Indole metabolites generated by microbiota inhibit Cryptosporidium growth

Funkhouser-Jones et al. recently identified gut metabolites that affected Cryptosporidium growth. A key focus, indole, was shown to inhibit the parasite in vivo and in vitro by decreasing the host mitochondria function and the membrane potential of parasite mitosomes. These findings help clarify the role microflora and metabolites play in host resistance.

Present and future control of cryptosporidiosis in humans and animals

Although water treatment processes to remove Cryptosporidium are improving and detection methods for identifying the parasite in water are becoming more sensitive, outbreaks of cryptosporidiosis continue in the human population. Animals, especially dairy calves, often become infected as C. parvum oocysts are present in high numbers, remain viable for long periods of time after excretion and no disinfectants, prophylactic or therapeutic reagents exist. Vaccination against C. parvum is being attempted in ruminants for the purpose of generating hyperimmune colostrum containing antibodies that may be effective in passive immunotherapy against cryptosporidiosis in the young. A number of recombinant C. parvum surface or internal antigens have been expressed by DNA-cloning technology. Immune colostrum specific for several recombinant C. parvum proteins have demonstrated efficacy in murine and ruminant models against cryptosporidiosis. The P23 and CP15 antigens appear to be the most promising candidates for vaccine development. Recent studies have demonstrated efficacy of the drug nitazoxanide against C. parvum infection in humans. In the near future, control of this parasitic disease in humans and animals will rely on a combination of passive immunotherapy and selective drug treatment.

Human immune responses in cryptosporidiosis

Immune responses play a critical role in protection from, and resolution of, cryptosporidiosis. However, the nature of these responses, particularly in humans, is not completely understood. Both innate and adaptive immune responses are important. Innate immune responses may be mediated by Toll-like receptor pathways, antimicrobial peptides, prostaglandins, mannose-binding lectin, cytokines and chemokines. Cell-mediated responses, particularly those involving CD4(+) T cells and IFN-gamma play a dominant role. Mucosal antibody responses may also be involved. Proteins mediating attachment and invasion may serve as putative protective antigens. Further knowledge of human immune responses in cryptosporidiosis is essential in order to develop targeted prophylactic and therapeutic interventions. This review focuses on recent advances and future prospects in the understanding of human immune responses to Cryptosporidium infection.

Minireview: clinical cryptosporidiosis

Cryptosporidium has emerged as an important cause of diarrhoeal illness worldwide, especially amongst young children and patients with immune deficiencies. Usually presenting as a gastro-enteritis-like syndrome, disease ranges in seriousness from mild to severe and signs and symptoms depend on the site of infection, nutritional and immune status of the host, and parasite-related factors. Sources and routes of transmission are multiple, involving both zoonotic and anthroponotic spread, and facilitated by the resistance of the parasite to many commonly used disinfectants. Prevention and control measures are important for the protection of vulnerable groups since treatment options are limited. This review covers the life cycle, pathogenesis, clinical presentations, diagnosis, prevention and management of cryptosporidiosis in humans.

Immunochemotherapy for cryptosporidiosis in immunosuppressed mouse model

Immunochemotherapy as a dual regimen (Nitazoxanide NTZ and Interferon gamma INF-gamma) and a triple one (NTZ, INF-gamma & Paromomycin PRM), administered to immunosuppressed Cryptosporidium infected mice for 10 days (4th-13th day post-infection) was evaluated during and after treatment by determination of parasite count in ileum, associated histopathological changes, oocyst count in Kinyoun's acid fast stained faecal smears, percent reduction in oocyst excretion and cure rate. Both regimens induced nearby efficacy (P > 0.05) with significant reduction in parasite count in the ileum on 7th (P < 0.01) & 14th (P < 0.001) P.I. days, partial regression of histopathological changes and reduction in oocyst count from the 2nd day post-treatment. Oocyst excretion reduction percent was reached zenith on 13th P.I day in both dual (95.76%) and triple (94.86%) regimens (P > 0.05). Complete cure was not achieved. Three days post-treatment relapse occurred in both regimens (P < 0.001) increase in oocyst count (P < 0.01) increase in parasite count in ileum, more severe histopathological changes with rapid deterioration and then, death of all remaining treated mice

Nitazoxanide or CD3+/CD4+ lymphocytes for recovery from severe Cryptosporidium infection after allogeneic bone marrow transplant?

We describe a case of Cryptosporidium infection occurring in a child after allogeneic SCT for acute non-lymphoblastic leukemia. This patient presented an intestinal, biliar, and pancreatic Cryptosporidium disease associated with an intestinal aGvHD. The increase in CD3+/CD4+ cells secondary to the reduction of steroid therapy associated with the improvement of aGvHD and the use of antiparasitic treatments (especially nitazoxanide) improved the infection-related symptoms and led to a complete clearance of the Cryptosporidium.

