Fulminant cryptosporidiosis after near-drowning: a human Cryptosporidium parvum strain implicated in invasive gastrointestinal adenocarcinoma and cholangiocarcinoma in an experimental model

Newly fabricated zinc oxide nanoparticles loaded materials for therapeutic nano delivery in experimental cryptosporidiosis

Cryptosporidiosis is a global health problem that threatens the lives of immunocompromised patients. This study targets to fabricate and investigate the efficiency of zinc oxide nanoparticles (ZnO-NPs), nitazoxanide (NTZ)-loaded ZnO-NPs, and Allium sativum (A. sativum)-loaded ZnO-NPs in treating cryptosporidiosis. Further FTIR, SEM, XRD, and zeta analysis were used for the characterization of ZnO-NPs and loaded materials. The morphology of loaded materials for ZnO-NPs changed into wrapped layers and well-distributed homogenous particles, which had a direct effect on the oocyst wall. The charge surface of all particles had a negative sign, which indicated well distribution into the parasite matrix. For anti-cryptosporidiosis efficiency, thirty immunosuppressed Cryptosporidium parvum-infected mice, classified into six groups, were sacrificed on the 21st day after infection with an evaluation of parasitological, histopathological, and oxidative markers. It was detected that the highest reduction percent of Cryptosporidium oocyst shedding was (81.5%) in NTZ, followed by (71.1%) in A. sativum-loaded ZnO-NPs-treated groups. Also, treatment with A. sativum and NTZ-loaded ZnO-NPs revealed remarkable amelioration of the intestinal, hepatic, and pulmonary histopathological lesions. Furthermore, they significantly produced an increase in GSH values and improved the changes in NO and MDA levels. In conclusion, this study is the first to report ZnO-NPs as an effective therapy for treating cryptosporidiosis, especially when combined with other treatments that enhance their antioxidant activity. It provides an economical and environment-friendly approach to novel delivery synthesis for antiparasitic applications.

Therapeutic Potency of Ginger, Garlic, and Pomegranate Extracts Against Cryptosporidium parvum-Mediated Gastro-Splenic Damage in Mice

PURPOSE

Cryptosporidium parvum is a protozoan parasite infecting most mammalian hosts and causing major health issues. The present study investigated the efficacy of ginger (Zingiber officinale), garlic (Allium sativum), and pomegranate (Punica granatum) peel extracts on the development and progression of experimental cryptosporidiosis in mice.

METHODS

Eighty-two mice were assigned to 6 groups: control, infected non-treated, metronidazole (MTZ), ginger, garlic, and pomegranate. The control group topically received no treatments. The infected non-treated group was experimentally infected by 104 C. parvum oocysts per mouse using a stomach tube. The MTZ group was infected with C. parvum oocysts combined with MTZ (50 mg/kg b.w./day). The ginger, garlic, and pomegranate groups daily received different plant extracts at doses of 100 mg/kg BW, 50 mg/kg BW, and 3 gm/kg BW, respectively, followed by infection with C. parvum oocysts. All treatments were applied orally one day after the infection for continuous 30 days.

RESULTS

Histopathological and immunohistochemical examinations for P53 and caspase-3 expressions in stomach and spleen tissues showed that MTZ and garlic-treated mice had a more significant effect on infected mice.

CONCLUSION

The garlic extract was found to exert a more pronounced effect on infected mice compared with the other treatments as well as to improve health. Garlic extracts, therefore, represent an effective and natural therapeutic alternative for the treatment of cryptosporidiosis with low side effects and without drug resistance.

