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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.
Identification of Pythium insidiosum by nested PCR in cutaneous lesions of Brazilian horses and rabbits. Pythium insidiosum is a fungus-like organism present in subtropical and tropical areas, such as Brazil, known to infect humans and various animal species. P. insidiosum is the etiological agent of pythiosis, an emerging and granulomatous disease characterized mainly by cutaneous and subcutaneous lesions in horses, the principal species affected. Accurate diagnosis of pythiosis and identification of its causal agent by microbiological and serological tests can be often difficult and inconclusive principally for horses and humans. The aim of this study was to evaluate the application of the prev...
Pharmacokinetics in pulmonary epithelial lining fluid and plasma of ampicillin and pivampicillin administered to horses. Ampicillin concentrations in pulmonary epithelial lining fluid (PELF) and plasma was studied after single intravenous ampicillin administration (15mg/kg) or single intragastric administration of its prodrug, pivampicillin (19.9mg/kg) to horses and discussed in relation to minimum inhibitory concentrations (MIC) of common equine respiratory pathogens. After intravenous administration, elimination of ampicillin was fast and not detectable in plasma after 12h in three out of six horses. Pivampicillin was absorbed well in non-fasted horses with an oral bioavailability of 36%. The degree of penetra...
Retrospective study of necropsy-associated coagulase-positive staphylococci in horses. Coagulase-positive staphylococci (CoPS) are potential causative agents of equine infections, but they are rarely responsible for the death of the animal. In the current study, staphylococci implicated in the death or euthanasia of horses were retrospectively studied in 3,457 necropsies performed over a decade (1995-2006). Morbidity associated with CoPS was 1.7%, representing 60 isolates of CoPS, which were identified as Staphylococcus aureus (59) and Staphylococcus pseudintermedius (1). Coagulase-positive staphylococci (alone or in association with another bacterial species) were associated wi...
Pharmacokinetics of ceftiofur sodium and ceftiofur crystalline free acid in neonatal foals. Ceftiofur, a third generation cephalosporin, demonstrates in vitro efficacy against microorganisms isolated from septicemic neonatal foals. This pharmacokinetic study evaluated the intravenous and subcutaneous administration of ceftiofur sodium (5 mg/kg body weight; n = 6 per group) and subcutaneous administration of ceftiofur crystalline free acid (6.6 mg/kg body weight; n = 6) in healthy foals. Plasma ceftiofur- and desfuroylceftiofur-related metabolite concentrations were measured using high performance liquid chromatography following drug administration. Mean (±SD) noncompartmental pharma...
Improved detection of equine antibodies against Sarcocystis neurona using polyvalent ELISAs based on the parasite SnSAG surface antigens. Equine protozoal myeloencephalitis (EPM) is a common neurologic disease of horses that is caused by the apicomplexan pathogen Sarcocystis neurona. To help improve serologic diagnosis of S. neurona infection, we have modified existing enzyme-linked immunosorbent assays (ELISAs) based on the immunogenic parasite surface antigens SnSAG2, SnSAG3, and SnSAG4 to make the assays polyvalent, thereby circumventing difficulties associated with parasite antigenic variants and diversity in equine immune responses. Two approaches were utilized to achieve polyvalence: (1) mixtures of the individual recombin...
Genome sequence conservation of Hendra virus isolates during spillover to horses, Australia. Bat-to-horse transmission of Hendra virus has occurred at least 14 times. Although clinical signs in horses have differed, genome sequencing has demonstrated little variation among the isolates. Our sequencing of 5 isolates from recent Hendra virus outbreaks in horses found no correlation between sequences and time or geographic location of outbreaks.
Immunotherapy for pythiosis: Effect on NTPDase activity in lymphocytes of an experimental model. NTPDase (EC 3.6.1.5) occurs in lymphocytes and plays an important role in immune function, in that hydrolyzes extracellular nucleoside tri- and/or diphosphates to form AMP. Pythium insidiosum causes the disease pythiosis, a pyogranulomatous disease of horses, dogs, cattle, cats and humans. Most antifungal drugs are ineffective against this pathogen, and immunotherapy, a treatment approach that relies on the injection of P. insidiosum antigen, has been successfully used in humans and horses to manage this disease. In this study, we investigated NTPDase activity in lymphocytes from rabbits inocu...
