Pathogenesis in horses refers to the biological mechanisms that lead to the development and progression of diseases within equine species. This process involves a complex interaction between the horse's immune system, genetic predispositions, environmental factors, and infectious agents such as bacteria, viruses, or parasites. Understanding pathogenesis is essential for identifying how diseases manifest and progress in horses, which can inform diagnostic and therapeutic strategies. Research in this area often focuses on specific diseases, examining factors such as pathogen entry, immune response, tissue damage, and recovery processes. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of pathogenesis in equine health.
Yager JA.The pathogenesis of Rhodococcus equi pneumonia in foals is reviewed. The main routes of infection are respiratory and alimentary. The latter is probably the chief route of exposure in all foals and probably leads to development of specific immunity. Susceptible foals, those whose maternal immunity wanes before generation of their own immune response, readily develop disease if exposed aerogenously to sufficient numbers of R. equi. Management and environmental circumstances have a major role to play in determining the magnitude of this challenge and, therefore, in the prevalence of the disease....
Keane DP, Little PB.Rabies, equine herpesvirus type I, and eastern and western encephalomyelitis viruses, known causes of equine neurological disease, are reviewed with emphasis on epidemiology, pathogenesis, clinical signs, and diagnosis.Several arboviruses known to be active in Canada and capable of producing neurological disease in humans (Powassan, St. Louis encephalitis, snowshoe hare, and Jamestown Canyon viruses) are discussed as potential causes of encephalomyelitis in horses.
Baker D, Kreeger J.An expansile, yellow, soft mass was observed in the free wall of the right ventricle of a 3-year-old, male, Morgan, horse at necropsy. The mass was composed of well differentiated adipocytes in solid sheets or infiltrating between muscle fibers with associated myofiber degeneration. The mass was interpreted to be an infiltrative lipoma of the heart.
Cahill JI, Goulden BE.Recent research on the muscular and nervous changes which occur in idiopathic equine laryngeal hemiplegia has indicated that many of the traditional concepts of the aetiology of this disease are erroneous. In light of the new knowledge gained, the various predispositions and possible causes of laryngeal hemiplegia are discussed, and it is suggested that the underlying mechanism of axonal damage in this neuropathy of horses may be related to abnormal energy metabolism in the axon.
Minnick PD, Brown CM, Braselton WE, Meerdink GL, Slanker MR.An aqueous extract of the heartwood of black walnut (Juglans nigra) was given via stomach tube to 10 horses. Eight developed Obel grade 3 or 4 laminitis within 12 hr. Limb edema and mild sedation were the only other clinical signs observed. One horse was euthanized due to severe signs. The other 7 recovered within 6 days. Gas chromatography/mass spectrometry of aqueous extracts of heartwood, bark and nuts of black walnut identified juglone in the bark and nuts, but not in the heartwood. It was concluded that the aqueous extract of heartwood is laminogenic to horses, but the active ingredient i...
Lloyd K, Hintz HF, Wheat JD, Schryver HF.Many cases of enteroliths were reported in the nineteenth century but the number greatly decreased in the early twentieth century. However, in recent years the number of cases in certain parts of the United States such as California has greatly increased. The reasons for the increase are obscure. The intake of nitrogen, magnesium and phosphorus (the primary components of enteroliths) from water and food is likely to be a factor. Arabians may be more likely to develop enteroliths than horses of other breeds. A nidus such as a small stone is needed because a nidus has been found in every enterol...
Hietala SK, Ardans AA.This study was undertaken to examine the neutrophil response to Corynebacterium (Rhodococcus) equi, and to assess the possibility of neutrophil immaturity or malfunction in predisposition to C. equi pneumonia in foals. Neutrophil phagocytosis of Corynebacterium (Rhodococcus) equi was studied in foals from birth to 6 months of age. Chemiluminescence (CL) and bactericidal assays were used to assay the phagocytic response of peripheral blood neutrophils to C. equi in vitro. Results of in vitro bactericidal and CL assays indicate that foal neutrophils are able to ingest and kill C. equi, however a...
