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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.
Mucinous hyperplasia in the kidney and ureter of a horse. A case of mucinous hyperplasia in the right renal pelvis and ureter is reported in a 23-year-old, male, Quarter horse. The affected right renal pelvis was markedly distended and filled with inspissated yellowish-green mucous material compressing the adjacent cortical and medullary parenchyma. Multiple, similar masses were present protruding from the right urethral mucosa. Histologically, the masses were characterized by a cystic glandular and papillary hyperplasia of the mucosa of the renal pelvis and ureter. This is believed to be the first reported case in an equine species.
Musculoskeletal disorders of the neonate. Musculoskeletal disorders in newborn foals are complex, multifactorial, and associated with prematurity, dysmaturity, and twinning. They include incomplete ossification of cuboidal bones, tendon laxity, congenital angular limb deformities, septic arthritis, osteomyelitis, and septicemia. Other deformities associated with nutrition, large size, and rapid growth include osteochondrosis, physitis, ruptured tendons, acquired flexural deformities, and postnatal angular limb deformities. Optimal management of the complexly interrelated musculoskeletal disorders of the neonate also is discussed.
Examination of the foal. Recent advances in veterinary diagnostics have improved our ability to diagnose and treat foal diseases. However, these advances do not replace the physical examination as the most valuable diagnostic aid available to the equine practitioner. The basic physical examination provides the majority of information needed to make a presumptive diagnosis, provide a direction for ancillary tests, and formulate a plan for emergency therapy if needed.
Right hepatic lobe atrophy in horses: 17 cases (1983-1993). The case records of 17 horses with atrophy of the right hepatic lobe were reviewed. Fifteen horses had signs of colic. Two horses had clinical problems that were unassociated with gastrointestinal tract disease. Ages ranged from 5 to 30 years (mean, 12.6 years) and there was no breed or sex predisposition. In clinically normal horses, the right hepatic lobe constitutes half of the total liver weight. The right hepatic lobe in the 17 horses in this study ranged from 11.0 to 38.3% of the total liver weight (mean, 27.8%). Findings on histologic examination of hepatic tissue from horses in the stu...
Peripartum asphyxia. The abysmal survival rates for the first barking foals described more than 60 years ago were probably due to the cumulative effects of asphyxia on multiple organ systems. Successful treatment of asphyxiated foals requires recognition of periparturient conditions associated with the syndrome and appreciation of the spectrum of clinicopathologic complications that can ensue.
Hepatic cirrhosis and hemochromatosis in three horses. Hemochromatosis, an iron storage disease, was diagnosed in 3 horses with hepatic cirrhosis. Each horse had bridging portal fibrosis and abundant iron deposits in the cytoplasm of hepatocytes. Serum concentrations of liver-derived enzymes and total bile acids were high. However, serum iron concentration was not high, and iron binding capacity was only 46% saturated in the 1 horse in which it was measured. However, the concentration of iron in the liver of this horse was 20 times the reference limits. Hemochromatosis is common in mynah birds and human beings. There are several types of this iron...
Geographical variation of seropositivity to Ehrlichia risticii (equine monocytic ehrlichiosis) of horses in New York state. A total of 2,579 serum samples from horses in New York state during 1985-1986 were examined for seropositivity to Ehrlichia risticii using the indirect fluorescent antibody technique. Cluster analysis statistical technique was used to group counties according to their estimated EME-disease rate (seropositive proportion of sampled horses). Counties were clustered into 4 groups of different EME-disease rates, representing high (86% seropositive), medium (66% seropositive), medium-low (47% seropositive) and low (6% seropositive) risk regions. The logistic regression statistical technique was used...
Investigation of association between alpha-1 proteinase inhibitor haplotype and endometritis in the thoroughbred mare. Failure to inhibit proteinases can lead to excessive tissue damage. The possibility that the severity of endometritis in Thoroughbred mares correlates with the haplotypes of plasma alpha 1-proteinase inhibitor (alpha 1-PI) expressed was investigated in two groups of mares. In mares with pyometritis before treatment, the frequency of the N haplotype, which is already high in the Thoroughbred population, was significantly increased when compared with that in a large published population. In mares with acute endometritis which persisted after treatment followed by sexual rest, the absence of S an...