Molecular targets for detection and immunotherapy in Cryptosporidium parvum

Cryptosporidium parvum is an obligate protozoan parasite responsible for the diarrheal illness cryptosporidiosis in humans and animals. Although C. parvum is particularly pathogenic in immunocompromised hosts, the molecular mechanisms by which C. parvum invades the host epithelial cells are not well understood. Characterization of molecular-based antigenic targets of C. parvum is required to improve the specificity of detection, viability assessments, and immunotherapy (treatment). A number of zoite surface (glyco)proteins are known to be expressed during, and believed to be involved in, invasion and infection of host epithelial cells. In the absence of protective treatments for this illness, antibodies targeted against these zoite surface (glyco)proteins offers a rational approach to therapy. Monoclonal, polyclonal and recombinant antibodies represent useful immunotherapeutic means of combating infection, especially when highly immunogenic C. parvum antigens are utilized as targets. Interruption of life cycle stages of this parasite via antibodies that target critical surface-exposed proteins can potentially decrease the severity of disease symptoms and subsequent re-infection of host tissues. In addition, development of vaccines to this parasite based on the same antigens may be a valuable means of preventing infection. This paper describes many of the zoite surface glycoproteins potentially involved in infection, as well as summarizes many of the immunotherapeutic studies completed to date. The identification and characterization of antibodies that bind to C. parvum-specific cell surface antigens of the oocyst and sporozoite will allow researchers to fully realize the potential of molecular-based immunotherapy to this parasite.

Experimental study of the effects of probiotics on Cryptosporidium parvum infection in neonatal rats

To date, there is no efficient treatment for cryptosporidiosis and parasite eradication relies on innate and acquired immunity. In this study, we investigated the effect of administration of probiotic bacteria on the development and progression of the experimental infection in suckling rats. Rats were fed daily with 2.10(7) CFU of Lactobacillus casei-containing mixture, starting 2 days before the infection until the spontaneous clearance of the parasite. Effects on weight gain, parasite burden, mucosal histology and production of mucosal cytokines (IFNgamma, IL10 and TNFalpha) were studied. Although a trend to a more rapid clearance of parasites was noted in rats treated with probiotics, no significant effect of probiotics administration was observed in terms of weight gain, parasite burden, mucosal damage, or kinetics of mucosal cytokines during the course of infection. Overall, our results showed that the daily administration of L. casei-containing mixtures was unable to eradicate the parasite in our model.

Cryptosporidiosis in children

Cryptosporidiosis is an important enteric parasitic infection that is associated with significant morbidity and mortality, especially among individuals who are immunosuppressed and infants and children in the developing world. The seroprevalence of this pathogen is high worldwide, suggesting that exposure occurs commonly. The routes of Cryptosporidium spp. transmission are waterborne, food-borne, and occasionally person-to-person. Infected patients can be asymptomatic or develop watery diarrhea and associated enteric symptoms, which are self-limited in immunocompetent persons. In contrast, immunodeficient individuals develop severe, chronic diarrhea that rarely can lead to extra intestinal cryptosporidiosis. Although the diagnosis of Cryptosporidium infection can be established by examining a modified acid-fast stain of stool for the presence of oocysts, enzyme-linked immunoassays are now the diagnostic modalities of choice. Recent clinical trials in pediatric cryptosporidiosis have shown nitazoxanide to be effective therapy.

Treating opportunistic infections among HIV-exposed and infected children: recommendations from CDC, the National Institutes of Health, and the Infectious Diseases Society of America

In 2001, CDC, the National Institutes of Health, and the Infectious Diseases Society of America convened a working group to develop guidelines for therapy of human immunodeficiency virus (HIV)-associated opportunistic infections to serve as a companion to the Guidelines for Prevention of Opportunistic Infections Among HIV-Infected Persons. In recognition of unique considerations related to HIV infection among infants, children, and adolescents, a separate pediatric working group was established. Because HIV-infected women coinfected with opportunistic pathogens might be more likely to transmit these infections to their infants than women without HIV infection, guidelines for treating opportunistic pathogens among children should consider treatment of congentially acquired infections among both HIV-exposed but uninfected children and those with HIV infection. In addition, the natural history of opportunistic infections among HIV-infected children might differ from that among adults. Compared with opportunistic infections among HIV-infected adults, which are often caused by reactivation of pathogens acquired before HIV infection when host immunity was intact, opportunistic infections among children often reflect primary acquisition of the pathogen and, among children with perinatal HIV infection, infection acquired after HIV infection has been established and begun to compromise an already immature immune system. Laboratory diagnosis of opportunistic infections can be more difficult with children. Finally, treatment recommendations should consider differences between adults and children in terms of drug pharmacokinetics, dosing, formulations, administration, and toxicities. This report focuses on treatment of opportunistic infections that are common in HIV-exposed and infected infants, children, and adolescents in the United States.

