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Topic:Immunology

The equine immune system is a complex network of cells, tissues, and organs that work collaboratively to defend against pathogens and maintain homeostasis. It consists of innate and adaptive components, each with distinct functions and mechanisms. The innate immune system provides the first line of defense through physical barriers, phagocytic cells, and the complement system. The adaptive immune system involves lymphocytes, such as B cells and T cells, which generate specific responses to antigens and provide immunological memory. Research in equine immunology explores the interactions between these components, the impact of genetic and environmental factors on immune function, and the development of vaccines and therapeutics. This page gathers peer-reviewed studies and scholarly articles focusing on the mechanisms, regulation, and clinical applications of the equine immune system in health and disease.
Presence of CD4+ and CD8+ T cells and expression of MHC class I and MHC class II antigen in horses with Borna disease virus-induced encephalitis.
Brain pathology (Zurich, Switzerland)    July 1, 1995   Volume 5, Issue 3 223-230 doi: 10.1111/j.1750-3639.1995.tb00598.x
Bilzer T, Planz O, Lipkin WI, Stitz L.Tissues from 9 horses and 1 donkey suffering from natural Borna disease were investigated immunomorphologically. Lymphocytic inflammatory reactions and increased expressions of MHC class I and class II antigen were found in the brain as well as in the trigeminal and olfactory system. Perivascular inflammatory infiltrates were dominated by CD4+ T cells, whereas the majority of CD8+ T cells were disseminated intraparenchymally. No evidence of inflammation was found in the retina. Borna disease virus proteins and nucleic acids were present in the hippocampus, thalamus and medulla oblongata in all...
Detection of tetanus toxoid-specific memory T cells in equine lymph nodes but not in peripheral blood.
Research in veterinary science    July 1, 1995   Volume 59, Issue 1 79-81 doi: 10.1016/0034-5288(95)90035-7
Frayne J, Stokes CR.The use of tetanus toxoid as a recall antigen to investigate equine immune responses would be, in theory, a useful and cost-effective model in vitro. However, by using various regimens for culturing peripheral blood mononuclear cells from horses previously immunised with toxoid no proliferative response to the antigen was obtained in vitro, whereas lymph node mononuclear cells from the same animals proliferated significantly in response to it. The lack of response by the peripheral blood mononuclear cells was not due to the presence of a suppressive factor but to a lack of recognition of the a...
Development and evaluation of an ELISA using recombinant fusion protein to detect the presence of host antibody to equine arteritis virus.
Journal of virological methods    July 1, 1995   Volume 54, Issue 1 1-13 doi: 10.1016/0166-0934(95)00020-u
Chirnside ED, Francis PM, de Vries AA, Sinclair R, Mumford JA.A recombinant glutathione-S-transferase fusion protein expressing amino acids 55-98 of equine arteritis virus (EAV) GL (rGL 55-98) was tested in an ELISA for its ability to detect serum antibodies to EAV. Host antibodies induced following EAV infection bound the recombinant antigen by ELISA. The ELISA specificity and sensitivity were determined with a panel of equine sera including postinfection and postvaccination samples. A good correlation existed between EAV neutralizing antibody titers and ELISA absorbance values (r = 0.827). The sensitivity and specificity of the ELISA were 99.6 and 90.1...
In vitro and in vivo evidence on the site of neutralization of equine chorionic gonadotrophin (eCG) by an eCG antiserum.
Journal of reproduction and fertility    July 1, 1995   Volume 104, Issue 2 237-241 doi: 10.1530/jrf.0.1040237
Wang X, Kole AR, Greenwald GS.This study was designed to determine whether the major site of eCG neutralization by an antiserum to the hormone is at the peripheral or ovarian level. Hamsters hypophysectomized at oestrus were injected s.c. with 25 iu eCG. Three days later, preovulatory follicles were dissected and cultured for 5 h and the medium was changed every hour. At the end of the first hour of incubation, oestradiol and androstenedione accumulation was high, with a sharp drop over the next 4 h, whereas progesterone concentrations did not change over the entire period. Addition of eCG antiserum to the incubated follic...
