Seasonal modulation of platelet indices in mares.

Overview

• This study investigates how platelet characteristics in mares change with the seasons over one year.
• It finds that many platelet indices show significant seasonal variation, which could impact clinical assessments in horses.

Introduction and Background

• Platelet indices are measurements that provide insight into platelet activation (how platelets respond to stimuli), size variability (heterogeneity), and production rates.
• In horses, platelet counts have been noted to vary seasonally, but how derived indices (such as platelet size and activation markers) fluctuate throughout the year, especially in mares, is not well understood.
• The study focuses on Spanish Purebred mares aged 6-12 years living under natural environmental conditions in Valencia, Spain.

Purpose and Objectives

• To evaluate seasonal variation in platelet count and platelet-derived indices in clinically healthy mares.
• To analyze the interrelations among these platelet indices to better understand underlying physiological changes.

Methodology

• Population: 40 clinically healthy Spanish Purebred mares between 6-12 years old.
• Duration: One year of monitoring under natural seasonal changes.
• Sampling: Monthly blood samples were collected.
• Parameters measured: Platelet count (PLT) and derived indices including platelet size, heterogeneity, plateletcrit (PCT), aggregation index, platelet mass, and density.
• Analysis: Non-parametric repeated-measures statistics were used to evaluate seasonal effects on platelet parameters.

Key Findings

• Many platelet indices showed significant seasonal variation (p < 0.05).
• Platelet count was lowest in autumn, indicating fewer circulating platelets during that season.
• Indices reflecting platelet size and heterogeneity increased both in warm seasons (spring/summer) and cold seasons (winter), suggesting larger and more variable platelets during these times.
• Plateletcrit (PCT) and aggregation index did not show significant seasonal changes.
• Correlation analyses revealed:
• Strong relationships between platelet size, mass, and heterogeneity, indicating these characteristics change in synchrony.
• Inverse relationships between platelet density and markers related to platelet activation, which could imply changes in platelet function or composition across seasons.

Interpretation and Implications

• The observed seasonal modulation suggests that platelet dynamics in mares adapt to environmental conditions such as temperature and daylight variations.
• Lower platelet counts in autumn might reflect physiological downregulation during transitional environmental periods.
• Increases in platelet size and heterogeneity during cold and warm seasons could indicate heightened platelet production or altered activation states influenced by seasonal factors.
• These physiological adaptations could impact how blood clotting and immune responses operate across the year.
• Clinically, these findings emphasize the need to account for seasonal variation when interpreting platelet test results in horses to avoid misdiagnosis.
• The study supports establishing seasonally adjusted reference intervals for platelet indices in equine clinical practice to improve diagnostic accuracy.