Virulence in horses refers to the degree of pathogenicity exhibited by infectious agents, such as bacteria, viruses, or parasites, that affect equine health. It encompasses the mechanisms and factors that enable these pathogens to invade, cause disease, and spread within horse populations. Understanding virulence involves studying the genetic, molecular, and environmental factors that contribute to the severity of infections in horses. This topic includes research on the interaction between equine hosts and pathogens, the impact of virulence factors on disease progression, and strategies for managing and mitigating infections. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, impacts, and management of virulence in equine diseases.
Su Y, Zhang Z, Wang L, Zhang B, Su L. subsp. () is one of the important zoonotic and opportunistic pathogens. In recent years, there has been growing evidence that supports the potential role of in severe diseases in horses and other animals, including humans. Furthermore, the clinical isolation and drug resistance rates of have been increasing yearly, leading to interest in its in-depth genomic analysis. In order to deepen the understanding of the characteristics and genomic features, we investigated the genomic islands, mobile genetic elements, virulence and resistance genes, and phenotype of strain ZHZ 211 (ST147), isolat...
Gravey F, Sévin C, Castagnet S, Foucher N, Maillard K, Tapprest J, Léon A, Langlois B, Le Hello S, Petry S.Klebsiella pneumoniae is a major cause of infections and reproductive disorders among horses, ranked in recent French studies as the sixth most frequently isolated bacterial pathogen in equine clinical samples. The proportion of multidrug-resistant (MDR) K. pneumoniae is therefore significant in a context where MDR K. pneumoniae strains are considered a major global concern by the World Health Organization. Unassigned: In this study, we used a genomic approach to characterize a population of 119 equine K. pneumoniae strains collected by two laboratories specialized in animal health in Normandy...
Legere RM, Poveda C, Ott JA, Bray JM, Villafone EG, Silveira BPD, Kahn SK, Martin CL, Mancino C, Taraballi F, Criscitiello MF, Berghman L, Bordin AI....Design and evaluate immune responses of neonatal foals to a mRNA vaccine expressing the virulence-associated protein A (VapA) of Rhodococcus equi. Methods: Cultured primary equine respiratory tract cells; Serum, bronchoalveolar lavage fluid (BALF), and peripheral blood mononuclear cells (PBMCs) from 30 healthy Quarter Horse foals. Methods: VapA expression was evaluated by western immunoblot in cultured equine bronchial cells transfected with 4 mRNA constructs encoding VapA. The mRNA construct with greatest expression was used to immunize foals at ages 2 and 21 days in 5 groups: (1) 300 μg neb...
Zhang Y, Lv F, Su Y, Zhang H, Zhang B.Streptococcus equi subspecies equi (S. equi) is the causative agent of strangles, which is one of the most common and highly contagious respiratory infectious illnesses in horses. Streptococcus equi (S. equi) is a horse-specific pathogen that originated from the closely related zoonotic pathogen Streptococcus equi subspecies zooepidemicus (S. zooepidemicus). Despite decades of research, the movement of genetic material across host-restricted diseases remains a mystery. Unassigned: Three S. equi donkey isolates (HTP133, HTP232, and HT1112) were recently isolated from a strangles epidemic on don...
Zúñiga MP, Badillo E, Abalos P, Valencia ED, Marín P, Escudero E, Galecio JS.Rhodococcus equi is responsible for foal pneumonia worldwide, with a significant economic impact on the production and breeding of horses. In Chile, the first case was reported in 2000, and since then, its incidence has been increasing. Distinctive characteristics of R. equi as an intracellular pathogen in macrophages, emergence of virulence plasmids encoding surface lipoprotein antigens, and appearance of antibiotic resistance against macrolides and rifampicin have significantly complicated the treatment of R. equi pneumonia in foals. Therefore, in vitro susceptibility studies of first-line a...
Nwobi OC, Anyanwu MU, Jaja IF, Nwankwo IO, Okolo CC, Nwobi CA, Ezenduka EV, Oguttu JW.Staphylococcus aureus was isolated from a total of 360 nasal and groin skin swabs from 180 systematic randomly-selected horses slaughtered for meat at Obollo-Afor, Enugu State, Southeast Nigeria and antimicrobial, methicillin and heavy metal resistance profile and virulence potentials of the isolates established. Baird-Parker agar with egg yolk tellurite was used for S. aureus isolation. S. aureus isolates were confirmed biochemically and serologically using a specific S. aureus Staphytect Plus™ latex agglutination test kit. The antimicrobial resistance profile, methicillin, vancomycin and i...
