of diseases in horses encompasses a wide range of conditions affecting equine health, including infectious diseases, metabolic disorders, and genetic abnormalities. These diseases can impact various systems within the horse, such as respiratory, gastrointestinal, and musculoskeletal systems, and can lead to significant health challenges. Research in this area focuses on understanding the pathophysiology, diagnosis, prevention, and treatment of equine diseases. Common diseases studied include equine influenza, equine herpesvirus, and laminitis. This page provides access to peer-reviewed research studies and scholarly articles that explore the etiology, clinical presentation, and management strategies of diseases in horses, contributing to the advancement of equine veterinary medicine.
Reimer JM, Reef VB, Sommer M.Pulmonic valve rupture was determined to be the cause of severe right-sided heart failure in a 20-year-old Thoroughbred gelding. A flail in the intermediate pulmonic valve cusp was detected by 2-dimensional echocardiography. Significant pulmonic and tricuspid valvular regurgitation were confirmed by Doppler echocardiography. Despite treatment, the horse's condition deteriorated, and euthanasia was performed. At necropsy, a tear in the pulmonary artery extending into the right valve cusp and a tear at the base of the intermediate valve cusp were identified at the junction of the right and inter...
Chong YC, Duffus WP, Field HJ, Gray DA, Awan AR, O'Brien MA, Lunn DP.Over a period of two years, a total of 22 full term foals from Welsh Mountain pony mares were raised in conditions that were free from infection by Equid herpesvirus (EHV-1/4). Parturition dates were predicted by monitoring colostrum electrolytes, and the mares allowed to foal naturally under supervision or following induction with intravenous oxytocin. Immediately following birth, foals were separated from their dams and transferred to a specially built, positive pressure isolation unit. They were given antibiotic prophylaxis and fed bovine colostrum during the first 24 h, and then mare's mil...
Takai S, Koike K, Ohbushi S, Izumi C, Tsubaki S.Antigens of Rhodococcus equi were analyzed by immunoblotting with naturally infected foal sera. Immunoblots of whole-cell antigen preparations of clinical isolates of R. equi revealed that major protein bands with molecular masses of 15 to 17 kDa were present in all clinical isolates tested and all isolates virulent for mice. In contrast, the 15- to 17-kDa antigens were not identified by immunoblotting in ATCC 6939, a type strain of R. equi that was avirulent for mice. Whole-cell antigens of 102 environmental isolates were investigated by immunoblotting and the mouse pathogenicity test. Twenty...
Duncan ID, Reifenrath P, Jackson KF, Clayton M.The terminal branches of the recurrent laryngeal nerve (RLN) of three normal ponies and six horses with sub-clinical laryngeal disease were examined qualitatively and quantitatively in an attempt to explain the preferential denervation of the laryngeal adductor muscles in the neuropathy of idiopathic laryngeal hemiplegia (ILH). The myelinated fibre spectra of all the motor nerve fibres in the left and right abductor and adductor branches of the RLN in three normal ponies were measured. The density of myelinated fibres was also calculated. There was no significant difference between the larger ...
Baxter GM, Humphries GB.A large abscess in the lateral neck region of a horse was treated with percutaneous drainage. The abscess was localized with ultrasonography and aspirated by use of a 7.7-cm spinal needle. A stainless-steel guide wire was passed through the needle, and tissue dilators were used to enlarge the percutaneous hole. A multiperforated polyvinylchloride catheter that was placed within the abscess cavity permitted aspiration and lavage of the abscess. The abscess resolved over the next 10 days with no complications. Percutaneous abscess drainage is commonly performed in people and may have application...
Perdue BD, Collier MA, Dzata GK, Mosier DA.A one-year-old Thoroughbred filly was examined because of poor body condition and reluctance to move its neck. Complete blood count revealed leukocytosis (15,700 WBC/microliters) and hyperproteinemia (8 g/dl). Radiography of the cervical vertebrae revealed multifocal lesions of bone lysis surrounded by zones of sclerosis. The horse was euthanatized and necropsied. Granulomatous lesions were identified in the heart, spleen, lungs, bones, and lymph nodes. The multifocal granulomatous inflammatory lesions in this horse were suggestive of mycobacteriosis.
Machang'u RS, Prescott JF.Rhodococcus equi produces two exoenzymes (REE), a cholesterol oxidase in large amounts and a phospholipase C, which cause lysis of sheep red blood cells (SRBC) sensitized with Staphylococcus aureus beta toxin. Two immunization studies were done in foals to determine the role of antibody to REE in protection against R. equi pneumonia. In the first study, three foals (mean age 10 days) were vaccinated four times at 2-week intervals with over 1 million units of partially purified exoenzymes (PREE). In the second study, three foals (mean age 19 days) were administered plasma from an adult horse va...
