Application of Sartwell’s Model (Lognormal Distribution of Incubation Periods) to Age at Onset and Age at Death of Foals with Rhodococcus equi Pneumonia as Evidence of Perinatal Infection

Horowitz, Miriam L.; Cohen, Noah D.; Takai, Shigemasa; Becu, Teotimu; Chaffin, M. Keith; Chu, Karin K.; Magdesian, K. Gary; Martens, Ronald J.

doi:10.1892/0891-6640(2001)015<0171:aosmld>2.3.co;2

Cited by 53 publications

(65 citation statements)

References 16 publications

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“…The ubiquity of R. equi in the environment of horses and suggestions that foals may be infected at a very young age limit the capacity to conduct studies that adequately mimic natural infection and establish contagious transmission under controlled experimental conditions (3,10). There is no certainty that an intratracheal or intrabronchial bolus of cultured R. equi, the method currently used to experimentally infect foals, would accurately mirror natural infection (12,28).…”

Section: Discussionmentioning

confidence: 99%

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Detection of VirulentRhodococcus equiin Exhaled Air Samples from Naturally Infected Foals

2009

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Virulent Rhodococcus equi causes pyogranulomatous bronchopneumonia in foals. The route of infection of foals has been considered to be inhalation of aerosolized bacteria from soil that is contaminated with equine feces. Thus, disease caused by R. equi has been regarded as an opportunistic infection of environmental origin and not a contagious disease. In this study, we report the exhalation of virulent R. equi from the respiratory tract of naturally infected foals. A handheld air-monitoring system was used to recover virulent R. equi from the exhaled breath of foals, and the concentration of virulent R. equi organisms in exhaled air was compared to the concentration in environmental air samples taken from the holding pens and lane areas on farms. R. equi strains carrying the vapA gene of the virulence plasmid were detected by using colony blotting and DNA hybridization techniques in cultures of exhaled air from 67% (37/55) of foals tested. The concentration of virulent R. equi organisms in exhaled air from foals was significantly higher than that in environmental air (P < 0.001). There were no significant differences in the median concentrations of virulent R. equi bacteria exhaled by clinically healthy or diseased foals. The high concentrations of virulent R. equi bacteria in exhaled air suggested that aerosol transmission between foals is possible and may have a significant impact on the prevalence of R. equi pneumonia on farms. The air sampling technique described is potentially useful as a noninvasive method for the detection and quantification of virulent R. equi in the respiratory tract of foals.

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Section: Discussionmentioning

confidence: 99%

“…Virulent strains of R. equi cause bronchopneumonia in horses, primarily affecting foals between 1 and 4 months of age (5,10,19,29). Virulent R. equi contains an 85-to 90-kb plasmid that carries genes for virulence-associated proteins (Vaps) (24,25).…”

mentioning

confidence: 99%

Detection of VirulentRhodococcus equiin Exhaled Air Samples from Naturally Infected Foals

2009

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“…Many studies of the pathogenesis of R. equi in foals have used an overwhelming challenge dose (Ͼ10 9 CFU/foal) that induces considerable pulmonary lesions within 3 days and fulminating clinical signs within 10 days of infection (18,24,28). Epidemiological evidence indicates that most foals on farms where the disease is endemic become infected very early in life (27). However, the median age at the time of diagnosis of R. equi pneumonia on such farms is approximately 37 days (17).…”

Section: Discussionmentioning

confidence: 99%

Experimental Infection of Neonatal Foals withRhodococcus equiTriggers Adult-Like Gamma Interferon Induction

