Seroprevalence, risk factors and hematological parameters associated with Equine Infectious Anemia from Casanare, Colombia.

Overview

• This study investigated the presence (seroprevalence), risk factors, and blood parameter changes associated with Equine Infectious Anemia (EIA) in horses from Casanare, Colombia.
• The research aimed to generate updated epidemiological data to improve control strategies against EIA in this region.

Background and Objective

• EIA is a persistent lentivirus infection affecting horses, with significant health and economic consequences, especially in tropical regions.
• Despite its importance, epidemiological data on EIA in Colombia are limited.
• The study objectives were to:
• Estimate the seroprevalence of EIA among horses in Casanare.
• Identify demographic and management risk factors associated with infection.
• Assess hematological (blood) changes occurring in infected horses.

Methods

• The study design was cross-sectional, including 1,228 horses from 204 production units across 121 rural districts.
• The key diagnostic technique used was agar gel immunodiffusion (AGID), which detects antibodies against EIA virus, indicating infection.
• Data collection included:
• Demographic and management information through epidemiological surveys (e.g., age, gender, breed, management practices).
• Hematological parameters measured by automated analyzers, assessing various blood cell counts and indices.
• Statistical analysis involved:
• Estimation of seroprevalence with 95% confidence intervals (CI).
• Initial risk factor screening using Chi-square tests and calculation of odds ratios (OR).
• Variables with p ≤ 0.50 entered into a multivariable logistic regression model using backward likelihood ratio (LR) approach.
• Final adjusted ORs estimated to identify significant risk factors.
• Comparisons of hematological parameters between positive and negative horses using Student’s t-test.

Key Results

• The overall seroprevalence of EIA was 6.7% (95% CI: 5.4–8.2%).
• Identified risk factors significantly increasing the likelihood of EIA infection:
• Muleas (i.e., female mules) had higher odds (OR 4.98; CI: 1.26–19.72) compared to males.
• Horses aged over 24 months were more likely infected (OR 3.11; CI: 1.60–6.04).
• Geldings (castrated males) had increased risk (OR 2.37; CI: 1.33–4.20).
• Protective factor identified:
• Quarter Horse breed showed a reduced risk of infection (OR 0.63; CI: 0.15–0.85).
• Hematological findings in seropositive horses showed mild alterations:
• Changes involved leukocyte (white blood cells) and erythrocyte (red blood cells) parameters.
• These mild changes suggested subclinical infection rather than acute illness.

Interpretation and Conclusions

• The presence of lifelong carrier status and cyclical viremia in EIA means infected horses can intermittently spread the virus without clear symptoms.
• The continued detection of seropositive horses in Casanare emphasizes the necessity for ongoing systematic serological surveillance to control disease spread.
• The identification of specific risk and protective factors highlights populations and management practices for targeted interventions.
• The hematological data provide insights into the typical subclinical nature of EIA infection in this region, which may complicate clinical diagnosis without laboratory testing.
• Overall, this study contributes valuable epidemiological evidence to support enhanced and focused EIA control programs in endemic tropical regions like Casanare, Colombia.