Hurni JI, Kaiser-Thom S, Gerber V, Keller JE, Collaud A, Fernandez J, Schwendener S, Perreten V.A total of 100 nasal swabs were collected from healthy horses in Switzerland between January 2020 and August 2020. The samples were taken from horses at 40 different stables in 12 different cantons and screened for both methicillin-resistant (MRSA) and methicillin-susceptible S. aureus (MSSA) using selective agar plates. S. aureus were tested for antibiotic susceptibility by measurement of the minimal inhibitory concentration (MIC) and for virulence factors, antibiotic resistance genes and phylogenetic characteristics using whole genome sequence analysis. Ten horses were found to be positiv...
Takai S, Ohashi M, Suzuki Y, Sasaki Y, Kakuda T, Broens EM, Wagenaar JA, van Duijkeren E.Clinical samples from 123 foals with suspected rhodococcosis submitted to the Veterinary Microbiological Diagnostic Centre of the Faculty of Veterinary Medicine between 1993 and 2006 were tested for the presence of the virulence gene vapA. Of the 123 samples, 120 were vapA-positive and 3 vapA-negative Rhodococcus equi were isolated. The 120 vapA-positive R. equi were isolated from 70 tracheal wash, 19 lung tissues, 7 lymph nodes, 6 synovial fluids, 13 abscesses or pus and single isolates from the uterus, gut, cerebrospinal fluid, abdomen fluid and faeces. Of the 120 isolates, 46 were from Dutc...
Suzuki Y, Takai S, Kubota H, Hasegawa N, Ito S, Yabuuchi Y, Sasaki Y, van Duijkeren E, Kakuda T.Rhodococcus equiis the causative agent of pyogenic pneumonia in foals, and a virulence-associated protein A (VapA) encoded on the pVAPA virulence plasmid is important for its pathogenicity. In this study, we analyzed the virulence of R. equi strain U19, originally isolated in the Netherlands in 1997 and the genetic characteristics of the pVAPA_U19 plasmid. U19 expressed VapA that was regulated by temperature and pH and underwent significant intracellular proliferation in macrophages. The restriction fragment length polymorphism of pVAPA_U19 digested with EcoRI was similar to that of pREAT701 (...
Samir A, Abdel-Moein KA, Zaher HM. has been associated with both nosocomial and community-acquired infections with mounting public health concern throughout the world. The purpose of this study was to investigate the burden of virulent extended-spectrum β-lactamase (ESBL)-producing among diarrheic horses or those with respiratory illness to underscore the public health implication of such strains. Rectal and nasal swabs were gathered from 100 diseased horses (50 diarrheic and 50 with respiratory illness). The collected swabs were processed for isolation of ESBL-producing using a selective medium followed by phenotypic and ...
Sears KP, Knowles DP, Fry LM.The global importance of the hemoparasite to equine health was recently shown by its resistance to imidocarb dipropionate (ID) and its interference with clearance by ID in some co-infected horses. Genetic characterization of revealed marked genomic reduction compared to , and initial experiments demonstrated reduced clinical severity in spleen-intact horses. Furthermore, in early experiments, splenectomized horses survived infection and progressed to an asymptomatic carrier state, in stark contrast to the high fatality rate of in splenectomized horses. Thus, we hypothesized that is less ...
Allegro AR, Barhoumi R, Bordin AI, Bray JM, Cohen ND.Rhodococcus equi is a soil saprophytic bacterium and intracellular pathogen that causes pneumonia in foals. Strains of R. equi that are virulent in foals contain a plasmid that encodes a virulence-associated protein A (VapA) necessary for replication in macrophages. Because other intracellular pathogens survive and replicate inside amoebae, we postulated that the VapA-bearing plasmid (pVAPA) confers a survival advantage for R. equi against environmental predators like amoebae. To test this hypothesis, we compared phagocytosis by and survival in Acanthamoeba castellanii of isogenic strains of p...
Wall GV, Wright IM, Barnardo C, Erasmus BJ, van Staden V, Potgieter AC.African horse sickness virus (AHSV) non-structural protein NS4 is a nucleocytoplasmic protein that is expressed in the heart, lung, and spleen of infected horses, binds dsDNA, and colocalizes with promyelocytic leukemia nuclear bodies (PML-NBs). The aim of this study was to investigate the role of AHSV NS4 in viral replication, virulence and the host immune response. Using a reverse genetics-derived virulent strain of AHSV-5 and NS4 deletion mutants, we showed that knockdown of NS4 expression has no impact in cell culture, but results in virus attenuation in infected horses. RNA sequencing (RN...
Zhang H, Zhou T, Su L, Wang H, Zhang B, Su Y.Strangles, which is caused by Streptococcus equi subspecies equi (S. equi), is one of the most prevalent equine infectious diseases with worldwide distribution and leads to serious economic loss in the horse industry. Sortase A (srtA) is a transpeptidase that anchors multiple virulence-associated surface proteins to the cell surface of S. equi. srtA plays a major role in S. equi infection and colonization of the host cell. In this study, we aimed to investigate the effects of srtA mutation on the phagocytic activity and immunogenicity of S. equi. The point-mutated recombinant sortases, includi...