Detection of unusual Cryptosporidium parvum subtype in patients with gastrointestinal cancer in Egypt

While the importance of cryptosporidiosis in immunocompromised persons is well known, the prevalence of Cryptosporidium spp. in cancer patients is not clear. The current study was designed to assess the occurrence and genetic characteristics of Cryptosporidium spp. in patients with gastrointestinal (GI) cancer in Egypt. Stool samples were collected from 100 patients with GI malignancies and 20 healthy individuals without any GI manifestations (control group). They were screened by microscopy and the immunochromatographic RIDA®QUICK Cryptosporidium kit. Subtyping of Cryptosporidium spp. was conducted by sequence analysis of the glycoprotein 60 (gp60) locus. Sociodemographic, environmental data and information on GI symptoms, cancer types, and clinical treatment were obtained via a questionnaire. By microscopy and RIDA®QUICK, only 7% (7/100) of GI cancer patients were positive for Cryptosporidium, compared with 40% (40/100) by gp60 nPCR. No positives were obtained from the control group. Male sex (P = 0.02) and younger age (P = 0.004) were major Cryptosporidium risk factors for infection. The occurrence of Cryptosporidium was also significantly more frequent (P = 0.003) in watery stool samples. Sequence analysis of the gp60 amplicons (~ 400 bp) identified a novel C. parvum subtype with nine TCA repeats and eleven ACATCA repeats. A formal subtype designation could not be made due to the short sequence length. More studies should be conducted to verify the common occurrence of this unusual C. parvum subtype and establish its genetic identity.

Is Cryptosporidium a hijacker able to drive cancer cell proliferation?

The pathophysiological mechanisms of Cryptosporidium infection are multifactorial and not completely understood. Some advances achieved recently revealed that the infection by Cryptosporidium parvum induces cytoskeleton remodeling and actin reorganization through the implication of several intracellular signals involving, for example, PI3K, Src, Cdc42 and GTPases. It has also been reported that the infection by C. parvum leads to the activation of NF-κβ, known to induce anti-apoptotic mechanisms and to transmit oncogenic signals to epithelial cells. Despite the growing evidence about the hijacking of cellular pathways, potentially being involved in cancer onset, this information has rarely been linked to the tumorigenic potential of the parasite. However, several evidences support an association between Cryptosporidium infection and the development of digestive neoplasia. To explore the dynamics of Cryptosporidium infection, an animal model of cryptosporidiosis using corticoid dexamethasone-treated adult SCID (severe combined immunodeficiency) mice, orally infected with C. parvum or Cryptosporidium muris oocysts was implemented. C. parvum-infected animals developed digestive adenocarcinoma. When mechanisms involved in this neoplastic process were explored, the pivotal role of the Wnt pathway together with the alteration of the cytoskeleton was confirmed. Recently, a microarray assay allowed the detection of cancer-promoting genes and pathways highly up regulated in the group of C. parvum infected animals when compared to non-infected controls. Moreover, different human cases/control studies reported significant higher prevalence of Cryptosporidium infection among patients with recently diagnosed colon cancer before any treatment when compared to the control group (patients without colon neoplasia but with persistent digestive symptoms). These results suggest that Cryptosporidium is a potential oncogenic agent involved in cancer development beyond the usual suspects. If Cryptosporidium is able to hijack signal transduction, then is very likely that this contributes to transformation of its host cell. More research in the field is required in order to identify mechanisms and molecular factors involved in this process and to develop effective treatment interventions.

Dual transcriptomics to determine interferon-gamma independent host response to intestinal Cryptosporidium parvum infection

Animals with a chronic infection of the parasite Toxoplasma gondii are protected against lethal secondary infection with other pathogens. Our group previously determined that soluble T. gondii antigens (STAg) can mimic this protection and be used as a treatment against several lethal pathogens. Because treatments are limited for the parasite Cryptosporidium parvum, we tested STAg as a C. parvum therapeutic. We determined that STAg treatment reduced C. parvum Iowa II oocyst shedding in gamma interferon knockout (IFN-γ-KO) mice. Murine intestinal sections were then sequenced to define the IFN-γ-independent transcriptomic response to C. parvum infection. Gene Ontology and transcript abundance comparisons showed host immune response and metabolism changes. Transcripts for type I interferon-responsive genes were more abundant in C. parvum-infected mice treated with STAg. Comparisons between phosphate-buffered saline (PBS) and STAg treatments showed no significant differences in C. parvum gene expression. C. parvum transcript abundance was highest in the ileum and mucin-like glycoproteins and the GDP-fucose transporter were among the most abundant. These results will assist the field in determining both host- and parasite-directed future therapeutic targets.