Firth EC.The site of occurrence of 490 bone sequestra in horses and cattle was investigated. Most sequestra occurred in the proximal half of the third metatarsal bone and the third metacarpal bone. The most common clinical features included swelling, presence of a draining tract, impaired function and delayed wound healing. These diagnostic features, and the preferred time to confirm the diagnosis by radiological examination are discussed. The surgical treatment is relatively simple and the prognosis favourable in most cases. It is suggested that soft tissue injury and the presence of infection are of ...
Brownie CF, Cullen J.An isolate of Fusarium moniliforme (M-1225 Cairo #1) was cultured on autoclaved corn and fed daily to 5 ponies at a rate of 2.5 g corn/kg body wt. One pony developed clinical signs of toxicity after 28 days and was sacrificed. The remaining 4 ponies developed no clinical sign of toxicity even after extended exposure. Hematology, serum chemistry, cerebrospinal fluid (CSF), and liver and brain pathology were evaluated as possible diagnostic and prognostic indicators. Hematology was not informative. Aspartate aminotransferase and gamma-glutamyltranspeptidase activities were elevated only in the c...
von Fellenberg R.The importance of proteases and protease inhibitors for the pathogenesis of pulmonary emphysema and chronic bronchitis of the horse is described. Endogenous elastases from neutrophil granulocytes and macrophages, which probably provoke emphysema in the human being, are not relevant in horse emphysema. Exogenous elastases from different species of streptomyces may be responsible for emphysema generation in this species. Part of the exogenous elastases are poorly or not inhibited at all by the equine blood protease inhibitors especially by alpha 1-protease inhibitors. A disorder similar to genet...
Sentsui H, Kono Y.Horse erythrocytes treated with equine infectious anemia virus hemagglutinin were found to be lysed after incubation with fresh horse serum at 37 degrees C. Fresh guinea pig serum induced more efficient hemolysis than horse serum. Direct immunofluorescence test revealed the adsorption of complement factors on the surface of the erythrocytes. Calcium and magnesium ions were necessary for the hemolysis to take place. Antibody against equine infectious anemia virus enhanced the virus-induced complement-mediated hemolysis. These observations indicated that the classical pathway of complement activ...
Clyne MJ.Proteoglycan degradation is central to the development of degenerative joint disease. Proteoglycans may be degraded by lysosomal enzymes from chondrocytes, synoviocytes or leucocytes. Collagen and matrix degradation occurs either by direct damage or due to degrading enzymes released into synovial fluid. Once the pathological sequence has begun it continues in a cyclic manner unless arrested by the ability of chondrocytes to synthesise sufficient matrix components. Treatment should ideally be directed to this end.
Bouchey D, Evermann J, Jacob RJ.Examination of six field isolates of equine herpesvirus 3, the causative agent of equine coital exanthema, indicates that all were temperature sensitive (ts) at the body temperature, 39 degrees C, of their host (Equine asinus and callabus) when grown in cell culture. The isolates were characterized by fingerprint analysis with the restriction endonucleases XbaI, EcoRI, BamHI and Hind III to establish possible epidemiologic relatedness. Three of the six isolates may be considered related. Variation in the mobility of the BamHI-A and Hind III-K fragments indicates that a small plaque isolate may...
Ziemer EL, Whitlock RH, Palmer JE, Spencer PA.The clinical and hematologic variables of 10 ponies with experimentally induced equine ehrlichial colitis (EEC; syn: Potomac horse fever) were studied for a 30-day period (6 ponies) or until death (4 ponies). The earliest clinical sign indicative of EEC was fever (rectal temperature exceeding 39 C). All ponies became depressed (CNS) at various times during the disease, and 90% of the ponies developed diarrhea between 9 and 15 days after infection was induced. The most significant hematologic change was an increase in plasma protein concentration after the onset of fever (P less than 0.05). The...
