While waters might be contaminated by oocysts from >40 Cryptosporidium species, only viable oocysts of C. parvum and C. hominis truly pose the main health risk to the immunocompetent population. Oocyst viability is also an important but often neglected risk factor in monitoring waterborne parasites. However, commonly used methods in water monitoring and surveys cannot distinguish species (microscopic observation) or oocyst viability (PCR), as dead oocysts in water could retain gross structure and DNA content for weeks to months. Here, we report new TaqMan qRT-PCR/qPCR assays for quantitative detection of viable C. parvum and C. hominis oocysts. By targeting a hypothetical protein-encoding gene cgd6_3920 that is highly expressed in oocysts and variable between species, the qRT-PCR/qPCR assays achieve excellent analytical specificity and sensitivity (limit of quantification [LOQ] = 0.25 and 1.0 oocyst/reaction). Using calibration curves, the number and ratio of viable oocysts in specimens could be calculated. Additionally, we also establish a TaqMan-18S qPCR for cost-effective screening of pan-Cryptosporidium-positive specimens (LOQ = 0.1 oocyst/reaction). The assay feasibility is validated using field water (N = 43) and soil (79) specimens from 17 locations in Changchun, China, which detects four Cryptosporidium species from seven locations, including three gp60-subtypes (i.e., IIdA19G1, IIdA17G1 and IIdA24G2) of C. parvum oocysts showing varied viability ratios. These new TaqMan q(RT)-PCR assays supplement current methods in the survey of waters and other samples (e.g., surfaces, foods and beverages), and are applicable to assessing the efficiency of oocyst deactivation protocols.

Cryptosporidium is a major cause of diarrhoeal disease and mortality in young children in resource-poor countries, for which no vaccines or adequate therapeutic options are available. Infection in humans is primarily caused by two species: C. hominis and C. parvum. Despite C. hominis being the dominant species infecting humans in most countries, very little is known about its growth characteristics and life cycle in vitro, given that the majority of our knowledge of the in vitro development of Cryptosporidium has been based on C. parvum. In the present study, the growth and development of two C. parvum isolates (subtypes Iowa-IIaA17G2R1 and IIaA18G3R1) and one C. hominis isolate (subtype IdA15G1) in HCT-8 cells were examined and compared at 24 h and 48 h using morphological data acquired with scanning electron microscopy. Our data indicated no significant differences in the proportion of meronts or merozoites between species or subtypes at either time-point. Sexual development was observed at the 48-h time-point across both species through observations of both microgamonts and macrogamonts, with a higher frequency of macrogamont observations in C. hominis (IdA15G1) cultures at 48-h post-infection compared to both C. parvum subtypes. This corresponded to differences in the proportion of trophozoites observed at the same time point. No differences in proportion of microgamonts were observed between the three subtypes, which were rarely observed across all cultures. In summary, our data indicate that asexual development of C. hominis is similar to that of C. parvum, while sexual development is accelerated in C. hominis. This study provides new insights into differences in the in vitro growth characteristics of C. hominis when compared to C. parvum, which will facilitate our understanding of the sexual development of both species.

Introduction. In England and Wales, cryptosporidiosis cases peak in spring and autumn, associated with zoonotic/environmental exposures (Cryptosporidium parvum, spring/autumn) and overseas travel/water-based activities (Cryptosporidium hominis, autumn). Coronavirus disease 2019 (COVID-19) restrictions prevented social mixing, overseas travel and access to venues (swimming pools/restaurants) for many months, potentially increasing environmental exposures as people sought alternative countryside activities.Hypothesis. COVID-19 restrictions reduced incidence of C. hominis cases and potentially increased incidence of C. parvum cases.Aim. To inform/strengthen surveillance programmes, we investigated the impact of COVID-19 restrictions on the epidemiology of C. hominis and C. parvum cases.Methodology. Cases were extracted from the Cryptosporidium Reference Unit (CRU) database (1 January 2015 to 31 December 2021). We defined two periods for pre- and post-COVID-19 restrictions implementation, corresponding to before and after the first UK-wide lockdown on 23 March 2020. We conducted a time series analysis, assessing differences in C. parvum and C. hominis incidence, trends and periodicity between these periods.Results. There were 21 304 cases (C. parvum=12 246; C. hominis=9058). Post-restrictions implementation incidence of C. hominis dropped by 97.5 % (95 % CI: 95.4-98.6 %; P<0.001). The decreasing incidence trend pre-restrictions was not observed post-restrictions implementation due to lack of cases. No periodicity change was observed post-restrictions implementation. There was a strong social gradient; there was a higher proportion of cases in deprived areas. For C. parvum, post-restrictions implementation incidence fell by 49.0 % (95 % CI: 38.4-58.3 %; P<0.001). There was no pre-restrictions incidence trend but an increasing incidence trend post-restrictions implementation. A periodicity change was observed post-restriction implementation, peaking 1 week earlier in spring and 2 weeks later in autumn. The social gradient was the inverse of that for C. hominis. Where recorded, 22 % of C. hominis and 8 % of C. parvum cases had travelled abroad.Conclusion. C. hominis cases almost entirely ceased post-restrictions implementation, reinforcing that foreign travel seeds infections. C. parvum incidence fell sharply but recovered post-restrictions implementation, consistent with relaxation of restrictions. Future exceedance reporting for C. hominis should exclude the post-restriction implementation period but retain it for C. parvum (except the first 6 weeks post-restrictions implementation). Infection prevention and control advice should be improved for people with gastrointestinal illness (GI) symptoms to ensure hand hygiene and swimming pool avoidance.

