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Topic:Pathogens
Pathogens are microorganisms, such as bacteria, viruses, fungi, and parasites, that can cause disease in horses. These microorganisms interact with the equine immune system, often leading to a range of health issues that can affect individual horses or entire populations. Pathogens can be transmitted through various routes, including direct contact, vectors, or environmental exposure. Common equine pathogens include Streptococcus equi, Equine Herpesvirus, and Strongylus vulgaris. Understanding the interactions between equine hosts and pathogens is essential for disease prevention, management, and treatment. This page compiles peer-reviewed research studies and scholarly articles that explore the identification, transmission, and impact of pathogens on equine health.
Sero types, phage types and antibiotic susceptibilities of Salmonella strains isolated from horses in The Netherlands from 1993 to 2000. We studied 232 Salmonella strains from horses with salmonellosis in The Netherlands, isolated in the period from 1993 to 2000 in order to provide insight in the dynamics of sero-, phage types (pt) and antibiotic susceptibilities over time. The strains were tested for susceptibility to seven antimicrobial agents using the agar diffusion method. In addition, the isolates were sero typed and Salmonella enterica subspecies enterica Typhimurium and Enteritidis strains were further phage typed. S. Typhimurium strains of phage type 506 and 401 (both classified as DT 104 in the English phage typing sy...
Development of a nested polymerase chain reaction assay for the detection and identification of Pythium insidiosum. Pythium insidiosum is an important cause of cutaneous and gastrointestinal disease in horses and dogs in the southeastern United States. Culture-based diagnosis of pythiosis is rarely definitive because production and identification of reproductive structures is difficult. The purpose of this study was to develop a polymerase chain reaction (PCR)-based assay for the identification of P insidiosum. Genomic DNA was extracted from 3 clinical isolates of P insidiosum and I isolate each of Pythium graminicola and Pythium arrhenomanes. The ITS I region of the ribosomal RNA gene of each isolate was a...
Surface immunolocalisation of HPr in the equine pathogen Streptococcus equi. We have investigated the surface localisation of the phosphotransferase system protein HPr in the equine pathogen Streptococcus equi subsp. equi using immunogold localisation and transmission electron microscopy. Like the LppC acid phosphatase lipoprotein, a reference surface antigen, the S. equi HPR could be clearly detected on the surfaces of intact cells. This study is consistent with previous reports that some streptococcal HPr is cell surface associated and suggests that the extracytoplasmic mobilisation and transfer of phosphate groups by streptococci warrant further investigation.
Identification of virulence attributes of gastrointestinal Escherichia coli isolates of veterinary significance. The pathogenic strains of Escherichia coli recovered from the intestinal tract of animals fall into categories called enterotoxigenic, enteropathogenic, enterohemorrhagic and necrotoxigenic. The other two categories, enteroinvasive and enteroaggregative, have not been reported in animals. The pathogenicity of these strains is determined by the presence of certain genes that encode adhesins and toxins, are generally organized in large blocks in chromosomes, large plasmids or phages, and are often transmitted horizontally between strains. In this review, we summarize current knowledge of the vir...
Molecular analysis of Neorickettsia risticii in adult aquatic insects in Pennsylvania, in horses infected by ingestion of insects, and isolated in cell culture. Upon ingestion of adult aquatic insects, horses developed clinical signs of Potomac horse fever, and Neorickettsia risticii was isolated from the blood. 16S rRNA and 51-kDa antigen gene sequences from blood, isolates, and caddis flies fed to the horses were identical, proving oral transmission of N. risticii from caddis flies to horses.
Analysis of non-porcine isolates of Actinobacillus suis. Twenty-four Actinobacillus suis isolates obtained from several species of non-porcine mammals were compared to the representative porcine strains, ATCC 15557 (serotype O1) and H89-1173 (serotype O2), by O serotyping, DNA fingerprinting, PCR amplification of apxICA, apxIICA and apxIIICA toxin genes and by rrs (16S rRNA) gene sequencing. Only two strains, both equine, reacted with O1 antiserum while two others, one canine and the other feline, reacted with O2 antiserum. One equine strain reacted weakly with both antisera. No amplification of apx genes was found with the non-porcine O1 or the "no...