Vandeplassche MM.From a total of 601 severe dystocias in mares, 408 (68%) of the fetuses were in anterior, 95 (16%) in posterior and 98 (16%) in transverse presentation, compared with 99%, 1% and 0.1% respectively for spontaneous parturitions. From the cases with anterior presentation, 151 (37%) showed reflected heads and necks. From the cases with posterior presentation, 47 (50%) presented hip flexions, 25% had hock flexions, and 25% had stretched hind legs, 45 (47%) of the fetuses were in lateral or ventral position, and 28 (30%) of the fetuses were malformed (mainly torticollis and head scoliosis). All 98 c...
Sentsui H, Kono Y.Horse erythrocytes treated with equine infectious anemia virus hemagglutinin were phagocytized by cultivated horse leukocytes (mainly macrophage-like cells and partly polymorphonuclear cells) after incubation with fresh horse serum but not with inactivated horse serum. The phagocytosis began as soon as the erythrocytes were added to the leukocyte cultures, and the majority of the reaction proceeded within 30 minutes. Addition of antiserum showed a slightly suppressing but no enhancing effect on the phagocytosis. Phagocytosis seemed to be caused by the recognition of the third complement compon...
Liu IK, Cheung AT, Walsh EM, Ayin S.The functional competence of uterine-derived polymorphonuclear neutrophils (PMNs) from 28 mares was measured for migration responsiveness by use of a chamber (filter) assay. Uterine infection was induced with Streptococcus zooepidemicus in mares considered resistant to chronic uterine infection (Grade I). In sequential analysis of uterine flushings obtained from these mares 5, 12, 15, 20, and 25 h after infection was induced, PMNs showed an initial rise at 12 h (from 5), then a general decline in migration response and in concentration of cells per ml from 12 through 25 h post-inoculation. In ...
Buergelt CD, Hines SA, Cantor G, Stirk A, Wilson JH.Proliferative and fibrosing interstitial lung disease was diagnosed in 20 horses submitted for necropsy between 1982 and 1985. Most of the horses were foals ranging from 3 days to 6 months in age. Six adult horses were affected. The macroscopic and microscopic characteristics of the lesions consisted of proliferative interstitial pneumonia and were similar to those of atypical interstitial pneumonia of ruminants. Based on morphologic features of the lesions, a toxic etiology is suspected for the induction of this naturally acquired primary equine lung disorder, but could not be specifically di...
Yaniv A, Dahlberg J, Gazit A, Sherman L, Chiu IM, Tronick SR, Aaronson SA.Molecular clones of the integrated form of the genome of equine infectious anemia virus (EIAV), the etiologic agent of a naturally occurring, worldwide disease of horses, were obtained. The restriction map of a full-length genome was determined. Additional evidence for the close evolutionary relationship between EIAV and a prototype lentivirus (caprine arthritis encephalitis virus) was acquired by Southern blotting and immunological analyses. An interspecies radioimmunoassay was developed in which EIAV and ovine and caprine lentiviruses could be detected equally well. These studies make availa...
Hillidge CJ.Corynebacterium (Rhodococcus) equi is becoming increasingly significant as a cause of bronchopneumonia and lung abscessation in foals. The organism can survive within macrophages and may thus escape normal pulmonary defence mechanisms, particularly in immunocompromised animals. The disease has hitherto been associated with mortality rates as high as 80 per cent, partly as a result of inappropriate therapy. The selection of lipid-soluble antibiotics capable of intracellular penetration is critical for the successful treatment of C equi lung abscesses. A combination of two such antibiotics, eryt...
Grünig G, Von Fellenberg R, Maier R, Corboz L.Seventeen out of 21 horses had pulmonary microbial organisms which reached considerable numbers in seven cases. Elastase-producing microorganisms from the environment (Streptomyces species and to a lesser extent Bacillus species) constituted 22 per cent to 99 per cent (mean 79 per cent) of the total growth. There was a considerable number of microorganisms with in vitro-produced elastases which were not or only slightly affected by horse serum. There was no correlation between numbers of organisms and pulmonary histopathological findings thus the significance of these microorganisms in the pat...
