THEILERIA EQUI INFECTION IN WORKING HORSES OF PAKISTAN: EPIDEMIOLOGY, MOLECULAR CHARACTERIZATION, AND HEMATOBIOCHEMICAL ANALYSIS.

Overview

• The study investigated the prevalence, molecular characteristics, diagnostic test comparison, risk factors, and blood biochemistry of Theileria equi infection in working horses in Pakistan.
• It aimed to better understand the disease’s impact, diagnostic accuracy, and associated factors in this region.

Background and Aim

• Theileria equi is a tick-borne protozoan parasite affecting horses worldwide, including Pakistan.
• The infection causes equine piroplasmosis, which affects horse health and work performance.
• This study focused on:
• Determining the prevalence of T. equi infection in working horses.
• Comparing three diagnostic methods: microscopy, competitive enzyme-linked immunosorbent assay (cELISA), and polymerase chain reaction (PCR).
• Characterizing the molecular genetics of the parasite isolates.
• Identifying risk factors associated with infection.
• Analyzing hematological and biochemical changes in infected horses.

Methodology

• Blood samples were collected from 194 working horses in Pakistan.
• Each sample was tested by:
  • Microscopic examination of blood smears.
  • cELISA to detect antibodies against T. equi.
  • PCR for parasite DNA detection.
• Molecular characterization was performed using phylogenetic analysis of PCR-positive samples.
• Risk factors were analyzed statistically, including variables like tick control, hygiene, vaccination, etc.
• Hematobiochemical parameters were compared between infected and uninfected horses.

Results: Prevalence and Diagnostic Comparison

• Prevalence rates found were:
  • Microscopy: 9.79%
  • cELISA: 21.13%
  • PCR: 13.40%
• Diagnostic test comparison (using PCR as reference):
  • cELISA had higher sensitivity (84.62%) but lower specificity (88.69%) and accuracy (88.14%) than microscopy.
  • Microscopy had lower sensitivity (57.69%) but higher specificity (97.62%) and accuracy (92.27%).
• This indicates cELISA detects more true positives but also has more false positives compared to microscopy.

Molecular Characterization

• Phylogenetic analysis showed:
  • Study isolates shared 61% similarity among themselves with two isolates (OL662926 and OL662925).
  • One isolate (OL662924) showed 82% similarity with the others.
  • All isolates shared homology with T. equi strains from South Africa, South Korea, India, Pakistan, and Brazil.
• This suggests some genetic diversity within Pakistani isolates and global relatedness of strains.

Risk Factors Associated with Infection

• Significant risk factors (p < 0.05) identified for T. equi infection included:
  • Tick control status (lack of effective tick prevention linked to higher infection).
  • Previous tick infestation history.
  • Current tick infestation levels.
  • Poor house hygiene.
  • Inadequate deworming or vaccination practices.
  • Presence of other livestock species close to horses.
• These factors influence exposure and susceptibility to tick-borne infection.

Hematobiochemical Findings

• Infected horses showed significant changes (p < 0.05) in blood parameters:
  • Decrease in:
    • Red blood cell count (RBCs).
    • Hemoglobin concentration (Hb).
    • Packed cell volume (PCV).
    • White blood cells (WBCs).
    • Platelet count (PLT).
    • Phosphorus levels.
  • Increase in:
    • Lymphocyte and granulocyte counts.
    • Aspartate aminotransferase (AST) enzyme activity indicating liver stress.
    • Blood glucose levels.
    • Bilirubin concentration.
    • Blood urea nitrogen (BUN) and creatinine, indicating kidney function changes.
• These alterations reflect anemia, immune response, and possible liver and kidney impairments linked to T. equi infection.

Significance and Contributions

• This is the first comprehensive study in Pakistan evaluating:
  • Comparative diagnostic test performance for T. equi in working horses.
  • Molecular diversity of T. equi strains circulating regionally.
  • Risk factors contributing to infection prevalence.
  • Hematobiochemical disruption caused by infection.
• Findings provide important information to improve diagnosis, control, and management of equine piroplasmosis in Pakistan.
• Results may help in strategy planning for tick control, horse health monitoring, and treatment approaches.