Molecular and serological survey on Theileria equi and Babesia caballi infecting Arabian horses in the northern provinces of Syria.

Overview

• This study investigated the presence of two tick-borne parasites, Theileria equi and Babesia caballi, in Arabian horses from the northern provinces of Syria using both molecular and serological methods.
• The research found widespread exposure to Theileria equi but no evidence of Babesia caballi infection, informing future disease control efforts in the region.

Background and Rationale

• Equine babesiosis is a common tick-borne disease affecting horses globally, caused primarily by Theileria equi and Babesia caballi.
• The disease’s presence in Syria, particularly in the northern provinces, was previously unknown, partly due to disrupted veterinary services caused by the ongoing civil war.
• The war has hampered disease control measures and veterinary infrastructure, increasing the risk of spreading tick-borne diseases like equine babesiosis.
• This study was motivated by the need to fill the knowledge gap regarding the prevalence of these parasites in northern Syria’s horses, especially Arabian breeds which are common in the area.

Study Design and Methods

• A total of 110 Arabian horses, aged 2 to 10 years, were selected from northern Syrian provinces significantly affected by the civil war.
• Each horse received a clinical examination to observe symptoms such as fever, jaundice, anorexia, and lethargy, which are associated with piroplasmosis.
• Blood samples were collected from all horses and analyzed using:
  • Hematological analysis to assess blood cell counts (lymphocytes, hematocrit, platelets, eosinophils, etc.).
  • Competitive Enzyme-Linked Immunosorbent Assay (cELISA) to detect antibodies specific to Theileria equi and Babesia caballi.
  • Polymerase Chain Reaction (PCR), specifically nested PCR targeting the EMA-1 gene for Theileria equi, and targeting the RAP-1 gene for Babesia caballi to detect parasite DNA presence.

Key Findings

• Clinical signs consistent with piroplasmosis were observed in only 4 out of 110 horses, demonstrating a low percentage of symptomatic cases.
• Hematological analysis indicated that symptomatic horses had significantly reduced lymphocyte counts, hematocrit (red blood cell concentration), and platelet counts compared to healthy horses.
• The cELISA results showed:
  • 47% of sampled horses (52/110) had antibodies against Theileria equi.
  • No horses tested positive for antibodies against Babesia caballi.
  • Horses positive for Theileria equi antibodies exhibited:
    • Higher eosinophil percentages (a type of white blood cell involved in immune response).
    • A decrease in red blood cell distribution width, indicating changes in red blood cell size variability.
• Molecular PCR analysis revealed:
  • Theileria equi DNA was detected in 9 out of 10 horses initially positive by screening PCR, confirmed by the presence of a specific 274 base pair amplicon.
  • No Babesia caballi DNA was found in any samples, as no 566 base pair fragment corresponding to the RAP-1 gene was observed.
  • Horses with PCR-confirmed Theileria equi infection also showed higher eosinophil percentages and lower platelet counts.

Conclusions and Implications

• The study confirms that Arabian horses in the northern provinces of Syria are widely exposed to Theileria equi, but there is no current evidence of Babesia caballi infection in the surveyed population.
• The findings suggest that control and prevention programs in Syria should prioritize Theileria equi, especially as veterinary services recover post-conflict.
• Monitoring the health status of horses, particularly focusing on hematological changes such as eosinophil and platelet counts, could help in early detection and management of equine theileriosis in the region.
• This research fills an important knowledge gap, establishing baseline data on tick-borne infections in a region where conflict and disruption have hampered veterinary care and disease surveillance.