Klei TR.This article briefly reviews new information on trichostrongylid stomach worms, spirurid stomach worms, tapeworms, threadworms, pinworms, intestinal protozoa, lungworms, eye worms, and numerous other aberrant parasites as it relates to prevalence, pathogenesis of diseases, and treatments.
Drudge JH, Lyons ET.This review cites recent advances in the knowledge pertaining to infections of large strongyles in equids. Emphasis is placed on Strongylus vulgaris and attention is focused on pathogenesis of clinical manifestations of infections and treatment and control, including chemotherapy of migrating larvae and drug resistance.
Weiss M, Horzinek MC.In equine dermis cells infected with Berne virus particles were first detected 10 h after infection. Virions were encountered in all parts of the Golgi system and, infrequently, in the rough endoplasmic reticulum. A unique form of budding of preassembled rigid tubular nucleocapsids was demonstrated. Masses of tubular nucleocapsids of a lesser diameter and electron density were prominent in the cytoplasm and the nucleus of infected cells. Within the Golgi system and cytoplasmic cisternae virions appeared as straight or slightly curved rods. Extremely long, aberrant virions (250 nm) were occasio...
Winder NC, von Fellenberg R.Pulmonary parenchymal tissues from 6 healthy horses and from 9 horses with chronic bronchiolitis were evaluated by use of an indirect immunofluorescent technique. In horses of both groups, the diffuse interstitial immunofluorescence was most intense for immunoglobulin (Ig)G, moderate for IgA, and minimal for IgM. Intensity of fluorescence was increased markedly in diseased lungs exposed to anti-IgA and anti-IgG. Around small bronchi and large bronchioles of healthy horses, IgA-containing cells generally were more numerous than were IgG-Fc fragment (Fc)-containing cells; in small bronchioles, h...
Adeyefa CA.The clinicopathological features and treatment of cases of dermatomycotic infections in horses are reported. Organisms isolated from these cases include Trichophyton mentagrophyte, T. equinum and Micosporum equinum. The Veterinary, medical and economic importance of the disease is discussed.
Ambrose NC, Mijinyawa MS, Hermoso de Mendoza J.Dermatophilus congolensis is a filamentous branching actinomycete that causes dermatophilosis, an exudative dermatitis in ruminants. The pathogenesis of this disease is poorly understood and virulence factors of D. congolensis have not been characterised. Culture filtrate (CF) of 14 D. congolensis isolates from cattle, 15 from sheep and four from horses were examined for proteolytic activity using azocasein as a non-specific substrate. The isolates were from a variety of geographical locations. All the isolates examined produced extracellular proteolytic activity. CF from 24 and 48 h cultures ...
de Laat MA, Spence RJ, Sillence MN, Pollitt CC.Equine laminitis is a disease of the digital epidermal lamellae typified by epidermal cell proliferation and structural collapse. Most commonly the disease is caused by hyperinsulinemia, although the pathogenesis is incompletely understood. Insulin can activate the epidermal growth factor (EGF) system in other species and the present study tested the hypothesis that upregulation of EGF receptor (EGFR) signalling is a key factor in laminitis pathophysiology. First, we examined lamellar tissue from healthy Standardbred horses and those with induced hyperinsulinemia and laminitis for EGFR distrib...
Cook CP, Scott DW, Erb HN, Miller WH.A retrospective study using light microscopy was performed to assess the prevalence of surface and follicular bacteria and fungi in skin biopsy specimens from 247 horses with inflammatory dermatoses and from 27 horses with healthy skin. Cocci were found on the surface of specimens from 23% (95% confidence interval 18%, 29%) and 7% (95% confidence interval, 0%, 19%), respectively, of horses with skin disease and horses with healthy skin. Of the nine dermatoses with at least 10 cases in our series of horses, bacterial folliculitis had a higher prevalence of surface bacteria (57%; 95% confidence ...
