<i>Rhodococcus Equi</i> and Genetic Susceptibility: Assessing Transferrin Genotypes from Paraffin-Embedded Tissues

Mousel, Michelle R.; Harrison, Lenn R.; Donahue, James M.; Bailey, Ernest

doi:10.1177/104063870301500512

Cited by 23 publications

(16 citation statements)

References 19 publications

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“…We failed to identify significant association with candidate genes previously associated with R. equi pneumonia in other breeds of foals [1], [7], [8]. This may have been attributable to differences among populations of foals studied (e.g, breeds) or study methodology (e.g, case definitions, methods for detecting polymorphisms, etc.).…”

Section: Discussionmentioning

confidence: 72%

“…Although the factors contributing to R. equi pneumonia are complex, recent evidence suggests that some horses may be genetically predisposed to this condition [1], [7], [8]. Identifying the genetic and biological basis of susceptibility, or perhaps resistance, to R. equi pneumonia in foals is important, because it might lead to the development of diagnostic and therapeutic tools to manage at-risk foals on breeding farms and might shed light on critical host defense mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Identification of Genomic Loci Associated with Rhodococcus equi Susceptibility in Foals

et al. 2014

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Pneumonia caused by Rhodococcus equi is a common cause of disease and death in foals. Although agent and environmental factors contribute to the incidence of this disease, the genetic factors influencing the clinical outcomes of R. equi pneumonia are ill-defined. Here, we performed independent single nucleotide polymorphism (SNP)- and copy number variant (CNV)-based genome-wide association studies to identify genomic loci associated with R. equi pneumonia in foals. Foals at a large Quarter Horse breeding farm were categorized into 3 groups: 1) foals with R. equi pneumonia (clinical group [N = 43]); 2) foals with ultrasonographic evidence of pulmonary lesions that never developed clinical signs of pneumonia (subclinical group [N = 156]); and, 3) foals without clinical signs or ultrasonographic evidence of pneumonia (unaffected group [N = 49]). From each group, 24 foals were randomly selected and used for independent SNP- and CNV-based genome-wide association studies (GWAS). The SNP-based GWAS identified a region on chromosome 26 that had moderate evidence of association with R. equi pneumonia when comparing clinical and subclinical foals. A joint analysis including all study foals revealed a 3- to 4-fold increase in odds of disease for a homozygous SNP within the associated region when comparing the clinical group with either of the other 2 groups of foals or their combination. The region contains the transient receptor potential cation channel, subfamily M, member 2 (TRPM2) gene, which is involved in neutrophil function. No associations were identified in the CNV-based GWAS. Collectively, these data identify a region on chromosome 26 associated with R. equi pneumonia in foals, providing evidence that genetic factors may indeed contribute to this important disease of foals.

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Section: Discussionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Identification of Genomic Loci Associated with Rhodococcus equi Susceptibility in Foals

et al. 2014

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“…The chronic disease seen in some horses, particularly 2-year-olds affected with IAD for more than two-thirds of the year, is likely to include increased airway reactivity (26) and dysregulation of inflammation (6), although this possibility needs further investigation. Genetic factors may also influence susceptibility to IAD, as found with another equine bacterial lung disease (39).…”

Section: Discussionmentioning

confidence: 99%

Association between Respiratory Disease and Bacterial and Viral Infections in British Racehorses