Fescue toxicosis. Most of the tall fescue pastures in the United States are infected by an endophyte, N. coenophialum. The fungus derives nutrients from the plant while supplying the plant with toxins for defense. The most detrimental toxins for animals in tall fescue are ergopeptine alkaloids, especially ergovaline. Ergovaline functions as a dopamine D2 agonist and alters prolactin and several other hormones in the body. Pregnant mares are most susceptible during their last month of gestation. Clinical signs include prolonged gestation, dystocia, retained placentas, agalactia, and dysmature foals that are eith...
Handling forensic necropsy cases. Immediately record the findings. A tape recorder would be excellent for this. If none is available, findings should be written down as soon as possible before memory of the examination fades. It is important to record comments on every organ that you examined. Three years from now in a court deposition, it may be difficult for the practitioner to remember if he looked at the adrenal glands or if there was no gross evidence of hyperplasia. When writing a report, it is a good idea to describe the tissue changes rather than just to give an interpretation. An example of the latter would be, "The h...
[Enterotoxin-producing Bacteroides fragilis strains isolated from horses]. Seven Bacteroides fragilis strains were cultured from samples collected from horses. From all the tested strains, as well as from the reference B. fragilis strains: enterotoxigenic NCTC 11925 and nonenterotoxigenic IPL 323 strain, DNA was isolated using Genomic DNA PREP PLUS isolation kit manufactured by A&A Biotechnology (Poland). To detect the enterotoxin (fragilysin) gene, polymerase chain reaction (PCR) was applied, using the following starters: 404 (GAG CCG AAG ACG GTG TAT GTG ATT TGT) and 407 (TGC TCA GCG CCC AGT ATA TGA CCT AGT). DNA obtained from bacterial cells was amplified in a ...
Prevalence of virulent Rhodococcus equi in soil from five R. equi-endemic horse-breeding farms and restriction fragment length polymorphisms of virulence plasmids in isolates from soil and infected foals in Texas. Rhodococcus equi isolates (462) obtained from 64 soil samples collected on 5 R. equi-endemic horse-breeding farms and isolates from 100 infected foals in Texas were examined to determine the prevalence and genotypic diversity of virulence-associated plasmids. Isolates were tested for the presence of 15-17-kDa virulence-associated protein antigens (VapA) by immunoblotting and virulence-associated plasmids by PCR. Plasmid DNAs were isolated and analyzed by digestion with restriction endonucleases for estimation of size and comparison of polymorphisims. Rhodococcus equi were isolated from soil of...
Enterotoxigenic potential of Staphylococcus intermedius. Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In contrast to Staphylococcus aureus, a systematic screening for the enterotoxins has not yet been performed on the genomic level for the coagulase-positive species S. intermedius. Therefore, the enterotoxigenic potential of 281 different veterinary (canine, n = 247; equine, n = 23; feline, n = 9; other, n = 2) and 11 human isolates of S. intermedius was tested by using a multiplex PCR DNA-enzyme immunoassay system targeting the staphylococcal enterotoxin genes sea, seb, sec, sed...
Molecular characterization of thermoinduced immunogenic proteins Q1p42 and Hsp15 of Leptospira interrogans. Leptospira interrogans is a mammalian pathogen which must adapt to a range of new environmental conditions including temperature change when it infects new hosts. In vitro studies of organisms cultured at 30 degrees C and shifted to 37 degrees C for 5 to 7 days have confirmed that synthesis of several proteins involved in equine infection is regulated in response to temperature change (J. E. Nally, J. F. Timoney, and B. Stevenson, Infect. Immun. 69:400-404, 2001). In order to specifically identify antigenic proteins upregulated at 37 degrees C, groups of three ponies were immunized with organi...
High-dose Borna disease virus infection induces a nucleoprotein-specific cytotoxic T-lymphocyte response and prevention of immunopathology. Experimental Borna disease virus (BDV) infection of rats and natural infection of horses and sheep leads to severe central nervous system disease based on immunopathological pathways. The virus replicates slowly, and the cellular immune response results in immunopathology. CD8(+) T cells exert effector cell functions, and their activity results in the destruction of virus-infected cells. Previously, Oldach and colleagues (D. Oldach, M. C. Zink, J. M. Pyper, S. Herzog, R. Rott, O. Narayan, and J. E. Clements, Virology 206:426-434, 1995) have reported protection against Borna disease after inocu...