Lopes MA, Salter CE, Vandenplas ML, Berghaus R, Hurley DJ, Moore JN.To investigate the effect of ex vivo exposure to lipopolysaccharide (LPS) on the expression of inflammatory genes in leukocytes from horses with gastrointestinal (Gl) disease and determine whether the pattern or magnitude of the response to LPS correlated with the type of disease and outcome. Methods: 49 horses with Gl disease and 10 healthy horses Methods: Leukocytes were isolated from blood samples and submitted to 3 protocols: immediate freezing, freezing after 4-hour incubation in medium, and freezing after 4-hour incubation in medium containing LPS. Expression of 14 genes associated with ...
Janicke H, Taylor PM, Bryant CE.Equine endotoxaemia is an important cause of morbidity and mortality in horses caused by the interaction of bacterial lipopolysaccharide (LPS) with cells such as macrophages and vascular smooth muscle. In this study we isolated equine vascular smooth muscle from a variety of vessels and stimulated it with LPS and human interferon (hIFN)-gamma. Using reverse transcriptase polymerase chain reaction (rt-PCR) and Western blot analysis we show that cyclooxygenase-2 (COX-2) is readily expressed in equine vascular smooth muscle. Vascular smooth muscle cells produced prostaglandin E2 in response to LP...
Rickards KJ, Page CP, Hamblin AS, Goode NT, Cunningham FM.Lymphocytes play an important role in allergic inflammation and have been implicated in the pathogenesis of equine allergic skin and respiratory disease. Targeting intracellular signalling pathways in human lymphocytes has demonstrated a role for both phosphodiesterase and protein kinase C in cell activation. The aim of this study was to measure total cyclic nucleotide hydrolysing phosphodiesterase activity and to identify the phosphodiesterase and protein kinase C isoenzymes present in equine lymphocytes. The functional significance of these isoenzymes was then investigated by examining their...
Sellon DC, Russell KE, Monroe VL, Walker KM.Seven ponies were infected with the virulent wild-type Wyoming strain of equine infectious anaemia virus (EIAV). Infection status was monitored by serum reverse transcriptase activity, rectal temperature, and complete blood count. Preinfection serum and serum obtained during the initial febrile episode following infection were assayed for interleukin 6 (IL-6) activity. Postinfection IL-6 activity was significantly increased as compared to preinfection values. The magnitude of increase in IL-6 was positively correlated with reverse transcriptase activity (an indirect measure of viraemia) but wa...
Wong SS, Ngan AH, Riggs CM, Teng JL, Choi GK, Poon RW, Hui JJ, Low FJ, Luk A, Yuen KY.The newly described brittle tail syndrome causes weakening and breakage of the tail hair of horses. Extensive mycological and molecular studies showed that a novel fungus Equicapillimyces hongkongensis gen. nov., sp. nov. is the most likely cause of this syndrome. It is a septate branching hyaline mould which grows optimally at 30°C, requires nicotinic acid but is inhibited by cycloheximide, and specifically infects horse hair. Hyphae fill the core of infected hair shafts with short-necked structures resembling ascomata containing banana-shaped septate ascospore-like structures perforating th...
Anthauer K, Mülling C, Budras KD.This study aimed to carry out a comprehensive morphological examination of the structure and ultrastructure of the membrane-coating granules (MCG) and membrane-coating material (MCM) common to all hoof segments as well as segment-specific features in the MCG and MCM regarding their synthesis, structure and biochemical composition. Tissue samples from the hooves of the left front and right hind limb of 20 adult riding horses were used. Samples were preserved and embedded for histological routine methods as well as for histochemical techniques and tracer techniques for light and electron microsc...
Liu Q, Yu YY, Wang HY.Increasing evidence suggests that DNA methylation has key roles in the replication of retroviruses, including lentiviruses, and pathogenesis of diseases. However, the precise characteristics of CpG islands are not known for many retroviruses. In this study, we compared the distribution of CpG islands among strains of equine infectious anemia virus (EIAV), a lentivirus in the family Retroviridae and a model for HIV research. We identified CpG islands in 32 full-length EIAV genomic sequences obtained from the GenBank database using MethPrimer. Only one CpG island, from 100 to 120 bp, was identi...
