Intestinal microbial eukaryotes at the human, animal and environment interface in rural Iraq

Intestinal microbial eukaryotic parasites represent a significant public and veterinary health burden, especially in low- and middle-income countries, yet their transmission dynamics at the human–animal–environment interface remain poorly characterized in certain countries. This study investigated the prevalence and genetic diversity of key microbial eukaryotes, including Cryptosporidium spp., Giardia duodenalis, Blastocystis spp., Entamoeba histolytica, and Enterocytozoon bieneusi, in a rural village in Iraq. Samples collected from humans (n = 50), livestock (sheep and goats, n = 50), water (n = 20), and soil (n = 20) were analysed using microscopy and molecular methods (qPCR and nested PCR). Blastocystis spp. (78% animals, 16% humans, 45% soil, 5% water) and Cryptosporidium spp. (26% animals, 12% humans, 5% soil, 15% water) were the most frequently found microeukaryotes using either microscopy and/or molecular detection. Molecular methods identified Cryptosporidium parvum in humans and sheep, hinting at zoonotic transmission potential. Enterocytozoon bieneusi and Giardia were also found. Cryptosporidium ubiquitum and E. bieneusi genotypes BEB6 and COS-I, respectively, were detected exclusively in sheep, suggesting roles as potential reservoirs. Blastocystis ST1 was detected in humans, while ST4 and ST10 occurred in sheep. Notably, molecular detection rates of Blastocystis were much lower than those of microscopy. Entamoeba histolytica was not detected. The detection of the same organisms in humans, animals and the environment suggest zoonotic and environmental transmission pathways, which warrant further investigation using the One Health approach.