Topic:Pathogenesis
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.
Effects of road transport on indices of stress in horses. Stress associated with road transport is believed to be a significant contributor to the pathogenesis of post transport respiratory disease in horses. To determine the effects of road transport on pulmonary function, pulmonary aerosol clearance rates were measured in 4 horses 24 h before, and immediately after, 24 h of road transport by delivering aerosolised 99mtechnetium-labelled diethylenetriaminepentacetate (99mTc-DTPA) to the lungs and monitoring its washout. Each horse was transported twice, once while the trailer was equipped with a leaf-spring suspension and bias-ply tyres (trailer's o...
Phorbol ester stimulation of equine macrophage cultures alters expression of equine infectious anemia virus. Equine infectious anemia virus (EIAV) is a lentivirus that replicates predominantly in mature tissue macrophages. Viral expression is strongly influenced by the state of differentiation of the host cell. While blood monocytes can be infected, viral transcription is limited until the cell differentiates into a mature macrophage. Activation of mature macrophages infected with EIAV might also alter viral expression, presumably through binding of cellular transcription factors to viral nucleic acid sequences within the long terminal repeat (LTR). Using DNA amplification techniques, we compared LTR...
Experimental contact of bighorn sheep (Ovis canadensis) with horses and cattle, and comparison of neutrophil sensitivity to Pasteurella haemolytica cytotoxins. Peripheral blood neutrophils from horses, cattle, and Rocky Mountain bighorn sheep (Ovis canadensis canadensis) were evaluated for susceptibility to cytotoxin-dependent lysis of different biotypes and serotypes of Pasteurella haemolytica of domestic sheep, cattle, bighorn sheep, or mountain goat (Oreamnos americana) origin utilizing a cytotoxicity assay which measures the degree of bacteria cytotoxin-killing of neutrophils. All isolates of P. haemolytica (biotypes A and T) were noncytotoxic to horse neutrophils. Thirteen of 18 R haemolytica biotype A isolates were cytotoxic (> 50% neutrophi...
Effects of ozone and airway inflammation on glutathione status and iron homeostasis in the lungs of horses. To investigate the effects of ozone and airway inflammation on indices of oxidant injury in horses. Methods: 5 clinically normal horses and 25 horses referred for poor performance. Methods: Blood, tracheal wash, and bronchoalveolar lavage fluid samples were collected before and after ozone exposure (n = 5) or from clinical cases (n = 25), and were analyzed for reduced glutathione (GSH), glutathione disulfide (GSSG), and free and total iron (Fe) values. A scoring system (0 to 5) was used to assess airway inflammation on the basis of clinical signs and cytologic analysis of the tracheal wash and...
Effects of fusarium moniliforme isolates on tissue and serum sphingolipid concentrations in horses. Disruption in sphingolipid (SL) metabolism is a biomarker of exposure to fumonisins. The role of altered SL metabolism in the pathogenesis of fumonisin toxicoses is not understood. A 27-d feeding trial in horses compared the toxic effects of 3 strains of Fusarium moniliforme: RRC 415, cultured from corn in MS; AU 2/3, cultured from feed associated with clinical signs of duodenitis-proximal jejunitis (DPJ) in horses in AL; and MRC 826, cultured from corn in South Africa and shown to cause equine leukoencephalomalacia (ELEM). These were cultured on corn and diluted with clean corn and grain mixe...
Comparison of the deduced matrix and fusion protein sequences of equine morbillivirus with cognate genes of the Paramyxoviridae. The nucleotide sequence of the matrix protein of equine morbillivirus (EMV) was determined to be 1062 nucleotides and coded for a deduced protein of M(r) 40148 having a net charge of + 19 at neutral pH. The matrix protein gene was separated from the P and F genes by intercistronic regions of 546 and 469 nucleotides, respectively. The nucleotide sequence which coded for the F protein was 1641 nucleotides and coded for a deduced protein of 546 amino acids having an M(r) of 60,447 and a charge + 4 at neutral pH. Partial sequence information was also determined for the P/V proteins. M, P and F pro...
Genomic quasispecies associated with the initiation of infection and disease in ponies experimentally infected with equine infectious anemia virus. Equine infectious anemia virus (EIAV) provides a uniquely dynamic system in which to study the mechanism and role of genomic variation in lentiviral persistence and pathogenesis. We have used a Shetland pony model of infection to investigate the association of specific long terminal repeat (LTR) and env gene genomic sequences with the initiation of infection and the onset of disease. We analyzed viral RNA isolated from a pathogenic stock of virus (EIAV PV) and from plasma taken during the first disease episode from two ponies infected with EIAV PV. Overall sequence variation within gp90 was lo...
Elevation of serum G-CSF level in horses with transportation-induced fever. Levels of granulocyte-colony stimulating factor (G-CSF) in the blood of horses were measured before and after a long-distance transportation to clarify the pathogenesis of transportation-induced fever. The serum G-CSF level was measured by its ability to stimulate growth in a mouse myeloblastic cell line, NFS-60. Of 26 horses transported for a long distance, 9 had fever more than 39.0 degrees C during or after transportation. After transportation, the serum G-CSF level significantly increased in horses with transportation-induced fever but not in those without fever, and the serum G-CSF level ...