Experimental transmission of eastern equine encephalitis virus by strains of Aedes albopictus and A. taeniorhynchus (Diptera: Culicidae). The vector competence of Aedes taeniorhynchus (Wiedemann) and four strains of Aedes albopictus (Skuse) was assessed for eastern equine encephalitis (EEE) virus isolated from Ae. albopictus collected in Polk County, Florida. Both species became infected with and transmitted EEE virus by bite after feeding on 1-d-old chicks that had been inoculated with EEE virus (viremia = 10(10.1) plaque-forming units [PFU] per ml of blood). However, when fed on an older chick with a lower viremia (viremia = 10(6.1) PFU per ml of blood), Ae. albopictus was significantly more susceptible to infection (90%, n = ...
Skeletal muscle mitochondrial myopathy as a cause of exercise intolerance in a horse. Although exertional myopathies are commonly recognized in horses, specific etiologies have not been identified. This is the first report in the horse of a deficiency of Complex I respiratory chain enzyme associated with profound exercise intolerance. Physical examination, routine blood tests, endoscopy, and ultrasonograms of the heart and iliac arteries were unremarkable. With slow, incremental exercise (speeds 1.5-7 m/s), the Arabian mare showed a marked lactic acidosis, increased mixed venous PVO2, and little change in oxygen consumption. Muscle biopsies contained large accumulations of mito...
Epidemiological observations on sarcoids in a population of donkeys (Equus asinus). An epidemiological study of equine sarcoid in a population of 4126 donkeys showed that the peak incidence of the disease was 15.2 cases per 100 animal-years and occurred in animals in their fourth year of life. The crude incidence of the disease was 0.6 cases per 100 animal-years. The disease occurred most frequently in younger, male animals during their first five years in the population. The lesions were observed most commonly in the paragenital region. Pre-entry quarantine procedures did not appear to play a significant role in the spread of the disease but there was an indication that clos...
Enhancement of EIAV replication and disease by immunization with a baculovirus-expressed recombinant envelope surface glycoprotein. The potential for antibody-dependent enhancement of replication of macrophage/monocyte tropic viruses has posed a significant problem in the development of vaccines for several animal and human viruses and has raised significant concern in the design of potential AIDS vaccines. Using the previously described equine infectious anemia virus/Shetland pony system as a model for HIV-1 vaccine development, we have evaluated the efficacy of a recombinant subunit vaccine containing a baculovirus-expressed envelope surface glycoprotein (gp90) of EIAV. The results of these trials demonstrate not only th...
A new phenogroup in the horse D system of red cell alloantigens found in the Caspian pony. A new D blood group phenogroup consisting of the specificities adeo was observed in a stallion family of Caspian ponies from Iran. An additional six undescribed genetic variants were seen in a total of 82 Iranian horses. This result suggests extensive new genetic variation may be present in domestic horses from geographic regions that have not yet received scientific attention.
Jean-François Bouley (Bouley jeune). Pioneer investigator in intermittent claudication. Reports of pathologic investigations as to the cause of intermittent claudication in horses were made in France in October, 1831, by veterinarian Jean-François Bouley. Obstructive clots in the femoral arteries were found to be responsible for the muscular changes causing limping. Bouley's work in the horse was used by Charcot in 1858 to understand the mechanism of claudication in the case of a soldier with gunshot wound in whom a traumatic aneurysm, clotting, and ischemia of the legs developed. This was not, however, the first medically reported case of human claudication from vascular occlus...
Echinococcus granulosus (Taeniidae) and autochthonous echinococcosis in a North American horse. We report the first documented case of autochthonous echinococcosis in a horse of North American origin. Three fully mature and viable unilocular hydatid cysts of Echinococcus granulosus (Batsch, 1786) were an incidental finding at necropsy in the liver of a 14-yr-old gelding thoroughbred that had been foaled in Virginia and raised in Maryland. Protoscolices were armed with 2 rows of 28-37 rostellar hooks; small hooks measured 23-30 microns; large hooks measured 26-33 microns. Morphologically, these were compatible with rostellar armature considered typical for the equine strain of E. granulos...
Effects of heparin, venous strangulation obstruction of the small intestine, and reperfusion of the small intestine on plasma diamine oxidase activity in horses. Diamine oxidase (DAO), an enzyme of small intestinal origin, is released from mucosal storage sites by IV administration of heparin, to yield the plasma postheparin DAO (PHD) curve. The PHD curve is diminished when mucosal surface area is lost, and baseline (without heparin) plasma DAO activity increases when mucosal storage sites are damaged. Plasma DAO activity was measured after 2 doses of heparin were administered IV in healthy, conscious horses. In anesthetized horses, the PHD curve was studied: during sham small intestinal surgery, and during venous strangulation obstruction (VSO) of the...
