Global Prevalence of Haemonchus contortus in Ruminants: A Systematic Review and Meta-analysis.

Haemonchus contortus is a highly pathogenic gastrointestinal nematode that significantly impacts ruminant health and productivity. Despite extensive research, a comprehensive understanding of the global prevalence of H. contortus infections and associated risk factors remains lacking. A systematic review and meta-analysis were conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Literature on H. contortus in ruminants was retrieved from PubMed, Web of Science, ScienceDirect, Scopus, and Google Scholar up to January 1, 2025. Pooled prevalence and 95% confidence intervals were estimated using a random-effects model. A meta-analysis of 64 studies on H. contortus infection in ruminants worldwide revealed a pooled prevalence of 37%. Continent subgroup significantly influenced prevalence (p < 0.05), with the highest rate reported in Europe and the lowest in Oceania. Environmental factors played a critical role, with regions classified under the Cwb climate exhibiting significantly higher infection rates than other climate zones (p < 0.05). Higher prevalence was also associated with high-altitude areas, annual rainfall ≥800 mm, and lower temperatures. Host-related factors were equally important, with animals over 1 year of age and females showing greater susceptibility. These findings underscore the importance of developing control strategies adapted to different climates and host species, with a particular emphasis on targeted surveillance and deworming efforts against H. contortus in high-risk regions to reduce infection burden and support sustainable ruminant production.