et al. 2005

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Respiratory disease is important in horses, particularly in young Thoroughbred racehorses, and inflammation that is detected in the trachea and bronchi (termed inflammatory airway disease [IAD]) is more significant in this population in terms of impact and frequency than other presentations of respiratory disease. IAD, which is characterized by neutrophilic inflammation, mild clinical signs, and accumulation of mucus in the trachea, may be multifactorial, possibly involving infections and environmental and immunological factors, and its etiology remains unclear. This 3-year longitudinal study of young Thoroughbred racehorses was undertaken to characterize the associations of IAD and nasal discharge with viral and bacterial infections. IAD was statistically associated with tracheal infection with Streptococcus pneumoniae (capsule type 3), Streptococcus zooepidemicus, Actinobacillus spp., and Mycoplasma equirhinis and equine herpesvirus 1 and 4 infections, after adjustment for variation between training yards, seasons, and age groups. The association with S. pneumoniae and S. zooepidemicus was independent of prior viral infection and, critically, was dependent on the numbers of organisms isolated. S. pneumoniae was significant only in horses that were 2 years old or younger. The prevalence and incidence of IAD, S. zooepidemicus, and S. pneumoniae decreased in parallel with age, consistent with increased disease resistance, perhaps by the acquisition of immunity. The study provided evidence for S. zooepidemicus and S. pneumoniae playing an important etiological role in the pathogenesis of IAD in young horses.Respiratory disease is common in racehorses in training (10,15,29), as it is in most young domestic animals species. Both the incidence and prevalence of respiratory disease in racehorses vary widely between yards and between years (38, 46, 58), but the reasons underlying this variation, including the causes of the disease, are not defined.Inflammatory lower airway disease (IAD), which is usually associated with increased amounts of mucus visible in the trachea after exercise and increased proportions of inflammatory cells (44), is common in young racehorses around the world, despite marked differences in management and climate. Clinical signs associated with IAD include coughing (10, 16) and poor performance in racing (30,37,44,45). IAD is considerably more common than signs of upper respiratory disease and in young racehorses has a mean monthly prevalence of around 12% and an incidence of around 10 cases/100 horses/month (10, 58). The mean duration of each incident is around 8 weeks, and the disease is often recurrent in individuals. The monthly prevalence and incidence of signs of upper respiratory disease are around 5% and 5 cases/100 horses/month (10, 38, 58).The etiology and pathogenesis of IAD are poorly defined, but the etiology is probably multifactorial (10, 44). Studies focusing on individual agents suggest the possible involvement of viral infection (59), bacterial infection (10,14,16,42,43,56), and...

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“…The susceptibility of foals under six months of age to respiratory infections may be due to a number of factors, including: immunodeficiency; overcrowding; heavy parasite burden; poor nutritional status; and heat stress [16]. There may also be a genetic basis for foal susceptibility to Rhodococcus equi infection based on the type of transferrin, an iron-binding protein that has bacteriostatic properties, in the blood [12]. Also, only certain types of Rhodococcus equi are pathogenic: those that contain virulence-associated protein A -Vap A [6].…”

Section: Introductionmentioning

confidence: 99%

Resistance studies of erythromycin and rifampin for Rhodococcus equi over a 10-year period

2007

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This study sought to determine whether an increase in resistance of Rhodococcus equi to the antibiotics rifampin and erythromycin occurred over a 10-year period. This was carried out by the use of E test strips for rifampin and erythromycin to determine the MIC (minimum inhibitory concentration) values of Rhodococcus equi to this combination of antibiotics.The findings of this study indicated that there was an increase in resistance of Rhodococcus equi to rifampin and erythromycin over the 10-year period. The MIC for rifampin increased from 0.081 μg/ml in 1996 to 0.187 μg/ml in 2006 and from 0.258 μg/ml for erythromycin during the years prior to 2000 to 0.583 μg/ml in 2006.This finding suggests that there may be a problem in the treatment of Rhodococcus equi infections in foals in the future, particularly as the number of drugs available for treatment of Rhodococcus equi infection is limited because of the intracellular capabilities of this bacterium. Antibiotics used in its treatment have to be able to penetrate the polysaccharide cell wall of Rhodococcus equi as well as the alveolar macrophages in which the bacterium is capable of surviving.

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Rhodococcus Equi and Genetic Susceptibility: Assessing Transferrin Genotypes from Paraffin-Embedded Tissues

Cited by 23 publications

References 19 publications

Identification of Genomic Loci Associated with Rhodococcus equi Susceptibility in Foals

Identification of Genomic Loci Associated with Rhodococcus equi Susceptibility in Foals

Association between Respiratory Disease and Bacterial and Viral Infections in British Racehorses

Resistance studies of erythromycin and rifampin for Rhodococcus equi over a 10-year period

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