Giardia duodenalis in domestic cats from the US and Canada: Prevalence and zoonotic potential

Giardia duodenalis is a flagellated commensal protozoan that can infect both humans and animals. Infection can result in clinical signs such as diarrhea or, more often, the infection can be subclinical. Within the G. duodenalis species, there are several major genetic assemblages, A – H. Certain assemblages are species specific (C and D in dogs, F in cats) while assemblages A and B can infect humans as well as other mammals. This retrospective study used data collected from a commercial reference laboratory (Antech Diagnostics, Mars Petcare Science & Diagnostics). Real-time PCR data using fecal qPCR panel (KeyScreen™ GI Parasite PCR) for Giardia duodenalis and potential zoonotic assemblages A/B in 157,616 domestic cat stool samples from North America collected between March 8, 2022, to August 31, 2023, was used. Variables including age, sex, altered status, season, and geographic region were assessed to identify associations with cats that were detected for G. duodenalis and potential zoonotic assemblages A/B. The overall prevalence of G. duodenalis was 6.3% (9,962/157,616) and of those detected, 18.5% (1,840/9,962) were assemblages A/B. Cats that were G. duodenalis detected were more likely to be male, intact, less than one-year old, and in the Midwest. In general, lowest detection occurred during the summer months. Zoonotic potential detection was highest in cats aged less than one-year (19.7%; 1,011/5,137). These data highlight the importance of routine fecal screening in domestic cats to detect parasites, particularly those, like Giardia , of One Health concern, and provides prevalence, and risk factor information that aids clinical veterinary decision-making.