Bailey GD, Love DN.Two hundred and seventy bacterial isolates were obtained from the pharyngeal tonsillar surface of 12 normal horses and 98 obligatory anaerobic bacteria were characterised. Of these, 57 isolates belonging to 7 genera (Peptostreptococcus (1); Eubacterium (9); Clostridium (6); Veillonella (6); Megasphera (1); Bacteroides (28); Fusobacterium (6)) were identified, and 16 of these were identified to species level (P. anaerobius (1); E. fossor (9); C. villosum (1); B. fragilis (1); B. tectum (2); B. heparinolyticus (2)). Three hundred and twenty isolates were obtained from 23 samples from horses with...
Wright JD, Kelly WR, Waddell AH, Hamilton J.Verminous encephalomyelitis due to Angiostrongylus cantonensis larvae was diagnosed in 2 foals at necropsy. The principal clinical feature was tetraparesis, although history and neurological examination revealed progressive and multifocal neurological disease. At presentation, a tentative diagnosis of parasitic larval migration involving the central nervous system (CNS), presumably due to Strongylus vulgaris, was proposed. Dissection of the spinal cord in one case resulted in recovery of intact larvae of both sexes of A. cantonensis. In both foals, histopathology of the brain and spinal cord r...
Madison JB, Dreyfuss DJ, Charlton C.A 4-year-old Thoroughbred gelding with a history of chronic colic was referred for evaluation of signs of abdominal pain. Exploratory laparotomy revealed a diverticulum of the distal portion of the ileum located between the layers of the mesentery. The diverticulum was similar in location and appearance to acquired ileal diverticula described in human beings. Complete bypass of the diverticulum by ileocecostomy resulted in apparent resolution of the chronic colic in this horse.
Kölbl S, Schuller W, Pabst J.944 serum samples of horses, collected in 1988 and 1989, were examined for the occurrence of antibodies against equine arteritis virus by a microneutralizations test. In 10.9% of all sera reactors could be found. The distribution of seropositive horses varied from 4.6% (Salzburg) to 15.7% (Lower Austria). From Tyrol and Vorarlberg no samples could be obtained. It was not possible, to correlate clinical symptoms (infertility, respiratory symptoms, fever and edema) with the infection. It is assumed, that the disease appears in Austria only in a clinical inapparent form.
Specht TE, Breuhaus BA, Manning TO, Miller RT, Cochrane RB.A 12-year-old Arabian stallion was evaluated for a refractory skin problem of 2 years' duration. Skin nodules and pustules, which would rupture, had developed over the right lumbar muscles. Anaerobic culturing from the pustules yielded Actinomyces viscosus, and histologic examination of biopsy specimens revealed globular eosinophilic structures. Concomitant treatment with isoniazid (8 mg/kg of body weight, q 24 h for 8 weeks), trimethoprim-sulfadiazine (30 mg/kg, q 24 h for 8 weeks), and sodium iodide solution (66 mg/kg, every 1, 2, or 4 weeks, for 32 weeks) resolved the condition.
Götz HJ.A case of diprosopus in a foal is described. This is only the second report of such a deformity in the equine species. Hereditary pathology and pathogenesis are discussed.
Dart AJ, Snyder JR, Pascoe JR.A 17-year-old Quarter Horse, Arabian crossbred mare presented with a history of having had abdominal pain for 2 d. At surgery there was 2.6 m of descending colon strangulated within the pedicle of a mesenteric lipoma. The lipoma was resected and the descending colon appeared viable so was replaced, and the mare recovered from anaesthesia. Post-operatively, the mare failed to stabilise so was taken back to surgery. There was 2 m of infarcted descending colon which was resected and anastomosed. A drain and stainless steel stay sutures were incorporated into the ventral suture line. Post-operativ...
Daels PF, Stabenfeldt GH, Hughes JP, Odensvik K, Kindahl H.The role of prostaglandin F2 alpha (PGF2 alpha) in embryonic loss following induced endotoxemia was studied in mares that were 21 to 44 days pregnant. Thirteen pregnant mares were treated with a nonsteroidal anti-inflammatory drug, flunixin meglumine, to inhibit the synthesis of PGF2 alpha caused by Salmonella typhimurium endotoxin given IV. Flunixin meglumine was administered either before injection of the endotoxin (group 1, -10 min; n = 7), or after endotoxin injection into the mares (group 2, 1 hour, n = 3; group 3, 2 hours, n = 3); 12 pregnant mares (group 4) were given only S typhimurium...