Effect of egg yolk antibody on experimental infection in mice

In this study the effect of chicken egg yolk antibody (IgY) against Cryptosporidium parvum infection was examined. IgY sample was prepared from eggs of chickens immunized with C. parvum oocyst antigens. In vitro, antibody-treated sporozoites showed reduced binding to Caco-2 cells and lost vitality. These phenomena were not observed with a control IgY sample prepared from eggs of non-immunized chickens. Scid mice orally administered with the antibody demonstrated partial reduction in oocyst shedding after challenge with 10(3) oocysts. IgY, however, could not eliminate the infection after 17 days of continuous treatment. The potentials of using specific IgY for treatment and prevention of cryptosporidiosis were discussed.

Resolution of cryptosporidiosis with probiotic treatment

Cryptosporidium infection is usually self limited, but can be a life threatening illness in immunocompromised patients. Probiotics have been used successfully in the treatment of acute diarrhoea and they have also been shown to limit Cryptosporidium parvum infection in animal models. The first case of successful resolution of prolonged cryptosporidiosis with probiotic treatment is reported.

Integrated mapping, chromosomal sequencing and sequence analysis of Cryptosporidium parvum

The apicomplexan Cryptosporidium parvum is one of the most prevalent protozoan parasites of humans. We report the physical mapping of the genome of the Iowa isolate, sequencing and analysis of chromosome 6, and approximately 0.9 Mbp of sequence sampled from the remainder of the genome. To construct a robust physical map, we devised a novel and general strategy, enabling accurate placement of clones regardless of clone artefacts. Analysis reveals a compact genome, unusually rich in membrane proteins. As in Plasmodium falciparum, the mean size of the predicted proteins is larger than that in other sequenced eukaryotes. We find several predicted proteins of interest as potential therapeutic targets, including one exhibiting similarity to the chloroquine resistance protein of Plasmodium. Coding sequence analysis argues against the conventional phylogenetic position of Cryptosporidium and supports an earlier suggestion that this genus arose from an early branching within the Apicomplexa. In agreement with this, we find no significant synteny and surprisingly little protein similarity with Plasmodium. Finally, we find two unusual and abundant repeats throughout the genome. Among sequenced genomes, one motif is abundant only in C. parvum, whereas the other is shared with (but has previously gone unnoticed in) all known genomes of the Coccidia and Haemosporida. These motifs appear to be unique in their structure, distribution and sequences.

Reversible sclerosing cholangitis secondary to cryptosporidiosis in a renal transplant patient

Cryptosporidium parvum is a well-known cause of chronic diarrhea. In human immunodeficiency virus (HIV)-infected patients as well as in other immunocompromised patients it has also been shown to cause sclerosing cholangitis. We report a case of reversible C. parvum-induced sclerosing cholangitis in a renal transplant patient. This 40-year-old female received a renal transplant 9 years prior to presentation. She had no history of liver disease and was doing well on tacrolimus, prednisone, and azathioprine. She developed diarrhea and was found to have C. parvum present in the stool. Shortly after, she developed clinical, biochemical, radiologic, and histologic features of SC. After accidental reduction in her immunesuppression secondary to starting her on rifampin to treat her itching, she cleared C. parvum from her stool and had a marked improvement in her diarrhea, jaundice, and general health. Her liver enzymes normalized and magnetic resonance cholangiography showed complete resolution of biliary abnormalities. To our knowledge, this is the first case of C. parvum-induced sclerosing cholangitis in a renal transplant patient and one of a few in non-HIV patients. It is also the first to document resolution of sclerosing cholangitis after eradication of C. parvum in a non-HIV patient.

Evaluation of chronic diarrhea in patients with human immunodeficiency virus infection

Chronic diarrhea is a common problem for patients with human immunodeficiency virus infection, especially those with advanced disease. The extent of evaluation and whether to do flexible sigmoidoscopy, colonoscopy, and/or upper endoscopy have been areas of significant debate. Based upon the marked improvement in long-term survival since the introduction of highly active antiretroviral therapy, a comprehensive evaluation is currently justified. A stepwise approach to the evaluation of chronic diarrhea appears to be the best approach. The first step is a history, with a focus on any association between the onset of diarrhea and the institution of protease inhibitor therapy, which is associated with significant diarrhea in many patients. If there is no temporal association with antiretroviral therapy, the next step is examination of stool for bacterial and protozoal pathogens. If the stool studies are negative, the next step is to proceed to colonoscopy. Flexible sigmoidoscopy alone has been noted to miss up to 39% of cases of cytomegalovirus colitis. The inclusion of ileoscopy and biopsy of the terminal ileum during colonoscopy has a significant yield for microsporidiosis, which may obviate the need for upper endoscopy. The highest yield can be expected in patients with fever, weight loss, and a CD4 count of under 200 cells/mm3, especially those with a CD4 count less than 50 cells/mm3.

