Enterocytozoon bieneusi in European Domestic Ungulates and Pets: Occurrence, Genetic Diversity, and Public Health Perspectives from a Narrative Review.

Enterocytozoon bieneusi is the most frequently diagnosed microsporidian parasite in humans and a recognized cause of diarrheal disease, particularly in immunocompromised individuals. Its broad host range, which includes livestock, companion animals, and wildlife, highlights its zoonotic potential and warrants careful epidemiological assessment. This narrative review synthesizes available data on the occurrence and genetic diversity of E. bieneusi in European domestic ungulates (cattle, pigs, sheep, goats, horses, and water buffaloes) and pets (dogs and cats), aiming to provide an integrated perspective on animal reservoirs and their relevance for public health. Publications retrieved from the Web of Science Core Collection database were systematically screened, and country-specific results were extracted, emphasizing prevalence rates, genotype distributions, and zoonotic implications. Across Europe, cattle and pigs emerged as the most studied hosts, frequently harboring zoonotic group 1 genotypes such as I, J, BEB4, BEB6, and EbpA, while small ruminants, horses, and buffaloes remain comparatively undocumented. In pets, the dog-adapted genotype PtEb IX was predominant, but several zoonotic genotypes were also identified. Overall, the current evidence confirms the wide host range of E. bieneusi in Europe but also reveals significant data gaps compared to regions such as China, underlining the need for broader surveillance and harmonized molecular approaches within a One Health framework.