Acute phase proteins in Andalusian horses infected with Theileria equi.

This study investigated the clinical symptoms and laboratory results of Andalusian horses infected with Theileria equi. The most common symptoms included anorexia, anaemia, depression and icterus, with lower serum iron concentrations compared to healthy horses. Inflammatory response levels were mildly elevated in some infected horses.

Study Design and Participants

• The study conducted clinical and laboratory investigations on 23 Andalusian horses in southern Spain infected with Theileria equi. This group was divided into two, with 16 mares out in pasture (group A1), and seven stabled stallions (Group B1).
• To serve as control groups, five healthy mares at pasture (group A2) and five healthy stalled stallions (group B2) were also evaluated. All horses in the control group tested negative for the Theileria equi parasite.

Clinical Observations

• The most frequent clinical signs observed in infected horses were anorexia, anaemia, depression, and icterus (yellowing of skin and eyes due to increased bile pigments in the blood) in mares (group A1), while stallions (group B1) experienced performance loss or failed to train, and displayed signs of depression.
• Thrombocytopenia, a condition characterized by low blood platelets, was evident in five out of the seven horses in group B1.

Laboratory Findings

• Both infected mare and stallion groups had lower serum iron concentrations compared to their respective healthy control groups. Iron is a vital component for hemoglobin and other cellular metabolic processes.
• However, there was no significant difference in Acute Phase Protein (APP) concentrations between the infected and control horses. All affected horses had APP concentrations within the normal range.
• Despite this, serum haptoglobin, serum amyloid A, and plasma fibrinogen concentrations—indicators of systemic inflammation—were higher than the reference limits in some horses. Specifically, five out of 23 had higher haptoglobin, three out of 23 had higher serum amyloid A, and one out of 23 had higher fibrinogen concentrations.

Conclusion

• The study concluded that Andalusian horses infected with theileriosis (caused by Theileria equi infection) demonstrated only a mild systemic inflammatory response. While some horses showed elevated levels of inflammatory markers, these changes were relatively minor, suggesting that the organism’s defense mechanisms do not strongly react to the Theileria equi infection.