Polyclonal Fab phage display libraries with a high percentage of diverse clones to Cryptosporidium parvum glycoproteins

The protozoan parasite Cryptosporidium parvum is regarded as a major public health problem world-wide, especially for immunocompromised individuals. Although no effective therapy is presently available, specific immune responses prevent or terminate cryptosporidiosis and passively administered antibodies have been found to reduce the severity of infection. Therefore, as an immunotherapeutic approach against cryptosporidiosis, we set out to develop C. parvum-specific polyclonal antibody libraries, standardised, perpetual mixtures of polyclonal antibodies, for which the genes are available. A combinatorial Fab phage display library was generated from the antibody variable region gene repertoire of mice immunised with C. parvum surface and apical complex glycoproteins which are believed to be involved in mediating C. parvum attachment and invasion. The variable region genes used to construct this starting library were shown to be diverse by nucleotide sequencing. The library was subjected to one round of antigen selection on C. parvum glycoproteins or a C. parvum oocyst/sporozoite preparation. The two selected libraries showed specific reactivity to the glycoproteins as well as to the oocyst/sporozoite preparation, with 50-73% antigen-reactive members. Fingerprint analysis of individual clones from the two antigen-selected libraries showed high diversity, confirming the polyclonality of the selected libraries. Furthermore, immunoblot analysis on the oocyst/sporozoite and glycoprotein preparations with selected library phage showed reactivity to multiple bands, indicating diversity at the antigen level. These C. parvum-specific polyclonal Fab phage display libraries will be converted to libraries of polyclonal full-length antibodies by mass transfer of the selected heavy and light chain variable region gene pairs to a mammalian expression vector. Such polyclonal antibody libraries would be expected to mediate effector functions and provide optimal passive immunity against cryptosporidiosis.

Humoral and cellular immunity against Cryptosporidium infection

Protozoans of the genus Cryptosporidium are the etiological agents of opportunistic infections mainly of the gastrointestinal tract of animals and humans. Young and elderly persons, those with concomitant infections, with AIDS, under an immunosuppressive therapy, with congenital T-cell, B-cell or other effector cell deficiencies develop persistent progressive infections of different degree of severity related to the level of immunodepression. Both humoral and cellular immunity play a role in the control of this infection, but the latter plays the major role, mainly in the intestinal mucosa. However, a natural resistance to these coccidian parasites is also involved. IgG, IgM and IgA have been detected in serum and mucosa of humans and animals with the resolution of the infection; but also high levels of these immunoglobulins have been detected in persons with AIDS with chronic cryptosporidiosis. In HIV-positive persons, CD4+ T-cells are required to prevent the establishment of the infection and IFN-gamma and CD4+ T-cells can also limit the duration and the clinical manifestations of the infection. In persons exposed to cryptosporidial infections, it has been possible to show the important role of IFN-gamma in both the innate and acquired cell mediated immunity. The severity of cryptosporidiosis has been also associated with the inability to produce IFN-gamma. An antibody therapy using bovine colostrum from cows hyperimmunised with Cryptosporidium oocysts or monoclonal antibodies against sporozoite antigens has been developed at the experimental level mainly for persons with AIDS or with other immunodeficiencies; however, these preparations of antibodies have shown only a limited degree of efficacy both in animals and humans.

Recent advances in cryptosporidiosis: the immune response

An increased understanding of host immune responses to Cryptosporidium parvum which are responsible for clearance of primary infection and resistance to reinfection, and characterization of the parasite molecules to which they are directed, are essential for discovery of effective active and passive immunization strategies against cryptosporidiosis. In this article, recent advances in knowledge of humoral and cellular immune responses to C. parvum, their antigen specificities, and mechanisms of protection are briefly reviewed.

Vitamin B12 and folic acid in children with intestinal parasitic infection

OBJECTIVE

To determine prospectively plasma levels of vitamin B12 and folic acid in children with intestinal parasitic infection before and three months after antiparasitic treatment.

METHODS

3036 stool samples were collected from 1959 children and 939 cello-tape anal swabs were taken from 688 children for intestinal parasite investigation. Of these, 155 children were identified as having a parasitic infection; however, only 86 were followed up during this study: 26 children with Giardia lamblia infection were treated with tinidazole and metronidazole, pyrantel pamoate was used in the treatment of 40 children with Enterobius vermicularis, and 20 patients infected with Cryptosporidium parvum received only symptomatic treatment. Vitamin B12 and folic acid levels were measured by radioimmunoassay, before and three months after the completion of treatment.

RESULTS

Vitamin B12 serum concentrations did not show any significant differences among the three groups. There was a significant increase in vitamin B12 serum concentrations after three months of anti-parasitic treatment (630.57+/-200.97 vs. 667.97+/-181.55 pg/dL, p = 0.002, n = 86). Paired analysis in each group showed only significant increases for vitamin B12 in the Giardia lamblia group and in the Enterobius vermicularis group. No statistically significant differences were found for folic acid serum concentrations before and three months after treatment.