Application of an equine herpesvirus 1 (EHV1) type-specific ELISA to the management of an outbreak of EHV1 abortion.
The Veterinary record    June 10, 1995   Volume 136, Issue 23 579-581 doi: 10.1136/vr.136.23.579
Drummer HE, Reynolds A, Studdert MJ, MacPherson CM, Crabb BS.Sera from 33 Australian thoroughbred mares were tested during an outbreak of equine herpesvirus 1 (EHV1) abortion with an enzyme-linked immunosorbant assay (ELISA) for the presence of EHV1-specific antibodies. The ELISA used a recombinant EHV1 antigen derived from glycoprotein G (gG) and distinguished antibodies to EHV1 from those of the antigenically related and widespread herpesvirus EHV4. Sera were obtained from most of the mares on three occasions, three, 13 and 67 days after the first abortion. Mares which were negative in the ELISA were kept separate from mares which were positive. A sec...
The DNA sequence of equine herpesvirus 2.
Journal of molecular biology    June 9, 1995   Volume 249, Issue 3 520-528 doi: 10.1006/jmbi.1995.0314
Telford EA, Watson MS, Aird HC, Perry J, Davison AJ.The complete DNA sequence of equine herpesvirus 2 (EHV-2) strain 86/67 was determined. The genome is 184,427 bp in size and has a base composition of 57.5% G + C. Unusually for a herpesvirus, about a third of the sequence distributed in several large blocks appears not to encode proteins. The 79 open reading frames that were identified as probably polypeptide-coding are predicted to encode 77 distinct proteins. Amino acid sequence comparisons confirmed that EHV-2 is a gamma-herpesvirus that is genetically collinear with herpesvirus saimiri (HVS; a gamma 2-herpesvirus) and Epstein-Barr virus (E...
Effect of enzymes on the growth of human and animal rotaviruses.
The Journal of veterinary medical science    June 1, 1995   Volume 57, Issue 3 569-570 doi: 10.1292/jvms.57.569
Sato K, Tokuhisa S, Inaba Y.The growth of group A human, bovine, equine and porcine rotaviruses were enhanced by pretreatment of virus with pancreatin, trypsin, protease, alkaline phosphatase or pepsin and incorporation of these enzymes in maintenance medium. In contrast, alpha-amylase or lipase inhibited the growth of equine and porcine rotaviruses. The other enzymes, adenosine deaminase, lactase, lysozyme, ribonuclease or triose-phosphate isomerase gave little or no change in the growth of all four rotaviruses.
At least four MHC class I genes are transcribed in the horse: phylogenetic analysis suggests an unusual evolutionary history for the MHC in this species.
European journal of immunogenetics : official journal of the British Society for Histocompatibility and Immunogenetics    June 1, 1995   Volume 22, Issue 3 249-260 doi: 10.1111/j.1744-313x.1995.tb00239.x
Ellis SA, Martin AJ, Holmes EC, Morrison WI.Nineteen horse MHC class I specificities have been serologically identified previously at a single locus (ELA-A), and two other specificities appear to be coded at other loci. Biochemical studies indicate that there are at least two expressed loci. In order to establish the number of transcribed horse MHC class I genes, we made a cDNA library from a heterozygous animal (ELA-A3/A7), and screened for positive clones using a bovine class I probe. More than 200 class I clones were isolated in this way, and so far seven unique full length sequences have been identified. All of the sequences are pre...
Immunohistochemical localization of cytochrome P450 aromatase in equine gonads.
The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society    June 1, 1995   Volume 43, Issue 6 571-577 doi: 10.1177/43.6.7769228
Almadhidi J, Seralini GE, Fresnel J, Silberzahn P, Gaillard JL.Estrogens are the major steroids produced by equine gonads. To identify the cells responsible for estrogen synthesis, an antiserum against purified equine testicular cytochrome P450 aromatase was produced in rabbits. The reactivity and specificity of the antiserum were assessed by ELISA, immunoblot analysis, and immunoneutralization studies. Immunofluorescence microscopy demonstrated that in the male gonad, cytochrome P450 aromatase (P450arom) was localized in the interstitial tissue, whereas, under the experimental conditions used, the Sertoli and germ cells did not show any specific staining...
