Cryptosporidium species a "new" human pathogen

The emerging paradigm of calcium homeostasis as a new therapeutic target for protozoan parasites

Calcium channels (CCs), a group of ubiquitously expressed membrane proteins, are involved in many pathophysiological processes of protozoan parasites. Our understanding of CCs in cell signaling, organelle function, cellular homeostasis, and cell cycle control has led to improved insights into their structure and functions. In this article, we discuss CCs characteristics of five major protozoan parasites Plasmodium, Leishmania, Toxoplasma, Trypanosoma, and Cryptosporidium. We provide a comprehensive review of current antiparasitic drugs and the potential of using CCs as new therapeutic targets. Interestingly, previous studies have demonstrated that human CC modulators can kill or sensitize parasites to antiparasitic drugs. Still, none of the parasite CCs, pumps, or transporters has been validated as drug targets. Information for this review draws from extensive data mining of genome sequences, chemical library screenings, and drug design studies. Parasitic resistance to currently approved therapeutics is a serious and emerging threat to both disease control and management efforts. In this article, we suggest that the disruption of calcium homeostasis may be an effective approach to develop new anti-parasite drug candidates and reduce parasite resistance.

Practical Guidance for Clinical Microbiology Laboratories: Laboratory Diagnosis of Parasites from the Gastrointestinal Tract

This Practical Guidance for Clinical Microbiology document on the laboratory diagnosis of parasites from the gastrointestinal tract provides practical information for the recovery and identification of relevant human parasites. The document is based on a comprehensive literature review and expert consensus on relevant diagnostic methods. However, it does not include didactic information on human parasite life cycles, organism morphology, clinical disease, pathogenesis, treatment, or epidemiology and prevention. As greater emphasis is placed on neglected tropical diseases, it becomes highly probable that patients with gastrointestinal parasitic infections will become more widely recognized in areas where parasites are endemic and not endemic. Generally, these methods are nonautomated and require extensive bench experience for accurate performance and interpretation.

Evaluation of enzyme linked immunosorbent assay for stool antigen detection for the diagnosis of cryptosporidiosis among HIV negative immunocompromised patients in a tertiary care hospital of northern India

The diagnosis of cryptosporidiosis among HIV positive patients has been the focus of many studies worldwide. However, there is a paucity of data on HIV negative immunocompromised patients like post-renal transplant recipients and those with haematological malignancies. Stool microscopy, the conventional method of diagnosis, is fraught with difficulties like cumbersome sample processing and subjective interpretation. Enzyme linked immunosorbent assay (ELISA), on the other hand, is quicker and easier. The present study was conducted in a tertiary care and super speciality hospital of north India. Stool specimens from HIV negative immunocompromised patients were subjected to both modified acid fast staining for oocysts of Cryptosporidium and ELISA for detection of Cryptosporidium copro-antigen, over a period of six years. Of the 637 specimens evaluated, 97 (15.23%) samples were positive for Cryptosporidium by both techniques; 25 (3.92%) specimens were positive by ELISA and negative by microscopy, 14 (2.20%) specimens were positive by microscopy but negative by ELISA, while 501 (78.65%) specimens were negative for Cryptosporidium by both techniques. Significant correlation was observed as a measure of agreement (Kappa test value 0.795) between modified ZN stained microscopy and ELISA for the detection of Cryptosporidium oocysts. The sensitivity, specificity, positive and negative predictive value of ELISA, keeping stool microscopy as gold standard were 87.38%, 95.25%, 87.39% and 97.28% respectively. We conclude that ELISA may be used as a reliable substitute for microscopy in setups where the case load is higher or expertise in special staining techniques is not available. The cost of the kit can be justified if the sample load is sufficiently high or if immunocompromised patients form a significant patient population.

