Risk factors associated with Corynebacterium pseudotuberculosis infection in California horses

Exploration of Nitrate Reductase Metabolic Pathway in Corynebacterium pseudotuberculosis

Based on the ability of nitrate reductase synthesis, Corynebacterium pseudotuberculosis is classified into two biovars: Ovis and Equi. Due to the presence of nitrate reductase, the Equi biovar can survive in absence of oxygen. On the other hand, Ovis biovar that does not have nitrate reductase is able to adapt to various ecological niches and can grow on certain carbon sources. Apart from these two biovars, some other strains are also able to carry out the reduction of nitrate. The enzymes that are involved in electron transport chain are also identified by in silico methods. Findings about pathogen metabolism can contribute to the identification of relationship between nitrate reductase and the C. pseudotuberculosis pathogenicity, virulence factors, and discovery of drug targets.

Assessing the Genotypic Differences between Strains of Corynebacterium pseudotuberculosis biovar equi through Comparative Genomics

Seven genomes of Corynebacterium pseudotuberculosis biovar equi were sequenced on the Ion Torrent PGM platform, generating high-quality scaffolds over 2.35 Mbp. This bacterium is the causative agent of disease known as "pigeon fever" which commonly affects horses worldwide. The pangenome of biovar equi was calculated and two phylogenomic approaches were used to identify clustering patterns within Corynebacterium genus. Furthermore, other comparative analyses were performed including the prediction of genomic islands and prophages, and SNP-based phylogeny. In the phylogenomic tree, C. pseudotuberculosis was divided into two distinct clades, one formed by nitrate non-reducing species (biovar ovis) and another formed by nitrate-reducing species (biovar equi). In the latter group, the strains isolated from California were more related to each other, while the strains CIP 52.97 and 1/06-A formed the outermost clade of the biovar equi. A total of 1,355 core genes were identified, corresponding to 42.5% of the pangenome. This pangenome has one of the smallest core genomes described in the literature, suggesting a high genetic variability of biovar equi of C. pseudotuberculosis. The analysis of the similarity between the resistance islands identified a higher proximity between the strains that caused more severe infectious conditions (infection in the internal organs). Pathogenicity islands were largely conserved between strains. Several genes that modulate the pathogenicity of C. pseudotuberculosis were described including peptidases, recombination enzymes, micoside synthesis enzymes, bacteriocins with antimicrobial activity and several others. Finally, no genotypic differences were observed between the strains that caused the three different types of infection (external abscess formation, infection with abscess formation in the internal organs, and ulcerative lymphangitis). Instead, it was noted that there is a higher phenetic correlation between strains isolated at California compared to the other strains. Additionally, high variability of resistance islands suggests gene acquisition through several events of horizontal gene transfer.

Bayesian Geostatistical Analysis and Ecoclimatic Determinants of Corynebacterium pseudotuberculosis Infection among Horses

Kansas witnessed an unprecedented outbreak in Corynebacterium pseudotuberculosis infection among horses, a disease commonly referred to as pigeon fever during fall 2012. Bayesian geostatistical models were developed to identify key environmental and climatic risk factors associated with C. pseudotuberculosis infection in horses. Positive infection status among horses (cases) was determined by positive test results for characteristic abscess formation, positive bacterial culture on purulent material obtained from a lanced abscess (n = 82), or positive serologic evidence of exposure to organism (≥1:512)(n = 11). Horses negative for these tests (n = 172)(controls) were considered free of infection. Information pertaining to horse demographics and stabled location were obtained through review of medical records and/or contact with horse owners via telephone. Covariate information for environmental and climatic determinants were obtained from USDA (soil attributes), USGS (land use/land cover), and NASA MODIS and NASA Prediction of Worldwide Renewable Resources (climate). Candidate covariates were screened using univariate regression models followed by Bayesian geostatistical models with and without covariates. The best performing model indicated a protective effect for higher soil moisture content (OR = 0.53, 95% CrI = 0.25, 0.71), and detrimental effects for higher land surface temperature (≥35°C) (OR = 2.81, 95% CrI = 2.21, 3.85) and habitat fragmentation (OR = 1.31, 95% CrI = 1.27, 2.22) for C. pseudotuberculosis infection status in horses, while age, gender and breed had no effect. Preventative and ecoclimatic significance of these findings are discussed.