Hepatic disease associated with administration of tetanus antitoxin in eight horses.
Journal of the American Veterinary Medical Association    June 1, 1995   Volume 206, Issue 11 1737-1740 
Guglick MA, MacAllister CG, Ely RW, Edwards WC.Seven horses developed clinical or subclinical hepatitis 48 to 87 days after administration of tetanus antitoxin. One horse had mildly high hepatic enzyme activity 120 days after inoculation with tetanus antitoxin. The first horse developed signs of depression, lethargy, and anorexia. During hospitalization, signs of hepatoencephalopathy were noticed, and laboratory data were consistent with hepatic disease. Another horse that was found dead had gross and histologic lesions compatible with serum hepatitis. Screening of serum gamma-glutamyltransferase (GGT) and aspartate transaminase activities...
The relationship between single radial hemolysis, hemagglutination inhibition, and virus neutralization assays used to detect antibodies specific for equine influenza viruses.
Veterinary microbiology    June 1, 1995   Volume 45, Issue 1 81-92 doi: 10.1016/0378-1135(94)00105-6
Morley PS, Hanson LK, Bogdan JR, Townsend HG, Appleton JA, Haines DM.Antibodies specific for equine influenza viruses are usually quantified using single radial hemolysis (SRH), hemagglutination inhibition (HI) or virus neutralization (VN). Neutralizing antibodies are thought to provide optimum protection to challenged animals. The purpose of this study was to determine the extent to which SRH and HI assays detect antibodies which neutralize equine influenza viruses. Acute and convalescent sera from 41 horses were analyzed using VN, SRH, and HI assays. These horses were present in a population of Thoroughbred racehorses during an epidemic of upper respiratory t...
An overview of equine dermatoses characterized by scaling and crusting.
The Veterinary clinics of North America. Equine practice    April 1, 1995   Volume 11, Issue 1 43-51 doi: 10.1016/s0749-0739(17)30330-9
Fadok VA.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...
Synthesis and processing of equine herpesvirus 1 glycoprotein D.
Virology    April 1, 1995   Volume 208, Issue 1 9-18 doi: 10.1006/viro.1995.1124
Flowers CC, Flowers SP, Jennings SR, O'Callaghan DJ.Previous studies (C. C. Flowers and D. J. O'Callaghan, 1992, Virology 190, 307-315) employed peptide-specific antibodies to identify the product of the glycoprotein D (gD) gene of equine herpesvirus 1 strain Kentucky A (KyA). gD polypeptides of 55 and 58 kDa were detected in EHV-1-infected L-M cells, and the 58-kDa protein was observed in the membrane fraction of EHV-1 virions. In this report, the kinetics of synthesis and processing of gD polypeptides are described. One-hour pulse-labeling of EHV-1-infected L-M cells revealed that gD proteins are first detected at 6 hr after infection and tha...
Entomologic evaluation of insect hypersensitivity in horses.
The Veterinary clinics of North America. Equine practice    April 1, 1995   Volume 11, Issue 1 29-41 doi: 10.1016/s0749-0739(17)30329-2
Greiner EC.Potential methods of incriminating insects as the cause of insect hypersensitivity are presented. A listing of the biting midges known to attack horses in North America is presented also. An example of how species may be determined to be the cause of the hypersensitivity is given using data from a recent study in Florida. Light trap collections indicated the temporal and geographic distribution of potential contributing species and collections made by vacuuming horses further delineated species by proving they feed on horses and the correct locations on the horses to match lesion distribution....
Cloning and sequence analysis of a protective M-like protein gene from Streptococcus equi subsp. zooepidemicus.