Costa LR, Santos IK, Issel CJ, Montelaro RC.Cardinal features of equine infectious anemia (EIA) include fever, hemolytic anemia and thrombocytopenia during the acute phase of the disease, and cachexia and anemia seen during the chronic phase. These signs are thought to result from the release of inflammatory cytokines such as TNF-alpha. In order to determine if TNF-alpha has a role in the pathogenesis of acute EIA and vaccine-induced disease enhancement, we measured plasma concentrations of TNF-alpha in ponies immunized with virus enriched major core protein-p26 and/or experimentally infected with EIAV. Naturally infected inapparent EIA...
Clyne MJ.Proteoglycan degradation is central to the development of degenerative joint disease. Proteoglycans may be degraded by lysosomal enzymes from chondrocytes, synoviocytes or leucocytes. Collagen and matrix degradation occurs either by direct damage or due to degrading enzymes released into synovial fluid. Once the pathological sequence has begun it continues in a cyclic manner unless arrested by the ability of chondrocytes to synthesise sufficient matrix components. Treatment should ideally be directed to this end.
Apprich V, Spergser J, Rosengarten R, Stanek C.The effects of two dermatophytes (Microsporum gypseum and Trichophyton mentagrophytes) and four moulds (Scopulariopsis brevicaulis, Alternaria alternata, Geotrichum candidum and Penicillium spp.) on living keratinocyte cultures were examined in vitro using primary human keratinocytes. Rates of apoptosis of infected cells were determined using a colorimetric TUNEL system which detects the characteristic nuclear DNA fragmentation of apoptotic cells. The cytotoxicity of the individual fungi was tested by quantitatively measuring cytosolic enzyme lactate dehydrogenase, released upon cell lysis, in...
Timoney JF.An R antigen of the group C streptococcus S. equi that cross reacts with a similar antigen of S. zooepidemicus has been identified and characterized. It is acid, heat and trypsin resistant, but pepsin sensitive and has an isoelectric point of 4.8. The amino acids in highest concentration are glutamic, aspartic, alanine, leucine, and valine. Bacterial components released in a French Press contain large amounts of R antigen, which is present also in culture supernatants and acid extracts. It has a molecular weight of about 82,000. Trypsin extraction of cells yields molecules of predominantly 56,...
Sanclemente JL, Rivera-Velez SM, Horohov DW, Dasgupta N, Sanz MG.Foals that develop pulmonary ultrasonographic lesions on Rhodococcus equi (R. equi) endemic farms are treated with antibiotics because those at risk of developing clinical pneumonia (~20%) cannot be recognised early. Candidate biomarkers identified using metabolomics may aid targeted treatment strategies against R. equi. Objective: (1) To describe how foal ageing affects their plasma metabolome (birth to 8 weeks) and (2) to establish the effects that experimental infection with Rhodococcus equi (R. equi) has on foal metabolome. Methods: Experimental study. Methods: Nine healthy newborn foals...
Popović N, Djuricić B, Valcić M.A study of literature concerning Lyme borreliosis related to animals was done. In the research work the epidemiology, pathogenesis, diagnosis and treatment of horses, cattle and dogs affected with Lyme borreliosis have been discussed. The clinical signs of Lyme borreliosis in horses are: chronic weight loss, sporadic lameness, laminitis, low grade fever, swollen joints, muscle tenderness and anterior uvetitis. In addition to these clinical sings, neurological sings such as depression, behavioral changes, dysphagia and encephalitis can be seen in chronic cases. Cattle affected with acute Lyme b...
Grünig G, Von Fellenberg R, Maier R, Corboz L.Seventeen out of 21 horses had pulmonary microbial organisms which reached considerable numbers in seven cases. Elastase-producing microorganisms from the environment (Streptomyces species and to a lesser extent Bacillus species) constituted 22 per cent to 99 per cent (mean 79 per cent) of the total growth. There was a considerable number of microorganisms with in vitro-produced elastases which were not or only slightly affected by horse serum. There was no correlation between numbers of organisms and pulmonary histopathological findings thus the significance of these microorganisms in the pat...