Inhibition of the protease activity in tracheobronchial aspirates of horses with chronic obstructive pulmonary disease. To clarify the role of proteolytic enzymes in the pathogenesis of chronic obstructive pulmonary disease (COPD) in horses, and to investigate new possibilities for treatment of this disease by interfering in the proteolytic process. Methods: Effect of antiproteolytic activity of selected protease inhibitors on tracheal aspirates was studied in vitro, and the inhibition profiles were compared with those of purified proteases. Methods: Respiratory tract secretions with antiproteolytic activity from 9 horses with COPD. Methods: Caseinolytic agar-diffusion assay. Results: The protease-inhibition pr...
Histopathological and immunofluorescent studies on transplacental infection in experimentally induced abortion by equine arteritis virus. Five pregnant mares, at between 6 and 8 months gestation, were experimentally infected with the Bucyrus strain of equine arteritis virus (EAV). Of the five mares, four aborted and one died. The pathogenesis of the abortions was studied, using histopathologic techniques, tissue immunofluorescence and virus isolation. Common microscopic lesions in the maternal reproductive organs indicated myometritis with a degeneration of the myocytes and an infiltration of the mononuclear cells. Epithelial cells of the endometrial gland showed sporadic degeneration. Lesions in the fetal tissue included an atr...
Detection of eastern equine encephalomyelitis virus RNA in formalin-fixed, paraffin-embedded tissues using DNA in situ hybridization. Eastern equine encephalomyelitis (F.EE) virus was detected in infected formalin-fixed horse and emu tissues and in infected chicken embryo fibroblasts. Results of in situ hybridization using a digoxigenin-labeled 40-base DNA probe complementary to a conserved region of the EEE virus RNA compared favorably with results of both virus isolation and serum neutralization tests. This technique may be useful for diagnosis of EEE virus infection in various animal species, especially when fresh tissues are not available for analysis, and also will provide a means for studying the involvement of alphavi...
Clinical and pathological studies in horses with hepatic disease. In horses with hepatic necrosis, lipidosis, neoplasia and cirrhosis, progression of the disease was studied by serial measurements of total serum bile acid concentrations and of plasma glutamate dehydrogenase (GD) and gamma glutamyl transferase (gamma GT) and by liver biopsy. Plasma ammonia concentrations were significantly elevated compared to clinically normal horses, but such changes were not always accompanied by a decline in plasma urea concentration. A fall in plasma glucose concentration carried a guarded prognosis. These were all invaluable aids in early diagnosis and throughout the di...
Attempts to find phenotypic markers of the virulence plasmid of Rhodococcus equi. Four isolates of Rhodococcus equi, from pneumonic foals, and containing the 85 kb virulence plasmid, a porcine isolate containing an 80 kb plasmid, and their plasmid cured derivatives, were examined for 239 phenotypic properties in an attempt to find characters other than the virulence-associated protein (VapA) which might be encoded by the virulence plasmid in organisms grown at 37 degrees C. Tests chosen included those which have previously given variable results for R. equi isolates, since such variability might be attributed to plasmid curing, and characteristics which have been described ...
Congenital cleft vertebral centrum and intra- and extraspinal cyst in a foal. A midsagittal centrum cleft of T5-6, malformation and fusion of T3-7, intra- and extraspinal cyst, and myelodysplasia were found in a 3-month-old female Arabian foal that had experienced posterior ataxia since birth. Based on studies in other species, ecto-endodermal adhesions early in embryogenesis leading to formation of an enterogenous cyst is the most probable pathogenesis.
Ixodes pacificus (Acari: Ixodidae) as a vector of Ehrlichia equi (Rickettsiales: Ehrlichieae). Ehrlichia equi, a rickettsia described from horses in California 30 yr ago, causes equine granulocytic ehrlichiosis throughout the Americas and possibly Europe. Here, we report experimental transmission of E. equi from infected to susceptible horses through bites of western blacklegged ticks, Ixodes pacificus (Cooley & Kohls). In preliminary field studies, only I. pacificus consistently infested horses and vegetation at 3 locations with contemporary cases of equine ehrlichosis, and in particular, I. pacificus was the only species found attached to all of the infected horses. Exposure to bites ...
Equine viral arteritis with abortions: serological and virological evidence in Germany. An outbreak of clinical disease with abortions, suspected to be equine viral arteritis in Germany was examined serologically and virologically. Three of five animals tested seroconverted to EAV, and EAV was isolated from an aborted fetus. In view of the significant increase in seropositive horses, the need for control measures is emphasized.
Osteochondrosis of the articular-epiphyseal cartilage complex in young horses: evidence for a defect in cartilage canal blood supply. The objectives of this study were to determine in horses 1) the ages at which viable cartilage canal vessels are present in the articular-epiphyseal cartilage complex of three predilection sites and one nonpredilection site of osteochondrosis (OC), 2) the prevalence of lesions of OC in these sites, and 3) whether there was an association of lesions of OC with necrotic cartilage canal blood vessels. The medial femoral condyle, lateral femoral trochlear ridge, and distal ends of the tibia and proximal phalanx were examined grossly, microradiographically, and histologically in 35 horses 18 months...
