Veterinary microbiology1997; 56(3-4); 167-176; doi: 10.1016/s0378-1135(97)00085-0

Epidemiology of Rhodococcus equi infections: a review.

Abstract: An overview of epidemiology of R. equi infection in foals is presented, emphasizing the importance of the virulence-associated antigens and plasmids as epidemiological markers. The monoclonal antibody-based colony blot test has been developed to identify rapidly and accurately virulent R. equi. Epidemiological studies conducted during the recent 5 years have revealed that: (1) avirulent R. equi are widespread in the feces of horses and their environment on every farm; (2) the feces of horses and the environment of the horse farms having endemic R. equi infections demonstrated heavy contamination with virulent R. equi, but the farms without the problem did not, thus suggesting that foals bred on a farm with endemic disease are exposed more frequently to virulent R. equi in their environment than those of a farm without the problem; (3) only virulent R. equi are isolated from lesions of naturally infected foals, showing that natural infections in foals are principally by virulent R. equi, but not avirulent organisms; (4) infected foals which constantly shed large quantities of virulent R. equi in their feces are the major source of virulent R. equi, which this may be the mechanism of progressive development of infection on farms with a history of the disease. At present, farms with a potential for endemic infection can be distinguished on the basis of the contamination with virulent R. equi, so regular examination of foals and their environment by virulence markers might be the most practical approach to control R. equi infection on endemic farms.
Publication Date: 1997-06-16 PubMed ID: 9226831DOI: 10.1016/s0378-1135(97)00085-0Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't
  • Review


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This research provides an examination of Rhodococcus equi infection in foals, focusing on the significance of virulence-associated antigens and plasmids as indicators of infection. The study further reveals the prevalent contamination of both equine feces and their environment with virulent R. equi, initiating the infection progress on endemic farms.

Overview of R. equi Infection

  • Rhodococcus equi is a pathogenic bacterium that causes pulmonary disease in foals, imposing a significant health threat on farms.
  • The study emphasizes the importance of virulence-associated antigens and plasmids as epidemiological markers in detecting the bacterium.
  • A monoclonal antibody-based colony blot test was developed for quick and accurate identification of virulent R. equi.

Environmental Prevalence and Contamination

  • Epidemiological studies conducted over a five-year period revealed widespread prevalence of avirulent (non-disease causing) R. equi in the feces of horses and their environment across all farms.
  • Farms with endemic R. equi infections showed heavy contamination of virulent (disease-causing) R. equi in horse feces and the environment.
  • On the other hand, farms without R. equi issues exhibited no such contamination, implying that exposure to virulent R. equi is greatly increased for foals bred on endemic farms.

Natural Infection and Disease Progression

  • Natural R. equi infections in foals were found to be primarily due to virulent strains of the bacterium, not the avirulent ones.
  • Foals that were infected and consistently shed large amounts of virulent R. equi in their feces were identified as a major source of the bacterium, possibly facilitating the progressive development of infection on farms with a history of the disease.

Disease Control and Prevention

  • The study suggests that the presence of virulent R. equi can be used to identify farms with a potential for endemic infection.
  • Regular examination of foals and their environment using virulence markers is proposed as a practical approach to control and prevent R. equi infection on endemic farms.

Cite This Article

Takai S. (1997). Epidemiology of Rhodococcus equi infections: a review. Vet Microbiol, 56(3-4), 167-176.


ISSN: 0378-1135
NlmUniqueID: 7705469
Country: Netherlands
Language: English
Volume: 56
Issue: 3-4
Pages: 167-176

Researcher Affiliations

Takai, S
  • Department of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan.

MeSH Terms

  • Actinomycetales Infections / diagnosis
  • Actinomycetales Infections / epidemiology
  • Actinomycetales Infections / veterinary
  • Animals
  • Antigens, Bacterial / analysis
  • Breeding
  • Disease Outbreaks / veterinary
  • Horse Diseases / epidemiology
  • Horses
  • Lymph Nodes / microbiology
  • Plasmids
  • Rhodococcus equi / isolation & purification
  • Rhodococcus equi / pathogenicity
  • Virulence


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