Molecular characterization of Cryptosporidium isolates from humans in Ontario, Canada

Rebecca A Guy,Andrea K Boggild,Marisa A Rankin,Karine Thivierge,Pia K Muchaal,Christine A Yanta,Rachel Lau

doi:10.1186/s13071-020-04546-9

Abstract

BackgroundCryptosporidiosis is a gastrointestinal disease with global distribution. It has been a reportable disease in Canada since 2000; however, routine molecular surveillance is not conducted. Therefore, sources of contamination are unknown. The aim of this project was to identify species and subtypes of Cryptosporidium in clinical cases from Ontario, the largest province in Canada, representing one third of the Canadian population, in order to understand transmission patterns.MethodsA total of 169 frozen, banked, unpreserved stool specimens that were microscopy positive for Cryptosporidium over the period 2008–2017 were characterized using molecular tools. A subset of the 169 specimens were replicate samples from individual cases. DNA was extracted directly from the stool and nested PCR followed by Sanger sequencing was conducted targeting the small subunit ribosomal RNA (SSU) and glycoprotein 60 (gp60) genes.ResultsMolecular typing data and limited demographic data were obtained for 129 cases of cryptosporidiosis. Of these cases, 91 (70.5 %) were due to Cryptosporidium parvum and 24 (18.6%) were due to Cryptosporidium hominis. Mixed infections of C. parvum and C. hominis occurred in four (3.1%) cases. Five other species observed were Cryptosporidium ubiquitum (n = 5), Cryptosporidium felis (n = 2), Cryptosporidium meleagridis (n = 1), Cryptosporidium cuniculus (n = 1) and Cryptosporidium muris (n = 1). Subtyping the gp60 gene revealed 5 allelic families and 17 subtypes of C. hominis and 3 allelic families and 17 subtypes of C. parvum. The most frequent subtype of C. hominis was IbA10G2 (22.3%) and of C. parvum was IIaA15G2R1 (62.4%).ConclusionsThe majority of isolates in this study were C. parvum, supporting the notion that zoonotic transmission is the main route of cryptosporidiosis transmission in Ontario. Nonetheless, the observation of C. hominis in about a quarter of cases suggests that anthroponotic transmission is also an important contributor to cryptosporidiosis pathogenesis in Ontario.Graphical

Highlights

Cryptosporidiosis is a gastrointestinal disease with global distribution
The one case not identified using the small subunit ribosomal RNA (SSU) Nested PCR (nPCR) was identified as C. felis using an HSP70 nPCR
The distribution of species detected in the Ontario cryptosporidiosis cases mirrors a study in Prince Edward Island (PEI), the province with the highest cattle-to-human ratio in Canada, where 64% of the isolates were C. parvum and 37% were C. hominis [17], similar to levels reported in Scotland and Sweden [11, 12]

Summary

Introduction

Cryptosporidiosis is a gastrointestinal disease with global distribution. It has been a reportable disease in Canada since 2000; routine molecular surveillance is not conducted. The aim of this project was to identify species and subtypes of Cryptosporidium in clinical cases from Ontario, the largest province in Canada, representing one third of the Canadian population, in order to understand transmission patterns. Cryptosporidium is a protozoan parasite that causes gastrointestinal disease worldwide and is a major cause of severe morbidity and mortality in young children in developing countries [1]. National reporting in the UK, Ireland, France, Sweden and the USA has revealed national and regional differences in species distribution and subtypes of Cryptosporidium in humans and high under-ascertainment of this disease [8]

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