Daels PF, Stabenfeldt GH, Hughes JP, Odensvik K, Kindahl H.The role of decreased luteal activity in embryonic loss after induced endotoxemia was studied in mares 21 to 35 days pregnant. Fourteen pregnant mares were treated daily with 44 mg of altrenogest to compensate for the loss of endogenous progesterone secretion caused by prostaglandin F2 alpha (PGF2 alpha) synthesis and release following intravenous administration of Salmonella typhimurium endotoxin. Altrenogest was administered daily from the day of endotoxin injection until day 40 of gestation (group 1; n = 7), until day 70 (group 2; n = 5), or until day 50 (group 3; n = 2). In all mares, secr...
Grabner A, Fischer A.In a retrospective study of 38 horses with Borna encephalitis which were clinically and histopathologically examined in the "I. Medizinische Tierklinik" in Munich between 1977 and 1990, the epidemiology, the clinical symptomatic and the diagnostic procedures available are presented. Indirect immunofluorescence showed antibodies in the serum of 12 out of 29 cases (41%) and in the cerebrospinal fluid (CSF) of 17 out of 28 cases (61%). The evaluation of 23 cases in which indirect immunofluorescence of serum and CSF, and also the post mortem virological and histopathological examination of the bra...
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...
Taylor FG, Wotton PR, Hillyer MH, Barr FJ, Lucke VM.Clinical examination of a four-and-a-half-month old foal revealed evidence of progressive heart failure associated with an atrial septal defect and atrial fibrillation. Atrial septal defects are rarely reported in foals and the foal's growth, development and demeanour were normal until a sudden onset of lethargic behaviour. The value of B-mode echocardiography in identifying the congenital lesion is indicated.
van der Kolk JH, Bernadina WE, Visser IJ.A four year old Dutch warmblooded mare was born and raised in the province of North-Brabant, the Netherlands. On May 16, 1989, she showed signs of colic, anorexia, depression, ileus, severe dehydration and leukopenia. When the mare collapsed, euthanasia was carried out. Acute colitis and cytoplasmic inclusion bodies in macrophages were observed at autopsy. When an indirect immunofluorescence assay was performed, the Ehrlichia risticii titre of the serum was found to be 1:640.
Panciera RJ, Slusher SA, Hayes KE.Simultaneous and successive occurrence of ovarian teratoma and granulosa cell tumor is reported in 2 mares. Simultaneous occurrence of the tumors may obscure clinical diagnosis. Whereas size, unilaterality, and the cystic nature of each may be similar, differentiating features include the potentially palpable presence of bone, cartilage, or teeth in teratoma, and the hormone-induced behavioral and reproductive effects of granulosa cell tumors. Thorough examination of surgical specimens may reveal the existence of a neoplastic process, previously obscured by the more obvious presence of another...
Kirisawa R, Hosoi Y, Yamaya R, Taniyama H, Okamoto M, Tsunoda N, Hagiwara K, Iwai H.We isolated a variant equine herpesvirus-1 (EHV-1), strain 5089, from the lung of a dead neonatal foal in Japan and characterized the biological nature of the virus. The virus spread in cultured cells mainly by cell-to-cell infection, unlike wild-type EHV-1, which spreads efficiently as a cell-free virus. The virus titer in cultured supernatant and the intracellular virus titer were low compared to those of wild-type EHV-1. Heparin treatment of the virus had no effect on viral infectivity in cell culture. Glycoprotein C (gC) was not detected by Western blotting and fluorescent antibody tests i...
Hovda LR, Shaftoe S, Rose ML, Clemmons LH.A mediastinal squamous cell carcinoma and thyroid carcinoma were found in an aged horse. Clinical signs consisted of bilateral thyroid gland enlargement, chronic cough, and mild respiratory distress. The neoplasms were not treated. Squamous cell carcinoma is a common neoplasm in horses, but not in the cranial portion of the mediastinum. Thyroid carcinomas in horses are uncommon. This combination of neoplasms is rare and may have been associated with a defect in the immune system.
Sokół R, Raś-Noryńska M, Michalczyk M, Raś A, Rapacz-Leonard A, Koziatek S.Studies were carried out in year 2014 during the pasture period (from April to October) in Warmia and Mazury Region. Fecal samples were taken from cold- and warmblood horses from individual and agrotouristic farms with the different housing, feeding and pasture- care practices. Total of 512 horses were examined (320 mares, 170 geldings and 22 stallions). In the group of 185 horses from individual farms, 119 animals (64.3%) were infected with gastro-intestinal parasites. Among the 372 horses from agrotouristic farms 169 (51.7%) were infected with parasites. Most of the animals expelled the eggs...