Assessment of chitosan nanoparticles in improving the efficacy of nitazoxanide on cryptosporidiosis in immunosuppressed and immunocompetent murine models

Cryptosporidiosis is one of the major causes of diarrhea in immunocompetent and immunocompromised patients. It is self-limited in immunocompetent individuals. However, in the immunocompromised it can cause life-threatening diarrhea and results in chronic malabsorption of fluids, vitamins and electrolytes resulting in wasting. Our study is concerned with assessing and comparing the efficacy of nitazoxanide (NTZ) alone and NTZ loaded chitosan nanoparticles (NTZ loaded CS NPs) in the treatment of experimental cryptosporidiosis using parasitological and histopathological parameters. One hundred mice were divided into 5 groups (20 mice each). Each group was divided into 2 subgroups according to the immune status [a-immunocompetent, b-immunosuppressed]. group 1: control (healthy), group 2: control infected by Cryptosporidium oocysts, group 3: infected treated by NTZ, group 4: infected then treated by NTZ loaded CS NPs and group 5: infected then treated by chitosan nanoparticles (CS NPs) alone. Treatment of Cryptosporidium infected mice with NTZ loaded on CS NPs resulted in the highest significant reduction in oocysts shedding in both immunocompetent and immunosuppressed groups followed by treatment with NTZ form then by treatment with CS NPs alone. The treatment with NTZ loaded CS NPs displayed a remarkable improvement of the histopathological changes of the intestine, liver and lung while NTZ treated group showed some improvement. Treatment with NTZ loaded CS NPs in murine cryptosporidiosis gave the best results as it caused marked reduction in fecal oocysts counts and improvement of histopathological changes in immunocompetent and immunosuppressed groups.

Cryptosporidium and Colon Cancer: Cause or Consequence?

The number of cancers attributable to infectious agents represents over 20% of the global cancer burden. The apicomplexan intracellular parasite Cryptosporidium is currently considered one of the major causes of mild and severe diarrhea worldwide. However, less attention has been paid to its tumorigenic potential despite the high exposure of humans and animals to this ubiquitous parasite. Herein, we discuss the potential causal link between Cryptosporidium infection and digestive cancer, with particular emphasis on colon cancer, based on increasing clinical, epidemiological and experimental pieces of evidence supporting this association. In addition, we highlight the current knowledge about the potential mechanisms by which this parasite may contribute to cell transformation and parasite-induced cancer.

Genetic basis for virulence differences of various Cryptosporidium parvum carcinogenic isolates

Cryptosporidium parvum is known to cause life-threatening diarrhea in immunocompromised hosts and was also reported to be capable of inducing digestive adenocarcinoma in a rodent model. Interestingly, three carcinogenic isolates of C. parvum, called DID, TUM1 and CHR, obtained from fecal samples of naturally infected animals or humans, showed higher virulence than the commercially available C. parvum IOWA isolate in our animal model in terms of clinical manifestations, mortality rate and time of onset of neoplastic lesions. In order to discover the potential genetic basis of the differential virulence observed between C. parvum isolates and to contribute to the understanding of Cryptosporidium virulence, entire genomes of the isolates DID, TUM1 and CHR were sequenced then compared to the C. parvum IOWA reference genome. 125 common SNVs corresponding to 90 CDSs were found in the C. parvum genome that could explain this differential virulence. In particular variants in several membrane and secreted proteins were identified. Besides the genes already known to be involved in parasite virulence, this study identified potential new virulence factors whose functional characterization can be achieved through CRISPR/Cas9 technology applied to this parasite.