Geotrichum candidum as etiological agent of horse dermatomycosis. Fungi of the genus Geotrichum are commonly found in the environment and, in some circumstances, they may cause diseases in humans and animals. Although these fungi have been isolated from skin lesions of some animal species, their pathogenic role in horses remains uncertain. With the aim to investigate the role of Geotrichum candidum as etiological agent of dermatomycoses, a retrospective study of 64 horses presenting skin lesions and suspected to have fungal infections was carried out. For each animal, anamnestic data were recorded and fungal culture were performed using hair. Out of 64 cases...
Historical thoughts on influenza viral ecosystems, or behold a pale horse, dead dogs, failing fowl, and sick swine. To understand human influenza in a historical context of viral circulation in avian species, mammals, and in the environment. Methods: Historical review. Methods: Global events in a variety of circumstances over more than 3,000 years time. Methods: Comprehensive review of the historical literature including all major publications on pandemic and panzootic influenza. Methods: Influenza pandemics, panzootics, major epidemics and epizootics, and instances of interspecies transmission of influenza A. Results: Extensive documentation of human and animal influenza over many centuries suggests that i...
Antimicrobial activity of tulathromycin and 14 other antimicrobials against virulent Rhodococcus equi in vitro. This study determined the antimicrobial activity of tulathromycin against Rhodococcus equi in vitro. Ninety-eight virulent isolates of R. equi from equine clinical cases were examined, of which 20 isolates were macrolide resistant. A custom 96-well antimicrobial susceptibility testing plate was used, allowing 14 additional antimicrobials to be tested against R. equi. Isolates were cultured with various concentrations of antimicrobials, and minimal inhibitory concentration (MIC) values were determined. Tulathromycin was found to have poor activity in vitro against R. equi isolates susceptible o...
Evaluation of virulence factor profiling in the characterization of veterinary Escherichia coli isolates. Escherichia coli has been used as an indicator organism for fecal contamination of water and other environments and is often a commensal organism in healthy animals, yet a number of strains can cause disease in young or immunocompromised animals. In this study, 281 E. coli isolates from bovine, porcine, chicken, canine, equine, feline, and other veterinary sources were analyzed by BOXA1R PCR and by virulence factor profiling of 35 factors to determine whether they had utility in identifying the animal source of the isolates. The results of BOXA1R PCR analysis demonstrated a high degree of dive...
Adaptation of Staphylococcus aureus to ruminant and equine hosts involves SaPI-carried variants of von Willebrand factor-binding protein. Staphylococci adapt specifically to various animal hosts by genetically determined mechanisms that are not well understood. One such adaptation involves the ability to coagulate host plasma, by which strains isolated from ruminants or horses can be differentiated from closely related human strains. Here, we report first that this differential coagulation activity is due to animal-specific alleles of the von Willebrand factor-binding protein (vWbp) gene, vwb, and second that these vwb alleles are carried by highly mobile pathogenicity islands, SaPIs. Although all Staphylococcus aureus possess c...
Pharmacokinetics and tissue distribution of minocycline hydrochloride in horses. To determine the pharmacokinetics and tissue distribution of minocycline in horses. Methods: 5 healthy Thoroughbred mares for the pharmacokinetic experiment and 6 healthy Thoroughbred mares for the tissue distribution experiment. Methods: Each mare was given 2.2 mg of minocycline hydrochloride/kg, IV. Blood samples were collected once before minocycline administration (0 hours) and 10 times within 48 hours after administration in the pharmacokinetics study, and 24 tissue samples were obtained at 0.5 and 3 hours in the distribution study. Results: No adverse effects were observed in any of the ...
Molecular characterisation of ‘strangles’ outbreaks in the UK: the use of M-protein typing of Streptococcus equi ssp. equi. Strangles is the most commonly diagnosed and important infectious disease of horses worldwide. Very little is known about the temporo-spatial and molecular epidemiology of strangles. The disease is not notifiable in the UK and there are few published data on the geographical locations of outbreaks. Objective: To investigate whether typing of a surface protein (SeM) of Streptococcus equi ssp. equi (S. equi), the causative agent of strangles, is a useful epidemiological tool. Methods: The variable region of the SeM gene was amplified from 145 isolates of S. equi by PCR and sequenced. Different S...
