Molecular characterization of Cryptosporidium isolates from humans in Ontario, Canada

Abstract

Background Cryptosporidiosis 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. Methods A 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. Results Molecular 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%). Conclusions The 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.

High Diversity of Cryptosporidium Species and Subtypes Identified in Cryptosporidiosis Acquired in Sweden and Abroad

“…In terms of the analysis of cases according to age, the observed bimodal distribution (Figure 1) supports previous observations [9], with a relatively high number of cases observed among infants and toddlers and with a second peak-and the largest one-in the 30-44-year-olds. Quite similar age distributions have been observed in studies from Denmark, France, and Canada, but with the second peak in the 20-35-year-olds [34,36,41]. The bimodal age distribution may reflect transmission between parents and their children; however, no such family clusters were detected during the present study.…”

“…Mixed C. hominis and C. parvum infection was observed only in 1 patient, and for 10 of the patients infected with C. parvum , the origin of infection was unknown or uncertain. The high occurrence of C. parvum compared with C. hominis observed in Sweden is similar to the situation in other industrial countries, such as France, Ireland, and Canada [ 34 , 35 , 36 ], although a higher percentage of C. hominis has been observed in Spain and Australia [ 37 , 38 ]. Shifting trends have been seen over time in the Netherlands and New Zealand, showing the importance of longitudinal studies [ 39 , 40 ].…”

“…The success rate of PCR for SAF-fixed samples was 80% (56/70), compared with 99% (323/328) for native stool samples. One recent study pointed out the limited availability of native stool material for the molecular analyses of stool parasites [ 34 ], but with the increased use of DNA-based diagnostics, the availability of unfixed material has increased, and the problem with fixed samples is in decline.…”

Cross-border Investigations on the Prevalence and Transmission Dynamics of Cryptosporidium Species in Dairy Cattle Farms in Western Mainland Europe

“…IIaA15G2R1, is deemed as the most prevalent IIa subtype in humans in developed countries, with several cases of human cryptosporidiosis linked to it [6,44,67,87,88,[91][92][93]. Several previous outbreaks with this subtype in the United Kingdom were traced back to contact between farm animals and humans pointing towards zoonotic potential [35].…”

Prevalence of Cryptosporidium spp. in Yaks (Bos grunniens) in China: A Systematic Review and Meta-Analysis

“…ryanae , C. baileyi , C. andersoni , C. parvum , C. hominis , C. canis , C. struthionis , C. xiaoi , and C. ubiquitum ( Ma et al., 2014b ; Qi et al., 2015 ; Wang et al., 2018 ). More importantly, some of them, such as C. parvum , C. hominis , and C. ubiquitum , were also frequently found in humans ( Widmer, 2009 ; Li et al., 2014 ; Ryan et al., 2016 ), and the infection rate is 36.4%, 9.3% and 1.6% ( Guy et al., 2021 ). Cryptosporidium may cause fatal persistent diarrhea in infants and people with weakened or immune function and cognitive development, thus representing a public health threat ( Xiao et al., 2004 ).…”