CONCLUSIONS

Patients with symptomatic infection by Giardia lamblia and Enterobius vermicularis have lower vitamin B12 levels than asymptomatic patients. This could reflect a more affected intestinal mucous. These results could present the opportunity to treat these parasitic infections and to use vitamin B12 supplementation in symptomatic children with Giardia lamblia and Enterobius vermicularis infection.

Cryptosporidiosis: an update

Cryptosporidiosis was recognised in human beings in 1976, and was prominent in the 1980s and 1990s as a cause of severe diarrhoeal illness in patients with AIDS. It is now additionally recognised as a major cause of waterborne diarrhoeal illness in developed regions, and as a pathogen with long-term effect on childhood growth and development in impoverished areas. This update focuses on recent changes in our understanding of the taxonomy of cryptosporidium, its epidemiology, effects, pathogenesis, diagnosis, and treatment.

Post-infective diarrhoea

When diarrhoea caused by gastroenteritis persists for more than two weeks it is referred to as persistent diarrhoea in developing countries. Whilst the Control of Diarrhoeal Diseases programme has decreased mortality from acute diarrhoea, mortality from persistent diarrhoea has not been so responsive. A number of factors have been identified which are determinants for the progression of an acute episode to one which persists in developing communities. In one study from west Africa, current infection with Cryptosporidium parvum was the most significant factor. In studies from Brazil and India, continuing infection with enteropathogenic Escherichia coli was identified in 50% of infants with persistent diarrhoea. Persistent small intestinal mucosal damage is of key importance in such children. Management of established cases is complex and difficult. However, there is clear evidence that zinc is involved in the recovery of small intestinal mucosa after injury. Zinc supplementation may indeed significantly reduce the duration of persistent diarrhoea. However, the whole question of public health supplementation with zinc, vitamin A, or other supplements, is contentious at present.

Molecular cloning and expression of a gene encoding Cryptosporidium parvum glycoproteins gp40 and gp15

Cryptosporidium parvum is a significant cause of diarrheal disease worldwide. The specific molecules that mediate C. parvum-host cell interactions and the molecular mechanisms involved in the pathogenesis of cryptosporidiosis are unknown. In this study we have shown that gp40, a mucin-like glycoprotein, is localized to the surface and apical region of invasive stages of the parasite and is shed from its surface. gp40-specific antibodies neutralize infection in vitro, and native gp40 binds specifically to host cells, implicating this glycoprotein in C. parvum attachment to and invasion of host cells. We have cloned and sequenced a gene designated Cpgp40/15 that encodes gp40 as well as gp15, an antigenically distinct, surface glycoprotein also implicated in C. parvum-host cell interactions. Analysis of the deduced amino acid sequence of the 981-bp Cpgp40/15 revealed the presence of an N-terminal signal peptide, a polyserine domain, multiple predicted O-glycosylation sites, a single potential N-glycosylation site, and a hydrophobic region at the C terminus, a finding consistent with what is required for the addition of a GPI anchor. There is a single copy of Cpgp40/15 in the C. parvum genome, and this gene does not contain introns. Our data indicate that the two Cpgp40/15-encoded proteins, gp40 and gp15, are products of proteolytic cleavage of a 49-kDa precursor protein which is expressed in intracellular stages of the parasite. The surface localization of gp40 and gp15 and their involvement in the host-parasite interaction suggest that either or both of these glycoproteins may serve as effective targets for specific preventive or therapeutic measures for cryptosporidiosis.

Successful hyperimmune bovine colostrum treatment of Savanna monitors (Varanus exanthematicus) infected with Cryptosporidium sp

Therapy based on the protective passive immunity of hyperimmune bovine colostrum (HBC) (raised against Cryptosporidium parvum in cows) was applied to 4 Savanna monitors (Varanus exanthematicus) with gastric Cryptosporidium sp. infections. All lizards were moderately emaciated, and their fecal and gastric lavage samples contained moderate numbers of Cryptosporidium sp. oocysts. The first 3 of 7 gastric HBC treatments at 1-wk interval each decreased the numbers of oocysts in the fecal and gastric samples to undetectable levels. Neither feces nor lavages of the HBC-treated lizards contained Cryptosporidium sp. oocysts after the HBC therapy, whereas such samples of a single control lizard remained positive for oocysts. Two of the HBC-treated lizards died spontaneously due to metastasized carcinoma and septicemia of unknown etiology, respectively, and 2 lizards treated and killed during the experiment were histologically negative for developmental stages of Cryptosporidium sp. The control lizard died spontaneously of septicemia of unknown etiology and contained developmental stages of Cryptosporidium sp. in the gastric region. The HBC therapy was efficacious in V. exanthematicus and is recommended for lizards with gastric cryptosporidiosis.

