Fecal shedding of Rhodococcus equi in mares and foals after experimental infection of foals and effect of composting on concentrations of R. equi in contaminated bedding.
Abstract: Rhodococcus equi, a soil saprophyte, is a common cause of pneumonia in foals and a frequent opportunistic pathogen in immunosuppressed people. Because it is widespread in the environment, R. equi can be detected in the feces of most horses. However, the exact timing and rate of shedding relative to infection is unknown. The objectives of this study were to quantify shedding of R. equi in mares and foals after experimental infection of foals with 2 different inocula and to determine the effect of composting on concentrations of R. equi in contaminated bedding. Foals were infected intratracheally with virulent R. equi using inocula of 1 × 10 CFU/mL (n = 16) or 1 × 10 CFU/mL (n = 12) at 23 ± 2 days (range 21 to 27 days) of age. Fecal samples were collected from mares and foals prior to infection and on days 3, 7, and 14 post-infection for quantitative culture of total and virulent R. equi. Waste from the horses was composted for 7 days. Concentrations of total and virulent R. equi in foal feces were significantly higher on day 14 post-infection compared to day 0, regardless of inoculum size. Concentration of total R. equi in mare feces was significantly higher on days 3, 7 and 14 compared to day 0 regardless of inoculum size, whereas shedding of virulent R. equi only increased on day 14 post-infection. Composting for 7 days significantly decreased concentrations of total R. equi and virulent R. equi by an average of 1.08 ± 0.21 and 0.59 ± 0.26 log CFU/g, respectively.
Copyright © 2018 Elsevier B.V. All rights reserved.
Publication Date: 2018-07-21 PubMed ID: 30173750DOI: 10.1016/j.vetmic.2018.07.017Google Scholar: Lookup
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- Journal Article
Summary
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The research article examines the fecal shedding patterns of the bacterial pathogen, Rhodococcus equi, in mares and foals after experimental infections, and evaluates the impact of composting on the density of this pathogen in horse bedding.
Objective and Context
- The study aimed to determine the shedding rates and pattern of Rhodococcus equi in mares and foals after the foals were artificially infected with this bacteria. This bacterium is a leading cause of pneumonia in foals and can affect immunosuppressed humans.
- The researchers also wanted to ascertain how composting of contaminated horse bedding affects the concentration of R. equi.
- Understanding these aspects can contribute valuable knowledge to the treatment and prevention strategies for diseases caused by this bacterium.
Methodology
- Two groups of foals were exposed to different inocula of R. equi when they were about 23 days old.
- Fecal samples from both mares and foals were taken before the infection and then on days 3, 7, and 14 after the infection. These samples were cultured to quantify both total and virulent R. equi.
- The horse waste was composted for a week to study the effect of composting on the concentration of R. equi.
Findings
- Regardless of the size of the inoculum, the concentration of R. equi in the feces of foals significantly increased on the 14th day following the infection as compared to the day of infection.
- In the case of mare feces, there was a noticeable rise in the total concentration of R. equi throughout the study period. Virulent R. equi, however, only increased on the 14th day after infection.
- Composting of horse bedding for a week significantly decreased the concentration of both total and virulent R. equi. The reduction averaged at about 1.08 and 0.59 log CFU/g, respectively. This indicates that composting could be an effective way to manage contaminated horse bedding and reduce the spread of this bacterial pathogen.
Cite This Article
APA
Huber L, Giguère S, Berghaus LJ, Hanafi A, Ryan C.
(2018).
Fecal shedding of Rhodococcus equi in mares and foals after experimental infection of foals and effect of composting on concentrations of R. equi in contaminated bedding.
Vet Microbiol, 223, 42-46.
https://doi.org/10.1016/j.vetmic.2018.07.017 Publication
Researcher Affiliations
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA. Electronic address: laura.huber16@hotmail.com.
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
MeSH Terms
- Actinomycetales Infections / microbiology
- Actinomycetales Infections / veterinary
- Animals
- Animals, Newborn
- Bedding and Linens / microbiology
- Composting
- Feces / microbiology
- Female
- Horse Diseases / microbiology
- Horses
- Rhodococcus equi / growth & development
- Rhodococcus equi / pathogenicity
- Virulence
Citations
This article has been cited 5 times.- Rakowska A, Marciniak-Karcz A, Bereznowski A, Cywińska A, Żychska M, Witkowski L. Less Typical Courses of Rhodococcus equi Infections in Foals. Vet Sci 2022 Oct 31;9(11).
- Rakowska A, Cywinska A, Witkowski L. Current Trends in Understanding and Managing Equine Rhodococcosis. Animals (Basel) 2020 Oct 18;10(10).
- Boneva-Marutsova B, Marutsov P, Kerner K, Zhelev G. First Detection of Rhodococcus equi in a Foal in Bulgaria-A Case Report. Animals (Basel) 2025 Jul 12;15(14).
- da Silveira BP, Cohen ND, Lawhon SD, Watson RO, Bordin AI. Protective immune response against Rhodococcus equi: An innate immunity-focused review. Equine Vet J 2025 May;57(3):563-586.
- Rakowska A, Czopowicz M, Bereznowski A, Witkowski L. Investigation of the relationship between pulmonary lesions based on lung ultrasound and respiratory clinical signs in foals with suspected pulmonary rhodococcosis. Sci Rep 2023 Nov 8;13(1):19401.
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