Prevalence and Genotyping of Cryptosporidium parvum in Gastrointestinal Cancer Patients

Gastrointestinal cancers are the most commonly occurring malignancies which contributing to over 1/5 of cancer incidences worldwide. Increasing evidences have shown that Cryptosporidium spp., an apicomplexan protozoan, is highly associated with gastrointestinal cancers. However, the prevalence of Cryptosporidium spp. infections among gastrointestinal cancer patients in China has not been estimated yet. We here performed a case-control study to evaluate the occurrences of Cryptosporidium spp. in patients with digestive malignancies before chemotherapy and in control population. Nested PCR amplifying 18S rRNA gene was used to detect the presence of Cryptosporidium spp. in each fecal sample. The results herein confirmed the correlation of Cryptosporidium spp. infection with colorectal and liver cancers, while first identified the high frequencies of Cryptosporidium spp. in esophageal cancer and small intestine cancer. The infection rates of Cryptosporidium spp. in colorectal, esophageal, liver and small intestine cancers were 17.24% (20/116, P<0.001), 6.25% (1/16, P=0.029), 14.29% (1/7, P<0.001) and 40% (2/5, P<0.001), respectively. In addition, molecular characterization indicated that all the Cryptosporidium spp. obtained were Cryptosporidium parvum (C. parvum), and the 18S rRNA sequences were identical to the reference sequences isolated from cattle, suggesting potential zoonotic transmission. Furthermore, subtyping analyses revealed that IIaA15G2R1 and IIaA15G2R2 were the predominant subtypes in colorectal cancer, while IIaA13G2R2 subtype was first named and identified in colorectal and liver cancers. Taken together, for the first time, the prevalence of Cryptosporidium spp. infections in digestive cancer patients has been estimated among Chinese. Our results indicated that C. parvum were highly associated with gastrointestinal cancers, supporting that cryptosporidiosis could be a potential risk factor for these diseases.

The new trend in the treatment of experimental cryptosporidiosis and the resulting intestinal dysplasia

Aim: Cryptosporidiosis causes colon dysplasia. This research aimed to evaluate the effect of a novel combination between artesunate and nitazoxanide on intensity of infection and the resulting intestinal dysplasia. Materials & methods: Subjects were divided into five groups. Artesunate was used alone, then combined with nitazoxanide. Results: The highest efficacy in reducing oocyst shedding obtained from the combined therapy (68.5, 75.9, 99%) after 7, 14 and 21 days. The histopathology of infected colonic mucosa showed marked improvement and low-grade of dysplasia in the infected and treated group with the combined therapy. The immunohistochemistry of the same group revealed mild dysplastic changes in colonic epithelium without nuclear expression for cyclin D1. Conclusion: These results give hope for treatment of Cryptosporidium and improving intestinal dysplasia.

Colorectal cancer and Cryptosporidium spp. infection

Transient or constant impaired immunity is often associated with neoplastic disease or oncological treatment. Among the most common pathogens found in patients with HIV or patients undergoing chemotherapy are protozoans of the Cryptosporidium genus, which cause diarrhea in humans and animals. The present study determined the frequency of Cryptosporidium spp. infections in patients with colorectal cancer (N = 108; 42 women; 66 men; median age, 65 years), before beginning oncological treatment, compared to a control group (N = 125; 56 women, 69 men; median age, 63 years) without colorectal cancer or a history of oncological disease. We also assessed whether Cryptosporidium spp. infections were associated with age, gender, cancer stage (based on Astler-Coller or TNM classification), histological grade, or cancer location. Patients were treated at the Pomeranian Medical University, in 2009-2014. The presence of Cryptosporidium spp. antigen was determined in stool samples, analyzed with a commercial immunoenzymatic test. Cryptosporidium spp. infections occurred significantly more often (p = 0.015) in patients (13%) compared to controls (4%). The patient group showed no significant relationship between Cryptosporidium spp. infection and sex, age, tumor location, cancer grade, or stage. A multivariate logistic regression analysis adjusted for age and sex that included all subjects (patient + control groups, n = 233) showed that the odds of a Cryptosporidium spp. infection were more than three-fold higher in patients than in controls, and more than six-fold higher among men than among women.

CONCLUSIONS

1) Cryptosporidium spp. infections occurred significantly more frequently in patients with colorectal cancer (before oncological treatment) compared to controls, independent of age and sex. 2) Cryptosporidium spp. infections were not associated with the colorectal cancer stage, grade, or location or with patient age. 3) Male gender was significantly related to the frequency of Cryptosporidium spp. infections, independent of age and the presence of colorectal cancer.

