Introduction and objective:
Giardia duodenalis is an important intestinal protozoan of dogs and a potential environmental and zoonotic concern. The aim of the study is to determine the occurrence of G. duodenalis in Polish dogs, assess selected host factors associated with infection, compare microscopy and rapid immunochromatographic assay, and characterise positive Giardia isolates by PCR-RFLP.

Material and methods:
Between October – December 2025, 2,251 dogs in Poland were examined using 3-day faecal sample sets. Microscopy was performed by zinc sulfate flotation. A subset of 818 sample sets was additionally tested with a rapid immunochromatographic coproantigen assay. Microscopy-positive samples were subjected to PCR-RFLP targetting the gdh and beta-giardin loci.

Results:
Microscopy-based prevalence was 13.06% (294/2,251; 95% CI: 11.73–14.52). Infection was strongly associated with age, with the highest prevalence in dogs aged <1 year (26.86%). The immunochromatographic assay showed 98.18% sensitivity and 96.78% specificity relative to microscopy. At least one molecular marker was detected in 241/294 microscopy-positive samples (81.97%). Assemblages D and C predominated, accounting for 48.96% and 48.13% of genotyped samples, respectively, whereas assemblages B (2.07%) and A (0.83%) were rare.

Conclusions:
Giardia duodenalis is common in dogs in Poland, especially in young animals. Canine-adapted assemblages C and D were the most prevalent, while potentially zoonotic assemblages A and B were only occasionally detected. Combined use of microscopy and immunochromatographic testing may improve routine diagnosis.