The Veterinary clinics of North America. Equine practice2023; 39(1); 1-14; doi: 10.1016/j.cveq.2022.11.002

Rhodococcus equi-What is New This Decade?

Abstract: Foals become infected shortly after birth; most develop subclinical pneumonia and 20% to 30% develop clinical pneumonia that requires treatment. It is now well established that the combination of screening programs based on thoracic ultrasonography and treatment of subclinical foals with antimicrobials has led to the development of resistant Rhodococcus equi strains. Thus, targeted treatment programs are needed. Administration of R equi-specific hyperimmune plasma shortly after birth is beneficial as foals develop less severe pneumonia but does not seem to prevent infection. This article provides a summary of clinically relevant research published during this past decade.
Publication Date: 2023-03-11 PubMed ID: 36898784DOI: 10.1016/j.cveq.2022.11.002Google Scholar: Lookup
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This article discusses the development of resistance in Rhodococcus equi, a bacterium that commonly causes pneumonia in foals, as a result of extensive use of antimicrobials. It stresses the need for specific treatment programs and the use of hyperimmune plasma in pre-emptive treatments.

Overview of Rhodococcus equi Infections in Foals

  • Rhodococcus equi is a bacterium that causes pneumonia in foals (baby horses) shortly after their birth.
  • While most foals develop a subclinical form of the pneumonia, about 20-30% develop a clinical form that requires treatment.

Use of Antimicrobials and Resulting Resistance

  • The practice of using screening programs based on thoracic ultrasonography, and treatment of affected foals with antimicrobials, has become common.
  • However, this widespread usage of such drugs has led to the development of Rhodococcus equi strains that are resistant to the drugs commonly used to treat them.

The Need for Targeted Treatment Programs

  • The growing resistance of R. equi strains to conventional treatment points towards the need for more targeted treatment programs.
  • Adaptation of these pathogen-specific strategies are fundamental for the control of this bacterial infection and the reduction of resistance occurrence.

Use of Hyperimmune Plasma as Preemptive Treatment

  • The administration of R. equi-specific hyperimmune plasma shortly after birth has been found to be beneficial.
  • Although it does not seem to prevent the infection entirely, foals treated this way were observed to develop less severe forms of pneumonia.
  • The use of hyperimmune plasma can therefore be seen as a form of pre-emptive treatment that can hold utility in checkmating the severity of the ailment while the research for more comprehensive solutions is in progress.

Summary of Recent Research

  • This research article constitutes a summary of clinically relevant research related to Rhodococcus equi infections in foals over the past decade.
  • The research indicates shifts in perspectives towards the management of this infection- with emphasis on development of pathogen-specific strategies and the use of preemptive measures like hyperimmune plasma.

Cite This Article

Sanz MG. (2023). Rhodococcus equi-What is New This Decade? Vet Clin North Am Equine Pract, 39(1), 1-14.


ISSN: 1558-4224
NlmUniqueID: 8511904
Country: United States
Language: English
Volume: 39
Issue: 1
Pages: 1-14
PII: S0749-0739(22)00066-9

Researcher Affiliations

Sanz, Macarena G
  • Washington State University, Pullman, WA, USA. Electronic address:

MeSH Terms

  • Animals
  • Horses
  • Rhodococcus equi
  • Actinomycetales Infections / prevention & control
  • Actinomycetales Infections / veterinary
  • Horse Diseases / prevention & control
  • Pneumonia / veterinary


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