Giardiasis is a diarrheal disease that can affect many species, including dogs, cats, and humans. It is caused by Giardia, a single-celled parasite that attacks the gastrointestinal tract of infected animals. Among experts, there is some question about (1) the number of Giardia subtypes that can cause disease in animals and (2) the potential of these subtypes to also infect humans. While humans are susceptible to infection with Giardia, infection by the same subtypes prevalent in animals is thought to be exceedingly rare but remains a point of controversy and investigation.
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