First Molecular Survey of Equine Adenovirus Type 1 Infection Among Horses in Poland.

Overview

• This study investigated the presence and genetic diversity of equine adenovirus type 1 (EAdV-1) among horses in Poland by analyzing nasal swabs from a large sample of horses over several years using molecular methods.

Background

• Equine adenovirus type 1 (EAdV-1) is a virus known to infect horses globally.
• The virus primarily infects the respiratory tract but can also be found in other body systems.
• Before this study, there was no molecular data available about EAdV-1 infections specifically in Polish horses.

Study Objectives

• To determine how often EAdV-1 infection occurs in selected horse populations across Poland.
• To assess the genetic variability of EAdV-1 viruses obtained from these horses.

Methods

• Sample Collection:
  • 1150 nasal swabs were collected from 1145 horses across 19 different horse studs in Poland.
  • Samples were collected opportunistically over a long period from 2012 to 2025.
• Detection of Virus:
  • A quantitative PCR (qPCR) assay targeting a partial gene segment of EAdV-1 was used to identify infected samples.
• Sequencing and Genetic Analysis:
  • PCR primers were designed to amplify the partial gene from qPCR-positive samples.
  • Between 1 and 5 clones per PCR product were sequenced to assess genetic diversity.
  • Analyses included sequence identity matrix, phylogenetic trees, and median-joining haplotype networks to understand relationships between viral sequences.

Results

• Prevalence:
  • EAdV-1 was detected in 49 out of 1150 samples, representing a 4.3% infection rate.
  • Infected horses were mostly healthy, with only one horse showing clinical respiratory disease.
• Genetic Relatedness:
  • Partial gene sequences from different horses showed close genetic similarities, indicating related viral strains.
  • Sequences from the same studs were clustered together, even when samples were collected years apart, suggesting persistence or recurrent infection with similar virus strains within studs.

Conclusions and Significance

• This is the first molecular survey that provides evidence of active EAdV-1 infections in Polish horse populations.
• The study reveals a relatively low prevalence of infection but confirms that the virus circulates among horses in Poland.
• Genetic analyses show limited variability among EAdV-1 strains within horse studs, suggesting stable virus populations or common sources of infection within these groups.
• These insights improve understanding of the epidemiology of EAdV-1 and can aid in future monitoring, diagnosis, and possibly control measures in horse populations.