Aquatic birds are known to be suitable hosts for a number of avian-specific species and genotypes of the enteric protozoan parasites Giardia and Cryptosporidium. Waterbirds have also been reported as sporadic carriers of species of both pathogens from human or domestic animal origin via environmental contamination. Because aquatic birds can shed substantial amounts of infective Giardia and Cryptosporidium (oo)cysts to the environment including surface waters intended for human consumption, this situation may pose a potential risk of waterbone zoonotic disease.