Zamora CS, Vitums A, Nyrop KA, Sande RD.The heart of a 6-week old Arabian filly with a history of poor health and exercise intolerance revealed at postmortem examination, multiple cardiac malformations which included atresia of the right atrioventricular orifice (tricuspid atresia, with associated atrial and ventricular septal defects), complete transposition of the great arteries, anomalous drainage of the venae cavae and coronary sinus into the left atrium, coarctation of the aorta, and a small but patent ductus arteriosus. The course of blood through the heart was suggested and discussed.
Grauerholz H.Interrelations between respiration and changes in amplitudes of the QRS-complex of the ECG of horses were investigated. The value of the R-vector and both its components Rx and Ry decrease during inspiration and increase in the expiration phase. It means, that the R-waves in leads from cranial to caudal (y, II, aVF) and from right to left (I) become smaller with inspiration and larger with expiration. The difference of the amplitudes may be important, especially in horses with respiratory problems, so that it has to be noted when evaluating electrocardiograms. For that purpose it is not necess...
Moore PF, Hacker DV, Buyukmihci NC.Angiosarcomas arising in ocular tissues of four aging horses are described. Tumors were locally invasive and eventually metastasized via the mandibular and cervical lymph nodes. Pathologically, the tumors contained well-differentiated regions, in which vascular channels were lined by pleomorphic endothelial cells, as well as poorly-differentiated regions, in which vascular channels were either rudimentary or absent. Red blood cells were scare in vascular structures formed by the tumors. Factor VIII related antigen (VIII:RAg), a blood vascular endothelial marker, was demonstrated by immunohisto...
Lindsell CE, Hilbert BJ, McGill CA.Osteochondrosis dissecans was diagnosed clinically and radiographically in 31 joints of 21 horses. The horses ranged in age from 8 months to 5 years at the time of presentation. The usual age of onset of clinical signs was 18 to 24 months. Presenting complaints included joint effusion and lameness of either gradual or sudden onset. In Thoroughbred horses, the stifle joint was the most common site of lesions and in Standardbred horses lesions occurred more commonly in the hock. In 16 of the 21 horses, the contralateral joint was radiographed and 9 of these horses had bilateral lesions. Thorough...
Wilson DA, Foreman JH, Boero MJ, Didier PJ, Lerner DJ.A large granulosa cell tumor was believed to be responsible for causing obstruction and subsequent rupture of the small colon in a 10-year-old Quarter Horse mare. Two months earlier, a mass, tentatively diagnosed as granulosa cell tumor of the left ovary, had been identified by means of rectal palpation and ultrasonography. The mare was evaluated for clinical signs of acute, severe, abdominal pain, increased heart rate, cyanotic mucous membranes, clinical dehydration, with high PCV, leukopenia, and extreme abdominal distension. A large soft tissue mass and taut band that constricted the lumen ...
Gunson DE, Rooney JR.An 8-year-old gelding with a long-standing, streptococcal respiratory infection developed dyspnoea and colic. Laparotomy disclosed numerous, discrete, hemorrhagic, thick areas of necrosis throughout the intestinal tract. At postmortem examination similar lesions were seen in the laryngeal mucosa and in many skeletal muscles. Microscopically these lesions had massive necrosis and hemorrhage with a leucocytoclastic vasculitis in adjacent tissue. This condition resembled anaphylactoid purpura (Henoch-Schönlein disease) in man. Fungal infection was ruled out by special stains which failed to show...
Menzies-Gow NJ, Young NJ.Enterococcus faecium, a major cause of potentially life-threatening hospital-acquired human infections, can be resistant to several antimicrobials, such that streptogramin quinupristin-dalfopristin (Q/D) is one of the few antibiotics still effective. Consequently use of the streptogramin virginiamycin as an animal growth promoter was banned in the EU in 1999 as some believed this contributed to the emergence of Q/D resistant E. faecium. Virginiamycin is advocated for preventing equine pasture-associated laminitis, but its effect on equine faecal bacterial Q/D resistance has not been determined...
Green P, Tong JM.Although wood chewing by horses is recognised as a common vice, there are few reports of specific disease associated with the habit. Two cases of acute obstruction of the small intestine by solid aggregations of wood splinters are described in horses which were both habitual wood chewers. Details are presented of the clinical findings in these cases, including the surgical treatment of acute colic. Both horses returned to full working fitness. The authors review the syndrome of enterolithiasis in horses, and discuss the causes and significance of wood chewing as a stable vice.