High association of Cryptosporidium spp. infection with colon adenocarcinoma in Lebanese patients

Background

The association between Cryptosporidium and human colon cancer has been reported in different populations. However, this association has not been well studied. In order to add new strong arguments for a probable link between cryptosporidiosis and colon human cancer, the aim of this study was to determine prevalence and to identify species of Cryptosporidium among Lebanese patients.

Methodology and principal findings

Overall, 218 digestive biopsies were collected in Tripoli, Lebanon, from three groups of patients: (i) patients with recently diagnosed colon intraepithelial neoplasia/adenocarcinoma before any treatment (n = 72); (ii) patients with recently diagnosed stomach intraepithelial neoplasia/adenocarcinoma before any treatment (n = 21); and (iii) patients without digestive intraepithelial neoplasia/adenocarcinoma but with persistent digestive symptoms (n = 125). DNA extraction was performed from paraffin-embedded tissue. The presence of the parasite in tissues was confirmed by PCR, microscopic observation and immunofluorescence analysis. We identified a high rate (21%) of Cryptosporidium presence in biopsies from Lebanese patients with recently diagnosed colonic neoplasia/adenocarcinoma before any treatment. This prevalence was significantly higher compared to 7% of Cryptosporidium prevalence among patients without colon neoplasia but with persistent gastrointestinal symptoms (OR: 4, CI: 1.65–9.6, P = 0.001). When the comparison was done against normal biopsies, the risk of infection increased 11-fold in the group of patients with colon adenocarcinoma (OR: 11.315, CI: 1.44–89.02, P = 0.003).

Conclusions

This is the first study performed in Lebanon reporting the prevalence of Cryptosporidium among patients with digestive cancer. These results show that Cryptosporidium is strongly associated with human colon cancer being maybe a potential etiological agent of this disease.

Three-dimensional (3D) culture of adult murine colon as an in vitro model of cryptosporidiosis: Proof of concept

Cryptosporidium parvum is a major cause of diarrheal illness and was recently potentially associated with digestive carcinogenesis. Despite its impact on human health, Cryptosporidium pathogenesis remains poorly known, mainly due to the lack of a long-term culture method for this parasite. Thus, the aim of the present study was to develop a three-dimensional (3D) culture model from adult murine colon allowing biological investigations of the host-parasite interactions in an in vivo-like environment and, in particular, the development of parasite-induced neoplasia. Colonic explants were cultured and preserved ex vivo for 35 days and co-culturing was performed with C. parvum. Strikingly, the resulting system allowed the reproduction of neoplastic lesions in vitro at 27 days post-infection (PI), providing new evidence of the role of the parasite in the induction of carcinogenesis. This promising model could facilitate the study of host-pathogen interactions and the investigation of the process involved in Cryptosporidium-induced cell transformation.

Detection of Toxoplasma gondii DNA in Malignant Breast Tissues in Breast Cancer Patients

Breast cancer is the most prevalent malignancy in women throughout the world. Similar to other cancers, a strong relationship between breast cancer and environmental factors such as infectious agents has been reported. Toxoplasma gondii is a protozoan parasite which may play a role in cancer induction. The present study aimed to investigate a possible association between a history of T. gondii infection and breast cancer by detecting T. gondii DNA in malignant and non-malignant breast and lymph nodes tissues from breast cancer patients with latent toxoplasmosis. Formalin-fixed, paraffin-embedded (FFPE) tissue blocks from malignant/non-malignant breast and lymph nodes were obtained from twenty-nine breast cancer patients who were positive for anti-Toxoplasma antibodies (IgG). FFPE tissue blocks were deparaffinized using hot water method, and DNA was extracted. A conventional PCR analysis was performed to amplify partial regions of T. gondii B1 and REP-529 genes. Ninety-three samples from 29 patients were examined. All patients were negative for anti-T. gondii antibodies (IgM). T. gondii DNA was detected in 3 (10.3%) patients by PCR analysis of either B1 or REP-529 genes. These include two malignant breast and one normal lymph node samples. Sequence analysis of these genes showed a good similarity with previously published B1 and REP-529 sequences of T. gondii in NCBI GenBank. This study did not find any association between T. gondii infection and breast cancer. Furthermore, it is the first molecular identification of T. gondii in FFPE tissue samples obtained from breast cancer patients.