Schmitt S, Stephan R, Huebschke E, Schaefle D, Merz A, Johler S.Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe infections in humans and animals worldwide. Studies elucidating the population structure, staphylococcal cassette chromosome mec types, resistance phenotypes, and virulence gene profiles of animal-associated MRSA are needed to understand spread and transmission. Objective: The objective of this study was to determine 1) clonal complexes and spa types, 2) resistance phenotypes, and 3) virulence/resistance gene profiles of MRSA isolated from animals in Switzerland. Methods: We analyzed 31 presumptive MRSA isolates co...
Saied AA, Bryan LK, Bolin DC. infection in horses is common and is characterized by pyogranulomatous pneumonia and ulcerative enterocolitis. clinical disease in cattle, however, is rare and typically manifests as granulomatous lymphadenitis discovered in the abattoir. A 19-mo-old female Santa Gertrudis had a history of intermittent inappetence and weight loss for a 3-mo period before euthanasia. Gross and histologic examination revealed severe, chronic, ulcerative, and granulomatous inflammation in the tongue, pharynx, and small intestine. Also, the heifer had severe, granulomatous pharyngeal and mesenteric lymphadenitis...
Jaeger LH, Moreno LZ, Kremer FS, Dellagostin OA, Moreno AM, Lilenbaum W.The genome of a Brazilian strain of Leptospira kirschneri serogroup Grippotyphosa isolated from a mare post-abortion was sequenced and analyzed. High symmetrical identity and few structural differences were found when compared with a European strain of the same serogroup, L. kirschneri serovar Valbuzzi strain 200702274. Genes associated with virulence and antimicrobial resistance were found. Knowledge of the virulence evolution of Leptospira remains limited, especially in diseases of the reproductive sphere. We highlight the importance of virulence studies in the sphere of genital leptospirosi...
Willingham-Lane JM, Coulson GB, Hondalus MK.Rhodococcus equi is a facultative intracellular bacterium of macrophages and is an important pathogen of animals and immunocompromised people wherein disease results in abcessation of the lungs and other sites. Prior work has shown that the presence of the major virulence determinant, VapA, encoded on the pVAPA-type plasmid, disrupts normal phagosome development and is essential for bacterial replication within macrophages. pVAPA- type plasmids are typical of R. equi strains derived from foals while strains from pigs carry plasmids of the pVAPB-type, lacking vapA, and those from humans harbor ...
Kennedy CA, Walsh C, Karczmarczyk M, O'Brien S, Akasheh N, Quirke M, Farrell-Ward S, Buckley T, Fogherty U, Kavanagh K, Parker CT, Sweeney T....Extraintestinal pathogenic E. coli (ExPEC) possess the ability to cause extraintestinal infections such as urinary tract infections, neonatal meningitis and sepsis. While information is readily available describing pathogenic E. coli populations in food-producing animals, studies in companion/sports animals such as horses are limited. In addition, many antimicrobial agents used in the treatment of equine infections are also utilised in human medicine, potentially contributing to the spread of antibiotic resistance determinants among pathogenic strains. The aim of this study was to phenotypical...
Perrone T, Sánchez E, Hidalgo L, Mijares A, Balzano-Nogueira L, Gonzatti MI, Aso PM.The infectivity and virulence of seven Trypanosoma evansi and Trypanosoma equiperdum Venezuelan strains isolated from horses, donkeys and capybaras were compared in a mouse model up to 41 days, for parasitemia, animal weight, survival rates, packed cell volume, haemoglobin and erythrocyte count. Two T. equiperdum strains and three of the T. evansi strains resulted in 100% mice mortality, while the two T. evansi donkey strains exhibited lower infectivity and mortality. T. equiperdum strains had shorter pre-patent periods (4 days) than the T. evansi strains (4-12 days). In terms of pathoge...
Wang XF, Liu Q, Wang YH, Wang S, Chen J, Lin YZ, Ma J, Zhou JH, Wang X.The equine infectious anemia virus (EIAV) attenuated vaccine was developed by long-term passaging of a field-isolated virulent strain in cross-species hosts, followed by successive cultivation in cells To explore the molecular mechanism underlying the evolution of the EIAV attenuated vaccine, a systematic study focusing on long-terminal-repeat (LTR) variation in numerous virus strains ranging from virulent EIAV to attenuated EIAV was performed over time both and Two hypervariable regions were identified within the U3 region in the enhancer region (EHR) and the negative regulatory element (N...
