Genetic characterisation of Cryptosporidium and Giardia from dairy calves: discovery of species/genotypes consistent with those found in humans

Abstract

Cryptosporidium and Giardia are important genera of parasitic protists that can cause significant diarrhoeal diseases in humans and other animals. Depending on the species/genotype of parasite, human infection may be acquired via anthroponotic or zoonotic transmission routes. Here, we undertook a molecular epidemiological investigation of these two genera of parasites in pre- and post-weaned calves from eight locations in Canterbury, New Zealand, by PCR-coupled sequencing and phylogenetic analysis of sequence data for regions in the 60 kDa glycoprotein (pgp60) gene of Cryptosporidium and/or the triose-phosphate isomerase (ptpi) gene of Giardia. The pgp60 and ptpi regions were specifically amplified from 15 (8.3%) and 11 (6.1%) of the 180 individual faecal samples, respectively. The sequences derived from all of the amplicons were aligned with homologous reference sequences and subjected to phylogenetic analysis by Bayesian inference. For Cryptosporidium, three samples contained Cryptosporidium parvum genotype IIa, subgenotypes IIaA15G3R1, IIaA19G3R1 and IIaA23G4. Twelve samples contained Cryptosporidium hominis genotype Ib, subgenotype IbA10G2R2. While subgenotypes IIaA15G3R1 and IIaA23G4 are new records, IIaA19G3R1 and IbA10G2R2 are commonly found in humans in various countries. For Giardia, two samples contained Giardia duodenalis assemblage A, also common in humans. In contrast, nine samples contained G. duodenalis assemblage E, which is the first report of this assemblage in cattle in New Zealand. Therefore, the present results indicate that dairy calves on the South Island of New Zealand harbour 'zoonotic' genotypes of Cryptosporidium and Giardia, which is likely to have significant public health implications.