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Equine veterinary journal2025; doi: 10.1111/evj.70000

Plasma C-reactive protein and interleukin-6 concentrations in foals during health and respiratory disease.

Abstract: Early and specific diagnosis of bronchopneumonia in foals is important to prevent severe disease. In human medicine, C-reactive protein (CRP) and interleukin-6 (IL-6) are important diagnostic and prognostic biomarkers in neonatal pneumonia in other species. Evaluation of these markers in foals with naturally occurring respiratory diseases is lacking. Objective: To determine if CRP and IL-6 were useful predictors of respiratory disease in foals from birth to weaning. Methods: Prospective cohort study. Methods: Periodic blood samples from 200 initially healthy foals were collected from birth to weaning on a farm with endemic Rhodococcus equi and Streptococcus equi pneumonia. The foals were examined weekly by physical examination and trans-thoracic ultrasonography to determine the presence or absence of pulmonary consolidation and were divided into three groups after weaning: (1) foals that remained healthy; (2) foals that developed subclinical, mild, self-limiting pulmonary lesions; and (3) foals that developed severe pulmonary lesions and clinical pneumonia that required antimicrobial treatment. Thirty foals from each health group (N = 90 total foals) were randomly selected from the 200 initially enrolled for assessment of associations between CRP and IL-6 concentrations and health status. Data were analysed using linear mixed models, with p-values < 0.05 considered statistically significant. Results: Age-related changes were found in both plasma CRP and IL-6 concentrations. Circulating concentrations of CRP were increased through weaning, while plasma IL-6 concentrations decreased through weaning. Respiratory disease did not significantly impact concentrations of CRP or IL-6 at any age. Conclusions: Timing of sample collection, small sample size. Conclusions: Neither IL-6 nor CRP concentrations were suitable predictors of subclinical or clinical bronchopneumonia in foals in this study. Further studies are needed to determine if more frequent measurement of these markers in foals at the time of pneumonia diagnosis provides helpful diagnostic or prognostic information.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-07-20 PubMed ID: 40684375DOI: 10.1111/evj.70000Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study investigates whether C-reactive protein (CRP) and interleukin-6 (IL-6) can be used as predictive biomarkers for respiratory disease in young horses (foals). However, the researchers concluded that neither measure reliably indicated the onset of bronchopneumonia in the foals studied.

Objective and Methodology

  • The objective of this study was to assess the potential of CRP and IL-6, two proteins usually associated with inflammation and infection, as early predictors of respiratory disease in foals.
  • In total, 200 initially healthy foals were chosen for the study. These animals were regularly screened from birth to weaning for signs of respiratory disease, with blood samples collected incrementally for assessment of CRP and IL-6 levels.
  • The farm where the study was conducted had a known prevalence of both Rhodococcus equi and Streptococcus equi pneumonia, two common causes of bronchopneumonia in horses.
  • Following weaning, the foals were categorized into three groups based on their health status: healthy, foals with mild lung lesions that cleared up without treatment, and those with severe respiratory disease requiring medical intervention.
  • A subset of 90 animals (30 per health category) was selected for further analysis.

Results and Conclusions

  • The analysis revealed that while there were age-related changes in the blood concentration of both CRP and IL-6 in the foals, prevalence of respiratory disease did not significantly impact these levels at any age.
  • Specifically, CRP usually increased throughout weaning while IL-6 typically decreased.
  • Critically, the study concluded that neither CRP nor IL-6 were reliable indicators of future respiratory disease in the foals studied.
  • The researchers caution that this conclusion may be influenced by the timing of sample collection and the relatively small sample size.
  • They suggest further study is required to see if more frequent measurement of these proteins around the time of pneumonia diagnosis offers useful information for clinical decision-making.

Overall, this study presents important findings that challenge the potential of CRP and IL-6 proteins as diagnostic or prognostic biomarkers for bronchopneumonia in foals. Further research is necessary to ascertain the usefulness of these biomarkers in a clinical setting.

Cite This Article

APA
Hildebrandt D, Venner M, Hart KA, Berghaus L. (2025). Plasma C-reactive protein and interleukin-6 concentrations in foals during health and respiratory disease. Equine Vet J. https://doi.org/10.1111/evj.70000

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Hildebrandt, Dorothea
  • Clinic for Horses, University of Veterinary Medicine Hannover, Hanover, Germany.
Venner, Monica
  • Equine Clinic, Destedt, Germany.
Hart, Kelsey A
  • Department of Large Animal Medicine, University of Georgia, Athens, Georgia, USA.
Berghaus, Londa
  • Department of Large Animal Medicine, University of Georgia, Athens, Georgia, USA.

Grant Funding

  • Paul Schockemoehle Pferedhaltung GmbH, Lewitz Stud, Neustadt-Glewe, Germany
  • University of Georgia, College of Veterinary Medicine, Marguerite Thomas Hodgson Equine Studies Endowment

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