Cryptosporidial infections after solid organ transplantation in children

The diagnosis and treatment of moderate-to-severe diarrhea in solid organ transplant recipients is often a challenge because of the variety of infectious and non-infectious causes. The morbidity associated with this clinical condition is of particular significance in the pediatric population where malnutrition may lead to poor growth and development. Rarely, Cryptosporidium has been identified as the cause of clinically significant diarrhea in pediatric solid organ transplant patients. A retrospective review identified cases of cryptosporidiosis among the 1160 non-renal, abdominal organ transplant recipients cared for at the Children's Hospital of Pittsburgh between 1981 and June 1998. Four cases of clinically significant diarrhea were identified in three liver transplant recipients and one small bowel transplant recipient. Endoscopy and biopsy with histologic confirmation diagnosed three cases; ova and parasitic examination of stool specimens identified the fourth case. Therapy varied among the patients depending on when they had been diagnosed as, over the years, different and newer agents have been indicated for the treatment of cryptosporidiosis. All four patients resolved their infections. Hence, endoscopy and biopsy is recommended for pediatric transplant patients who present with chronic diarrhea of unknown etiology. The patients who may be at a higher risk for cryptosporidial infections include those with an increased immunosuppressive state (i.e. pre-existing immunodeficiency, malignancy, re-transplantation, and those receiving higher doses of immunosuppressive therapy). While cryptosporidiosis is a non-lethal complication, it allows the clinician to gain further insight into the degree of immunosuppression of their patient.

New insights into human cryptosporidiosis

Cryptosporidium parvum is an important cause of diarrhea worldwide. Cryptosporidium causes a potentially life-threatening disease in people with AIDS and contributes significantly to morbidity among children in developing countries. In immunocompetent adults, Cryptosporidium is often associated with waterborne outbreaks of acute diarrheal illness. Recent studies with human volunteers have indicated that Cryptosporidium is highly infectious. Diagnosis of infection with this parasite has relied on identification of acid-fast oocysts in stool; however, new immunoassays or PCR-based assays may increase the sensitivity of detection. Although the mechanism by which Cryptosporidium causes diarrhea is still poorly understood, the parasite and the immune response to it probably combine to impair absorption and enhance secretion within the intestinal tract. Important genetic studies suggest that humans can be infected by at least two genetically distinct types of Cryptosporidium, which may vary in virulence. This may, in part, explain the clinical variability seen in patients with cryptosporidiosis.

Cryptosporidium infection in beech martens (Martes foina)

Temporary episodes of diarrhea in captive beech martens (Martes foina) were accompanied by shedding of Cryptosporidium oocysts. Oocysts were detected in fecal samples by flotation and in acid-fast-stained smear preparations. The oocysts were 3-5 microns, which is consistent with C. parvum. The source of the Cryptosporidium infection remained unknown. This is the first demonstration of Cryptosporidium in beech martens.

Supplementation with Lactobacillus reuteri or L. acidophilus reduced intestinal shedding of cryptosporidium parvum oocysts in immunodeficient C57BL/6 mice

The effect of L. acidophilus supplementation to reduce fecal shedding of Cryptosporidium parvum oocysts was compared to L. reuteri using C57BL/6 female mice immunosuppressed by murine leukemia virus (strain LP-BM5) inoculation. After 12 weeks post LP-BM5 inoculation, 15 immunosuppressed mice each were randomly assinged to one of the following treatment groups: historical control (group A), LP-BM5 control (group B), C. parvum (group C), L. reuteri plus C. parvum (group D) or L. acidophilus plus C. parvum (group E). Mice were pre-fed the L. reuteri or L. acidophilus bacteria strains daily for 13 days, challenged with C. parvum oocysts and thereafter fed the specified Lactobacillus regimens daily during the experimental period. Animals supplemented with L. reuteri shed fewer (p<0.05) oocysts on day-7 post C. parvum challenge compared to controls. Mice supplemented with L. acidophilus also shed fewer (p<0.05) oocysts on days 7 and 14 post-challenge compared to controls. Overall, Lactobacillus supplementation reduced C. parvum shedding in the feces but failed to suppress the production of T-helper type 2 cytokines [interleukin-4 (IL-4), IL-8)] which are associated with immunosuppression. Additionally, Lactobacillus supplementation did not restore T-helper type 1 cytokines (interleukin-2 (IL-2) and gamma interferon (IFN-gamma), which are required for recovery from parasitic infections. Altered T-helper types 1 and 2 cytokine production as a consequence of immunodysfunction permitted the development of persistent cryptosporidiosis while mice with intact immune system were refractory to infection with C. parvum. Reduction in shedding of oocysts observed in the Lactobacillus supplemented mice during deminished IL-2 and IFN-gamma production may be mediated by factors released into the intestinal lumen by the Lactobacillus and possibly other host cellular mechanisms. These observations suggest that L. reuteri or L. acidophilus can reduce C. parvum parasite burdens in the intestinal epithelium during cryptosporidiosis and may serve potential benefits as probiotics for host resistance to intestinal parasitic infections. L. acidophilus was more efficacious in reducing fecal shedding than L. reuteri and therefore may also have implication in the therapy of cryptosporidiosis during immunosuppressive states including human AIDS.

