Influence of Housing and Fecal Egg Count on Cytokine Profiles (IL-4 and IL-13) in Equines.

Overview

• This study investigated how housing conditions and parasite load, as measured by fecal egg count (FEC), influence the immune response in horses by analyzing levels of cytokines IL-4 and IL-13.
• The research aimed to clarify the relationship between parasite infection intensity and environment on equine immune function.

Introduction and Background

• Strongyles are parasitic roundworms that infect the gastrointestinal tract of horses and are highly prevalent worldwide, affecting about 90% of horses.
• These parasites are transmitted primarily through contaminated soil, making environment and housing important factors in infection risk and immune response.
• Cytokines IL-4 and IL-13 play key roles in the immune system, particularly in type 2 immune responses often involved in fighting parasitic infections.

Study Objectives

• The main goal was to examine whether the parasite load (measured by fecal egg count) and type of housing affect the levels of IL-4 and IL-13 in horses.
• Specifically, the study aimed to determine correlations between high versus low fecal egg counts and two housing conditions in relation to cytokine concentrations.

Methods

• A total of 25 horses were selected and grouped based on their housing conditions:
• Pasture Housing (PS): Horses housed outdoors 24 hours a day (n=13).
• Semi-Intensive Housing (SI): Horses kept in stalls with overnight turnout (n=12).
• Within each housing group, horses were further divided into high or low fecal egg count groups, based on their strongyle infection levels.
• Fecal egg counts were performed using the McMaster method, a standard quantitative technique for measuring parasite eggs in feces.
• Blood samples were collected, and plasma was extracted to measure IL-4 and IL-13 concentrations through ELISA (enzyme-linked immunosorbent assay), a sensitive immunological method.
• Statistical analysis was conducted via two-way ANOVA to evaluate the independent and combined effects of housing type and FEC on cytokine levels.

Results

• Horses with high fecal egg counts showed significantly higher levels of both IL-4 and IL-13 compared to horses with low FEC (p < 0.05).
• The 95% confidence intervals for increased cytokine levels in high FEC horses were:
• IL-4: 60.39 to 115.3 pg/mL
• IL-13: 505.3 to 808.9 pg/mL
• When comparing housing types, IL-4 levels were significantly higher in the pasture (PS) group (p < 0.05), with a 95% CI ranging from -94.01 to -12.43 pg/mL.
• Conversely, IL-13 levels were significantly elevated in the semi-intensive (SI) housing group (p < 0.05), although the confidence interval indicated some variability (-592.0 to 401.7 pg/mL for IL-4 and -69.03 to 49.33 pg/mL for IL-13).
• There was no significant interaction effect between housing and fecal egg counts, indicating these factors independently influenced cytokine profiles.

Conclusions and Implications

• The study demonstrated that higher parasite loads, indicated by fecal egg counts, correlate with increased immune activity characterized by elevated IL-4 and IL-13 cytokines in horses.
• Housing conditions also affected immune response profiles, with pasture housing associated more with IL-4 increases, and semi-intensive stall housing linked to increased IL-13.
• The absence of interaction effects suggests parasite burden and housing conditions influence cytokine levels through separate mechanisms.
• These findings help clarify the immunological dynamics in equine strongyle infections and may assist in designing better parasite management and horse housing protocols to optimize immune health.