Characterization of vancomycin-resistant Enterococcus faecium isolated from swine in three Michigan counties. Vancomycin-resistant enterococci are a major cause of nosocomial infections but are rarely found in humans in the community and have not been identified in food animals in the United States. We evaluated a total of 360 fecal specimens from humans and their animals being raised for exhibit at three county fairs in Michigan. Fecal samples from 158 humans, 55 swine, 50 cattle, 25 horses, 57 sheep, 14 goats, and 1 llama were obtained and plated onto Enterococcosel agar containing 16 μg/ml of vancomycin. Vancomycin-resistant Enterococcus faecium (VREF) was isolated from six pigs but not from human...
Use of blood culture medium enrichment for synovial fluid culture in horses: a comparison of different culture methods. Standard methods for culturing equine synovial fluid (SF) are often unrewarding. Evidence-based information on the relative efficiency of different systems used for optimisation of isolation of microorganisms from equine SF is lacking. Objective: To compare the results of different culture systems performed in parallel on SF samples from horses clinically diagnosed with synovial sepsis. Methods: Synovial fluid specimens were collected between February 2007 and October 2008 from all horses admitted to a referral hospital that were clinically diagnosed with synovial sepsis and from control horse...
Identification of three novel superantigen-encoding genes in Streptococcus equi subsp. zooepidemicus, szeF, szeN, and szeP. The acquisition of superantigen-encoding genes by Streptococcus pyogenes has been associated with increased morbidity and mortality in humans, and the gain of four superantigens by Streptococcus equi is linked to the evolution of this host-restricted pathogen from an ancestral strain of the opportunistic pathogen Streptococcus equi subsp. zooepidemicus. A recent study determined that the culture supernatants of several S. equi subsp. zooepidemicus strains possessed mitogenic activity but lacked known superantigen-encoding genes. Here, we report the identification and activities of three novel ...
West Nile virus range expansion into British Columbia. In 2009, an expansion of West Nile virus (WNV) into the Canadian province of British Columbia was detected. Two locally acquired cases of infection in humans and 3 cases of infection in horses were detected by ELISA and plaque-reduction neutralization tests. Ten positive mosquito pools were detected by reverse transcription PCR. Most WNV activity in British Columbia in 2009 occurred in the hot and dry southern Okanagan Valley. Virus establishment and amplification in this region was likely facilitated by above average nightly temperatures and a rapid accumulation of degree-days in late summer....
Pythium insidiosum: an overview. Pythium insidiosum is an oomycete pathogenic in mammals. The infection occurs mainly in tropical and subtropical areas, particularly in horses, dogs and humans. Infection is acquired through small wounds via contact with water that contains motile zoospores or other propagules (zoospores or hyphae). The disease, though described as emerging has in fact already been described since 1884. Depending on the site of entry, infection can lead to different forms of pythiosis i.e. a cutaneous, vascular, ocular, gastrointestinal and a systemic form, which is rarely seen. The infection is not contagious...
A potential role for indoleamine 2,3-dioxygenase (IDO) in Rhodococcus equi infection. Rhodococcus equi is a facultative intracellular bacterial pathogen of foals and immunocompromised humans that infects and proliferates within host macrophages and dendritic cells (DC). Indoleamine 2,3-dioxygenase (IDO), the initial enzyme in the tryptophan catabolism pathway, is upregulated in R. equi infected equine monocyte-derived DC and alveolar macrophages. Tryptophan requirement of R. equi for extracellular and intracellular growth was assessed. Growth of R. equi in minimal media did not require tryptophan and pharmacologic inhibition of IDO had no effect on intracellular proliferation o...
Detection of strain variation in isolates of Rhodococcus equi from an affected foal using repetitive sequence-based polymerase chain reaction. Rhodococcus equi is an important pathogen of foals aged 1-6 months. Evidence exists that foals are exposed to a wide diversity of R. equi strains in their environment. However, limited data are available regarding the extent to which genotypic variation exists among isolates infecting individual foals. Therefore, electrophoresis of repetitive sequence-based polymerase chain reaction (rep-PCR) amplicons in an automated microfluidics chip format was used to genotype 9 virulent R. equi isolates obtained from distinct anatomic locations in a single foal. Four of the isolates were obtained from dif...