Infection and immunity    April 1, 1995   Volume 63, Issue 4 1440-1445 doi: 10.1128/iai.63.4.1440-1445.1995
Timoney JF, Walker J, Zhou M, Ding J.Streptococcus equi subsp. zooepidemicus, a Lancefield group C streptococcus, is a frequently isolated opportunist pathogen from a variety of animal hosts, including the horse. Previous studies have indicated that equine strains carry antigens with characteristics of the antiphagocytic M proteins on the Lancefield groups A and G streptococci. We have cloned a protective M-like protein gene (SzPW60) of an equine strain of S. equi subsp. zooepidemicus W60 and determined its sequence. This gene encodes a protein with a molecular weight of 40,123 which protects mice against subsp. zooepidemicus but...
Delineating minimal protein domains and promoter elements for transcriptional activation by lentivirus Tat proteins.
Journal of virology    April 1, 1995   Volume 69, Issue 4 2605-2610 doi: 10.1128/JVI.69.4.2605-2610.1995
Southgate CD, Green MR.Lentivirus Tat proteins comprise a novel class of RNA-binding transcriptional activators that are essential for viral replication. In this study, we performed a series of protein fusion experiments to delineate the minimal protein domains and promoter elements required for Tat action. We show that a 15-amino-acid region of equine infectious anemia virus (EIAV) Tat protein, when fused to the GAL4 or LexA DNA binding domain, can activate transcription in appropriate promoter contexts. In the natural human immunodeficiency virus type 1 long terminal repeat, activation by Tat is dependent on multi...
Cellular and antibody responses to equine herpesviruses 1 and 4 following vaccination of horses with modified-live and inactivated viruses.
Journal of the American Veterinary Medical Association    March 15, 1995   Volume 206, Issue 6 823-832 
Ellis JA, Bogdan JR, Kanara EW, Morley PS, Haines DM.The ability of monovalent and bivalent equine herpesvirus (EHV) vaccines to stimulate cellular and antibody responses to EHV-1 and EHV-4 was compared in healthy horses. Comparison of data from lymphocyte blastogenesis tests in which live viruses were used as antigens and that were conducted prior to vaccination and after 2 vaccinations revealed that horses given modified-live EHV-1 had significant increases in proliferative responses to EHV-1 (P = 0.03) and EHV-4 (P = 0.04). Responses to EHV-1 and EHV-4 in horses given the inactivated-virus bivalent vaccine were less; however, significant diff...
Abnormal patterns of equine leucocyte differentiation antigen expression in severe combined immunodeficiency foals suggests the phenotype of normal equine natural killer cells.
Immunology    March 1, 1995   Volume 84, Issue 3 495-499 
Lunn DP, McClure JT, Schobert CS, Holmes MA.Severe combined immunodeficiency (SCID) is a fatal autosommal disease of Arabian horses that leads to failure of maturation of T- and B-lymphocyte populations, although natural killer (NK) cells are unaffected. Thymic and lymph node tissues from two foals suffering from SCID were examined in an immunohistological study using a panel of monoclonal antibodies recognising equine leucocyte differentiation antigens. In both foals, the majority of cells in lymphoid tissues had an EqCD3-EqCD4-EqCD8+ phenotype, although rare EqCD3+ cells were also detected. The EqCD3-EqCD4-EqCD8+ cells may represent a...
Immunohistochemical localisation of met-enkephalin in the adrenal gland of the fetal and newborn horse.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 147-149 doi: 10.1111/j.2042-3306.1995.tb03052.x
Challis JR, Han X, Matthews SG, Fowden AL, Silver M, Holdstock N, McGladdery A, Ousey JC, Allen WR, Rossdale PD.No abstract available
Antiphagocytic properties of uterine isolates of Streptococcus zooepidemicus and mechanisms of killing in freshly obtained blood of horses.
