Oxidative Stress and Inflammatory Responses in Horses Naturally Infected with Theileria equi.

Oxidative stress and inflammation are elevated in horses naturally infected with Theileria equi, a tick-borne parasite, and these factors may contribute to the blood abnormalities and clinical signs seen in equine piroplasmosis.

Background of the Study

• Equine piroplasmosis is a tick-borne disease caused by the parasite Theileria equi.
• The disease is globally distributed and leads to persistent infection in horses with varying symptoms.
• Oxidative stress has been implicated in other hemoprotozoan (blood parasite) infections, but its role in Theileria equi infection in horses is not well studied.
• Understanding oxidative stress and inflammation in this disease could clarify its pathogenesis and guide treatment strategies.

Objectives

• To evaluate oxidative stress markers in horses naturally infected with Theileria equi.
• To assess antioxidant status in these infected horses.
• To measure inflammatory cytokines involved in the immune response.
• To document clinicopathological changes, including blood parameters and liver enzyme activities.

Methods

• Thirty-five horses naturally infected with Theileria equi were studied alongside twenty clinically healthy horses as controls.
• Infection was confirmed through various assessments:
  • Clinical examination
  • Hematological and biochemical analyses
  • Indirect fluorescent antibody test (IFAT)
  • Polymerase chain reaction (PCR)
• Measured serum levels of:
  • Interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), key pro-inflammatory cytokines.
  • Reduced glutathione (GSH), a critical antioxidant.
  • Malondialdehyde (MDA), a marker of lipid peroxidation and oxidative stress.

Key Findings

• Hematological and Biochemical Changes:
  • Infected horses had lower platelet counts, indicating possible thrombocytopenia.
  • Higher serum aspartate aminotransferase (AST) activities were seen, suggesting liver involvement or muscle damage.
• Inflammatory Cytokines:
  • Significantly elevated serum levels of IFN-γ and TNF-α in infected horses, indicating persistent inflammatory activation.
• Oxidative Stress and Antioxidant Status:
  • Increased MDA concentrations demonstrated enhanced lipid peroxidation, a hallmark of oxidative damage.
  • Decreased GSH levels indicated impaired antioxidant defense mechanisms.
• Correlation Analysis:
  • Negative correlation between GSH and white blood cell count, suggesting antioxidant depletion with inflammation.
  • Negative correlation between MDA and red blood cell count, indicating oxidative damage related to anemia or RBC destruction.
  • Positive correlation between MDA levels and clinical disease severity score, linking oxidative stress to disease manifestation.

Conclusions and Implications

• Chronic Theileria equi infection leads to ongoing oxidative stress and depletion of antioxidant defenses in horses.
• Sustained inflammatory responses mediated by cytokines such as IFN-γ and TNF-α accompany the infection.
• The interplay between oxidative stress and inflammation may contribute to the observed hematological abnormalities like thrombocytopenia and anemia.
• This interaction likely plays a significant role in the clinical signs and severity of equine piroplasmosis.
• Understanding these mechanisms could inform the development of adjunctive therapies targeting oxidative stress and inflammation to improve disease management.