Risseti RM, Zastempowska E, Twarużek M, Lassa H, Pantoja JCF, de Vargas APC, Guerra ST, Bolaños CAD, de Paula CL, Alves AC, Colhado BS....Trueperella pyogenes is an opportunistic pathogen that causes diverse pyogenic infections in livestock. The genes that encode the exotoxin pyolysin (plo) and other putative factors that promote adhesion of pathogen to host cells (fimbriae fimA, fimC, fimE, fimG, neuraminidases nanH, nanP, and collagen-binding protein cbpA) have been associated with virulence, particularly in mastitis and uterus infections of dairy cows. However, the role of these virulence markers in the pathogenicity of the agent in domestic animals infections still is incompletely understood. The genes plo, fimA, fimC, fimE,...
Olivo G, Lucas TM, Borges AS, Silva RO, Lobato FC, Siqueira AK, da Silva Leite D, Brandão PE, Gregori F, de Oliveira-Filho JP, Takai S, Ribeiro MG.Diarrhea is a major clinical problem affecting foals up to 3 months of age. The aim of this study was to identify enteric microorganisms involved in monoinfections and coinfections and the associated virulence factors in healthy and diarrheic foals. Diarrheic (D) ( = 56) and nondiarrheic (ND) foals ( = 60) up to three months of age were studied. Fecal samples were analyzed for identification of infectious agents (microbiological culturing, molecular techniques, and microscopic analyses). (30% versus 25%), spp. (25% versus 7%), (25% versus 25%), type A (21% versus 10%), (20% versus 35%), ...
Na W, Lyoo KS, Yoon SW, Yeom M, Kang B, Moon H, Kim HK, Jeong DG, Kim JK, Song D.Equine influenza virus (EIV) causes a highly contagious disease in horses and other equids. Recently, we isolated an H3N8 EIV (A/equine/Kyonggi/SA1/2011) from a domestic horse in South Korea that exhibited symptoms of respiratory disease, and found that the EIV strain contained a naturally mutated NS gene segment encoding a truncated NS1 protein. In order to determine whether there was an association between the NS gene truncation and viral virulence, a reverse genetics system was applied to generate various NS gene recombinant viruses using the backbone of the H1N1 A/Puerto Rico/8/1934 (PR/8)...
Yao Q, Ma J, Wang X, Guo M, Li Y, Wang X.Tetherin (BST-2) is an important host restriction factor that can inhibit the release of a diverse array of enveloped viruses from infected cells. Conversely, to facilitate their release and spread, many viruses have evolved various strategies to overcome the antiviral effect of tetherin in a species-specific manner. During the development of an attenuated equine infectious anemia virus (EIAV) vaccine in our laboratory, we found that serial passage of a field-isolated virulent EIAV strains in horse and donkey as well as the cultivated donkey cells, produces several typical EIAV strains, includ...
Willingham-Lane JM, Berghaus LJ, Giguère S, Hondalus MK.The soil-dwelling, saprophytic actinomycete is a multihost, facultative intracellular pathogen of macrophages. When inhaled by susceptible foals, it causes severe bronchopneumonia. It is also a pathogen of pigs, which may develop submaxillary lymphadenitis upon exposure. isolates obtained from foals and pigs possess conjugative plasmids housing a pathogenicity island (PAI) containing a novel family of genes of unknown function called the virulence-associated protein or family. The PAI regions of the equine and swine plasmids differ in gene composition, with equine isolates possessing six ...
Javed R, Taku AK, Gangil R, Sharma RK.The aim was to determine the occurrence of streptococci in equines in Jammu (R. S. Pura, Katra), characterization of Streptococci equi subsp. equi and Streptococcus equi subsp. zooepidemicus with respect to their virulence traits and to determine antibiotic sensitivity pattern of virulent Streptococcus isolates. Methods: A total of 96 samples were collected from both clinically affected animals (exhibiting signs of respiratory tract disease) and apparently healthy animals and were sent to laboratory. The organisms were isolated on Columbia nalidixic acid agar containing 5% sheep blood as well ...
Wang XF, Lin YZ, Li Q, Liu Q, Zhao WW, Du C, Chen J, Wang X, Zhou JH.The equine infectious anemia virus (EIAV) vaccine is the only attenuated lentiviral vaccine applied on a large scale that has been shown to be effective in controlling the prevalence of EIA in China. This vaccine was developed by successive passaging of a field-isolated virulent strain in different hosts and cultivated cells. To explore the molecular basis for the phenotype alteration of this vaccine strain, we systematically analyzed its genomic evolution during vaccine development. Results: Sequence analysis revealed that the genetic distance between the wild-type strain and six representati...
Guri A, Paligot M, Crèvecoeur S, Piedboeuf B, Claes J, Daube G, Corredig M, Griffiths MW, Delcenserie V.The aims of this study were to examine the effect of mare's milk on virulence gene expression of Salmonella Typhimurium and observe its potential activity on proliferation of adenocarcinoma Caco-2 cells. Different supernatants of mare's milk, raw or heat-treated at 65°C for 15 s or 30 min, were studied. The changes in hilA gene expression of Salmonella Typhimurium in presence of mare's milk supernatants were assessed using a reporter luminescent strain. A significant decrease in hilA gene expression was observed with all tested supernatants. Virulence gene expression was then assessed using q...