[Parasites and cancer: is there a causal link?]

Over 20 % of cancers have infectious origins, including well-known examples of microbes such as viruses (HPV, EBV) and bacteria (H. pylori). The contribution of intracellular eukaryotic parasites to cancer etiology is largely unexplored. Epidemiological and clinical reports indicate that eukaryotic protozoan, such as intracellular apicomplexan that cause diseases of medical or economic importance, can be linked to various cancers: Theileria and Cryptosporidium induce host cell transformation while Plasmodium was linked epidemiologically to the "African lymphoma belt" over fifty years ago. These intracellular eukaryotic parasites hijack cellular pathways to manipulate the host cell epigenome, cellular machinery, signaling pathways and epigenetic programs and marks, such as methylation and acetylation, for their own benefit. In doing so, they tinker with the same pathways as those deregulated during cancer onset. Here we discuss how epidemiological evidence linking eukaryotic intracellular parasites to cancer onset are further strengthened by recent mechanistic studies in three apicomplexan parasites.

Cryptosporidium parvum-induced ileo-caecal adenocarcinoma and Wnt signaling in a mouse model

Cryptosporidium species are apicomplexan protozoans that are found worldwide. These parasites constitute a large risk to human and animal health. They cause self-limited diarrhea in immunocompetent hosts and a life-threatening disease in immunocompromised hosts. Interestingly, Cryptosporidium parvum has been related to digestive carcinogenesis in humans. Consistent with a potential tumorigenic role of this parasite, in an original reproducible animal model of chronic cryptosporidiosis based on dexamethasone-treated or untreated adult SCID mice, we formerly reported that C. parvum (strains of animal and human origin) is able to induce digestive adenocarcinoma even in infections induced with very low inoculum. The aim of this study was to further characterize this animal model and to explore metabolic pathways potentially involved in the development of C. parvum-induced ileo-caecal oncogenesis. We searched for alterations in genes or proteins commonly involved in cell cycle, differentiation or cell migration, such as β-catenin, Apc, E-cadherin, Kras and p53. After infection of animals with C. parvum we demonstrated immunohistochemical abnormal localization of Wnt signaling pathway components and p53. Mutations in the selected loci of studied genes were not found after high-throughput sequencing. Furthermore, alterations in the ultrastructure of adherens junctions of the ileo-caecal neoplastic epithelia of C. parvum-infected mice were recorded using transmission electron microscopy. In conclusion, we found for the first time that the Wnt signaling pathway, and particularly the cytoskeleton network, seems to be pivotal for the development of the C. parvum-induced neoplastic process and cell migration of transformed cells. Furthermore, this model is a valuable tool in understanding the host-pathogen interactions associated with the intricate infection process of this parasite, which is able to modulate host cytoskeleton activities and several host-cell biological processes and remains a significant cause of infection worldwide.

The challenge of cholangiocarcinoma: dissecting the molecular mechanisms of an insidious cancer

Cholangiocarcinoma is a fatal cancer of the biliary epithelium and has an incidence that is increasing worldwide. Survival beyond a year of diagnosis is less than 5%, and therapeutic options are few. Known risk factors include biliary diseases such as primary sclerosing cholangitis and parasitic infestation of the biliary tree, but most cases are not associated with any of these underlying diseases. Numerous in vitro and in vivo models, as well as novel analytical techniques for human samples, are helping to delineate the many pathways implicated in this disease, albeit at a frustratingly slow pace. As yet, however, none of these studies has been translated into improved patient outcome and, overall, the pathophysiology of cholangiocarcinoma is still poorly understood. There remains an urgent need for new approaches and models to improve management of this insidious and devastating disease. In this review, we take a bedside-to-bench approach to discussing cholangiocarcinoma and outline research opportunities for the future in this field.