Enrofloxacin-based therapeutic strategy for the prevention of endometritis in susceptible mares. Enrofloxacin (EFX) is often used empirically to prevent uterine infections in mares in order to improve efficiency on Commercial Embryo Transfer Farms. This study investigated the uterine distribution of EFX and its metabolite ciprofloxacin (CFX) in mares and assessed the minimal inhibitory concentrations (MIC) of EFX against various common pathogens as a basis for establishing a rational dosing schedule. Plasma and uterine pharmacokinetic (PK) studies were performed in two groups (n = 5) of healthy mares following intravenous (i.v.) administration of EFX at either 2.5 and at 5 mg/kg bodyweigh...
Carriage of Clostridium difficile and other enteric pathogens among a 4-H avocational cohort. Clostridium difficile (CD), Salmonella, Campylobacter and enterohemorrhagic Escherichia coli (EHEC) are major causes of morbidity in a variety of enteric diseases in humans and animals, but subclinical carriage in both is probably more common than are clinical cases. Little is known regarding the prevalence of these pathogens in animals raised for exhibit at Michigan county fairs or the frequency with which Michigan citizens raising these animals may have been subclinically colonized. To address these issues, 361 fecal specimens from 158 humans and 203 of their farm animals were cultured for C...
Proinflammatory cytokine responses of cultured equine keratinocytes to bacterial pathogen-associated molecular pattern motifs. Further knowledge of equine keratinocyte physiology and keratinocyte response to various stimuli is important in developing a better understanding of disease states involving the epidermis. Objective: To assess the inflammatory cytokine response of cultured equine keratinocytes to various pathogen-associated molecular pattern molecules (PAMPs) from both Gram-negative and positive bacteria likely to be present in equine sepsis. Methods: Keratinocytes were isolated from skin of 2 horses and primary cultures performed. Keratinocytes were harvested for RNA extraction after exposure to lipopolysacc...
Vector competence of Culex (Melanoconion) taeniopus for equine-virulent subtype IE strains of Venezuelan equine encephalitis virus. The mosquito Culex (Melanoconion) taeniopus is a proven vector of enzootic Venezuelan equine encephalitis virus (VEEV) subtype IE in Central America. It has been shown to be highly susceptible to infection by this subtype, and conversely to be highly refractory to infection by other VEEV subtypes. During the 1990s in southern coastal Mexico, two VEE epizootics in horses were attributed to subtype IE VEEV. These outbreaks were associated with VEEV strains with an altered infection phenotype for the epizootic mosquito vector, Aedes (Ochlerotatus) taeniorhynchus. To determine the infectivity for ...
In vitro antimicrobial activity of gallium maltolate against virulent Rhodococcus equi. The objective of this study was to determine the in vitro antimicrobial activity of gallium maltolate (GaM) against Rhodococcus equi. A total of 98 virulent bacterial isolates from equine clinical cases were examined, of which 19 isolates were known to be resistant to macrolides and rifampin. Isolates were cultured with various concentrations of GaM and minimal inhibitory concentration (MIC) values were determined after 24 and 48 h. Both the MIC(50) and the MIC(90) after 24h of growth were 558 ng/mL (8 μM) and after 48 h of growth were 2230 ng/mL (32 μM). There were no apparent differences b...
Ceftiofur derivates in serum and endometrial tissue after intramuscular administration in healthy mares. Endometritis is one of the major problems in the horse breeding industry. The use of antibiotics for treatment of endometritis in the mare is recommended as best practice. The intrauterine application of antibiotics, however, has been under discussion over the last years because of concerns about its efficacy. The systemic use of antibiotics has been considered more effective because of its better distribution within the uterus. The objective of the present study was to determine the concentration of ceftiofur derivates in serum and endometrial tissue after intramuscular administration. Specif...
Pathological changes caused by Anoplocephala perfoliata in the equine ileocecal junction. Gastrointestinal motility disorders represent a significant cause of morbidity and mortality in horses. Previously regarded as a non-pathogenic tapeworm, Anoplocephala perfoliata has been recently associated with equine colic. In this study, pathological changes related to A. perfoliata at the ileocecal junction were investigated in 31 slaughtered horses. Our results showed a significant relationship between parasitic burden and grading of histopathological lesions in both the mucosa and submucosa. Moreover, in infested horses, hypertrophy of the circular muscle layer was determined. Finally, ...