Rückert C, Kriete M, Jaenicke S, Winkler A, Tauch A.The complete genome sequence of the type strain Corynebacterium uterequi DSM 45634 from an equine urogenital tract specimen comprises 2,419,437 bp and 2,163 protein-coding genes. Candidate virulence factors are homologs of DIP0733, DIP1281, and DIP1621 from Corynebacterium diphtheriae and of sialidase precursors from Trueperella pyogenes and Chlamydia trachomatis.
Frost MJ, Zhang J, Edmonds JH, Prow NA, Gu X, Davis R, Hornitzky C, Arzey KE, Finlaison D, Hick P, Read A, Hobson-Peters J, May FJ, Doggett SL....To determine the cause of an unprecedented outbreak of encephalitis among horses in New South Wales, Australia, in 2011, we performed genomic sequencing of viruses isolated from affected horses and mosquitoes. Results showed that most of the cases were caused by a variant West Nile virus (WNV) strain, WNV(NSW2011), that is most closely related to WNV Kunjin (WNV(KUN)), the indigenous WNV strain in Australia. Studies in mouse models for WNV pathogenesis showed that WNV(NSW2011) is substantially more neuroinvasive than the prototype WNV(KUN) strain. In WNV(NSW2011), this apparent increase in vir...
Timoney JF.Streptococci pathogenic for the horse include S. equi (S. equi subsp. equi), S. zooepidemicus (S. equi subsp. zooepidemicus), S. dysgalactiae subsp. equisimilis and S. pneumoniae capsule Type III. S. equi is a clonal descendent or biovar of an ancestral S. zooepidemicus strain with which it shares greater than 98% DNA homology and therefore expresses many of the same proteins and virulence factors. Rapid progress has been made in identification of virulence factors and proteins uniquely expressed by S. equi. Most of these are expressed either on the bacterial surface or are secreted. Notable e...
Turton JF, Baklan H, Siu LK, Kaufmann ME, Pitt TL.A multiplex PCR using targets within the serotype-specific region of the capsular polysaccharide synthesis gene cluster of serotypes K1, K2 and K5 was evaluated using the 77 reference serotype strains of Klebsiella, and a panel of clinical isolates subjected previously to conventional serotyping. The PCR was highly specific for these serotypes, which are those most associated with virulence in humans and horses. PCR confirmed that isolates of the K5 serotype had cross-reacted with antiserum for other serotypes, particularly for K7. K5 isolates received by our laboratory were almost exclusively...
Takai S, Koike K, Ohbushi S, Izumi C, Tsubaki S.Antigens of Rhodococcus equi were analyzed by immunoblotting with naturally infected foal sera. Immunoblots of whole-cell antigen preparations of clinical isolates of R. equi revealed that major protein bands with molecular masses of 15 to 17 kDa were present in all clinical isolates tested and all isolates virulent for mice. In contrast, the 15- to 17-kDa antigens were not identified by immunoblotting in ATCC 6939, a type strain of R. equi that was avirulent for mice. Whole-cell antigens of 102 environmental isolates were investigated by immunoblotting and the mouse pathogenicity test. Twenty...
Meijer WG, Prescott JF.Rhodococcus equi is an important cause of subacute or chronic abscessating bronchopneumonia of foals up to 3-5 months of age. It shares the lipid-rich cell wall envelope characteristic of the mycolata, including Mycobacterium tuberculosis, as well as the ability of pathogenic members of this group to survive within macrophages. The possession of a large virulence plasmid in isolates recovered from pneumonic foals is crucial for virulence. The plasmid contains an 27 kb pathogenicity island (PI) that encodes seven related virulence-associated proteins (Vaps), including the immunodominant surface...
Giguère S, Cohen ND, Chaffin MK, Hines SA, Hondalus MK, Prescott JF, Slovis NM.Pneumonia is a major cause of disease and death in foals. Rhodococcus equi, a gram-positive facultative intracellular pathogen, is a common cause of pneumonia in foals. This article reviews the clinical manifestations of infection caused by R. equi in foals and summarizes current knowledge regarding mechanisms of virulence of, and immunity to, R. equi. A complementary consensus statement providing recommendations for the diagnosis, treatment, control, and prevention of infections caused by R. equi in foals can be found in the same issue of the Journal.
Hondalus MK.Inhalation of the soil-borne organism, Rhodococcus equi, can lead to a chronic and severe pyogranulomatous pneumonia in young horses and immunocompromised people. In addition, ulcerative colitis is a common sequela to infection in foals, and dissemination from the lung to other body sites is not uncommon in either the horse or man. Although the facultative intracellular bacterium is susceptible to neutrophil-mediated killing, it is able to resist innate macrophage defenses and establish residence within the intracellular environment of that phagocyte. Definitive virulence factors of R. equi ha...
