Livestock, Humans, and the Environment as Reservoirs of Cryptosporidium and Giardia duodenalis: Evidence from a One Health Study in Türkiye

Cryptosporidium spp. and Giardia duodenalis are globally important intestinal protozoa causing diarrheal disease in humans and animals, with significant zoonotic potential. This study aimed to investigate the prevalence, molecular diversity, and potential transmission dynamics of these parasites in humans, livestock, and environmental samples from a rural community in Türkiye using a One Health approach, and to assess their associations with gut microbiome composition. Faecal samples were collected from 124 humans, 305 livestock (cattle, sheep, and goats), and 40 environmental samples (water and mud). Parasites were detected using qPCR and nested PCR, with positive samples genotyped by sequencing. Microbiome profiling was performed using 16S rRNA gene amplicon sequencing. Giardia duodenalis was detected in 12.1% of humans, 17.5% of livestock, and 2.5% of environmental samples, with assemblages A, B, and E identified, including the first detection of assemblage E in a human in Türkiye. Cryptosporidium spp. were found in 8.9% of humans, 19.3% of livestock, and 55% of environmental samples, with C. parvum as the dominant zoonotic species. Microbiome analysis revealed no significant differences in overall diversity. This study provides the first One Health assessment of Cryptosporidium spp. and Giardia duodenalis in Türkiye, emphasizing zoonotic transmission risks linked to livestock and the environment.