Seasonality and relative abundance of Tabanidae (Diptera) captured on horses in the Pantanal, Brazil. Once a month, from June 1992 to May 1993, collections of tabanids on horse were conducted in the Nhecolândia, Pantanal State of Mato Grosso do Sul, Brazil. Tabanid catches using hand nets were conducted from sunrise to sunset at grassland and cerradão (dense savanna) habitats. A total of 3,442 tabanids from 21 species,12 genera, and 3 subfamilies were collected. Although species abundance varied seasonally depending on habitat, no habitat specificity was observed for the most abundant species. In the grassland, 1,625 (47.2%) tabanids belonging to 19 species were collected, while 1,817 (52.8%...
Emergence of Salmonella typhimurium definitive type 104 (DT104) as an important cause of salmonellosis in horses in Ontario. Salmonella Typhimurium definitive type 104 (DT104) has emerged as a common cause of salmonellosis in humans and cattle, yet previous reports involving horses are sparse. This study reports the emergence of DT104 as an important pathogen in horses in Ontario. The first clinical case of DT104 infection at the Ontario Veterinary College was identified in 1997. Seventeen cases of DT104-associated salmonellosis were identified between 1997 and 2000. In 2000, 12 of 13 cases of salmonellosis were due to DT104. Salmonellosis in horses due to DT104 is of concern, since the organism is multiresistant to...
Pharmacokinetics of fluconazole following intravenous and oral administration and body fluid concentrations of fluconazole following repeated oral dosing in horses. To determine the pharmacokinetics of fluconazole in horses. Methods: 6 clinically normal adult horses. Methods: Fluconazole (10 mg/kg of body weight) was administered intravenously or orally with 2 weeks between treatments. Plasma fluconazole concentrations were determined prior to and 10, 20, 30, 40, and 60 minutes and 2, 4, 6, 8, 10, 12, 24, 36, 48, 60, and 72 hours after administration. A long-term oral dosing regimen was designed in which all horses received a loading dose of fluconazole (14 mg/kg) followed by 5 mg/kg every 24 hours for 10 days. Fluconazole concentrations were determined i...
Prevalence of virulent Rhodococcus equi in isolates from soil collected from two horse farms in South Africa and restriction fragment length polymorphisms of virulence plasmids in the isolates from infected foals, a dog and a monkey. The prevalence of virulent Rhodococcus equi in soil isolates from two horse farms in South Africa and nine clinical isolates from six foals, a foal foetus, a dog, and a monkey was investigated. The isolates were tested for the presence of virulence plasmid DNA and 15- to 17-kDa antigens by immunoblotting. Rhodococcus equi was isolated from almost all of the soil samples obtained from the two farms with 5.0 x 10(1) to 3.3 x 10(4) colony forming units per gram of soil. Virulent R. equi was isolated from three soil samples from one of the farms and appeared in 3.8% (three of 80 isolates), but not...
Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from Hereford cattle and ponies treated with permethrin. The blood feeding of mosquitoes and black flies from Hereford cattle and ponies treated with commercial formulations of permethrin was evaluated using an animal enclosure trap sample system that allowed comparison of insect blood-feeding levels between treated and nontreated animals. Blood feeding of both Aedes dorsalis Meigen and A. melanimon Dyar from heifers treated with pour-on concentrate and whole body spray treatments was reduced significantly by 79-88% at 4 d posttreatment, with apparent but not significant reductions of 61-68% at 11 d posttreatment. Simulium bivittatum Malloch and S. ...
Isolation of single-chain antibody fragments against Venezuelan equine encephalomyelitis virus from two different immune sources. Venezuelan equine encephalomyelitis (VEE) virus is an important human and veterinary pathogen of Central and South America. The virus can cause widespread epidemics, affecting hundreds of thousands of horses, and thousands of humans. Detection of the virus early in infection and in mosquito populations may allow epidemics to be predicted such that suitable prophylaxis, such as vaccination, can be used to reduce disease severity and transmission. The sensitivity and specificity of current immunoassays, based on conventional monoclonal and polyclonal antibodies, needs to be improved for the diag...
Serum and vitreous humor antibody titers in and isolation of Leptospira interrogans from horses with recurrent uveitis. To measure antibody titers against Leptospira interrogans in serum and vitreous humor and determine the prevalence of L interrogans in vitreous humor of horses with recurrent uveitis. Methods: Cross-sectional study. Methods: 242 horses (270 eyes) with recurrent uveitis undergoing vitrectomy and 39 control horses (54 eyes) without any history or clinical signs of recurrent uveitis undergoing euthanasia or enucleation for unrelated reasons. Methods: Serum and vitreous humor were tested for antibodies against 13 serovars of L interrogans. Vitreous humor was submitted for leptospiral culture; isol...