Tkachuk-Saad O, Prescott J.Fifty-four strains of Rhodococcus equi from different clinical sources (mainly horses and pigs) were examined for their plasmid content by two screening methods. Plasmids were detected in 49 of 54 strains. A plasmid of approximately 80 kb was isolated from 21 of 22 isolates from horses and 20 of 28 isolates from pigs, and a 105-kb plasmid was isolated from 7 of 28 isolates from pigs. The 80-kb plasmid was significantly associated with strains of equine rather than porcine origin, and the 105-kb plasmid was significantly associated with strains of porcine origin. The type strain, ATCC 6939, con...
Angenvoort J, Brault AC, Bowen RA, Groschup MH.West Nile virus (WNV) is a flavivirus transmitted between certain species of birds and mosquito vectors. Tangential infections of equids and subsequent equine epizootics have occurred historically. Although the attack rate has been estimated to be below 10%, mortality rates can approach 50% in horses that present clinical disease. Symptoms are most commonly presenting in the form of encephalitis with ataxia as well as limb weakness, recumbency and muscle fasciculation. The most effective strategy for prevention of equine disease is proper vaccination with one of the numerous commercially avail...
Prow NA.West Nile virus (WNV) is a mosquito-borne virus responsible for outbreaks of viral encephalitis in humans and horses, with particularly virulent strains causing recent outbreaks of disease in Eastern Europe, the Middle East and North America. A strain of WNV, Kunjin (WNVKUN), is endemic in northern Australia and infection with this virus is generally asymptomatic. However in early 2011, an unprecedented outbreak of encephalitis in horses occurred in south-eastern Australia, resulting in mortality in approximately 10%-15% of infected horses. A WNV-like virus (WNVNSW2011) was isolated and found ...
Wang E, Bowen RA, Medina G, Powers AM, Kang W, Chandler LM, Shope RE, Weaver SC.Following a 19-year hiatus, Venezuelan equine encephalitis (VEE) reemerged in western Venezuela in December 1992. This outbreak is important in understanding VEE emergence because phylogenetic studies imply that sympatric, enzootic, subtype ID VEE viruses mutated to generate the epizootic/epidemic. Although the 1992-1993 strains belong to subtype IC, a serotype implicated in extensive outbreaks during the 1960s and in 1995, relatively small numbers of human and equine cases occurred in 1992-1993. We, therefore, evaluated the pathogenicity of these Venezuelan enzootic ID and epizootic IC viruse...
Hamilton A, Robinson C, Sutcliffe IC, Slater J, Maskell DJ, Davis-Poynter N, Smith K, Waller A, Harrington DJ.Streptococcus equi is the causative agent of strangles, a prevalent and highly contagious disease of horses. Despite the animal suffering and economic burden associated with strangles, little is known about the molecular basis of S. equi virulence. Here we have investigated the contributions of a specific lipoprotein and the general lipoprotein processing pathway to the abilities of S. equi to colonize equine epithelial tissues in vitro and to cause disease in both a mouse model and the natural host in vivo. Colonization of air interface organ cultures after they were inoculated with a mutant ...
Kinney RM, Johnson BJ, Brown VL, Trent DW.A cDNA clone containing all of the 26 S mRNA coding region of the RNA genome of Venezuelan equine encephalitis (VEE) virus, virulent strain Trinidad donkey (TRD), has been constructed and sequenced. The nucleotide and deduced amino acid sequences of the 26 S RNA of VEE virus conform to the general organization of the alphavirus subgenomic mRNA. Excluding the poly(A) tail, the VEE 26 S RNA is 3913 nucleotides long with a protein coding region of 3762 nucleotides. Codon usage in the translated region is nonrandom and correlates well with that reported for Sindbis (SIN), Semliki Forest (SF), and ...
Gonzalez G, Marshall JF, Morrell J, Robb D, McCauley JW, Perez DR, Parrish CR, Murcia PR.Influenza A viruses (IAVs) can jump species barriers and occasionally cause epidemics, epizootics, pandemics, and panzootics. Characterizing the infection dynamics at the target tissues of natural hosts is central to understanding the mechanisms that control host range, tropism, and virulence. Canine influenza virus (CIV; H3N8) originated after the transfer of an equine influenza virus (EIV) into dogs. Thus, comparing CIV and EIV isolates provides an opportunity to study the determinants of influenza virus emergence. Here we characterize the replication of canine, equine, and human IAVs in the...