Intestinal Parasitosis in Relation to Anti-Retroviral Therapy, CD4(+) T-cell Count and Diarrhea in HIV Patients

Intestinal parasitic infections are one of the major causes of diarrhea in human immunodeficiency virus (HIV) seropositive individuals. Antiretroviral therapy has markedly reduced the incidence of many opportunistic infections, but parasite-related diarrhea still remains frequent and often underestimated especially in developing countries. The present hospital-based study was conducted to determine the spectrum of intestinal parasitosis in adult HIV/AIDS (acquired immunodeficiency syndrome) patients with or without diarrhea with the levels of CD4⁺ T-cell counts. A total of 400 individuals were enrolled and were screened for intestinal parasitosis. Of these study population, 200 were HIV seropositives, and the remaining 200 were HIV uninfected individuals with or without diarrhea. Intestinal parasites were identified by using microscopy as well as PCR assay. A total of 130 (32.5%) out of 400 patients were positive for any kinds of intestinal parasites. The cumulative number of parasite positive patients was 152 due to multiple infections. A significant association of Cryptosporidium (P<0.001) was detected among individuals with CD4⁺ T-cell counts less than 200 cells/μl.

Cryptosporidium pathogenicity and virulence

Cryptosporidium is a protozoan parasite of medical and veterinary importance that causes gastroenteritis in a variety of vertebrate hosts. Several studies have reported different degrees of pathogenicity and virulence among Cryptosporidium species and isolates of the same species as well as evidence of variation in host susceptibility to infection. The identification and validation of Cryptosporidium virulence factors have been hindered by the renowned difficulties pertaining to the in vitro culture and genetic manipulation of this parasite. Nevertheless, substantial progress has been made in identifying putative virulence factors for Cryptosporidium. This progress has been accelerated since the publication of the Cryptosporidium parvum and C. hominis genomes, with the characterization of over 25 putative virulence factors identified by using a variety of immunological and molecular techniques and which are proposed to be involved in aspects of host-pathogen interactions from adhesion and locomotion to invasion and proliferation. Progress has also been made in the contribution of host factors that are associated with variations in both the severity and risk of infection. Here we provide a review comprised of the current state of knowledge on Cryptosporidium infectivity, pathogenesis, and transmissibility in light of our contemporary understanding of microbial virulence.

R. Intestinal Cryptosporidiosis and the Profile of the CD4 Counts in a Cohort of HIV Infected Patients

BACKGROUND

Cryptosporidium is an infectious enteric pathogen which is capable of causing life-threatening illnesses in immunocompromised patients.

AIMS

This prospective study was planned to know the frequency of intestinal cryptosporidiosis in HIV infected patients and its correlation with their immune status. Also, the conventional diagnostic methods were compared with the copro-antigen detection test by using Enzyme Linked Immuno Sorbent Assay (ELISA).

SETTINGS AND DESIGN

This was a prospective cohort study.

METHODS AND MATERIAL

Three consecutive stool samples which were collected from 90 HIV seropositive patients and 50 seronegative controls were screened for cryptosporidiosis by wet mount, direct modified ZN (Ziehl Neelsen) staining, modified ZN staining with formol ether concentration and copro-antigen detection by ELISA. Their immune statuses were measured by CD4 + cell counting. Statistical Analytical Tests which were Used: Odds ratio, Chi square test, Fisher extract test.

RESULTS

Cryptosporidiosis was detected in 15 HIV seropositive cases. 13 cases had CD4 cell counts of < 100 cells/ μL. The formol ether concentration technique resulted in an increased number of oocysts/oil immersion field in 8 cases. ELISA was positive in 2 cases which were shown to be negative by modified ZN staining. All the controls were negative for cryptosporidium.

CONCLUSIONS

Cryptosporidiosis is an opportunistic infection in HIV infected people who present with diarrhoea. The wet mount technique, though it is simple and inexpensive, is insensitive for the detection of cryptosporidium. The conventional modified ZN staining and the modified ZN staining with concentration have a sensitivity and a specificity of 85.71% and 98.84% respectively. The copro antigen detection by ELISA which has a greater sensitivity and specificity, is a useful tool in epidemiological studies.

Advances in diagnosis of protozoan diseases

Microscopy still remains the gold standard procedure for the diagnosis of many protozoan infections in animals, but the specific identification requires skilled and experienced personnel. Immunoassays, detecting antibodies or specific protozoan antigens, have been developed but often lack sensitivity and specificity due to close relationship between many protozoa. Recent research has focussed almost exclusively on molecular based techniques for the identification and quantification of parasite DNA in samples. Opinion differ on most appropriate targets to use and there are very few diagnostic kits available making comparison between laboratories difficult. Future research needs to focus on robust, cheap field diagnostic assays.

