Occurrence and risk factors of equine piroplasmosis in Portugal: A five-year retrospective study.

Overview

• This study investigates the occurrence and risk factors of equine piroplasmosis (EP) in Portugal by analyzing diagnostic data collected over five years.
• The research confirms that EP is endemic in Portugal and identifies prevalence rates and factors influencing infection in horses.

Background

• Equine Piroplasmosis (EP): A tick-borne disease affecting horses, caused by three parasites: Theileria equi, Theileria haneyi, and Babesia caballi.
• Geographical Significance: Endemic mainly in tropical and subtropical regions, with suspicion of endemicity in Portugal prior to this study.
• Importance: EP affects horse health and has economic consequences, making it important to understand its presence and risk factors in regions like Portugal.

Study Objective

• To determine the seroprevalence and prevalence of EP in horses across Portugal over a five-year period.
• To analyze potential risk factors such as age, season, and location associated with EP infection.

Methodology

• Data Source: 3,063 diagnostic test records from horses were retrospectively analyzed.
• Diagnostic Tests Used:
  • Competitive Enzyme-Linked Immunosorbent Assay (cELISA): Detects antibodies indicating exposure.
  • Indirect Fluorescent Antibody Test (IFAT): Another antibody detection method.
  • Quantitative Polymerase Chain Reaction (qPCR): Detects current infection by identifying parasite DNA.
• Parasites Tested: Mainly Theileria equi and Babesia caballi.
• Analysis of Risk Factors: Assessed variables including horse age, season when samples were taken, and geographical location.

Key Findings

• Seroprevalence (cELISA results):
  • 32.7% positive for T. equi.
  • 15.7% positive for B. caballi.
  • 7.4% showed coinfection with both parasites.
• Seroprevalence (IFAT results):
  • 38.8% positive for T. equi.
  • 45.7% positive for B. caballi.
  • 23.1% had antibodies against both parasites.
• Prevalence (qPCR results):
  • 40.5% of tested horses were currently infected with T. equi.
  • 8.3% were currently infected with B. caballi.
  • 3.2% showed simultaneous infection with both parasites.
• Risk Factors:
  • Age: Older horses had higher rates of seropositivity.
  • Season: Certain seasons corresponded to increased infection rates, likely related to tick activity.
  • Geographical Location: Different regions in Portugal showed variations in infection rates.

Conclusions and Implications

• This is the first comprehensive retrospective study confirming that EP is endemic in Portugal.
• The coexistence of two major parasites causing EP, with notable coinfection rates, highlights the complexity of the disease.
• Identifying specific risk factors such as age, season, and location helps target future prevention and control measures.
• The data serves as a basis for further epidemiological research to better understand the true disease burden and dynamics among the Portuguese equine population.
• Findings will assist breeders, veterinary practitioners, and horse owners in minimizing health impacts and economic losses due to EP through informed management and potential tick control strategies.

Recommendations for Future Research

• Conduct prospective studies to validate the prevalence and seroprevalence estimates in a broader and more representative equine population.
• Investigate specific environmental and management factors influencing tick abundance and parasite transmission.
• Develop and assess prevention, diagnostic, and treatment protocols suited to the Portuguese context.