Giardia lamblia is most important intestinal protozoan worldwide. Giardiasis manifestation differ from asymptomatic infection to chronic diarrhea .The current study is performed to genotye G. lamblia isolates from Iraqi patients by molecular analysis. Ten hundred positive direct smear for giardiasis of different ages and sexes were exposed to nested polymerase chain reaction (PCR) for triose phosphates isomerase (TPI) and small subunit ribosomal RNA (ssrRNA) genes. The products of PCR were sequenced and the sequences were subjected to phylogenetic analysis by using multiple sequence alignment analysis of the partial triose phosphate isomerase (tpi)gene sequence in local Giardia lamblia genotypes isolates and NCBI-Genbank local Giardia lamblia genotypes based ClustalW alignment analysis by using (M`EGA 6.0, multiple alignment analysis tool). Only 80 samples gave positive results by molecular analysis. The phylogenetic analysis of the sequences was detected that assemblage A, B, mixed subtypes AB and F were isolated from stool samples. It was found that 18 (22.5%), 42 (52.5%), 8 (10% and 12(15%) corresponding to genotype A,B, AB, and F respectively. Phylogenetic tree analysis based on the partial sequence of triose phosphate isomerase (tpi) gene in local Giardia lamblia genotypes isolates that used for confirmative genetic detection and genetic relationship analysis. The evolutionary distances were computed using phylogenetic UPGMA tree type (MEGA 6.0 version). The local Giardia lamblia genotype AII were showed genetically closed related to NCBI-Blast Giardia lamblia genotype AII (KT235928.1), local Giardia lamblia genotype AI were showed genetically closed related to NCBI-Blast Giardia lamblia genotype AI (MF671916.1), local Giardia lamblia genotype F were showed genetically closed related to NCBI-Blast Giardia lamblia genotype F (KU378636.1), and local Giardia lamblia genotype B were showed genetically closed related to NCBI-Blast Giardia lamblia genotype B (JF918474.11 ) at total genetic change (0.05-0.15). A, B, and F were the genotypes that have a prevalence in the city of Najaf. assemblage B is the more prevalent subgroup compared with other assemblages. This is the first study that involved a phylogenetic analysis of Giardia strains and recorded assemblage F from Najaf patient. The present results provide to a better considerate of the molecular epidemiology of Giardia parasite.

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