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Equine veterinary journal2026; doi: 10.1002/evj.70177

The prevalence of Streptococcus equi subsp. equi carriers in the Netherlands.

Abstract: Streptococcus equi subspecies equi (S. equi) carriers are thought to be important drivers for strangles outbreaks. Limited data are available on the prevalence of carriers in European horse husbandry settings. Objective: To estimate the prevalence of S. equi carriers among apparently healthy adult horses and ponies in the Netherlands. Methods: Cross-sectional survey. Methods: The carrier prevalence in the Netherlands was estimated, detecting carriers by PCR analysis of three repeated nasopharyngeal lavages at weekly intervals. Bayesian methods were used for a true prevalence estimation. Results: One hundred and sixty-six horses on 86 premises were sampled. The posterior distribution gave a mean and median estimate for true prevalence of 2.0% and 1.6%, respectively, with a 95% credible interval of [0.1%, 5.9%]. Conclusions: The target of 200 participants in the cross-sectional survey was not reached. The sensitivity of three repeated nasopharyngeal lavages for the detection of carriership remains uncertain. Conclusions: The carrier prevalence estimate of 2.0% reported here is in the same order of magnitude as recent reports from other countries. INTRODUÇÃO: Portadores de Streptococcus equi subespécie equi (S. equi) são considerados importantes fatores na ocorrência de surtos de garrotilho. Há dados limitados sobre a prevalência de portadores em sistemas de criação de equinos na Europa. Objective: Estimar a prevalência de portadores de S. equi entre cavalos e pôneis adultos aparentemente saudáveis na Holanda. Unassigned: Estudo transversal. MÉTODOS: A prevalência de portadores na Holanda foi estimada por meio da detecção de portadores utilizando análise por PCR de três lavagens nasofaríngeas repetidas em intervalos semanais. Métodos bayesianos foram utilizados para estimar a prevalência verdadeira. Results: Foram amostrados 166 equinos em 86 propriedades. A distribuição a posteriori apresentou estimativas média e mediana da prevalência verdadeira de 2,0% e 1,6%, respectivamente, com um intervalo de credibilidade de 95% de [0,1%, 5,9%]. PRINCIPAIS LIMITAÇÕES: A meta de 200 participantes no estudo transversal não foi atingida. A sensibilidade de três lavagens nasofaríngeas repetidas para a detecção de portadores ainda é incerta. CONCLUSÕES: A estimativa de prevalência de portadores de 2,0% reportada neste estudo é da mesma ordem de magnitude que relatos recentes de outros países.
© 2026 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2026-04-26 PubMed ID: 42036105DOI: 10.1002/evj.70177Google Scholar: Lookup
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  • Journal Article

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.

Overview

  • This study estimated how common healthy carrier horses of Streptococcus equi subsp. equi are in the Netherlands.
  • Using repeated PCR testing from nasal samples, the researchers found about 2% of adult horses and ponies to be carriers, similar to rates reported elsewhere.

Introduction

  • Streptococcus equi subsp. equi (S. equi): A bacterium responsible for strangles, a highly contagious respiratory disease in horses.
  • Carrier horses: Horses who harbor S. equi without showing symptoms; they can unknowingly spread the disease during outbreaks.
  • Relevance: Understanding carrier prevalence in horse populations is crucial for outbreaks control and prevention.
  • Knowledge gap: Limited data exists on the prevalence of S. equi carriers in European horse populations, including the Netherlands.
  • Study goal: Estimate the prevalence of S. equi carriers among apparently healthy adult horses and ponies in the Netherlands.

Methods

  • Study design: Cross-sectional survey targeting healthy adult horses and ponies.
  • Sampling: A total of 166 horses on 86 different premises were sampled.
  • Sample collection: Nasopharyngeal lavages (a nasal wash technique) were collected three times at weekly intervals from each horse.
  • Detection technique: PCR analysis was used on lavage samples to detect the presence of S. equi genetic material.
  • Statistical approach: Bayesian statistical methods were employed to estimate the ‘true prevalence,’ accounting for test characteristics and uncertainty.

Results

  • Prevalence estimates: The Bayesian posterior distribution provided:
    • Mean true prevalence estimate: 2.0%
    • Median true prevalence estimate: 1.6%
    • 95% credible interval: 0.1% to 5.9%, reflecting uncertainty intervals.
  • Sampling size: The study did not meet the original target of 200 horses, which may affect precision.
  • Test sensitivity: The sensitivity of repeated nasopharyngeal lavage PCR tests to detect carriers is not fully certain, potentially influencing prevalence estimates.

Discussion and Conclusions

  • Carrier prevalence: Approximately 2% of clinically healthy adult horses in the Netherlands are carriers of S. equi.
  • Comparison to other studies: This prevalence aligns with recent estimates reported in other countries, suggesting consistency across horse populations.
  • Limitations:
    • Sample size lower than planned, limiting statistical power.
    • Uncertain sensitivity of the diagnostic method, meaning some carriers might have been missed or false positives could have occurred.
  • Implications: The presence of carriers even among healthy horses highlights the risk of unnoticed transmission and outbreaks, supporting the need for surveillance and biosecurity measures.

Cite This Article

APA
Houben RMAC, Broens EM, Broekhuizen-Stins MJ, Sloet van Oldruitenborgh-Oosterbaan MM, van Maanen C, Heesterbeek JAP. (2026). The prevalence of Streptococcus equi subsp. equi carriers in the Netherlands. Equine Vet J. https://doi.org/10.1002/evj.70177

Publication

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

Researcher Affiliations

Houben, R M A C
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
Broens, E M
  • Department of Infectious Diseases and Immunology, Clinical Infectiology, Utrecht University, Utrecht, The Netherlands.
Broekhuizen-Stins, M J
  • Department of Infectious Diseases and Immunology, Clinical Infectiology, Utrecht University, Utrecht, The Netherlands.
Sloet van Oldruitenborgh-Oosterbaan, M M
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
van Maanen, C
  • Royal GD, Deventer, The Netherlands.
Heesterbeek, J A P
  • Department of Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.

Grant Funding

  • Utrechts Universiteitsfonds

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