Carpenter S, Chesebro B.Similar to other human and animal lentiviruses, equine infectious anemia virus (EIAV) is detectable in vivo in cells of the monocyte-macrophage lineage. Owing to their short-lived nature, horse peripheral blood macrophage cultures (HMC) are rarely used for in vitro propagation of EIAV, and equine dermal (ED) or kidney cell cultures, which can be repeatedly passed in vitro, are used in most studies. However, wild-type isolates of EIAV will not grow in these cell types without extensive adaptation, a process which may attenuate viral virulence. To better define the effect of host cell tropism on...
Orrego A, Issel CJ, Montelaro RC, Adams WV.Five serial passages of a cell-adapted strain of equine infectious anemia (EIA) virus were conducted in Shetland ponies. The 13 recipient ponies became agar-gel immunodiffusion test-positive by 25 days after they were inoculated. The virulence of the cell-adapted strain of EIA virus markedly increased through 3 serial passages, although individual variation within passages was high. The 1st serial-passage recipient remained afebrile through 200 days, whereas a febrile episode occurred about every 185, 44, 35, and 33 days in the 2nd, 3rd, 4th, and 5th serial-passage recipients, respectively. Se...
Harrington DJ, Sutcliffe IC, Chanter N.Streptococcus equi is the aetiological agent of strangles, one of the most prevalent diseases of the horse. The animal suffering and economic burden associated with this disease necessitate effective treatment. Current antibiotic therapy is often ineffective and thus recent attention has focused on vaccine development. A systematic understanding of S. equi virulence, leading to the identification of targets to which protective immunity can be directed, is a prerequisite of the development of such a vaccine. Here, the virulence factors of S. equi are reviewed.
Li F, Craigo JK, Howe L, Steckbeck JD, Cook S, Issel C, Montelaro RC.Previous evaluations of inactivated whole-virus and envelope subunit vaccines to equine infectious anemia virus (EIAV) have revealed a broad spectrum of efficacy ranging from highly type-specific protection to severe enhancement of viral replication and disease in experimentally immunized equids. Among experimental animal lentivirus vaccines, immunizations with live attenuated viral strains have proven most effective, but the vaccine efficacy has been shown to be highly dependent on the nature and severity of the vaccine virus attenuation. We describe here for the first time the characterizati...
Wada R, Kamada M, Anzai T, Nakanishi A, Kanemaru T, Takai S, Tsubaki S.Twelve foals, between 27 and 83 days old, were infected with 2 strains of Rhodococcus equi by intratracheal administration. Ten of the 12 foals were inoculated with 10(4)-10(10) colony forming units (cfu) of ATCC 33701 strain. The other 2 foals were inoculated with 10(9) cfu of a plasmid-cured derivative of the ATCC 33701 strain (ATCC 33701P-). All of the 10 foals challenged with the ATCC 33701 strain showed clinical signs of pulmonary disease within 5-13 days, such as gross lesions associated with acute bronchopneumonia and microscopic lesions associated with granulomatous pneumonia. The two ...
Ulbert S.West Nile virus (WNV) is a zoonotic virus that circulates in birds and is transmitted by mosquitoes. Incidentally, humans, horses and other mammals can also be infected. Disease symptoms caused by WNV range from fever to neurological complications, such as encephalitis or meningitis. Mortality is observed mostly in older and immunocompromised individuals. In recent years, epidemics caused by WNV in humans and horses have become more frequent in several Southern European countries, such as Italy and Greece. In 1999, WNV was introduced into the USA and spread over North America within a couple o...
Van de Walle GR, May ML, Sukhumavasi W, von Einem J, Osterrieder N.Glycoprotein G (gG) of alphaherpesviruses has been described to function as a viral chemokine-binding protein (vCKBP). More recently, mutant viruses devoid of gG have been shown to result in increased virulence, but it remained unclear whether the potential of gG to serve as a vCKBP is responsible for this observation. In this study, we used equine herpesvirus type 1 (EHV-1) as a model to study the pathophysiological importance of vCKBP activity. First, in vitro chemotaxis assays studying migration of immune cells, an important function of chemokines, were established. In such assays, supernat...
Roy P, Bishop DH, Howard S, Aitchison H, Erasmus B.African horsesickness virus serotype 4 (AHSV-4) outer-capsid proteins VP2 or VP2 and VP5, prepared from single or dual recombinant baculovirus expression vectors grown in Sf9 insect cells, were administered in different amounts to horses and the neutralizing antibody responses were measured. Control and vaccinated horses were challenged with virulent AHSV-4 6 months later and monitored post challenge. The results indicated that two inoculations of extracts containing VP2 and VP5, or VP2 alone, in doses of 5 micrograms VP2 or more per horse, were sufficient to elicit protection against African ...
