Molecular characterization and zoonotic potential of Giardia and Cryptosporidium infections in dogs and cats in Central Spain

Giardia duodenalis and Cryptosporidium spp. are environmentally resistant protozoan parasites transmitted via the faecal-oral route, often through contaminated water or food. Although companion animals may contribute to environmental dissemination of infective stages, their role in zoonotic transmission remains debated. In this study, 75 Giardia -positive (65 dogs, 10 cats) and 20 Cryptosporidium -positive (11 dogs, 9 cats) faecal samples from central Spain were molecularly characterized at the gdh and bg loci for G. duodenalis and at the ssu rRNA and gp60 loci for Cryptosporidium spp. Host-adapted Giardia assemblages predominated, with assemblages C (33.9%) and D (47.7%) in dogs and assemblage F (50.0%) in cats, while zoonotic assemblages A and B occurred at moderate frequencies (10.8%–40.0%). Cryptosporidium canis and Cryptosporidium felis were the predominant species in dogs and cats, respectively, whereas C. parvum and C. hominis were sporadically detected. These findings expand molecular data on enteric protozoa in companion animals in Spain and highlight their potential relevance within a One Health context.