Challenges in understanding the immunopathogenesis of Cryptosporidium infections in humans

Water and foodborne enteric cryptosporidiosis is a globally emerging public health issue. Although the clinical manifestations of enteric cryptosporidiosis are generally limited to intestinal infection and subsequent diarrhoea, extra-intestinal invasion has also been diagnosed in immunocompromised individuals, particularly in those infected with human immunodeficiency virus (HIV) or AIDS. Due to an inadequate understanding of Cryptosporidium immunopathogenesis in humans, the development of vaccines or therapeutic agents and their application in diseases management is difficult. Current therapeutic measures are not fully effective in the treatment of the disease. Therefore, the implementation of strategies designed to control the chain of cryptosporidiosis transmission (environment ↔ human ↔ food/water ↔ animal) is a critical but challenging issue to public health authorities across the world. Several excellent studies have been done on innate, acquired and mucosal immunity against Cryptosporidium infections using animal models, in vitro human cell lines and human volunteers. However, there are still multiple challenges in understanding the intestinal immune response (immunopathogenesis) to Cryptosporidium infection in humans. This paper reviews recent updates on immunopathogenesis and immune responses to Cryptosporidium infection in humans, while also discussing the current limitations that exist regarding a precise understanding of the immunopathological mechanisms.

Risks of recreational exposure to waterborne pathogens among persons with HIV/AIDS in Baltimore, Maryland

OBJECTIVES

We assessed the prevalence of recreational activities in the waterways of Baltimore, MD, and the risk of exposure to Cryptosporidium among persons with HIV/AIDS.

METHODS

We studied patients at the Johns Hopkins Moore Outpatient AIDS Clinic. We conducted oral interviews with a convenience sample of 157 HIV/AIDS patients to ascertain the sites used for recreational water contact within Baltimore waters and assess risk behaviors.

RESULTS

Approximately 48% of respondents reported participating in recreational water activities (fishing, crabbing, boating, and swimming). Men and women were almost equally likely to engage in recreational water activities (53.3% versus 51.3%). Approximately 67% (105 of 157) ate their own catch or that of friends or family members, and a majority (61%, or 46 of 75) of respondents who reported recreational water contact reported consumption of their own catch.

CONCLUSIONS

Baltimoreans with HIV/AIDS are engaging in recreational water activities in urban waters that may expose them to waterborne pathogens and recreational water illnesses. Susceptible persons, such as patients with HIV/AIDS, should be cautioned regarding potential microbial risks from recreational water contact with surface waters.

Taxonomy and species delimitation in Cryptosporidium

Amphibians, reptiles, birds and mammals serve as hosts for 19 species of Cryptosporidium. All 19 species have been confirmed by morphological, biological, and molecular data. Fish serve as hosts for three additional species, all of which lack supporting molecular data. In addition to the named species, gene sequence data from more than 40 isolates from various vertebrate hosts are reported in the scientific literature or are listed in GenBank. These isolates lack taxonomic status and are referred to as genotypes based on the host of origin. Undoubtedly, some will eventually be recognized as species. For them to receive taxonomic status sufficient morphological, biological, and molecular data are required and names must comply with the rules of the International Code for Zoological Nomenclature (ICZN). Because the ICZN rules may be interpreted differently by persons proposing names, original names might be improperly assigned, original literature might be overlooked, or new scientific methods might be applicable to determining taxonomic status, the names of species and higher taxa are not immutable. The rapidly evolving taxonomic status of Cryptosporidium sp. reflects these considerations.

Cryptosporidium species found in cattle: a proposal for a new species

Humans and animals are infected worldwide by apicomplexan parasites of the genus Cryptosporidium. Yet, parasitologists are continuously surprised by the expanding complexity of this genus. Over the past 20 years, cattle were identified as being a reservoir host for taxa transmitted from animals to humans. However, a remarkable assemblage of species affects cattle, including both cattle-specific, in addition to a zoonotic, species. To clarify species classification, Cryptosporidium pestis n. sp. is proposed for the species formerly recognized as the "bovine genotype" of C. parvum. The observed increasing complexity of Cryptosporidium species, along with recent advances in knowledge, should be reconsidered in the context of past records, and not vice versa. In this way, the gaps in our understanding of Cryptosporidium species can be identified and addressed in a scientific manner.

