Prevalence and risk factors of gastrointestinal helminths infection in Brazilian horses: A retrospective study of a 12-year (2008-2019) diagnostic data.

Overview

• This study analyzed over 19,000 fecal samples from Brazilian horses over 12 years to determine the prevalence of gastrointestinal helminth infections and identify risk factors such as breed, age, climate, and season.
• It found a high overall prevalence of helminths, especially strongyles, with younger horses and certain breeds being at greater risk, information that is vital for improving horse parasite control programs.

Study Background and Purpose

• Gastrointestinal helminths (parasitic worms) cause significant health issues in horses, affecting their wellbeing and performance.
• Effective parasite control requires understanding how common these infections are and what factors increase infection risk.
• This study aimed to measure helminth prevalence and evaluate risk factors in Brazilian horses between 2008 and 2019.

Methodology

• Data Source: 19,276 fecal samples collected by the Laboratory of Veterinary Clinical Parasitology, Curitiba, Southern Brazil.
• Samples Origin: Collected from 153 stud farms across 60 municipalities in nine Brazilian states.
• Time Period: 12 years, from 2008 to 2019.
• Analyzed parasites: Focused on gastrointestinal helminths, specifically strongyles and Parascaris spp.
• Variables Studied: Horse breed, age, climate zone (based on Köppen classification), and season.
• Statistical Analysis: Logistic regression was used to identify odds ratios expressing the strength of risk factors related to parasite egg shedding.

Key Findings on Prevalence

• Overall helminth prevalence was 73.3% among sampled horses.
• Prevalence by Age:
  • Young horses had a higher prevalence at 80.6%.
  • Adults showed 72.1% prevalence.
• Strongyles were detected on 100% of horse farms and had a prevalence of 72.1% in individual horses, with a mean fecal egg count (FEC) of 453.53 eggs per gram (± 717.6).
• Parascaris spp. showed a lower prevalence of 5.8% with a mean FEC of 17.11 (± 149.2).

Influences of Climate and Season

• Tropical wet/monsoon climate (Am) was associated with the lowest FEC for both strongyles and Parascaris spp.
• Summer was identified as a season with significantly higher risk of egg shedding for both parasite types.
• Other climates aside from the Am had comparatively higher parasite loads.

Risk Factors Related to Age and Breed

• Younger horses had 4.6 times higher odds of shedding Parascaris spp. eggs compared to adults.
• For strongyles, young horses had a 1.2 times higher odds of egg shedding relative to adults.
• Breed-related risks for Parascaris spp. egg shedding were identified:
  • Mangalarga Marchador
  • Criollo
  • Crossbred horses
  • These breeds had higher odds compared to Thoroughbred horses.

Implications and Recommendations

• The ubiquitous presence of strongyles across all ages, breeds, seasons, and climatic zones indicates a continuous risk for clinical parasitic disease.
• Higher risk periods (summer) and vulnerable groups (young horses, specific breeds) should be targeted for enhanced monitoring and tailored parasite control strategies.
• Understanding these risk factors can help design better pasture management and deworming plans to reduce parasite burdens and improve horse health.
• Findings are relevant not only for Brazil but also for similar climatic regions worldwide where horses are raised on pastures.