Submitted to: Emerging Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2003
Publication Date: 11/1/2003
Citation: SULAIMAN, I.M., FAYER, R., BERN, C., GILMAN, R.H., TROUT, J.M., SCHANTZ, P.M., DAS, P., LAL, A.A., XIAO, L. TRIOSEPHOSPHATE ISOMERASE GENE CHARACTERIZATION AND POTENTIAL ZOONOTIC TRANSMISSION OF GIARDIA DUODENALIS. EMERGING INFECTIOUS DISEASES. 2003. 9:1444-1452. Interpretive Summary: Giardiasis is a common cause of diarrheal disease in almost all vertebrates, including humans worldwide. In developed countries, it is referred as re-emerging infectious agents because of its increasing role in outbreaks of diarrhea in daycare centers, and water- and food-borne outbreaks of diarrhea in the general public. It is also one of the most common parasites infecting dairy cattle and domestic dogs.The taxonomy of Giardia at the species level is complicated and unresolved because of limited morphologic differences. To date, based on the morphology, six species of this genus are considered valid. To address the source of infection in humans and public health importance of Giardia parasites from animals, the triosephosphate isomerase (TPI) gene was characterized from human, dog, muskrat, cattle, beavers, a rat, a rabbit, and one environmental sample. A major group contained most of the human and muskrat isolates, all beaver isolates, the isolate from a rabbit, and one sample from the wastewater. The finding of host-adapted Giardia genotype is of public health importance, considering the controversy regarding the zoonotic potential of Giardia from animals.
Technical Abstract: To address the source of infection in humans and public health importance of Giardia parasites from animals, the triosephosphate isomerase (TPI) gene was characterized. A two-step nested PCR protocol was developed to amplify a fragment (530 bp) of the TPI gene from various G. duodenalis isolates. Nucleotide sequences of the TPI gene were generated for 45 human isolates, 15 dog isolates, 8 muskrat isolates, 7 isolates each from cattle and beavers, and 1 isolate each from a rat and a rabbit, and one environmental sample. Phylogenetic analysis on the TPI sequences from this study and published sequences led to the formation of distinct groups for the isolates from humans, cattle, dogs, rat and cat within G. duodenalis. A major group (Assemblage B) contained most of the human and muskrat isolates, all beaver isolates, the isolate from a rabbit, and one sample from the wastewater. These findings should be useful in the detection and differentiation of various G. duodenalis parasites, and in the analysis of genetic and evolutionary relationships among Giardia parasites. They also confirm that G. duodenalis parasites from certain animals can potentially infect humans.