Newton-Clarke MJ, Divers TJ, Valentine BA.A study was conducted over a 12 month period to assess the accuracy of the 'slap test' in the diagnosis of laryngeal adductor myopathy. The thoraco-laryngeal reflexes of 15 horses with no clinical signs of idiopathic laryngeal hemiplegia (ILH) were recorded using a video-endoscope. These 'slap test' responses were examined independently by 3 assessors. The horses were subsequently subjected to euthanasia and samples taken from the cricoarytenoideus lateralis (CAL) muscles for histopathological examination and assessment of denervation atrophy. Despite normal adductory responses, moderate to se...
Steward KF, Harrison T, Robinson C, Slater J, Maskell DJ, Harris SR, Holden MTG, Waller AS.Opportunistic pathogens must adapt to and survive in a wide range of complex ecosystems. Streptococcus zooepidemicus is an opportunistic pathogen of horses and many other animals, including humans. The assembly of different surface architecture phenotypes from one genotype is likely to be crucial to the successful exploitation of such an opportunistic lifestyle. Construction of a series of mutants revealed that a serine recombinase, PinR, inverts 114 bp of the promoter of SZO_08560, which is bordered by GTAGACTTTA and TAAAGTCTAC inverted repeats. Inversion acts as a switch, controlling the tra...
Tennent-Brown BS, Morrice AV, Reed S.Neonatal encephalopathy is the most common neurologic condition affecting newborn foals and shares similarities with perinatal asphyxia syndrome of human infants. In many cases of neonatal encephalopathy there is no obvious episode of acute or chronic hypoxia and other mechanisms likely play a role in the pathogenesis. Increased concentrations of neuroactive progestagens are found in affected foals; whether these molecules are protective, as has been suggested, or play a role in the pathogenesis is unknown. Neurologic diseases other than neonatal encephalopathy affect foals occasionally and sh...
Winder NC, von Fellenberg R.Pulmonary parenchymal tissues from 6 healthy horses and from 9 horses with chronic bronchiolitis were evaluated by use of an indirect immunofluorescent technique. In horses of both groups, the diffuse interstitial immunofluorescence was most intense for immunoglobulin (Ig)G, moderate for IgA, and minimal for IgM. Intensity of fluorescence was increased markedly in diseased lungs exposed to anti-IgA and anti-IgG. Around small bronchi and large bronchioles of healthy horses, IgA-containing cells generally were more numerous than were IgG-Fc fragment (Fc)-containing cells; in small bronchioles, h...
Miszczak F, Pronost S, Vabret A.Equine arteritis virus (EAV) is the causative agent of equine viral arteritis, a disease observed only in equids. EAV is the prototype of the family Arteriviridæ within the order Nidovirales. EAV is an enveloped, positive-sense, single-stranded RNA virus with a considerable variation in the genome as observed in other RNA viruses. During natural infections, EAV may cause abortion and persistent subclinical infections in stallions which can shed the virus in the semen for years, or even lifetime. Chronically infected stallions represent the natural reservoir of the virus. They ensure the persi...
Geburek F, Deegen E, Hewicker-Trautwein M, Ohnesorge B.Verrucous pastern dermatitis is a chronic hyperplastic dermatopathy of the feet of horses which is characterized by a greasy, odorous coating of the skin and, in advanced stages, by clearly demarcated calluses and wart-like proliferations. The disease occurs almost exclusively in cold-blooded and other heavy horses, with certain breeds affected most frequently. It is considered a distinct disease entity within the framework of pastern dermatitis syndrome. There is no consensus in the literature about relationship of the disease to the sex and age of the horse. Horses with a high cannon circumf...
