Molecular characterization of Anaplasmataceae in Turkmen horses (Akhal-Teke breed) and ticks in racetracks, Iran.

Molecular analysis of Anaplasmataceae bacteria was conducted in Akhal-Teke horses and ticks from racetracks in Iran, revealing the presence of Ehrlichia canis and Anaplasma ovis in both horses and ticks, highlighting the risk these animals and ticks pose as reservoirs of infection.

Background and Purpose of Study

• Racetracks have open grassy areas conducive to tick populations.
• Ticks are known vectors for Anaplasmataceae bacteria which can infect horses and potentially humans.
• The study aimed to detect and characterize Anaplasmataceae in Turkmen (Akhal-Teke) horses and ticks collected from racetracks in Iran during 2024/2025.

Methods

• Sample Collection:
  • 200 blood samples were collected from Turkmen (Akhal-Teke breed) horses.
  • Ticks were collected by dragging methods in paddock areas of racetracks.
• Molecular Screening:
  • Sanger sequencing was used to identify bacterial DNA.
  • Gene targets included 16S rRNA (universal bacterial marker), TRP36, and dsb genes (specific for Anaplasmataceae).
• Tick Identification:
  • Collected ticks were identified morphologically as Hyalomma asiaticum and Haemaphysalis sulcata species.
• Statistical Analysis:
  • Prevalence comparisons by horse gender and age were conducted, with no significant difference (p>0.05).

Results

• In Horses:
  • 11 out of 200 horses (5.5%) tested positive for Anaplasmataceae DNA.
  • 8 horses (4%) were positive for Ehrlichia canis, a bacterial species usually associated with canine ehrlichiosis but here found in horses.
  • 3 horses (1.5%) tested positive for Anaplasma ovis, a pathogen primarily affecting sheep and goats but also detected in horses.
  • Horses showed no clinical signs or symptoms, indicating asymptomatic carriage.
• In Ticks:
  • Ticks were organized into 20 pools for testing.
  • 7 pools (35%) were positive for Anaplasmataceae DNA.
  • 4 pools (20%) harbored Ehrlichia canis DNA.
  • 3 pools (15%) carried Anaplasma ovis DNA.
• Phylogenetic Analysis:
  • Genetic sequences clustered closely with known sequences in GenBank database.
  • This confirms the identity of bacterial species and supports molecular findings.

Interpretations and Implications

• Asymptomatic horses:
  • Serve as reservoirs for Ehrlichia canis and Anaplasma ovis.
  • May contribute to silent transmission cycles involving ticks at racetracks.
• Zoonotic Risk:
  • Ehrlichia canis has zoonotic potential, posing infection risk to humans.
  • Visitors and workers at racetrack facilities could be exposed to infected ticks and thus at risk of infection.
• Tick Species:
  • Hyalomma asiaticum and Haemaphysalis sulcata identified as potential vectors in this ecosystem.
• Control Recommendations:
  • Surveillance of horses and ticks in racetrack areas is important for public and animal health.
  • Tick control measures could reduce pathogen transmission.