Global prevalence and risk factors of equine infectious anemia: A systematic review and meta-analysis

Equine infectious anemia (EIA) is a lentiviral disease affecting members of the Equidae family, with global distribution and significant implications for animal health and biosecurity. Despite numerous individual reports, a comprehensive synthesis of its global prevalence and risk factors remains lacking. This study aimed to conduct a systematic review and meta-analysis to estimate the global prevalence of EIA, identify diagnostic trends, and evaluate factors associated with heterogeneity across studies.

A systematic search was conducted in six major databases (PubMed, Scopus, Web of Science, ScienceDirect, Cochrane Library, and ProQuest), yielding 312 records. After Preferred Reporting Items for Systematic Reviews and Meta-Analyses-guided screening, 29 eligible studies published between 1975 and 2024 were included in the study. Meta-analysis was performed using R Studio (version 4.4.2) employing a random-effects model. Subgroup analyses and meta-regression were conducted to explore heterogeneity across host species, continent, diagnostic method, and study period. Publication bias was assessed through funnel plots and Egger's test.

The global pooled prevalence of EIA was estimated at 20.97% (95% confidence interval [CI]: 11.08-30.85), with substantial heterogeneity (I² = 99.3%). South America reported the highest regional prevalence (27.21%), while horses showed the greatest susceptibility among Equidae (25.40%). Diagnostic methods varied, with agar gel immunodiffusion being the most commonly used (18.62% prevalence detection). A declining trend in prevalence (2.19%-28.70%) was noted from 2015 to 2022. No significant publication bias was detected. Meta-regression revealed that climate and study period partially explained the heterogeneity.

This study highlights the substantial global burden and diagnostic variability of EIA, emphasizing the need for enhanced surveillance in endemic areas, standardized diagnostic protocols, and strengthened quarantine practices. Expanding serological monitoring in underrepresented regions and integrating climatic and ecological data into control strategies are vital for mitigating EIA transmission risks.