| The parasitic protozoa Giardia duodenalis is a genus of intestinal flagellates that infects a wide range of vertebrate hosts throughout the world. In humans,Giardia duodenalis which can cause gastrointestinal infections ranging from mild to severe as well as chronic disease were first found by Levin·Hook in 1681. Transmission of the Giardia duodenalis cysts to humans occurs by fecal oral route transmission, either by direct contact or by ingestion of contaminated food or water.The purpose of this study was to investigate the epidemiology and the genotypes of Giardia duodenalis from human feces in Henan province. Specimens were collected and examined by microscope of iodine wet mount smears and concentrated by sucrose density gradient centrifugation between august 2007 and December 2008 in Laboratory.23 of the 7519 fecal specimens were diagnosed as Giardia positive by microscopic examination. Thus, the Giardia infection rate was 0.31%(23/7519). The infection rate for persons aged 7-10 years old was 1.28%(5/392),0.46% (10/2190) for persons aged 0-6 years old, the infection rate for persons aged 10-20,21-40,41-60 and >60 years old was 0%,0.34%,0.11%,0.13%, respectively. There was a significant difference prevalence of Giardia in the different age groups, with a more frequent occurrence in 7-10 years children (P<0.01). The infection rate for female and male persons was 0.25%(14/3932) and 0.36% (9/3587), respectively. No significant difference of prevalence was observed between men and women (P>0.05).In order to determine species or genotype or subtype of Giardia duodenalis isolates from feces in Henan. In this study, all microscopy-positive samples were amplified by nested PCR. Then, Blast or Fasta methods was used to search homological sequences in NCB1, after that, homological sequences were alignmented. Phylogenetic tree and homological analysis were made by some biological softwares such as Clustal X 1.81, and DNAstar 4.0. Sequence analysis showed that, Of these,20 samples (87%) were PCR positive,3 samples (13%) were PCR negative. The presence of two major genotypes of Giardia duodenalis in the samples examined, assemblage A and assemblage B, with 19 samples belonging to assemblage A and only one samples belonging to assemblage B. Subtyping was identified by sequence analysis of the triosephosphate isomerase (TPI) gene, with 6 distinct subtypes identified in assemblage A,4 new subtypes was found, the only one assemblage B were new subtypes.Nucleotide sequences of the triosephosphate isomerase (TPI) gene also were procured for 22 isolates,12 isolates from rabbits,5 isolates from chinchillas,4 isolates from Voles,1 isolate from Hamster. The presence of two major genotypes of Giardia duodenalis in the animals samples examined, assemblage A and assemblage B. Among these,11/22(50%) were genotype A,11/22(50%) were genotype B. Subtypes were identified by sequence analysis of the triosephosphate isomerase (TPI) gene,8 distinct subtypes identified in assemblage A with 5 new subtypes and 5 distinct subtypes identified in assemblage B with 4 new subtypes, respectively.The results show that may exist different gene or subtypes of Giardia duodenalis, a total of 42 Giardia isolates from Henan Province,17 different subtypes with 14 new subtypes were found by the molecular identification. The study results will be useful for the prevalence of giardiasis and will be provide a reference in species or genotype. |
