Cryptosporidium and host resistance: historical perspective and some novel approaches

Effect of Caging on Cryptosporidium parvum Proliferation in Mice

Cryptosporidiosis is an enteric infection caused by several protozoan species in the genus Cryptosporidium (phylum Apicomplexa). Immunosuppressed mice are commonly used to model this infection. Surprisingly, for a pathogen like Cryptosporidium parvum, which is readily transmitted fecal-orally, mice housed in the same cage can develop vastly different levels of infection, ranging from undetectable to lethal. The motivation for this study was to investigate this phenomenon and assess the association between the severity of cryptosporidiosis and the fecal microbiota. To this aim, the association between severity of cryptosporidiosis and caging (group caged vs. individually caged) and between the microbiota taxonomy and the course of the infection was examined. In contrast to mice caged in groups of four, a majority of mice caged individually did not excrete a detectable level of oocysts. Microbiota α diversity in samples collected between three days prior to infection and one day post-infection was negatively correlated with the severity of cryptosporidiosis, suggesting a causal negative relationship between microbiota diversity and susceptibility to C. parvum.

Identification, molecular characterization and factors associated with occurrences of Cryptosporidium spp. in calves on dairy farms in Brazil

Cattle are an important source of zoonotic species of Cryptosporidium for humans. The aim of this study was to investigate the presence of Cryptosporidium, identify the species and determine the risk factors relating to environment, animals and management among dairy calves in eight Brazilian states. A total of 408 fecal samples from calves aged 1-60 days were analyzed. An epidemiological questionnaire was completed. Sample screening was performed using Ziehl-Neelsen technique and the positive samples were subjected to nested PCR. Cryptosporidium species were identified by means of the PCR-RFLP technique, using SSPI, ASEI and MBOII enzymes. The Ziehl-Neelsen technique showed that 89.7% (35/39) of the farms and 52.9% (216/408) of the samples were positive. Through nested PCR, these protozoa were detected in 54.6% of the samples. The 56 samples subjected to PCR-RFLP presented Cryptosporidium parvum. There was higher prevalence of the parasite in animals aged 7 to 28 days (62.6%). Diarrhea, ages between seven and 28 days and a spring water source were factors associated with the risk of infection. The calf hutch-type management system was associated with reduced infection. These findings demonstrate the high level of Cryptosporidium spp. circulation in cattle herds and the predominance of the species C. parvum.

Deprivation of dietary fiber enhances susceptibility of mice to cryptosporidiosis

Based on our initial observations showing that mice consuming a probiotic product develop more severe cryptosporidiosis, we investigated the impact of other dietary interventions on the intracellular proliferation of Cryptosporidium parvum and C. tyzzeri in the mouse. Mice were orally infected with oocysts and parasite multiplication measured by quantifying fecal oocyst output. High-throughput sequencing of 16S ribosomal RNA amplicons was used to correlate oocyst output with diet and with the composition of the intestinal microbiota. On average, mice fed a diet without fiber (cellulose, pectin and inulin) developed more severe infections. As expected, a diet without fibers also significantly altered the fecal microbiota. Consistent with these observations, mice fed a prebiotic product sold for human consumption excreted significantly fewer oocysts. The fecal microbiota of mice consuming no plant polysaccharides was characterized by a lower relative abundance of Bacteroidetes bacteria. Since bacterial metabolites play an important role in the physiology of intestinal enterocytes, we hypothesize based on these observations that the impact of diet on parasite proliferation is mediated primarily by the metabolic activity of the anaerobic microbiota, specifically by the effect of certain metabolites on the host. This model is consistent with the metabolic dependence of intracellular stages of the parasite on the host cell. These observations underscore the potential of dietary interventions to alleviate the impact of cryptosporidiosis, particularly in infants at risk of recurrent enteric infections.

The infection with Cryptosporidium parasite, a condition known as cryptosporidiosis, is a common cause of infant diarrhea in developing countries. We have previously shown that mice infected with C. parvum, one of the main cause of human cryptosporidiosis, develop a more severe infection if given probiotics. To investigate the mechanism of this effect, we fed mice prebiotics and diet lacking plant fiber. We found that fermentable fiber, whether administered as a prebiotic supplement or as part of the diet, has a protective effect against cryptosporidiosis in mice. We also observed a significant association between the severity of infection and the composition of the gut microbiota. A significant inverse correlation was found between severity of cryptosporidiosis and the ratio between the abundance of bacteria belonging to the phylum Bacteroidetes and the abundance of Firmicutes bacteria. This ratio is frequently viewed as a marker of a healthy microbiota. These results raise the possibility that dietary interventions could be used to alleviate the impact of cryptosporidiosis.