Cryptosporidium is an emerging opportunistic zoonotic pathogen that causes diarrheal illness in a wide range of hosts including livestock and humans. This study set out to establish the prevalence of Cryptosporidium as well as the circulating genotypes in order to elucidate the potential role of cattle in the spread of human cryptosporidiosis. Rectal coprological samples from 363 cattle in 11 households in Kiruhura district, Southwestern Uganda were collected and screened for the presence of Cryptosporidium oocysts using the phenol auramine staining method followed by fluorescent microscopy. DNA was extracted from the microscopy positive samples and the COWP gene amplified using PCR. PCR products were sequenced and subjected to phylogenetic analysis. Additionally a multiplex realtime PCR was used to identify the Cryptosporidium spp. Multivariable mixed effect logistic regression models were used to identify potential risk factors for Cryptosporidium infection. The overall prevalence of Cryptosporidium was 7.7% (95% CI 5.1-10.9), and herd level prevalence was 33.3% (95% CI 18.5-52.2). We found a statistically significant difference (OR = 30.78, 95% CI 4.31-219.95, p = 0.001) between infection in bulls as compared to cows. There was no significant difference in the prevalence among the different cattle breeds sampled. All the sequenced COWP gene DNA amplicons were confirmed to be C. hominis, with 93%-100% identity to sequences in the GenBank. The amplification of the small subunit rRNA by multiplex realtime PCR further established that the isolates in this study are C. hominis. This study represents the first time naturally occurring C. hominis has been detected from cattle in Uganda.

Molecular diagnostic assays for Cryptosporidium are usually based on PCR and may detect the entire genus or target specified species. Of the ~40 species, fewer than half have been reported from humans, and most human cases of cryptosporidiosis are caused by Cryptosporidium parvum or Cryptosporidium hominis. Here we describe a nested PCR for the detection of all Cryptosporidium spp. that can then be differentiated by sequencing the PCR amplicons, and a duplex, real-time PCR for the simultaneous detection and differentiation of C. parvum and C. hominis.

OBJECTIVE: To understand the prevalence of Cryptosporidium infection in diarrhea infants under 2 years old in Wuhan City, so as to provide the epidemiological evidence for the prevention and treatment of cryptosporidiosis.
METHODS: The fecal samples from infants under 2 years old with diarrhea were collected in Hubei General Hospital and Central South Hospital in Wuhan City, Hubei Province from August 2014 to July 2015. The fecal samples were stored in 2.5% potassium dichromate at 4 ℃ after filtered. The DNA was extracted from the fecal pellets with the phenol-chloroform method. The Cryptosporidium species were detected by a nested PCR assay targeting the SSU rRNA gene of the parasite. All the positive PCR products were sequenced on ABI 3100 automated sequencer, and the amplified sequences were compared to homologous sequences in the NCBI database by using the Basic Local Alignment Search Tool (BLAST). Phylogenetic analyses were performed by using the software MEGA (version 4.0) based on the Neighbour-Joining method.
RESULTS: The human stool specimens (n = 298) were screened for the presence of Cryptosporidium by nested PCR. The infection rate of Cryptosporidium was 3.02% (9/298). The infection rate of Cryptosporidium was 5.93% (7/118) in the infants between 1-2 years old, and the infection rate was 1.11% (2/180) in the infants under 1 year old, and there was a significant difference between the two groups (χ2 = 4.13, P < 0.05). The nine samples which were positive by nested PCR were successfully sequenced and compared with the reference sequences in GenBank. The results revealed the nine positive specimens were all infected with C. parvum, and two of them were co-infected with C. hominis. Neighbor-joining trees were constructed from the aligned partial SSU rRNA sequences of these nine isolates, and in the SSU rRNA locus, the nine isolates were grouped with C. parvum.
CONCLUSIONS: There exists Cryptosporidium infection in the infants under 2 years old with diarrhea in Wuhan City, and the main species of Cryptosporidium is C. parvum.
［摘要］目的 了解武汉市2岁以下婴幼儿腹泻患者的隐孢子虫感染状况, 为预防隐孢子虫感染提供分子流行病学依 据。方法 采集2014年8月—2015年7月在湖北省人民医院和武汉大学中南医院就诊的2岁以下婴幼儿腹泻患者粪 便, 过滤沉淀后于2.5%重铬酸钾溶液中4 ℃保存; 采用酚-氯仿法提取基因组DNA、18S rRNA巢式PCR (Nested-PCR) 扩增 技术检测隐孢子虫感染, 并对阳性PCR产物测序; 所获序列进行Blastn比对, 应用MEGA软件采用邻接法构建系统进化 树进行虫种鉴定。结果 共收集到298份婴幼儿腹泻患者的粪便样本。经巢式PCR扩增技术检测, 298份样品中有9份 扩增出隐孢子虫阳性条带, 阳性率为3.02% (9/298), 其中1～2岁腹泻幼儿阳性率为5.93% (7/118), < 1岁患儿的阳性率 为1.11% (2/180), 差异有统计学意义 (χ2 = 4.13, P < 0.05) 。9份阳性PCR产物经测序后与GenBank中的参照序列进行比 对,结果显示7份样本为微小隐孢子虫感染, 2份样本为微小隐孢子虫与人隐孢子虫混合感染。绘制种系发育进化树发 现, 9条SSU rRNA基因序列与已发表的微小隐孢子虫 (Cryptosporidium parvum) 位于同一个进化支上。结论 武汉地区 婴幼儿腹泻患者中存在隐孢子虫感染, 主要感染虫种为微小隐孢子虫。.