Molecular epidemiology of Cryptosporidium in livestock animals and humans in the Ismailia province of Egypt

The zoonotic potential of Cryptosporidium was studied in one of the most densely populated provinces of Egypt regarding livestock and people. In a representative survey, faecal samples from cattle, buffalo and stool samples from diarrhoeic children (<10 years) were investigated. Parameters assumed to be related to cryptosporidiosis were recorded for animals and children. Animal samples (804) were examined by the Copro-antigen RIDA(®)QUICK test, followed by PCRs targeting the 18S rDNA and gp60 genes for antigen-positive and 10% randomly selected negative samples. All 165 human samples were tested by both methods. The overall estimated prevalence of Cryptosporidium in ruminants was 32.2%, without significant difference between animal species. PCR identified 65.7% Cryptosporidium parvum, 11.8% Cryptosporidium ryanae, 4.1% Cryptosporidium bovis, and combinations of C. parvum plus C. ryanae (11.2%), C. parvum plus C. bovis (5.3%) and of C. parvum plus Cryptosporidium andersoni (1.8%), also without significant differences in species occurrence between cattle and buffalos. The human Cryptosporidium spp. prevalence was 49.1%, of which 60.5% were Cryptosporidium hominis, 38.2% C. parvum and 1.2% C. parvum plus C. bovis. Analysis of gp60 variants allocated C. parvum found in animals to the zoonotic subtype family IIa (18.9%, subtype IIaA15G1R1 only) and to IId (81.1%, mostly IIdA20G1). In humans 50% were classified as subtype family IIa (IIaA15G1R1 and IIaA15G2R1) and 50% were IIdA20G1. C. andersoni occurred only in cattle older than 1 year. In contrast, mono-infections with one of the three single Cryptosporidium species and the three combinations with C. parvum were more prevalent in cattle and buffaloes younger than 1 year, particularly in those younger than 3 months, and were predominantly subtype family IId. In human samples no Cryptosporidium were identified in children younger than 7 months. Neither place of residence nor the source of drinking-water had measurable effects on prevalence. Remarkably, however, all children with C. parvum subtype family IIa and 86% with subtype family IId had contact to animals. High prevalence and identical genotypes of C. parvum in animals and humans indicate zoonotic transmission due to contact with animals, involving IIdA20G1 as the most frequent subtype.

Cryptosporidium parvum infection in SCID mice infected with only one oocyst: qPCR assessment of parasite replication in tissues and development of digestive cancer

Dexamethasone (Dex) treated Severe Combined Immunodeficiency (SCID) mice were previously described as developing digestive adenocarcinoma after massive infection with Cryptosporidium parvum as soon as 45 days post-infection (P.I.). We aimed to determine the minimum number of oocysts capable of inducing infection and thereby gastrointestinal tumors in this model. Mice were challenged with calibrated oocyst suspensions containing intended doses of: 1, 10, 100 or 10⁵ oocysts of C. parvum Iowa strain. All administered doses were infective for animals but increasing the oocyst challenge lead to an increase in mice infectivity (P = 0.01). Oocyst shedding was detected at 7 days P.I. after inoculation with more than 10 oocysts, and after 15 days in mice challenged with one oocyst. In groups challenged with lower inocula, parasite growth phase was significantly higher (P = 0.005) compared to mice inoculated with higher doses. After 45 days P.I. all groups of mice had a mean of oocyst shedding superior to 10,000 oocyst/g of feces. The most impressive observation of this study was the demonstration that C. parvum-induced digestive adenocarcinoma could be caused by infection with low doses of Cryptosporidium, even with only one oocyst: in mice inoculated with low doses, neoplastic lesions were detected as early as 45 days P.I. both in the stomach and ileo-caecal region, and these lesions could evolve in an invasive adenocarcinoma. These findings show a great amplification effect of parasites in mouse tissues after challenge with low doses as confirmed by quantitative PCR. The ability of C. parvum to infect mice with one oocyst and to develop digestive adenocarcinoma suggests that other mammalian species including humans could be also susceptible to this process, especially when they are severely immunocompromised.