Prevalence of Rhodococcus equi from the nasal cavity of 1010 apparently healthy horses.
Abstract: Rhodococcus equi is an important cause of foal pneumonia. While its isolation from different sources has been widely evaluated, there is a need to better understand the R. equi epidemiology from samples of the nasal cavity of healthy horses. Objective: To determine the prevalence of R. equi from the nasal cavity of healthy horses, along with its virulence profile, antimicrobial susceptibility and environmental variables associated. Methods: Cross-sectional study. Methods: Swabs from the nasal cavity of 1010 apparently healthy horses from 341 farms were submitted for bacteriological analyses. The identity and virulence profile of the R. equi isolates were assessed by multiplex PCR; antimicrobial susceptibility was determined by the disk-diffusion method. The occurrence of R. equi was calculated at the level of both animal and farm. The association of seven specific environmental factors with R. equi isolation was assessed using logistic regression and by a spatial scan statistical method to determine the presence of local clusters. Results: Antimicrobial-sensitive R. equi was isolated from 10 (1%) of 1010 horses ranging between 3 and 29 years old. Ten farms (3%) had at least one positive horse. Only one R. equi isolate (10%) was classified as virulent. Red-Yellow Argisol (PVA/PV) soils were significantly associated with R. equi isolation (odds ratio (OR) 8.02; CI , 1.98-32.50, P = 0.01), and areas with well-drained soil were less likely to be test positive (OR 0.85; CI , 0.76-0.96, P = 0.03). Conclusions: The use of culture-based method instead of PCR-based assay and the lack of soil sampling. Conclusions: Antimicrobial-sensitive R. equi may be considered a minor part of the normal bacterial flora in the nasal cavity of healthy and immunologically functional horses breeding on pasture. Further studies are warranted to determine if soils rich in iron and well-drained are, in fact, associated with the occurrence of R. equi.
© 2018 EVJ Ltd.
Publication Date: 2018-02-05 PubMed ID: 29341220DOI: 10.1111/evj.12804Google Scholar: Lookup
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Summary
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This research investigates the prevalence of Rhodococcus equi, a bacterium causing pneumonia in foals, in the nasal cavities of healthy horses. It also explores the associated virulence profile, antimicrobial susceptibility, and environmental factors.
Objective
The main goal of the study was to determine the occurrence of R. equi in the nasal cavities of healthy horses and understand its characteristics and variables that could influence its prevalence.
Methods
- The researchers carried out a cross-sectional study involving 1010 healthy horses from 341 farms.
- Nasal cavity swabs from these horses underwent bacterial analyses.
- The identity and the virulence profile of the R. equi isolates were confirmed through multiplex PCR.
- Antimicrobial susceptibility was determined through a disk-diffusion method.
- R. equi’s prevalence was calculated at both the individual horse and farm level.
- The association between the isolation of R. equi and seven specific environmental factors was evaluated using logistic regression and a statistical method for identifying local clusters.
Results
- The team discovered that R. equi, which was sensitive to antimicrobials, was found in the nasal cavities of 10 horses (1% of the total). These horses were between 3 and 29 years old.
- Out of the 341 farms sampled, 10 (or 3%) had one or more horses testing positive for R. equi.
- Only a tenth of the isolates were classified as virulent.
- There was a significant association between the presence of R. equi and Red-Yellow Argisol soils (Iron-rich soils).
- Horses living in areas with well-drained soil were less likely to test positive.
Conclusions
- The researchers suggested that R. equi could be merely a minor component of the natural bacterial flora in the nasal cavities of healthy horses kept on pastures.
- The research’s limitation was the use of culture-based techniques instead of PCR-based assays and no soil sampling.
- They recommended further studies to confirm if iron-rich and well-drained soils genuinely influence the occurrence of R. equi.
Cite This Article
APA
Gressler LT, Machado G, da Silveira BP, Cohen ND, Corbellini LG, Leotti VB, Diehl GN, Dos Santos LC, de Vargas AC.
(2018).
Prevalence of Rhodococcus equi from the nasal cavity of 1010 apparently healthy horses.
Equine Vet J, 50(5), 667-671.
https://doi.org/10.1111/evj.12804 Publication
Researcher Affiliations
- Laboratory of Bacteriology, Federal University of Santa Maria (UFSM), Cidade Universitária, Bairro Camobi, Santa Maria - Rio Grande do Sul, Brazil.
- Department of Population Health and Pathobiology, College of Veterinary Medicine North, Carolina State University, Raleigh, North Carolina, USA.
- Laboratory of Bacteriology, Federal University of Santa Maria (UFSM), Cidade Universitária, Bairro Camobi, Santa Maria - Rio Grande do Sul, Brazil.
- College of Veterinary Medicine, Veterinary Large Animal Clinical Sciences, Texas A&M, College Station, Texas, USA.
- Department of Statistics, Institute of Mathematics and Statistics and Post-Graduate Program of Epidemiology, Faculty of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
- Department of Statistics, Institute of Mathematics and Statistics and Post-Graduate Program of Epidemiology, Faculty of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
- Department of Agriculture, Livestock and Agribusiness of the State of Rio Grande do Sul (SEAPA-RS), Brazil, Porto Alegre, Rio Grande do Sul, Brazil.
- Department of Agriculture, Livestock and Agribusiness of the State of Rio Grande do Sul (SEAPA-RS), Brazil, Porto Alegre, Rio Grande do Sul, Brazil.
- Laboratory of Bacteriology, Federal University of Santa Maria (UFSM), Cidade Universitária, Bairro Camobi, Santa Maria - Rio Grande do Sul, Brazil.
MeSH Terms
- Animals
- Brazil
- Carrier State / veterinary
- Cross-Sectional Studies
- Horses / microbiology
- Nasal Cavity / microbiology
- Rhodococcus equi / isolation & purification
Citations
This article has been cited 4 times.- Zúñiga MP, Badillo E, Abalos P, Valencia ED, Marín P, Escudero E, Galecio JS. Antimicrobial susceptibility of Rhodococcus equi strains isolated from foals in Chile. World J Microbiol Biotechnol 2023 Jun 22;39(9):231.
- Tapprest J, Foucher N, Linster M, Laloy E, Cordonnier N, Amat JP, Hendrikx P. Resumeq: A Novel Way of Monitoring Equine Diseases Through the Centralization of Necropsy Data. Front Vet Sci 2019;6:135.
- Yerlikaya Z, Karagülle B, Otlu B, Muz A. From Paddock to Foal: Prevalence and Genotypic Diversity of Rhodococcus equi on Stud Farms in Türkiye. Vet Sci 2026 Jan 10;13(1).
- Godoi APDS, Sobral GG, da Silva Vieira JC, Carneiro GF, Conceição FR, da Silva ER, Mendonça M. Phenotypical and molecular characterization of Rhodococcus equi isolated from foals in the Agreste region of Pernambuco - Brazil. Braz J Microbiol 2025 Jun;56(2):1321-1331.
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