American journal of veterinary research    March 1, 1995   Volume 56, Issue 3 321-328 
Causey RC, Paccamonti DL, Todd WJ.A total of 22 clinical streptococcal isolates, predominantly Streptococcus zooepidemicus, associated with endometritis in horses were tested for their ability to withstand the natural bactericidal properties of freshly obtained blood. During a 3-hour incubation in blood from a single horse, 8 of these isolates survived and grew, the remainder were killed. To determine whether this ability to grow extended to blood of other horses, 5 of these growing isolates were tested for their ability to grow in the blood of 5 additional horses. The same 5 horses were used for each isolate. The isolates gre...
Accumulation of chromotrope 2R positive cells in equine endometrium during early pregnancy and expression of transforming growth factor-beta 2 (TGF-beta 2).
Journal of reproduction and fertility    March 1, 1995   Volume 103, Issue 2 339-347 doi: 10.1530/jrf.0.1030339
Lea RG, Stewart F, Allen WR, Ohno I, Clark DA.Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1.2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF-beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes tra...
Spontaneous equine pulmonary granular cell tumors: morphologic, histochemical, and immunohistochemical characterization.
Veterinary pathology    March 1, 1995   Volume 32, Issue 2 101-106 doi: 10.1177/030098589503200201
Kelley LC, Hill JE, Hafner S, Wortham KJ.Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negati...
Evaluation of Directigen Flu A assay for detection of influenza antigen in nasal secretions of horses.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 131-134 doi: 10.1111/j.2042-3306.1995.tb03049.x
Morley PS, Bogdan JR, Townsend HG, Haines DM.The Directigen Flu A assay (Becton Dickinson, Microbiology Systems, Mississauga, Ontario, Canada) is a commercially available immunoassay designed for rapid in vitro recognition of influenza A nucleoprotein. The purpose of this study was to evaluate this assay for detection of influenza virus in nasal secretions of naturally infected horses. The assay was shown to react with representative strains of influenza virus which cause disease in horses and did not react with nasal secretions from uninfected horses kept in isolation. Between 33% and 45% of nasal secretions specimens obtained from clin...
Anti-collagen antibodies and immune complexes in equine joint diseases.
Veterinary immunology and immunopathology    March 1, 1995   Volume 45, Issue 1-2 19-30 doi: 10.1016/0165-2427(94)05325-m
Osborne AC, Carter SD, May SA, Bennett D.An investigation was made into the possible contribution of autoimmune mechanisms to equine arthropathies. Serum and synovial fluid (SF) immune complexes and anti-collagen Type II antibodies were measured, by ELISA, in groups of horses with naturally occurring osteoarthritis (OA), osteochondritis dissecans (OCD), bone fracture, traumatised joints, synovitis, infected joints and non-diseased (control) joints. Significantly raised anti-collagen Type II antibodies were found in osteoarthritic (P < 0.02) and traumatised joint synovial fluids (P < 0.01) compared with the control, where ten of...
Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal.
Equine veterinary journal    March 1, 1995   Volume 27, Issue 2 140-146 doi: 10.1111/j.2042-3306.1995.tb03051.x
Han X, Fowden AL, Silver M, Holdstock N, McGladdery AJ, Ousey JC, Allen WR, Rossdale PD, Challis JR.An increase in fetal adrenal cortisol output signals the onset of parturition in many animal species but, in the fetal horse, plasma concentrations of cortisol remain low for much of late pregnancy, with a rise occurring only very close to the time of birth (term 320-360 days). Immunohistochemistry was used to determine the localisation and changes in distribution of key steroidogenic enzymes for cortisol production; P450scc, P450C17 and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in adrenal tissue from fetal and newborn horses and these findings were correlated with the appearance of imm...
Enhanced sensitivity to neutralizing antibodies in a variant of equine infectious anemia virus is linked to amino acid substitutions in the surface unit envelope glycoprotein.
