Multilocus genotyping of Giardia duodenalis isolates from household cats and pet shop kittens

Giardia duodenalis is a pathogenic protozoan that causes diarrhea in mammalian hosts including humans and companion animals, and the host specificity differs depending on the genetic assemblages. The purpose of the present study is to perform multilocus genotyping at four loci of G. duodenalis isolates from household cats and pet shop kittens in Japan and evaluate the zoonotic potential. Fifty-seven fecal samples from cats (household cats: 13, pet shop kittens: 44), which were positive for Giardia-specific antigen as determined by an ELISA kit, were the subjects of our analysis. Nested or semi-nested PCRs targeting 18S ribosomal RNA (18S rRNA), glutamate dehydrogenase (GDH), beta-giardin (BG), and triosephosphate isomerase (TPI) were performed on all samples. All DNA amplicons were sequenced for genotyping. Forty-four isolates (household cats: 11, pet shop kittens: 33) were positive for at least one of the PCRs. Assemblage F was the most frequently detected (75%; 33/44), followed by assemblage A (13.6%; 6/44) and assemblage B (2.3%; 1/44). Four isolates (9.1%) showed the results as mixed assemblages F and A. Sub-genotyping of assemblage A isolates based on three loci (GDH, BG, and TPI) identified all of them as assemblage AI. DNA sequences of zoonotic G. duodenalis assemblages were detected from 25% of the genotyped specimens, and these were found at several shops and hospitals in Japan, which suggests that zoonotic G. duodenalis is prevalent among domestic cats in Japan, and that the considerable risk of zoonotic transmission of G. duodenalis from household cats or pet shop kittens to humans exists.