Abstract: Two strains of Giardia (GD1 and GD2) isolated from feces of naturally infected dogs in Guangdong were genotyped by nested PCR of tpi gene. The genomic DNA of Giardia identified by the iodine staining was extracted and the tpi gene was amplified by using nested PCR assay. The BLAST and DNAStar softwares were used to analyze their homology and phylogeny. As demonstrated by tpi gene analysis,the homology of GD1 strain with L02120 was 100％,and they situated at the same branch of the phylogenic tree,while that of GD2 strain with DQ220289 was 99.1％,they were also at the same branch of the phylogenic tree. It is concluded that the genotype of GD1 strain is assemblage AⅠ,having the potential to infect humans,whereas that of the GD2 strain is assemblage D.

Key words: dog; Giardia lamblia; tpi gene; nested PCR