Identification of a novel assemblage G subgenotype and a zoonotic assemblage B in rodent isolates ofGiardia duodenalisin the Canary Islands, Spain

Abstract

SUMMARY: The flagellated parasiteGiardia duodenalisis known as one of the most common causes of protozoal diarrhoea in both humans and animals worldwide. The aim of the present work was to perform the first study ofG. duodenalisin rodents in the Canary Islands (Spain) and analyse the level of genetic variation and the potential zoonotic role of the isolates. Stool samples were collected from 284 wild rodents andGiardiacysts were detected by light microscopy. The overall prevalence of giardiasis was 25·4% and ranged from 19·4% in El Hierro to 34% in Gran Canaria. Positive samples were further characterized by PCR and nucleotide sequencing of the triose phosphate isomerase (TPI),β-giardin (BG) and glutamate dehydrogenase (GDH) genes. Our study revealed assemblage G as the most frequent genotype and identified two rodent-infectingG. duodenalishaplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novelG. duodenalissub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore,G. duodenalisassemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk ofG. duodenalistransmission from rodents to humans.