Intestinal fibrosis and vascular remodeling in ten horses and two ponies. No abstract available
Proteolytic cleavage of VP2, an outer capsid protein of African horse sickness virus, by species-specific serum proteases enhances infectivity in Culicoides. Purified African horse sickness virus (AHSV) was fed, as part of a blood meal, to adult females from a susceptible colony of Culicoides variipennis, established in the insectories at the Institute for Animal Health, Pirbright Laboratory, UK. The meal consisted of heparinized blood obtained from ovine, bovine, equine (horse and donkey) or canine sources spiked with AHSV serotype 9 (AHSV9). The infectivity levels observed for C. variipennis varied significantly, according to the source of the blood sample. Comparison of the protein profiles obtained from AHSV9 incubated with the individual serum...
Role of navicular bone shape in the pathogenesis of navicular disease: a radiological study. From progeny lists of 30 Dutch Warmblood sires, 586 3-year-old females by these stallions were randomly selected, each progeny group aimed at 20 animals for statistical reasons. The front feet of the sires and female progeny were examined radiographically using lateromedial and dorsopalmar upright pedal projections. The radiological features associated with navicular disease were classified 0-4 using a standardised classification, grades 3 and 4 representing the more severe changes. The shape of the proximal articular border of the navicular bone outline on the dorsopalmar view was classified ...
Rheumatoid factor, anti-heat shock protein (65 kDa) antibodies and anti-nuclear antibodies in equine joint diseases. To consider the hypothesis that autoimmune mechanisms may contribute to the pathology of equine joint diseases, 3 autoimmune responses were assayed in sera and synovial fluids. IgM-rheumatoid factor and antibodies to heat shock protein 65 kDa were determined by ELISA; anti-nuclear antibodies were assayed by indirect immunofluorescence to whole cell nuclear components. All parameters showed only modest increases, if any and not in a pattern related to disease, although some statistically significant increases were detected. Group analysis showed significantly elevated synovial fluid IgM-rheumat...
Cytologic evaluation of bronchoalveolar lavage fluid obtained from standardbred racehorses with inflammatory airway disease. Cytologic examination of bronchoalveolar lavage fluid (BALF), including phenotypic analysis of lymphocytes, was performed on 32 Standardbreds with poor race performance and endoscopic examination findings characteristic of inflammatory airway disease (IAD). Nucleated cell counts in BALF from IAD-affected horses were higher than those in control horses; the cytologic profile of BALF in affected horses included mixed inflammation, characterized by mild neutrophilia, lymphocytosis, and monocytosis. Eosinophil and mast cell counts were not higher in the IAD-affected group, compared with those in t...
An overview of equine dermatoses characterized by scaling and crusting. Scaling and/or crusting are common clinical findings associated with equine skin diseases. Scaling and crusting may be associated with pruritic or nonpruritic dermatoses. This article focuses on those conditions that are usually nonpruritic in horses. They include the infectious dermatoses, the keratinization/seborrheic disorders, photosensitization, and the immunologic/inflammatory disorders, including pemphigus foliaceus, equine exfoliative eosinophilic dermatitis and stomatitis, and equine histiocytic dermatitis (sarcoidosis). Clinical signs that help differentiate the various disorders are...
Infectious crusting dermatoses. Although there are numerous dermatoses in the horse in which the formation of crusts occurs, there are two relatively common and important infectious crusting dermatoses, namely, dermatophytosis and dermatophilosis. This article reviews the current concepts regarding the etiology and pathogenesis of each disease, as well as the more common clinical presentations, methods of diagnosis, and treatment.
Clinical pathology and hemostatic abnormalities in experimental African horsesickness. Infection of naive North American horses with 10(4) cell culture infectious doses (CCID50) of virulence variants of African horsesickness virus (AHSV), designated AHSV/4SP, AHSV/9PI, and AHSV/4PI, reproduced three classical forms of African horsesickness: acute (pulmonary), subacute (cardiac), and febrile, respectively. Distinct clinicopathologic and hemostatic abnormalities were associated with each form of disease. Hemostatic abnormalities included increased concentration of fibrin degradation products and prolongation of prothrombin, activated partial thromboplastin, and thrombin clotting t...
Clinical, virological and serological responses of donkeys to intranasal inoculation with the KY-84 strain of equine arteritis virus. The clinical, virological and serological responses of seven female donkeys (Equus asinus) to inoculation with the KY-84 strain of equine arteritis virus (EAV), a strain that causes moderate to severe clinical signs in horses, was investigated. In the donkeys, the only clinical signs observed were fever (mainly 3-9 days after inoculation), mild depression in four animals, and a slight nasal or ocular discharge in three. All of the donkeys became infected with EAV as shown by recovery of the virus for periods of up to 14 days from the nasopharynx and buffy coat and, in three out of four donkeys...