Journal of virology    March 1, 1995   Volume 69, Issue 3 1493-1499 doi: 10.1128/JVI.69.3.1493-1499.1995
Cook RF, Berger SL, Rushlow KE, McManus JM, Cook SJ, Harrold S, Raabe ML, Montelaro RC, Issel CJ.Serial passage of the prototype (PR) cell-adapted Wyoming strain of equine infectious anemia virus (EIAV) in fetal donkey dermal (FDD) rather than fetal horse (designated fetal equine kidney [FEK]) cell cultures resulted in the generation of a variant virus strain which produced accelerated cytopathic effects in FDD cells and was 100- to 1,000-fold more sensitive to neutralizing antibodies than its parent. This neutralization-sensitive variant was designated the FDD strain. Although there were differences in glycosylation between the PR and FDD strains, passage of the FDD virus in FEK cells di...
The equine endometrial cup reaction: a review.
The veterinary quarterly    March 1, 1995   Volume 17, Issue 1 21-29 doi: 10.1080/01652176.1995.9694525
Koets AP.The function of eCG in equine pregnancy is far from clear but it has become evident that eCG has little or no FSH activity in the horse and is therefore probably not responsible for the secondary ovulations. eCG does have luteotrophic activity and it could play a role in the resurgence of the primary corpus luteum (1,7,44). Some evidence exists that the receptor population on the equine gonads is heterogenous in a way that makes it possible to distinguish eCG from eLH, resulting in different post-receptor effects (7). There is also evidence that eCG itself is heterogenous, both in glycosylatio...
An 80-kDa syncytiotrophoblast alloantigen bound to maternal alloantibody in term placenta.
American journal of reproductive immunology (New York, N.Y. : 1989)    March 1, 1995   Volume 33, Issue 3 213-220 doi: 10.1111/j.1600-0897.1995.tb00887.x
Jalali GR, Rezai A, Underwood JL, Mowbray JF, Surridge SH, Allen WR, Matthias S.We have shown that most of the IgG present on term syncytiotrophoblast, membrane, microvesicles is bound to an 80 kDa protein antigen (R80K). Methods: Microvesicles were prepared from term human placenta, and the IgG eluted at pH3. Results: When IgG antibody was eluted at pH3 and reacted with acid-treated vesicles of other placentae, the alloantibody always bound to the preparation from which it was obtained, but only to about 10% of acid-treated preparations from other placentae. A similar polymorphic protein found in association with IgG antibody was found in term horse placentae. Cross-reac...
Regulation of granule size in human and horse eosinophils by number of fusion events among unit granules.
The Journal of physiology    February 15, 1995   Volume 483 ( Pt 1), Issue Pt 1 201-209 doi: 10.1113/jphysiol.1995.sp020578
Hartmann J, Scepek S, Lindau M.1. We have investigated the granule size distributions in human and horse eosinophils by time-resolved patch-clamp capacitance measurements. 2. During exocytosis of single granules the electrical capacitance of the plasma membrane increases in discrete steps. The steps in horse cells are about six times larger than those in human cells in accordance with the difference in granule size. 3. In both species a multimodal capacitance step size distribution is observed with a first peak at 6-7 fF corresponding to granules with a diameter of about 450-500 nm and a surface area of about 0.7 microns2, ...
Polyclonal antibody-based antigen-detection immunoassay for diagnosis of Trypanosoma evansi in buffaloes and horses.
Veterinary parasitology    February 1, 1995   Volume 56, Issue 4 261-267 doi: 10.1016/0304-4017(94)00689-a
Singh V, Chaudhari SS, Kumar S, Chhabra MB.An enzyme-linked immunosorbent assay (ELISA) was employed for the detection of Trypanosoma evansi antigens in serum samples of field cases of buffaloes and horses in northern India. In 323 naturally infected/suspected buffaloes, circulating antigenaemia was detected in 180 (55.72%), whereas parasitaemia by wet blood smear examination was found in 62 (19.19%) only. The antigen-ELISA was positive in 47 of the 62 parasitologically proven cases and in 86 of the 116 cases with anti-trypanosome antibodies detected by ELISA. Of the 80 horses examined antigen-ELISA was positive in 45 (56.75%) sera. Th...