Tripathi VN, Harding WC, Willingham-Lane JM, Hondalus MK.Rhodococcus equi is a facultative intracellular, Gram-positive, soilborne actinomycete which can cause severe pyogranulomatous pneumonia with abscessation in young horses (foals) and in immunocompromised people, such as persons with AIDS. All strains of R. equi isolated from foals and approximately a third isolated from humans contain a large, ~81-kb plasmid which is essential for the intramacrophage growth of the organism and for virulence in foals and murine in vivo model systems. We found that the entire virulence plasmid could be transferred from plasmid-containing strains of R. equi (dono...
Matsumura T, Kondo T, Sugita S, Damiani AM, O'Callaghan DJ, Imagawa H.The cell culture-adapted KyA strain of equine herpesvirus type 1 (EHV-1) has been found to be attenuated in young horses (Matsumura et al., 1996, Vet. Microbiol. 48, 353-365). The KyA strain lacks at least six genes in its genome, including those encoding glycoproteins gE and gI. To elucidate whether EHV-1 glycoproteins gE and gI play a role in viral virulence, we have constructed an EHV-1 recombinant that has the genes encoding both gE and gI deleted from its genome and its revertant. Growth properties of the deletion mutant virus in vitro were compared with those of the parent and the revert...
Meehan M, Lynagh Y, Woods C, Owen P.The major cell-wall-associated protein of the equine pathogen Streptococcus equi subsp. equi is an M-like fibrinogen-binding protein (FgBP) which binds equine fibrinogen (Fg) avidly, through residues located at the extreme N-terminus of the molecule. In this study, it is shown that FgBP additionally binds equine IgG-Fc. When tested against polyclonal IgG from ten other animal species, it was found that FgBP binds human, rabbit, pig and cat IgG, but does not bind mouse, rat, goat, sheep, cow or chicken IgG. Through the use of a panel of recombinant FgBP truncates containing defined deletions of...
Makrai L, Takai S, Tamura M, Tsukamoto A, Sekimoto R, Sasaki Y, Kakuda T, Tsubaki S, Varga J, Fodor L, Solymosi N, Major A.Rhodococcus equi isolates (204) obtained from foals (lung abscesses, lymph nodes, nasal discharge, rectal swabs) bred in 15 studs located throughout Hungary, isolates from soil samples, lymph nodes of pigs and from lesions of human patients were examined to determine genotypic diversity of virulence-associated plasmids. Isolates were tested for the presence of 15-17 kDa virulence-associated protein antigen (VapA) and 20k Da (VapB) genes by polymerase chain reaction (PCR). Plasmid DNAs were isolated and analysed by digestion with restriction endonucleases for estimation of size and comparison o...
Wang XF, Lin YZ, Li Q, Liu Q, Zhao WW, Du C, Chen J, Wang X, Zhou JH.The equine infectious anemia virus (EIAV) vaccine is the only attenuated lentiviral vaccine applied on a large scale that has been shown to be effective in controlling the prevalence of EIA in China. This vaccine was developed by successive passaging of a field-isolated virulent strain in different hosts and cultivated cells. To explore the molecular basis for the phenotype alteration of this vaccine strain, we systematically analyzed its genomic evolution during vaccine development. Results: Sequence analysis revealed that the genetic distance between the wild-type strain and six representati...
Timoney JF, Kumar P.Little is known about entry and subsequent multiplication of Streptococcus equi following exposure of a susceptible horse. This information would have value in design of intranasal vaccines and understanding of shedding and protective immune responses. Objective: To determine entry points and sites of subsequent replication and dispersion of S. equi at different times after intranasal infection or commingling exposure. Methods: Previously unexposed horses and ponies were subjected to euthanasia 1, 3, 20 or 48 h following intranasal inoculation with biotin labelled or unlabelled S. equi CF32. S...
Matsumura T, O'Callaghan DJ, Kondo T, Kamada M.The virulence of the cell culture adapted KyA strain of equine herpesvirus type 1 (EHV-1), which lacks at least six genes by deletions in its genome, was assessed by intranasal inoculation of six young horses that were serologically negative for EHV-1. No horses showed clinical signs, and a neutralizing antibody response against EHV-1 was detected in two horses which had antibodies against EHV-4 prior to the inoculation. A challenge experiment using a highly virulent strain of EHV-1 conducted 4 weeks later against 4 of the 6 horses inoculated intranasally with the KyA strain and 2 control hors...
Willingham-Lane JM, Berghaus LJ, Giguère S, Hondalus MK.The soil-dwelling, saprophytic actinomycete is a multihost, facultative intracellular pathogen of macrophages. When inhaled by susceptible foals, it causes severe bronchopneumonia. It is also a pathogen of pigs, which may develop submaxillary lymphadenitis upon exposure. isolates obtained from foals and pigs possess conjugative plasmids housing a pathogenicity island (PAI) containing a novel family of genes of unknown function called the virulence-associated protein or family. The PAI regions of the equine and swine plasmids differ in gene composition, with equine isolates possessing six ...