The relationship between Corynebacterium pseudotuberculosis biovar equi phenotype with location and extent of lesions in horses

Equine infection with Corynebacterium pseudotuberculosis can manifest in several forms, including external or internal abscesses. The objective of this study was to phenotype clinical isolates of C. pseudotuberculosis and to investigate the relationship between lesion location and extent of lesions in the animals from which they were collected. One hundred and seventy-one C. pseudotuberculosis biovar equi isolates were collected from horses presenting to the University of California Veterinary Medical Teaching Hospital and two other sources in the period between September 1996 and December 2011. Bacterial isolates were grouped on the bases of biochemical characteristics and growth on brain heart infusion agar. Six phenotypes were identified: (1) large colonies that metabolized sucrose (n = 81); (2) large sucrose-negative colonies (n = 47); (3) medium sucrose-positive (n = 20); (4) medium sucrose-negative (n = 11); (5) small sucrose-positive (n = 7), and (6) small sucrose-negative (n = 5). Medical records corresponding to each isolate were accessed from the University's administrative computer system or from the submitting source in order to determine the anatomical site from which the isolate was collected (n = 171), as well as the extent of lesions (n = 164) in the patient. The relationship between phenotype, lesion location and extent of lesions was then investigated statistically. No significant relationship between strain and lesion location or extent of lesions was found. This suggests that phenotypic differences during in vitro culture does not account for external versus internal disease in horses. Further work to characterize strains genotypically and to identify determinants for bacterial virulence should be performed. Importantly, host and environmental factors should also be further investigated.

Isolation ofCorynebacterium pseudotuberculosisBiovarequifrom a Horse in Central Iowa

Corynebacterium pseudotuberculosisbiovarequiis the causative agent of “pigeon fever,” or “dryland distemper” in horses. The agent is typically identified in the Western United States but has recently been identified in Canada; it has not previously been documented as cause of infection in horses in Iowa. This report describes the clinical findings of two horses in Iowa that presented with pectoral abscessation, confirmed in one to beC. pseudotuberculosisbiovarequi.

Tips and tricks for the assembly of a Corynebacterium pseudotuberculosis genome using a semiconductor sequencer

New sequencing platforms have enabled rapid decoding of complete prokaryotic genomes at relatively low cost. The Ion Torrent platform is an example of these technologies, characterized by lower coverage, generating challenges for the genome assembly. One particular problem is the lack of genomes that enable reference-based assembly, such as the one used in the present study, Corynebacterium pseudotuberculosis biovar equi, which causes high economic losses in the US equine industry. The quality treatment strategy incorporated into the assembly pipeline enabled a 16-fold greater use of the sequencing data obtained compared with traditional quality filter approaches. Data preprocessing prior to the de novo assembly enabled the use of known methodologies in the next-generation sequencing data assembly. Moreover, manual curation was proved to be essential for ensuring a quality assembly, which was validated by comparative genomics with other species of the genus Corynebacterium. The present study presents a modus operandi that enables a greater and better use of data obtained from semiconductor sequencing for obtaining the complete genome from a prokaryotic microorganism, C. pseudotuberculosis, which is not a traditional biological model such as Escherichia coli.

Complete genome sequence of Corynebacterium pseudotuberculosis strain CIP 52.97, isolated from a horse in Kenya

In this work, we report the whole-genome sequence of Corynebacterium pseudotuberculosis bv. equi strain CIP 52.97 (Collection Institut Pasteur), isolated in 1952 from a case of ulcerative lymphangitis in a Kenyan horse, which has evidently caused significant losses to agribusiness. Therefore, obtaining this genome will allow the detection of important targets for postgenomic studies, with the aim of minimizing problems caused by this microorganism.

Pathologic findings in equine muscle (excluding polysaccharide storage): a necropsy study

Gross and histopathologic evaluation of skeletal muscle was performed in 229 equids (217 horses, 8 ponies, 3 donkeys, and 1 mule) 1 year of age or older undergoing postmortem examination at Oregon State University in a 2.5-year period. Animals were evaluated for grossly evident muscle lesions, and muscle samples were fixed in formalin, processed routinely, and stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) for glycogen. Muscle lesions were detected in 149 animals (65%). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses without polysaccharide storage myopathy and was the most common finding (36 animals; 15.7%). Chronic myopathic change was more common in older animals. Generalized muscle atrophy was present in 30 animals (13.1%). Myonecrosis was attributed to endotoxic injury (11 animals; 4.8%), bone fracture (8 animals; 3.5%), bacterial infection (5 animals; 2.2%), muscle rupture (3 animals; 1.3%), selenium deficiency (2 animals; 0.9%), and exertional rhabdomyolysis (1 horse; 0.4%); cause was not determined in 9 animals (3.9%). Intramyofiber protozoa were detected in 19 horses and ponies (8.3%). Denervation atrophy was detected in 14 animals (6.1%). Neoplasia involving muscle occurred in 3 animals (1.3%), injection site reactions were detected in 4 animals (1.7%), and focal lymphocytic infiltrates were found in 6 animals (2.6%). Other findings were ring fibers (2 horses; 0.9%), fiber splitting (2 horses; 0.9%), and fat infiltration (1 horse; 0.4%). Skeletal muscle lesions are common in equids examined at postmortem. Transverse sections stained with HE and PAS are invaluable when evaluating equine muscle.

Owner-reported equine health disorders: results of an Australia-wide postal survey

OBJECTIVE

To establish the prevalence of health disorders reported by horse owners registered with veterinary practices in Australia.