Cryptosporidium

This review discusses characteristics of the genus Cryptosporidium and addresses the pathogenesis, reservoirs, public health significance and current applications for the detection and typing of this important pathogen. By increasing knowledge in key areas of Cryptosporidium research such as aetiology, epidemiology, transmission and host interactions, the numbers of cases of human cryptosporidiosis should be reduced.

Concurrent response to challenge infection with Cryptosporidium parvum in immunosuppressed C57BL/6N mice

We investigated the response to challenge infection with Cryptosporidium parvum oocysts in immunosuppressed C57BL/6N mice. In the primary infection, fecal oocyst shedding and parasite colonization were greater in immunosuppressed mice than in nonimmunosuppressed mice. Compared with primary infection, challenge infection with C. parvum didn't show any oocyst shedding and parasite colonization. Especially, oocyst shedding and parasite colonization from the mice infected with heat-killed oocysts were not detected. After challenge infection with C. parvum oocysts, however, these mice were shedding small numbers of oocysts and parasite colonization. Except normal control and uninfected groups, the antibody titers of other groups appear similar. Based on the fecal oocyst shedding, parasite colonization of ilea, and antibody titers in the mice, these results suggest that the resistance to challenge infection with C. parvum in immunosuppressed C57BL/6N mice has increased.

The zoonotic transmission of Giardia and Cryptosporidium

The molecular characterisation of Giardia and Cryptosporidium has given rise to a more epidemiological meaningful and robust taxonomy. Importantly, molecular tools are now available for 'typing' isolates of the parasites directly from clinical and environmental samples. As a consequence, information on zoonotic potential has been obtained although the frequency of zoonotic transmission is still poorly understood. Analysis of outbreaks and case-control studies, especially when coupled with genotyping data, is slowly providing information on the public health significance of zoonotic transmission. Such studies support the hypothesis that Cryptosporidium hominis is spread only between humans but that the major reservoir for Cryptosporidium parvum is domestic livestock, predominantly cattle, and that direct contact with infected cattle is a major transmission pathway along with indirect transmission through drinking water. The situation is less clearcut for Giardia duodenalis but the evidence does not, in general, support zoonotic transmission as a major risk for human infections. However, for both parasites there is a need for molecular epidemiological studies to be undertaken in well-defined foci of transmission in order to fully determine the frequency and importance of zoonotic transmission.

Effects of pine bark extract administered to immunosuppressed adult mice infected with Cryptosporidium parvum

The treatment of cryptosporidiosis using pine bark extract (Pycnogenol) in immunosuppressed adult C57BL/6N mice infected with Cryptosporidium parvum was investigated. Five groups of 10 mice/group were used. Groups 1, 2, 3, and 5 served as normal, toxicity, placebo, and positive controls, respectively. Mice in groups 2-5 were immunosuppressed with dexamethasone phosphate administered ad libitum in drinking water at a dosage level of 12 microg/ml. Mice in groups 3-5 were inoculated per os with 10(6) C. parvum oocysts on the day immunosuppression was started. Mice in groups 2 and 4 were treated by administering Pycnogenol orally at 30 mg/kg/day. In group 4, Pycnogenol was first administered on day 3 postinoculation. Of the four groups of mice immunosuppressed with DEXp (groups 2-5), the two groups treated with Pycnogenol (groups 2 and 4) had no premature deaths. The other two groups (groups 3 and 5) had 3 and 4 mice die, respectively, before the experiment ended. Consequently, Pycnogenol was judged to be non-toxic at the dosage level used and even afforded mice some positive health benefits. Fecal oocyst shedding in groups 3-5 was initially detected on day 3 postinoculation. These mice continued to shed oocysts throughout the duration of the 28-day experiment. Oocyst shedding intensities were greater in group 3 and 5 than in group 4. However, histological examination of infected intestinal tissues in groups 3-5 revealed no significant difference with regard to parasite colonization and villus/crypt (V/C) length ratios. As a result, Pycnogenol was determined to be therapeutically effective against C. parvum at 30 mg/kg/day only when measured by fecal oocyst shedding intensity. There was no effect on parasite tissue colonization and V/C ratios in infected mice. We conclude that Pycnogenol is a useful dietary supplement for C. parvum-infected patients by affording some positive health benefits, significantly reduces fecal oocyst shedding, but does not decrease parasite colonization of intestinal tissue.