Jacks

Giguère

Crawford

et al. 2007

Clin Vaccine Immunol

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Rhodococcus equi is a facultative intracellular pathogen that causes pneumonia in young foals but does not induce disease in immunocompetent adult horses. Clearance of R. equi depends mainly on gamma interferon (IFN-␥) production by T lymphocytes, whereas the predominance of interleukin 4 (IL-4) is detrimental. Young foals, like neonates of many other species, are generally deficient in the ability to produce IFN-␥. The objective of this study was to compare the cytokine profiles, as well as cell-mediated and antibody responses, of young foals to those of adult horses following intrabronchial challenge with R. equi. The lymphoproliferative responses of bronchial lymph node (BLN) cells to concanavalin A were significantly higher in foals than in adult horses. In contrast, adult horses had significantly higher lymphoproliferative responses to R. equi antigens than did foals. Infected foals had significantly lower IL-4 mRNA expression but significantly higher IFN-␥ expression and IFN-␥/IL-4 ratio in R. equi-stimulated BLN lymphocytes than did infected adults. Infection with R. equi in foals resulted in a significant increase in the percentage of T lymphocytes and CD4 ؉ T lymphocytes in bronchoalveolar lavage fluid in association with a significant decrease in the percentage of these cell populations in BLNs. Infection of foals also resulted in a marked increase in serum immunoglobulin Ga (IgGa) and IgGb levels, resulting in concentrations in serum that were significantly higher than those of adult horses. This study demonstrates that the immune response to R. equi in foals is not biased toward IL-4 and is characterized by the predominant induction of IFN-␥.

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“…Forty-milliliter peripheral blood samples were collected from healthy adult horses (n ϭ 8) and foals (n ϭ 8) belonging to the Equine Park, Cornell University. Foal blood samples were collected in Vacutainer heparinized tubes within the first 5 days of life and monthly up to 3 months of age via jugular venipuncture (27,40). Adult horse blood samples were collected once for comparison.…”

Section: Methodsmentioning

confidence: 99%

Foal Monocyte-Derived Dendritic Cells Become Activated uponRhodococcus equiInfection

Flaminio

Nydam

Marquis

et al. 2009

Clin Vaccine Immunol

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Susceptibility of foals to Rhodococcus equi pneumonia is exclusive to the first few months of life. The objective of this study was to investigate the immediate immunologic response of foal and adult horse antigen-presenting cells (APCs) upon infection with R. equi. We measured the activation of the antigen-presenting major histocompatibility complex (MHC) class II molecule, costimulatory molecules CD40 and CD86, the cytokine interleukin-12 (IL-12), and the transcriptional factor interferon regulatory factor 1 (IRF-1) in monocytederived macrophages (mMOs) and dendritic cells (mDCs) of adult horses and foals of different ages (from birth to 3 months of age) infected with virulent R. equi or its avirulent, plasmid-cured derivative. Infection with virulent or avirulent R. equi induced (P < 0.01) the expression of IL-12p35 and IL-12p40 mRNAs in foal mMOs and mDCs at different ages. This response was likely mediated by the higher (P ‫؍‬ 0.008) expression of IRF-1 in foal mDCs at birth than in adult horse mDCs. R. equi infection promoted comparable expression of costimulatory molecules CD86 and CD40 in foal and adult horse cells. The cytokine and costimulatory response by foal mDCs was not accompanied by robust MHC class II molecule expression. These data suggest that foal APCs detect the presence of R. equi and respond with the expression of the Th1-inducing cytokine IL-12. Nevertheless, there seems to be a limitation to MHC class II molecule expression which we hypothesize may compromise the efficient priming of naïve effector cells in early life.

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Application of Sartwell’s Model (Lognormal Distribution of Incubation Periods) to Age at Onset and Age at Death of Foals with Rhodococcus equi Pneumonia as Evidence of Perinatal Infection

Cited by 53 publications

References 16 publications

Detection of VirulentRhodococcus equiin Exhaled Air Samples from Naturally Infected Foals

Detection of VirulentRhodococcus equiin Exhaled Air Samples from Naturally Infected Foals

Experimental Infection of Neonatal Foals withRhodococcus equiTriggers Adult-Like Gamma Interferon Induction

Foal Monocyte-Derived Dendritic Cells Become Activated uponRhodococcus equiInfection

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