DESIGN AND METHOD

Mailed questionnaire-based study of horse owners in Australia conducted in 2001.

RESULTS

Data were obtained for 3901 horses belonging to 621 owners. The most prevalent health disorders were non-laminitic lameness (13.0%), skin disorders (6.1%) and behavioural disorders (4.5%). Prevalence of health disorders varied among different age, breed and sex categories within the study population, and disorders were more prevalent in male and older horses.

CONCLUSION

The most frequent disorders reported by owners were lameness, skin disorders and behavioural disorders. The disease profile was similar to that described in other owner reported studies conducted in the UK and USA.

Treatment of suppurative facial cellulitis and panniculitis caused byCorynebacterium pseudotuberculosisin two horses

Two horses were examined for large head wounds suspected to be the result of trauma and characterized by extensive necrosis of the skin and subcutaneous tissue, with abundant purulent exudate. Corynebacterium pseudotuberculosis was isolated from the facial wounds in both horses. Histopathologic examination revealed severe suppurative cellulitis and panniculitis with fistulous tracts and granulation tissue in 1 horse. Both horses were treated with local wound care, nonsteroidal anti-inflammatory drugs, and administration of antimicrobials. The concept of moist wound care was used in the second horse, with products that have recently become available for veterinary wound management. Outcome in both horses was good.

Factors associated with fecal-shedding of Salmonella spp by horses on US operations

In a cross-sectional national study that included 972 operations with > 3 horses on 1/1/98 in 28 states in the USA, 8,417 fecal specimens were collected from horses and cultured to test for the presence of Salmonella spp. Operations were characterized as Salmonella spp-positive if at least one fecal specimen tested positive for Salmonella spp. Percentages of Salmonella spp-positive operations were computed by management and other factors (collected from operation-level questionnaires) that were hypothesized to be related to fecal shedding of Salmonella spp. A logistic-regression model was constructed to identify factors associated with horses’ shedding Salmonella spp in feces on an operation. The odds of an operation being Salmonella spp positive increased as the number of resident horses increased. In addition, the following factors were found to be associated with increased odds of an operation being Salmonella spp positive: horses were used primarily for breeding; operation cleanliness was characterized as poor by the data collector; and new resident equids had been added to the operation without routine quarantine.

Operation-management factors associated with early-postnatal mortality of US foals

Of 7320 equine foals reported born alive during 1997 on 1043 operations that had equids on 1 January 1997, and that participated in the United States National Animal Health Monitoring System (NAHMS) Equine 1998 Study, 120 foals were reported to have died (by either euthanasia or natural causes) within the first 2 days of a live birth. The weighted estimate was 1.7% mortality (standard error=0.5) within the first 2 days of live birth for all foals born on operations in the 28 states included in the study.A multivariable logistic-regression model revealed that foals born in the southern region were more likely to have been reported to have died within the first 2 days of live birth than in the western region. In addition, the following operation-level factors were associated with increased odds of a foal dying within the first 2 days of live birth: not routinely testing newborn foals for adequate absorption of colostral immunoglobulins during the first 2 days of life; adding new resident equids to the operation during 1997; having non-resident equids stay on the operation for 1-30 days during 1997; never requiring an official health certificate (for operations that had non-resident equids stay on the operation for 1-30 days); using something other than straw or hay as the predominant bedding type; and feeding equids a vitamin-mineral supplement/premix with forage and/or grain.

Application and evaluation of a mailed questionnaire for an epidemiologic study of Corynebacterium pseudotuberculosis infection in horses

The objective of this study is to describe the design, application and validity of a self-administered (mailed) questionnaire to collect data on potential risk factors for Corynebacterium pseudotuberculosis infection in California horses. Horses admitted to the UC Davis Veterinary Medical Teaching Hospital (VMTH) between 1 July 1992 and 30 June 1994 served as the study base for case identification and simple random sampling of 800 control horses. A questionnaire was mailed to owners of the study horses, followed by a reminder postcard and a second copy of a questionnaire. Data were collected on owner and horse identity and demographics, horse management and use, geographic location, and general health-related issues. Return pattern over time as well as differential return proportions were described. The overall return proportion was 66% (587/890), and the completion proportion 55% (491/890). The number of returns over time followed a negative binomial distribution, with over 90% of all returns being in by the end of the fifth week after mailing, and over 99% at the end of the tenth week. Some categories within the variables age (between 2 and 3 years), breed (Thoroughbred and Standardbred horses) and gender (stallions) had significantly lower return proportions than expected (differential return; p < 0.05). The profile of these horses fits a section of the racehorse population that is served by the VMTH. Age, breed and disease status information was available from the VMTH medical records and from the questionnaire, and was used to determine the validity of the survey data. There was good agreement between the data from the two sources, and we therefore concluded that the quality of the survey information was sufficient to perform a risk-factor analysis. The mailed survey provided a rapid and cost-effective method of collecting additional information to supplement existing medical records.