Characterization of A/eq-1 virus isolated during the equine influenza epidemic in India. The equine influenza virus, Ludhiana/5/87, isolated from the clinical material during the epidemic of equine influenza in India in 1987 was inhibited in haemagglutination-inhibition test by the antiserum against the prototype A/eq/Prague/1/56 (H7N7) virus and by post-epidemic horse sera. In haemagglutinin and neuraminidase analysis, the A/eq/Ludhiana/5/87 isolate appeared similar to the prototype A/eq/Prague/1/56 virus and was characterized as the H7N7 subtype.
[Detection of mycoplasmas in horses with respiratory diseases and their biochemical and serologic characterization]. Tracheal swabs were taken from 25 horses with respiratory diseases and investigated for mycoplasmas using three different media. Mycoplasmas could be isolated from 5 horses. The isolates were characterized by serological and biochemical methods. Four isolates could be identified as Mycoplasma equirhinis. The fifth isolate could not be typed. It did not react with antisera against mycoplasmas found in the respiratory tract of horses and its biochemical characteristics were different from the mycoplasmas described so far. It may represent a new species.
The molecular weight of therapeutic hyaluronan (sodium hyaluronate): how significant is it? Various molecular weight hyaluronic acid (HA) preparations have been injected into joints for the treatment of human and equine osteoarthritis. A therapeutic advantage has been claimed for commercial products with a molecular weight in the range found in normal synovial fluid (SF), compared to lower molecular weight products. But a correlation between molecular weight and efficacy is not borne out by an analysis of the available literature on clinical results. SF viscosity, HA concentration, HA molecular weight and rate of synthesis in joint disease. It is proposed that the beneficial effect o...
Adrenocortical carcinoma in a 12-year-old mare. A 12-year-old Dutch warmblood mare was examined because it had suffered colic intermittently for a few years and had lost weight in the previous two months. Palpation per rectum revealed a large firm mass in the left sublumbar region; the mass was classified post mortem as an adrenocortical carcinoma. The basal plasma cortisol concentration (at 10.00) of the mare was 94 nmol/litre, within the normal range. As in another case of adrenocortical neoplasm, a functional tumour could not be demonstrated. Only one of the 21 horses with a neoplasm of the pituitary-adrenocortical axis examined by the a...
[An outbreak of equine arteritis virus infection in a riding school]. A major part of the residing horses and ponies of a riding school in Noord-Holland became affected by a febrile disorder that included anorexia, depression, conjunctivitis, urticaria, edema of the legs and laborious locomotion. All remaining horses fell ill within one week. Based on the clinical symptoms the disorder was diagnosed as vasculitis. With serology the causative agent of the disorder appeared to be equine arteritis virus.
Prevalence and factors associated with development of laminitis in horses with duodenitis/proximal jejunitis: 33 cases (1985-1991). Medical records of 116 horses admitted to the Texas Veterinary Medical Center between Jan 1, 1984 and Dec 31, 1991 with duodenitis/proximal jejunitis (DPJ) were reviewed. The prevalence of laminitis was 28.4% (33/116; 95% confidence interval: 20.2 to 36.6%). The prevalence of DPJ and DPJ-associated laminitis did not appear to vary significantly by year during the study period. Anamnesis, physical examination, clinicopathologic data, and initial treatment recorded at the time of admission were reviewed to determine risk factors associated with development of laminitis associated with DPJ. A tre...
Serum hypoxanthine and xanthine concentrations in horses heterozygous for combined immunodeficiency. A group of diseases termed combined immunodeficiency (CID) results in a severe form of immunodeficiency. While CID in humans has two genetics bases, in Arabian it is inherited in an autosomal recessive manner. Kettler et al. (1989) determined that uric acid was significantly (p 0.05) between carrier and non-carrier horse's serum levels of hypoxanthine or xanthine. These data, combined with our previous ones suggest that an enzymatic lesion in the purine salvage pathway may occur at the urate oxidase step. ZUSAMMENFASSUNG: Serum-Hypoxanthin- und -Xanthin-Spiegel in Pferden mit Heterozygotie fÃ...
An analysis of 75 cases of intestinal obstruction caused by pedunculated lipomas. A retrospective study of 75 cases of pedunculated lipoma obstruction (PLO) of the intestine was conducted. Age, breed and sex distributions were compared to the non-PLO colic population. Horses in the PLO group were significantly older than in the non-PLO colic group (P < 0.001). A significant increase in risk of PLO was associated with geldings (O.R. 2.32) and with ponies (O.R. 3.75). Of the 75 PLO cases analysed, 69 were strangulating, 70 involved small intestine and 5 involved small colon. Cases of strangulation obstruction tended to have lipomas originating distant to the mesenteric border...