Reactivity of serum samples of dogs and horses tested by use of class-specific recombinant-based enzyme-linked immunosorbent assays for detection of granulocytic ehrlichiosis. To test serum samples of dogs and horses by use of class-specific recombinant-based ELISA for establishing a diagnosis of granulocytic ehrlichiosis attributable to infection with organisms from the Ehrlichia phagocytophila genogroup. Methods: Serum samples from 43 client-owned dogs and 131 horses (81 with signs of acute illness and 50 without signs of disease). Methods: Serum samples were analyzed, using ELISA with a recombinant 44-kd protein antigen for IgM and IgG antibodies to the human granulocytic ehrlichiosis (HGE) agent (NCH-1 strain). Western blot analyses, using infected human promyel...
Transmission of opportunistic pathogens in a veterinary teaching hospital. Acinetobacter baumannii, Enterococcus faecalis, Enterococcus faecium, and Staphylococcus intermedius isolates from infected surgical wounds and other types of infections in a veterinary teaching hospital were typed by pulsed field gel electrophoresis. A first cluster of infections with a multiresistant A. baumannii strain was observed in dogs and cats in 1998-1999. This strain disappeared after cleaning and disinfection of the companion animals intensive care unit. It was followed in 2000 by a second multiresistant strain, which caused another cluster of infections and was also transmitted to ...
Two new variants of the Rhodococcus equi virulence plasmid, 90 kb type III and type IV, recovered from a foal in Japan. This report describes the discovery of two new virulence plasmid types from a crossbred foal with Rhodococcus equi pneumonia in Kumamoto died with severe R. equi pneumonia and ulcerative enteritis. R. equi was isolated in large numbers and isolates from the foal were investigated for the presence of virulence-associated 15-17 kDa antigens (VapA) by colony blotting, using the monoclonal antibody 10G5, and by gene coding for VapA by PCR. Plasmid DNAs extracted from the isolates were digested with restriction endonucleases BamHI, EcoRI, EcoT22I, and HindIII. The digestion patterns that resulted d...
Pharmacokinetics of orbifloxacin and its concentration in body fluids and in endometrial tissues of mares. Pharmacokinetics and distribution of orbifloxacin into body fluids and endometrium was studied in 6 mares after intragastric (IG) administration at a single dose rate of 7.5 mg/kg body weight. Orbifloxacin concentrations were serially measured in serum, synovial fluid, peritoneal fluid, urine, cerebrospinal fluid, and endometrial tissues over 24 hours. Minimum inhibitory concentrations of orbifloxacin were determined for 120 equine pathogens over an 11-month period. The mean peak serum concentration (Cmax) was 2.41+/-0.30 microg/mL at 1.5 hours after administration and decreased to 0.17+/-0.01...
Characterization of mutations in the rpoB gene associated with rifampin resistance in Rhodococcus equi isolated from foals. Treatment with a combination of erythromycin and rifampin has considerably improved survival rates of foals and immunocompromised patients suffering from severe pneumonia caused by Rhodococcus equi. Frequently, because of monotherapy, emergence of rifampin-resistant strains has been responsible for treatment failure. Using consensus oligonucleotides, we have amplified and sequenced the rifampin resistance (Rif(r))-determining regions of 12 rifampin-resistant R. equi strains isolated from three foals and of mutants selected in vitro from R. equi ATCC 3701, a rifampin-susceptible strain. The ded...
A prospective study of the roles of clostridium difficile and enterotoxigenic Clostridium perfringens in equine diarrhoea. Faecal samples from adult horses and from foals with diarrhoea or with normal faeces were evaluated for the presence of Clostridium difficile, C. difficile toxins, C. perfringens enterotoxin (CPE) and C. perfringens spore counts. Clostridium difficile was isolated from 7/55 horses (12.7%) and 11/31 foals (35.5%) with colitis, but from 1/255 normal adults (0.4%) and 0/47 normal foals (P<0.001). Clostridium difficile toxins A and/or B were detected in 12/55 diarrhoeic adults (21.8%) and 5/30 diarrhoeic foals (16.7%) but in only 1/83 adults (1.2%) and 0/21 foals with normal faeces (P<0.001 and P<...