Cryptosporidium hominis and Cryptosporidium parvum are the major Cryptosporidium species that infect humans. Earlier studies in gnotobiotic piglets, model susceptible to both, showed that piglets recovered from infection with C. hominis were fully protected against challenge with same species but incompletely protected against C. parvum challenge. In the present study, piglets were infected with C. parvum first, and after recovery were re-challenged with C. parvum or C. hominis. Again, full protection was only observed when piglets were challenged with the homologous parasite strain. Although the two species are genetically/antigenically almost identical, they do not confer complete protection against each other.

Computational approaches to predict structure/function and other biological characteristics of proteins are becoming more common in comparison to the traditional methods in drug discovery. Cryptosporidiosis is a major zoonotic diarrheal disease particularly in children, which is caused primarily by Cryptosporidium hominis and Cryptosporidium parvum. Currently, there are no vaccines for cryptosporidiosis and recommended drugs are ineffective. With the availability of complete genome sequence of C. hominis, new targets have been recognized for the development of effective and better drugs and/or vaccines. We identified a unique hypothetical protein (TU502HP) in the C. hominis genome from the CryptoDB database. A three-dimensional model of the protein was generated using the Iterative Threading ASSEmbly Refinement server through an iterative threading method. Functional annotation and phylogenetic study of TU502HP protein revealed similarity with human transportin 3. The model is further subjected to a virtual screening study form the ZINC database compound library using the Dock Blaster server. A docking study through AutoDock software reported N-(3-chlorobenzyl)ethane-1,2-diamine as the best inhibitor in terms of docking score and binding energy. The reliability of the binding mode of the inhibitor is confirmed by a complex molecular dynamics simulation study using GROMACS software for 10 ns in the water environment. Furthermore, antigenic determinants of the protein were determined with the help of DNASTAR software. Our findings report a great potential in order to provide insights in the development of new drug(s) or vaccine(s) for treatment and prophylaxis of cryptosporidiosis among humans and animals.

Molecular PCR based diagnostic techniques have enabled us to distinguish between the different, morphologically identical, Cryptosporidium species that can infect humans. Of the 23 recognized species in the genus, at least 9 are able to infect humans. As the intensity of the clinical manifestations, pathogenicity, excretion of oocysts, and incidence, are different between this species, molecular studies are crucial for a better understanding of the epidemiology of human cryptosporidiosis. Samples form two independent studies are analyzed in this publication. One included 23 samples from Madrid, and the other, 72 samples from La Coruña. All of them positive for Cryptosporidium spp. by microscopic methods and belonging to isolated cases of human cryptosporidiosis. For the identification of the species responsible for the infection, the 18S rDNA diagnostic region and the COWP gene diagnostic regions were used. Out of the 95 samples tested, in 77 cases we were able to extract and amplify DNA. In those cases the species responsible for the infection were: C. parvum (40 cases, 2 Madrid and 38 La Coruña), C. hominis (30 cases, 10 Madrid and 20 La Coruña) and C. meleagridis (2 cases, 1 Madrid and 1 La Coruña). In 5 samples it was impossible to detect the species responsible for the infection, but their positivity was confirmed by PCR (4 Madrid and 1 La Coruña). The genotypes of the isolates from patients correlated well with animals from the same regions.