Prevalence and risk factors of Giardia duodenalis in sheep and goats in global: A systematic review and meta-analysis.

Giardia duodenalis is a significant intestinal parasite responsible for causing diarrhea in humans and animals globally. This study aimed to evaluate the worldwide distribution of G. duodenalis, as well as to determine its prevalence and identify risk factors associated with infections in sheep and goats. A comprehensive systematic review was performed utilizing international databases to collect relevant studies. A random-effects meta-analysis was applied to estimate the global prevalence of G. duodenalis. A total of 104 studies from 32 countries, published up to January 2025, fulfilled the inclusion criteria. The overall global prevalence of G. duodenalis in small ruminants was found to be 14 % (95 % CI: 11 %-17 %). Notably, the highest prevalence were recorded in temperate and tropical regions situated between latitudes -60° to 60° (18.9 %; 95 % CI: 14.7 %-24.0 %), and in areas above 45° latitude in both northern and southern hemispheres (21.3 %; 95 % CI: 13.4 %-32.2 %). Seasonal analysis revealed peak prevalence occurring during winter months (16.1 %; 95 % CI: 9.4 %-26.0 %). Mediterranean climates, characterized by wet winters and dry summers, demonstrated notably higher prevalence (40.5 %; 95 % CI: 19.6 %-65.5 %), particularly in regions with intensive sheep farming practices. Furthermore, age was identified as a significant risk factor, with lambs (≤1 year) exhibiting higher prevalence (17.3 %; 95 % CI: 13.5 %-22.4 %) compared to adult small ruminants (7.0 %; 95 % CI: 4.8 %-10.1 %). Within adult populations, ewes displayed slightly elevated prevalence. Temporal analysis indicated a significant decline in prevalence between 2010 and 2019 (7.7 %; 95 % CI: 5.4 %-10.9 %; p = 0.0097), followed by a resurgence after 2020. Overall, despite an observed downward trend over time (slope = -0.0282), this decline was not statistically significant (p = 0.1549). These findings underscore the necessity for implementing targeted, region-specific control and management strategies, particularly in regions with intensive farming practices and increased zoonotic potential, to mitigate the spread and impact of G. duodenalis.