Infectivity of Cryptosporidium parvum oocysts following cryopreservation

This study was undertaken to investigate the cryopreservation of Cryptosporidium parvum oocysts. Oocysts purified from mouse feces were suspended in distilled water, 10% glycerin, and 2.5% potassium dichromate. They were stored at -20 C and -80 C for 2, 7, and 30 days, respectively. In addition to the purified oocysts, the feces of C. parvum-infected mice were preserved under the same conditions described above. Purified and fecal oocysts were thawed at 4 C, and their viability was assessed by a nucleic acid stain, excystation test, tissue culture infectivity test, and infectivity to immunosuppressed adult mice. Oocysts purified from fecal material prior to cryopreservation lost most of their viability and all of their infectivity for tissue culture and mice. However, when oocysts were cryopreserved in feces, between 11.7 and 34.0% were judged to be viable and retained their infectivity for mice when stored at -20 C (but not -80 C) for 2, 7, and 30 days. Clearly, fecal material provides a cryoprotective environment for C. parvum oocysts stored at -20 C for at least 30 days.

Molecular characterization of Cryptosporidium isolates obtained from humans in France

Cryptosporidium parvum is usually considered the agent of human cryptosporidiosis. However, only in the last few years, molecular biology-based methods have allowed the identification of Cryptosporidium species and genotypes, and only a few data are available from France. In the present work, we collected samples of whole feces from 57 patients from France (11 immunocompetent patients, 35 human immunodeficiency virus [HIV]-infected patients, 11 immunocompromised but non-HIV-infected patients) in whom Cryptosporidium oocysts were recognized by clinical laboratories. A fragment of the Cryptosporidium 18S rRNA gene encompassing the hypervariable region was amplified by PCR and sequenced. The results revealed that the majority of the patients were infected with cattle (29 of 57) or human (18 of 57) genotypes of Cryptosporidium parvum. However, a number of immunocompromised patients were infected with C. meleagridis (3 of 57), C. felis (6 of 57), or a new genotype of C. muris (1 of 57). This is the first report of the last three species of Cryptosporidium in humans in France. These results indicate that immunocompromised individuals are susceptible to a wide range of Cryptosporidium species and genotypes.

Cryptosporidium infection in Bedouin infants assessed by prospective evaluation of anticryptosporidial antibodies and stool examination

An enzyme-linked immunosorbent assay system using oocyst lysate as antigen was used to detect serum- specific antibody responses to Cryptosporidium parvum between 1989 and 1994 in consecutive sera obtained at birth, and at the age of 6, 12, and 23 months, from 52 infants living in a Bedouin town located in the south of Israel. The serologic tests revealed high levels of immunoglobulin G anti-Cryptosporidium at birth that dropped significantly by the age of 6 months and then rose continuously to a geometric mean titer of 481 at age 23 months. The serum immunoglobulin M Cryptosporidium antibodies rose continuously from nearly undetectable levels at birth to a geometric mean titer of 471 (157-fold increase) at age 23 months. All the subjects already showed at 6 months a significant rise in immunoglobulin M. A significant rise in immunoglobulin A titers was detected in 48% and 91% of subjects at 6 and 23 months, respectively. By monthly surveillance, microscopy using the modified Ziehl-Neelsen method and confirmed by indirect immunofluorescence assay detected Cryptosporidium antigens in only 11% at age 6 months and 48% at age 23 months. The extent of exposure to Cryptosporidium immediately after birth as detected by serology is much higher than that predicted by frequent prospective assessment of stool samples.