Cryptosporidia and microsporidia--waterborne diseases in the immunocompromised host

Cryptosporidia and microsporidia are emerging parasitic pathogens in immunocompetent and immunocompromised individuals. Cryptosporidium infects several wild and domestic animals that excrete oocysts into the environment and contaminated water represents the major source of infection for humans. Waterborne transmission of Cryptosporidium is a major risk for humans and appropriate measures have to be taken to protect immunocompetent and immunocompromised individuals to become infected. For microsporidia, the sources and ways of transmission are not well documented. Although several animal hosts have been identified recently, the relevant reservoirs of human microsporidia are still unknown. Also, the routes of spreading are unknown. Is microsporidiosis a zoonotic disease that will be transmitted through close contact with infected animals or is contaminated surface water responsible for transmission and represents a relevant reservoir? This review is designed to give information on these two emerging intestinal parasites in a format that will be useful to clinical microbiologists, physicians interested in infectious diseases, and public health personnel.

Hyperimmune bovine colostrum treatment of moribund Leopard geckos (Eublepharis macularius) infected with Cryptosporidium sp

Therapy based on the protective passive immunity of hyperimmune bovine colostrum (HBC) was applied to 12 moribund Leopard geckos (Eublepharis macularius) infected with Cryptosporidium sp. The geckos were lethargic and moderately to severely emaciated, weighing on average 36% of the baseline body weight value. Seven gastric HBC treatments at 1-week intervals each decreased the relative output of Cryptosporidium sp. oocysts and the prevalence of oocyst-positive fecal specimens. Histologically, after 8 weeks of therapy, seven out of 12 geckos had only single developmental stages of Cryptosporidium sp. in the intestinal epithelium, and three, one and one geckos had low, moderate and high numbers, respectively, of the pathogen developmental stages. The HBC therapy was efficacious in decreasing the parasite load in moribund geckos. Morphometric and immunologic analysis of Cryptosporidium sp. oocyst isolates originating from Leopard geckos (E. macularius) demonstrated differences between gecko-derived oocyst isolates and isolates of C. serpentis recovered from snakes.

Antibody-based immunotherapy of cryptosporidiosis

Passive antibody immunotherapy (PAI) for cryptosporidiosis is a treatment strategy that has been actively pursued in laboratory studies and early-stage clinical studies for the last decade. Several experimental approaches have been initiated, including use of bovine colostrum and colostral antibodies (hyperimmune and natural), monoclonal antibodies, chicken egg yolk antibodies, and even orally administered human plasma antibodies. Most studies have employed oral administration to treat or prevent this intestinal infection. The interest in this treatment strategy has been sparked by the lack of an effective or approved therapy, increased awareness of the widespread nature of this parasite, epidemiological evidence that humoral immunity plays an important role in host resistance, and several early case reports of antibody therapy in which remarkable resolution of the disease was observed. Most studies using a variety of preparations of antibodies administered to animals and humans have shown some degree of efficacy, though the responses have been, for the most part, partial rather than complete resolution of the disease. This chapter examines critically the scientific rationale and the evidence for PAI for cryptosporidiosis, including practical considerations and future approaches.

Human cryptosporidiosis: epidemiology, transmission, clinical disease, treatment, and diagnosis

Cryptosporidiosis is now recognized as one of the most common human enteric infections. In this critical review, relatively unexplored details of transmission, the interaction with malnutrition and the development of chronic diarrhea, and the need for effective treatment are highlighted. Our inability to detect small numbers of foodborne oocysts limits our understanding of this transmission route, and the possibility of respiratory transmission is yet to be rigorously studied. The toll this disease imposes on children, especially the malnourished, has not been fully appreciated. Indeed, the dynamics of the progression from acute cryptosporidiosis to chronic diarrhea and death of malnourished children is still enigmatic. Our knowledge of the intestinal pathophysiology, while limited, is increasing. The lack of effective drug therapy is both remarkable and sobering. Overall, these unknown areas demonstrate how little we truly know about this parasite.