Leathwick DM, Sauermann CW, Donecker JM, Nielsen MK.Literature documenting the growth and development of Parascaris spp. infections was used to develop a model describing worm dynamics in the young horse. The model incorporates four main variables; the rate at which larvae migrate through host tissues to return to the small intestine, the proportion of migrating larvae which succeed in returning to the small intestine, the rate of growth in size of maturing and adult worms and the survival rate of maturing and adult worms. In addition, the number of eggs laid each day by adult female worms is calculated as a function of worm size (length) and i...
Oikawa M, Masawa N, Yoshikawa H.To test the hypothesis that mesenteric arterionecrosis (MA) occurs in horses with naturally occurring endotoxaemia (ET) and in those with experimentally induced ET, the mesentery and gastrointestinal tract of 21 Thoroughbred racehorses (15 with spontaneous colic suspected to be due to ET, and six with experimentally induced ET) were examined. MA, which occurred in 13 of the 15 horses with spontaneous colic and in all six of the cases of experimental ET, was morphologically similar in the two groups of animals. This suggested that the pathogenesis of the MA was fundamentally similar in the two ...
Clarke LL, Garner HE, Hatfield D.Acute laminitis-hypertension was produced by carbohydrate overloading of the gastrointestinal tract in 12 adult horses. Obel grade 3 (OG3) lameness developed 40 hours (+/- 3.5, SEM) after overfeeding. At OG3 lameness, mean plasma volume was significantly decreased (P less than 0.005) when compared with base-line values. Before OG3 lameness, transient decreases in serum phosphorus and calcium were recorded. Mild hyponatremia also developed before OG3 lameness and persisted. After establishment of OG3 lameness, persistent hypokalemia and increased plasma aldosterone concentration occurred coinci...
Zhu ZY, Lin YZ, Wang YH, Zhao LP, Zhu YM, Zhou JH.To disclose the potential roles of humoral immune response in the EIAV vaccine-induced protective immunity. In this study, major parameters of humoral immunity be compared between horses inoculated with the EIAV vaccine strain and the pathogenic virulent strain. Methods: Experimental horses were randomly assigned into the group inoculated with the vaccine strain EIAV(DLV); (the vaccinated group) and the group inoculated with sub-morbigenous dose of virulent strain EIAV(Liao); (the inapparent infection group). Humoral immunity parameters, including binding endpoint titer and avidity index of an...
Alber MT, Brown MP, Merritt KA, Trumble TN.Palmar osteochondral disease (POD) is an overload arthrosis that commonly affects fetlock joints of racing Thoroughbreds (TB) but the aetiopathogenesis of the disease has not been well defined. Objective: The aim of this study was to compare India ink perfusion in the dorsal and palmar condyles of the third metacarpal bone (McIII) in both passively flexed and maximally extended fetlock joints from paired equine cadaver limbs. Methods: Descriptive cadaver study comparing perfusion of condyles of McIII in paired cadaver limbs in flexion (control group) and maximal extension (intervention group)....
Hallauer C.1. Equine infectious anemia (EIA) is an immunologically-medicated disease. Immune complexes formed in blood and tissues are responsible for most symptoms and lesions (anemia, splenomegaly, lymphadenopathy, glomerulonephritis, etc.). In addition, a state of cellular hypersensitivity of the delayed type is involved in the pathogenesis. 2. Periodical attacks of pyrexia and clinical illness in the presence of immunity are caused by antigenically-modified variants of virus. By means of immunosuppressive treatments similar relapses of fever associated with the appearance of new virus variants can be...
Oikawa M, Ueno T, Yoshikawa H.This report describes the mesenteric arteriolar lesions in a Thoroughbred racehorse with endotoxaemia due to colic. The vascular lesions consisted of a striking loss of medial smooth muscle cells, associated with granular cell debris derived from necrosed muscle cells, plasma insudation, erythrocyte infiltration and the deposition of a fibrinoid substance (fibrinoid degeneration) in the entire arterial wall, possibly produced by the infiltration of blood components through endothelial cell junctions into the arterial wall. The morphology of the mesenteric arteriolar necrosis closely resembled ...