Spyrou V, Papanastassopoulou M, Psychas V, Billinis Ch, Koumbati M, Vlemmas J, Koptopoulos G.There appears to be a lack of information concerning responses of mules to natural infection or experimental inoculation with equine infectious anemia virus (EIAV). In the present study EIAV was isolated from mules, for the first time, and its pathogenicity in naturally infected and experimentally inoculated animals was investigated. Two naturally infected (A and B) and three EIAV free mules (C, D and E) were used for this purpose. Mule A developed clinical signs, whereas mule B remained asymptomatic until the end of the study. Mules C and D were each inoculated with 10ml of blood from mule A ...
Bunton TE.Developmental defects are rarely reported in the horse. Severe craniofacial and central nervous system defects in an equine foetus are described and their possible causation and pathogenesis are suggested.
Clark ES, Morris DD, Allen D, Tyler DE.A yearling Hanoverian filly had intermittent colic for 6 weeks, chylous peritoneal effusion, and a firm mass palpable per rectum. Exploratory laparotomy revealed mesenteric lymphadenopathy, adhesion of the mesenteric root to the duodenum and jejunum, distention of the mesenteric veins and lymphatic vessels, and increased jejunal venous pressure. Lesions in the duodenum, jejunum, and colon included infiltration of lymphocytes and plasma cells in the lamina propria.
Gonzales-Viera O, Fritz H, Mete A.A 7-month-old female mixed breed foal with a 2-day history of recumbency and inability to open its mouth convulsed acutely and died and was submitted for necropsy examination. The foal was thin and large patches of haemorrhage were present throughout the peritoneal wall, the diaphragmatic surfaces and the retroperitoneum. Numerous nematode larvae were visible on the serosal surfaces and penetrated and embedded into the subserosa associated with the haemorrhages. The dorsal portion of the abdominal diaphragm had a partial tear and large numbers of nematodes were within the muscle fibres. Histol...
Lazary S, Gerber H, de Weck AL, Arnold P.A new, non-MHC linked alloantigenic membrane antigen on the equine lymphocytes is described. This antigen was characterized with alloantisera in the two-stage microcytotoxicity test and designated as ELy-1 antigen. The frequency of ELy-1 antigen positive animals in various populations is close to 50%. ELy-1 shows an autosomal, dominant inheritance. Since an allelic antigen (s) could not be demonstrated in family studies, it is assumed that only two alleles ELy-1+ and ELy-1- exist. The ELy-1 antigen in positive animals is expressed on both T and B lymphocytes but it is not present on erythrocyt...
Laus F, Rossi G, Paggi E, Bordicchia M, Fratini M, Tesei B.Tumors involving the oral cavity of the horse are uncommon. No cases of equine adenocarcinoma on the dorsum of the tongue have been reported in the literature. We report a case of adenocarcinoma located on the dorsum of the posterior one-third of the tongue in a 29-year-old gelding with severe dysphagia. Endoscopy revealed an epiglottis involvement, and histology was consistent with adenocarcinoma arising from minor salivary glands, which was associated with a severe fungal colonization of affected tissues. The goals of this report are to present an uncommon case of dorsum of the tongue-associ...
Divers TJ, George LW, George JW.Signs of acute hemolytic anemia developed in 4 adult horses from 2 Georgia farms 3 to 4 days after the ingestion of wilted leaves from cut red maple trees (Acer rubrum). Clinical findings included weakness, polypnea, tachycardia, depression, icterus, cyanosis, and brownish discoloration of the blood and urine. Blood changes included methemoglobinemia, free plasma hemoglobin, decreased pcv, and Heinz bodies in erythrocytes. These findings plus hemoglobinuria suggested intravascular hemolysis. Three of the 4 horses diet 5 to 7 days after ingestion of the leaves. Gross pathologic changes included...
Slocombe JO, McCraw BM, Pennock P, Ducharme NG, Baird JD.Twenty pony foals (reared worm free), 6.5 to 10 weeks of age, were inoculated with Strongylus vulgaris and allocated to 5 groups, each with 4 foals. One week after inoculation, 1 group of 4 foals was given oxfendazole (OFZ) at a dosage rate of 10 mg/kg of body weight, another group was given 2 such treatments 48 hours apart, and a 3rd group was given a placebo. All treatments were administered by stomach tube. Three weeks later, foals were euthanatized and necropsied in a test for efficacy against early 4th-stage larvae. Oxfendazole was 80% and 94.9% effective against early 4th-stage S vulgari...
Barr AC, Reagor JC.Horses poisoned by a plant may show a myriad of clinical signs. Awareness of the poisonous plants growing in a given area and those that are likely to appear in hay and their associated clinical signs can be instrumental in making diagnoses. More importantly, the information can be shared with clients to help prevent plant poisonings in horses.