Innate and cell-mediated immune responses to Cryptosporidium parvum

Cryptosporidium parvum has gained much attention as a major cause of diarrhea in the world. Knowledge of the host immune mechanisms responsible for the clearance of this parasite from the gastrointestinal tract may prove to be vital for successful therapeutic treatment of cryptosporidiosis, particularly in the immunodeficient host. This chapter focuses on the innate and cell-mediated immune mechanisms associated with resistance to and resolution of a C. parvum infection. Much of the work in these areas is still in its infancy. Despite this, general consensus supports a role for interferon-gamma (IFN gamma) in mediating the initial resistance to C. parvum, although the mechanism by which this cytokine imparts resistance is unclear. It is also generally agreed that CD4+ T lymphocytes are required for the resolution of both acute and chronic cryptosporidiosis. However, the effector mechanism is again unclear. Several studies suggest that IFN gamma may also be involved in the resolution of cryptosporidiosis. However, the extent to which this cytokine is involved in the actual resolution of infection has been debated. Less extensive studies investigating the participation of other cells and cytokines in the innate and cell-mediated immune responses to C. parvum are also discussed.

Therapeutic efficacy of hyperimmune bovine colostrum treatment against clinical and subclinical Cryptosporidium serpentis infections in captive snakes

Therapy based on the protective passive immunity of Hyperimmune Bovine Colostrum (HBC) (raised against Cryptosporidium parvum in dairy cows immunized during gestation) was tested for heterologous efficacy in subclinical and clinical infections of 12 captive snakes with C. serpentis. Six gastric HBC treatments of 1% snake weight at 1-week intervals each, have histologically cleared C. serpentis in three subclinically infected snakes, and regressed gastric histopathological changes in one of these snakes. In all snakes, each subsequent HBC treatment significantly decreased the number of oocysts recovered in gastric lavage eluants (P < 0.03). The treatments induced oocyst-negative gastric eluants and stools in all snakes, and improved clinical signs of infection. Clinically infected snakes displayed severe histopathological changes in the gastric region; however, the numbers of developmental stages of C. serpentis were moderate. Considering the severity of pathology, much lower than expected pathogen numbers were observed, and it is believed that clinically infected snakes did not have enough time to repair tissue damage that had occurred over the years of infection. As the HBC treatment was safe and highly efficacious, it is recommended to gastrically administer the HBC therapeutically to snakes that are clinically or subclinically infected with C. serpentis. Hyperimmune bovine colostrum can also be used in snake supportive therapy or prophylaxis.

Influence of different systems of feeding in the appearance of cryptosporidiosis in goat kids

This study evaluated how different systems of feeding may influence the appearance, maintenance, or both of cryptosporidial infection. Animals reared with natural lactation, a traditional artificial feeding system, and a variety of the latter were studied for oocysts in feces. The diagnosis was made by examination of fecal smears stained with auramine-O. Morbidity and mortality were high, particularly in farms with bad hygienic conditions and natural feeding systems. The traditional artificial feeding system is not enough to reduce the presence of parasites. Isolation of newborns at birth and colostrum administration with a feeding bottle, obtained in the most aseptic conditions possible, seems to be an effective prophylactic method for cryptosporidiosis control.

Nosocomial transmission of Cryptosporidium in a veterinary hospital

An outbreak of cryptosporidiosis occurred at a veterinary hospital, involving multiple species, including humans. The index case was an infected dairy calf that presented with diarrhea. Several other cases of cryptosporidial diarrhea subsequently developed during a 1-month period. The key features of this outbreak were the multiple species affected, the increased morbidity in immunocompromised neonates, and the failure of implemented control measures to contain the disease.

Cryptosporidiosis in persons with HIV infection

Cryptosporidium parvum is an ubiquitous protozoan parasite that is a major cause of diarrhoea in individuals infected with human immunodeficiency virus. The hallmarks of infection include profuse watery diarrhoea which may become chronic in the severely immunosuppressed individual. No uniformly effective therapy exists. Current treatment relies upon a trial of anti-retroviral and specific anti-cryptosporidial medications, adequate fluid and nutritional support, and anti-motility agents.

Cryptosporidiosis and inflammatory bowel disease. Experience from the Milwaukee outbreak

The 1993 Milwaukee Cryptosporidium outbreak posed several questions regarding appropriate management and prognosis of inflammatory bowel disease patients acutely infected with this organism. We prospectively identified and monitored 12 patients with stable ulcerative colitis or Crohn's disease who suffered abrupt clinical decompensation during the outbreak. All recovered to baseline at < or = 60 days. In patients receiving immunosuppressive therapy, mean duration of symptoms was no longer than in patients without it. Antibiotics did not clearly reduce duration of illness. Two additional patients without a history of intestinal disease presented with ileitis and colitis, respectively, initially suggesting Crohn's disease. Both recovered completely without specific therapy. We conclude that cryptosporidiosis may present as an acute relapse of inflammatory bowel disease and responds to standard therapy; antibiotics confer no obvious benefit. Immunosuppressive therapy does not predispose to chronic or severe illness in these patients. Cryptosporidiosis may present with acute findings initially mimicking Crohn's disease.