Probiotic Product Enhances Susceptibility of Mice to Cryptosporidiosis

Cryptosporidiosis, a leading cause of diarrhea among infants, is caused by apicomplexan parasites classified in the genus Cryptosporidium The lack of effective drugs is motivating research to develop alternative treatments. With this aim, the impact of probiotics on the course of cryptosporidiosis was investigated. The native intestinal microbiota of specific pathogen-free immunosuppressed mice was initially depleted with orally administered antibiotics. A commercially available probiotic product intended for human consumption was subsequently added to the drinking water. Mice were infected with Cryptosporidium parvum oocysts. On average, mice treated with the probiotic product developed more severe infections. The probiotics significantly altered the fecal microbiota, but no direct association between ingestion of probiotic bacteria and their abundance in fecal microbiota was observed. These results suggest that probiotics indirectly altered the intestinal microenvironment or the intestinal epithelium in a way that favored proliferation of C. parvum IMPORTANCE The results of our study show that C. parvum responded to changes in the intestinal microenvironment induced by a nutritional supplement. This outcome paves the way for research to identify nutritional interventions aimed at limiting the impact of cryptosporidiosis.

Perturbation of the intestinal microbiota of mice infected with Cryptosporidium parvum

Understanding the interaction between the intestinal microbiota (microbiome) and enteric pathogens is of interest in the development of alternative treatments that do not rely on chemotherapy and do not lead to drug resistance. We undertook research in a rodent model of cryptosporidiosis to assess whether the bacterial gut microbiota is impacted by infection with the protozoan pathogen Cryptosporidium parvum. The profile of the faecal bacterial microbiota in infected and uninfected animals was compared using 16S amplicon sequencing. In four independent experiments, the intestinal microbiota of infected mice differed from that of uninfected animals, regardless of the C. parvum isolate used to infect mice. The use of replicated treatment groups demonstrated that microbiota divergence between treatments was driven by the infection and did not result from spontaneous changes in the intestinal ecosystem unrelated to the infection. Microbiota perturbation induced by C. parvum appeared to be reversible, as we observed a tendency for the phylogenetic distance between infected and uninfected mice to diminish after mice cleared the infection. As mice infected with C. parvum do not develop diarrhoea, these observations indicate that microbiota perturbation results from other mechanisms than an accelerated movement of gut content.

Integration of halofuginone lactate treatment and disinfection with p-chloro-m-cresol to control natural cryptosporidiosis in calves

Two field studies were accomplished on a dairy farm in Saxony to compare different strategies for the control of natural cryptosporidiosis in newborn calves. In the first study, 96 newborn calves were allocated to four different groups immediately after birth. Calves of group H and of group HN were treated orally with 120 μg/kg body weight (BW) of halofuginone lactate daily during the first seven days of life. Calves of group C and of group CN were treated with a same volume of tap water. As an additional measure, the pens of groups HN and CN were disinfected with 3% Neopredisan 135-1^®(p-chloro-m-cresol), the pens of groups C and H remained non-disinfected. Faeces were examined semi-quantitatively for oocyst excretion using carbolfuchsin-staining and the clinical course was recorded. While disinfection alone (group CN) had no effect on oocyst shedding and diarrhoea, treatment with halofuginone lactate (groups H and HN) reduced oocyst shedding and diarrhoea significantly. Combination of treatment and disinfection (group HN) controlled cryptosporidiosis completely during the first two weeks after birth. However, prevalence of diarrhoea and oocyst shedding was higher in the third week of life in group HN than in any of the other groups. This delayed occurrence of cryptosporidiosis was not seen in study 2 when all calves were similarly protected by treatment and specific disinfection. Oocyst shedding was not observed in peripartal cows either by carbolfuchsin staining, ELISA or PCR.

Cryptosporidium infection causes undernutrition and, conversely, weanling undernutrition intensifies infection

Cryptosporidium parvum is a leading pathogen in children in developing countries. To investigate whether early postnatal malnutrition leads to heavier C. parvum infections, we assessed intestinal adaptation and parasite load in suckling mice during the first 2 wk of life, analogous to the first postnatal yr in humans. Undernutrition was induced by daily C57BL6J pup separation from lactating dams. Half of the pups were separated daily, for 4 hr on day 4, 8 hr on day 5, and for 12 hr from day 6 until day 14. On day 6, each pup received an oral inoculum of 10(5) to 10(7) parasites in 10-25 microl of PBS. Littermate controls received PBS alone. Stools were assessed from days 8, 11, and 14 for oocyst counts. Mice were killed on day 14, 8 days postinoculation, at the peak of the infection. Ileal and colon segments were obtained for histology, real-time and reverse transcriptase PCR, and immunoassays. Villus and crypt lengths and cross-sectional areas were also measured. Undernourished and nourished mice infected with excysted 10(6) or 10(7) oocysts exhibited the poorest growth outcomes compared with their uninfected controls. Nourished 10(6)-infected mice had comparable weight decrements to uninfected undernourished mice. Body weight and villi were additively affected by malnutrition and cryptosporidiosis. Hyperplastic crypts and heavier inflammatory responses were found in the ilea of infected malnourished mice. Undernourished infected mice exhibited greater oocyst shedding, TNF-alpha and IFN-gamma intestinal levels, and mRNA expression compared to nourished mice infected with either 10(5) or 10(6) oocysts. Taken together, these findings show that Cryptosporidium infection can cause undernutrition and, conversely, that weanling undernutrition intensifies infection and mucosal damage.

