Parasite Biology Unit/Division of Enteric Diseases, National Microbiology Laboratory, Public Health Agency of Canada, 110 Stone Road West, Guelph, ON, N1G 3W4, Canada.
Centre for Food-borne, Environmental & Zoonotic Infectious Diseases, Public Health Agency of Canada, 370 Woodlawn Road West, Guelph, ON, N1H 7M7, Canada.
Parasit Vectors. 2021 Jan 22;14(1):69. doi: 10.1186/s13071-020-04546-9.
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.
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.
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%).
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.
隐孢子虫病是一种具有全球分布的胃肠道疾病。自 2000 年以来，它一直是加拿大的一种报告疾病；然而，并未进行常规分子监测。因此，污染的来源尚不清楚。本项目的目的是确定安大略省（加拿大最大的省份，代表加拿大三分之一的人口）临床病例中的隐孢子虫的种和亚型，以了解传播模式。
在 2008 年至 2017 年期间，对 169 份冷冻、保存、未经保存的粪便标本进行了隐孢子虫镜检阳性，并使用分子工具对其进行了特征描述。这 169 份标本中的一部分是个别病例的重复样本。直接从粪便中提取 DNA，进行巢式 PCR 后，对小亚基核糖体 RNA (SSU) 和糖蛋白 60 (gp60) 基因进行 Sanger 测序。
对 129 例隐孢子虫病的分子分型数据和有限的人口统计学数据进行了分析。其中，91 例（70.5%）由微小隐孢子虫引起，24 例（18.6%）由人隐孢子虫引起。4 例（3.1%）发生微小隐孢子虫和人隐孢子虫混合感染。另外还观察到 5 种其他种，分别为微小隐孢子虫（n=5）、猫隐孢子虫（n=2）、火鸡隐孢子虫（n=1）、兔隐孢子虫（n=1）和鼠隐孢子虫（n=1）。对 gp60 基因进行亚分型，发现人隐孢子虫有 5 个等位基因家族和 17 个亚型，微小隐孢子虫有 3 个等位基因家族和 17 个亚型。人隐孢子虫最常见的亚型是 IbA10G2（22.3%），微小隐孢子虫最常见的亚型是 IIaA15G2R1（62.4%）。
本研究中的大多数分离株为微小隐孢子虫，支持动物源性传播是安大略省隐孢子虫病传播的主要途径的观点。然而，观察到约四分之一的病例为人隐孢子虫，这表明人际传播也是安大略省隐孢子虫病发病的一个重要因素。
