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The flagellated parasite Giardia duodenalis is 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 of G. duodenalis in 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 and Giardia cysts 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-infecting G. duodenalis haplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novel G. duodenalis sub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore, G. duodenalis assemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk of G. duodenalis transmission from rodents to humans.

Histone H1 in Leishmania presents relevant differences compared to higher eukaryote counterparts, such as the lack of a DNA-binding central globular domain. Despite that, it is apparently fully functional since its differential expression levels have been related to changes in chromatin condensation and infectivity, among other features. The localization and the aggregation state of L. braziliensis H1 has been determined by immunolocalization, mass spectrometry, cross-linking and electrophoretic mobility shift assays. Analysis of H1 sequences from the Leishmania Genome Database revealed that our protein is included in a very divergent group of histones H1 that is present only in L. braziliensis. An antibody raised against recombinant L. braziliensis H1 recognized specifically that protein by immunoblot in L. braziliensis extracts, but not in other Leishmania species, a consequence of the sequence divergences observed among Leishmania species. Mass spectrometry analysis and in vitro DNA-binding experiments have also proven that L. braziliensis H1 is monomeric in solution, but oligomerizes upon binding to DNA. Finally, despite the lack of a globular domain, L. braziliensis H1 is able to form complexes with DNA in vitro, with higher affinity for supercoiled compared to linear DNA.