Molecular epidemiology of Cryptosporidium in humans and cattle in The Netherlands

The protozoan parasite Cryptosporidium is found world-wide and can cause disease in both humans and animals. To study the zoonotic potential of Cryptosporidium in The Netherlands we isolated this parasite from the faeces of infected humans and cattle and genotyped those isolates for several different markers. The overall genotyping results showed: for humans isolates, 70% Cryptosporidium hominis, 19% Cryptosporidium parvum, 10% a combination of C. hominis and C. parvum, and 1% Cryptosporidium felis; and for cattle isolates 100% C. parvum. Analysis of the genetic variants detected for the HSP70, ML1 and GP60 markers showed: for human isolates, one C. hominis and two C. parvum variants (C. parvum and C. parvum NL) for HSP70, one C. hominis and five C. parvum variants (C1, C2, C3, and C2 NL1 and C2 NL2) for ML1, four C. hominis (mainly IbA10G2) and four C. parvum variants (mainly IIaA15G2R1) for GP60; and the cattle isolates only C. parvum (not C. parvum NL1) for HSP70, C1 and C2 for ML1, and 17 different IIa sub-types (mainly IIaA15G2R1) for GP60. Molecular epidemiological analysis of the human data showed a C. hominis peak in autumn. The majority (80%) of the human cases were children aged between 0 and 9 years and >70% of these were caused by C. hominis. Patients >25 years of age were infected mainly with C. parvum. We conclude that C. hominis IbA10G2 is found at high frequencies in autumn in humans and not in cattle. The high prevalence of C. parvum IIaA15G2R1 in both humans and cattle indicates that cattle may be a reservoir for this sub-type in The Netherlands.

Characterization of a factor from bovine intestine that protects against Cryptosporidium parvum infection

Cryptosporidium parvum is a protozoan parasite that causes intestinal infection in a variety of mammals. We have previously described a factor in adult rat or adult bovine intestinal mucosa that protects against C. parvum infection when fed to susceptible infant rats. This factor is absent in intestinal mucosa from bovine calves. In the present study we describe the further characterization of the active component of bovine intestinal mucosa. The ability to protect infant rats against C. parvum infection was found to be associated with the extrinsic membrane protein fraction of the intestinal mucosa. Extrinsic membrane preparations from adult cows, adult rats, and calves were separated by SDS-PAGE. A band with apparent molecular mass of 54 kDa was seen in preparations from adult rat and cow, but not calf. Protein was transferred to PVDF membrane and from this the band was excised and subjected to N-terminal sequence analysis using a gas-phase protein sequenator. A 15-amino acid consensus sequence was generated with homology to leucine aminopeptidase (LAP). Purified LAP was purchased from a commercial source and tested for ability to protect infant rats against C. parvum infection. Rats fed LAP from 7 to 11 days of age and challenged with C. parvum at 9 days were significantly less infected than controls upon necropsy at 15 days of age. These data suggest that a protein with N-terminal sequence homology to LAP may reduce susceptibility of infant rats to C. parvum infection.

An Irish perspective on Cryptosporidium. Part 2

Cryptosporidiosis, a protozoal disease which causes significant morbidity in humans, is one of the chief causes of diarrhoea in neonatal ruminants. although the parasite poses a significant threat to public health and animal health in Ireland, its epidemiology on the island is only poorly understood. Environmental studies have shown the waterborne parasite to be widespread in some untreated waterbodies around Ireland. The island's hydrogeological situation, combined with high stocking rates of livestock and the absence of filtration from regular water treatment, render it vulnerable to large-scale outbreaks. This review discusses the parasite in the Irish context and underlines the need for a reference facility to provide active surveillance on the island.

An Irish perspective on Cryptosporidium. Part 1

Cryptosporidiosis, a protozoal disease which causes significant morbidity in humans, is one of the chief causes of diarrhoea in neonatal ruminants. Although the parasite poses a significant threat to public health and animal health in Ireland, its epidemiology on the island is only poorly understood. Environmental studies have shown the waterborne parasite to be widespread in some untreated waterbodies around Ireland. The island's hydrogeological situation, combined with high stocking rates of livestock and the absence of filtration from regular water treatment, render it vulnerable to large-scale outbreaks. This review discusses the parasite in the Irish context and underlines the need for a reference facility to provide active surveillance on the island.