Giardia duodenalis assemblages in cats from Virginia, USA

Giardia duodenalis is considered a species complex that is divided into 8 genetically distinct but morphologically identical assemblages (A-H). Assemblages C-H are generally host adapted, while A and B infect both people and animals and are considered potentially zoonotic. Furthermore, within assemblage A there are four subtypes (AI, AII, AIII, and AIV) of varying zoonotic potential; human isolates belong to AI and AII, while animal isolates belong to AI, AIII and AIV. Assemblages A, B, C, D, and F have all been reported from cats. The objective of this study was to determine the assemblage(s) of G. duodenalis present in cats from Virginia using multilocus genotyping and to assess if there were any differences among the assemblage(s) found in the populations of cats surveyed (free-roaming, shelter, owned) or their geographic location within Virginia. Samples that were positive for G. duodenalis cysts by microscopy using centrifugal flotation with ZnSO₄ solution and/or direct immunofluorescence assay were genotyped using PCR and sequencing targeting fragments of the SSU rRNA, gdh, bg, and tpi genes. In total, 54 cyst-positive samples were analyzed by PCR and sequencing: 43 produced amplicons, and 37 samples had interpretable sequence data at one or more loci. Assemblage F was detected in 21/37 samples, AI was detected in 12/37 samples, and in 4/37 samples both assemblages F and AI were detected. The potentially zoonotic assemblage AI was detected in cats from two widely separated animal shelters and from one free-roaming cat. These genotyping data demonstrate that potentially zoonotic G. duodenalis assemblages are present in cats in Virginia.