Molecular prevalence of equine herpesvirus type 1 and equine herpesvirus type 4 in thoroughbred and Arabian horse facilities in Türkiye.

Overview

• This study investigated how common equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4) infections are in thoroughbred and Arabian horse populations on eight stud farms in Türkiye using molecular testing methods.
• The research aimed to assess virus prevalence in horses showing respiratory illness symptoms, aborted foals, and asymptomatic horses to evaluate infection rates and the effectiveness of vaccination and biosecurity measures.

Background

• Equine herpesvirus-1 (EHV-1) and equine herpesvirus-4 (EHV-4) are contagious viruses that primarily cause respiratory disease and reproductive problems in horses.
• Both viruses can lead to symptoms like fever, respiratory distress, and abortions, causing significant economic losses in the equine industry.
• Understanding their prevalence helps inform control strategies such as vaccination, quarantine, and biosecurity practices.

Study Objectives

• To determine the molecular prevalence of EHV-1 and EHV-4 in horse populations on Turkish stud farms.
• To analyze samples from symptomatic horses, aborted foals, and asymptomatic horses to detect viral DNA using RT-PCR methods.
• To assess the active infection rates within a large, semi-enclosed, and well-managed equine population under strict biosecurity.

Methodology

• Sample Collection:
  • Deep nasal swabs were taken from 443 horses exhibiting acute fever and/or respiratory disease symptoms.
  • Uterine swabs and multiple tissue samples (lung, liver, spleen, thymus, kidney, heart) were collected from 152 aborted foal cases.
  • Additionally, nasal swabs were obtained from 4,915 asymptomatic horses for comparison.
• Testing Procedure:
  • RT-PCR (Reverse Transcription Polymerase Chain Reaction) was used to detect viral DNA presence of EHV-1 and EHV-4 in collected samples.

Key Findings

• Virus Detection in Symptomatic Horses:
  • EHV-1 DNA was identified in 2 out of 443 symptomatic horses (0.45%).
  • EHV-4 DNA was detected in 67 out of 443 symptomatic horses (15.1%).
  • One horse tested positive for both EHV-1 and EHV-4 (0.23%).
• Virus Detection in Aborted Foal Samples:
  • EHV-1 DNA was found in 2 out of 152 abortion-related samples (1.32%).
  • No EHV-4 DNA was detected in these abortion cases.
• Virus Detection in Asymptomatic Horses:
  • 13 out of 4,915 asymptomatic horses (0.26%) were carriers of EHV-4 DNA.
  • No asymptomatic horses tested positive for EHV-1.
• Overall infection rates in the studied population:
  • Active EHV-1 infections were found at 0.67% prevalence.
  • Active EHV-4 infections were considerably higher, at 11.26% prevalence.

Interpretation and Significance

• The low prevalence of EHV-1 and moderate prevalence of EHV-4 suggest that these viruses are not widely circulating actively in this stud farm equine population.
• The stud farms’ strict biosecurity measures, comprehensive vaccination programs, and PCR-based viral surveillance appear effective in controlling virus spread.
• The absence of EHV-4 in abortion samples, despite its respiratory prevalence, indicates different pathological impacts and virus behavior for EHV types 1 and 4.
• Though the data are not representative of all regional or national horse populations in Türkiye, they provide valuable epidemiological insights into virus dynamics under controlled conditions.

Implications for Equine Health Management

• This study reinforces the importance of continuous vaccination and quarantine measures to prevent herpesvirus outbreaks among horses.
• PCR-based surveillance serves as an effective tool for early detection and management of active infections, facilitating timely interventions.
• Understanding prevalence patterns can guide breeders and veterinarians in optimizing biosecurity protocols at stud farms and equine facilities.
• The findings support the implementation of tailored herpesvirus control strategies aimed at reducing respiratory disease and reproductive complications in horses.

Conclusion

• The molecular analysis of equine herpesvirus infections in well-managed Turkish stud farms showed minimal active circulation of EHV-1 and EHV-4.
• The research contributes to a better understanding of herpesvirus epidemiology in equine populations and underlines the effectiveness of integrated control programs.
• Future surveillance across wider regions will help map national prevalence and inform comprehensive equine health policies in Türkiye.