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Studying Cryptosporidium Infection in 3D Tissue-derived Human Organoid Culture Systems by Microinjection
Published on: September 14, 2019
Molecular characterization of Cryptosporidium isolates from humans in Ontario, Canada
Rebecca A Guy1, Christine A Yanta2, Pia K Muchaal3
1Parasite Biology Unit/Division of Enteric Diseases, National Microbiology Laboratory, Public Health Agency of Canada, 110 Stone Road West, Guelph, ON, N1G 3W4, Canada. rebecca.guy@canada.ca.
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.
Insights
Molecular surveillance in Ontario reveals Cryptosporidium parvum is the most common cause of cryptosporidiosis, suggesting zoonotic transmission. Cryptosporidium hominis also contributes significantly, indicating anthroponotic transmission plays a role in disease spread.
Area of Science:
- Medical Parasitology
- Infectious Disease Epidemiology
- Molecular Diagnostics
Background:
- Cryptosporidiosis is a globally prevalent gastrointestinal illness.
- In Canada, it's a reportable disease, but molecular surveillance for transmission source identification is lacking.
- Understanding Cryptosporidium species and subtypes is crucial for public health interventions.
Purpose of the Study:
- To identify Cryptosporidium species and subtypes in clinical cases from Ontario.
- To elucidate transmission patterns of cryptosporidiosis in the region.
- To inform public health strategies by characterizing the sources of infection.
Main Methods:
- Molecular characterization of 169 microscopy-positive stool specimens from 2008-2017.
- DNA extraction followed by nested PCR and Sanger sequencing of the SSU and gp60 genes.
- Analysis of species and gp60 allelic families/subtypes for Cryptosporidium isolates.
Main Results:
- 129 cases were characterized, with Cryptosporidium parvum (70.5%) being predominant, followed by Cryptosporidium hominis (18.6%).
- Multiple Cryptosporidium species were identified, including C. ubiquitum, C. felis, C. meleagridis, C. cuniculus, and C. muris.
- Seventeen subtypes each for C. hominis (most frequent: IbA10G2) and C. parvum (most frequent: IIaA15G2R1) were identified.
Conclusions:
- The high prevalence of C. parvum supports zoonotic transmission as a primary source of cryptosporidiosis in Ontario.
- The significant presence of C. hominis indicates anthroponotic transmission is also a key factor in disease occurrence.
- Molecular typing is essential for understanding cryptosporidiosis transmission dynamics and guiding control efforts.
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