The importance of clinicopathological correlation in the diagnosis of inflammatory conditions of the colon: histological patterns with clinical implications

Histological reaction patterns within the colon are not disease-specific but reflect mechanisms of injury and duration of disease. By correlating these patterns with known causes of colonic inflammation, we provide guidelines to enhance the diagnostic value of colonoscopic samples. Normal histological features are reviewed, and the sequence of inflammation and repair is used as the basis for appreciating pathological deviations. The common histological patterns of acute colitis with and without features of pseudomembranous or ischemic colitis and the morphological features of chronic colitis with and without crypt destruction are collated with clinical and endoscopic features to emphasize the importance of dialogue between the pathologist and gastroenterologist. Less common patterns, including eosinophilic colitis, graft-versus-host disease, chronic mucosal prolapse, portal hypertensive colopathy, and nonspecific or idiopathic ulcer, illustrate variations in the basic reaction patterns. Difficulties in differential diagnosis are underscored, and biopsy strategies are suggested.

Digestive System 1

This chapter deals with the digestive system. The major and minor salivary glands and their secretions also represent and integral part of the protective mechanism of the oral cavity, and derangement of saliva production may lead to loss of integrity of the oral mucosa. Drug-induced abnormalities of taste sensation are also well-described phenomena occurring in man although human studies are necessary for the detection of these effects. Inflammation of the oral cavity may involve the buccal mucosa, the gingiva (gingivitis), the tongue (glossitis), and the peridontal tissues (peridontitis). Therapeutic agents can induce inflammatory lesions in the tongue. Moreover, a protective layer of mucus, a visco-elastic material containing high molecular weight glycoproteins produced by the major and minor salivary glands, covers the stratified squamous mucosa of the oral cavity. Salivary secretions also possess digestive enzyme activity although in herbivores and carnivores, it is usually low in contrast to high digestive enzyme activity in omnivorous species.

Prevalence of Cryptosporidium spp. oocysts in cattle and wildlife in Morogoro region, Tanzania

Prevalences of Cryptosporidium spp. oocysts in cattle (n = 486) on five selected farms in Morogoro municipality and three species of herbivorous wildlife (n = 87) from Mikumi National Park, Morogoro, Tanzania, were determined using the modified Ziehl-Neelsen staining technique. Of 486 bovine faecal samples, 5.3% were positive for Cryptosporidium spp. The prevalence of Cryptosporidium was higher in calves less than 3 months of age compared to weaned calves and adults. Cryptosporidium spp. oocysts were detected in both diarrhoeic and non-diarrhoeic animals, but there was a significantly higher prevalence (P < 0.001) of oocyst shedding in diarrhoeic than in non-diarrhoeic animals. Of the 87 faecal specimens from the wildlife species, 36 were from the African buffaloes (Syncerus caffer), 25 from zebra (Equus zebra) and 26 from the wildebeest (Connochaetes gnou). Cryptosporidium spp. oocysts were detected in eight (22%) buffaloes, seven (28%) zebras and seven (27%) wildebeests. Confirmation of the diagnosis was performed using anti-Cryptosporidium monoclonal antibody specific for Cryptosporidium muris. Cryptosporidium parvum and Cryptosporidium baileyi (Pathasure Cryptosporidium test kit).

Cryptosporidiosis reservoir in wild brown rats (Rattus norvegicus) in the UK

Rats (n = 73) were trapped from nine rural farms around Oxfordshire and faeces were examined using the auramine-phenol and the Modified Ziehl-Neelsen techniques. Cryptosporidium parvum oocysts were detected in the faeces from 46 (63%) rats. This suggests that wild rats represent a risk to human and livestock health through the carriage and transmission of this zoonotic protozoan.

Duodenal morphology and intensity of infection in AIDS-related intestinal cryptosporidiosis

BACKGROUND

The pathogenesis of intestinal cryptosporidiosis is not known. Previous studies have shown that the intensity of infection varies between patients. The hypothesis of this study is that intestinal injury is related to the intensity of infection.

METHODS

The histological abnormalities associated with Cryptosporidium infection were evaluated in duodenal biopsy specimens from 18 patients with acquired immunodeficiency syndrome-associated cryptosporidiosis. The intensity of Cryptosporidium infection was assessed histologically in all patients as the percentage of mucosa covered by organisms and by quantitation of oocyst excretion in the stools of 14 patients.

RESULTS

Duodenal biopsy specimens from 13 patients (72%) showed normal villous architecture. In these patients, the inflammatory component of the lamina propria was either normal or moderately increased. This increase consisted mostly of lymphocytes and plasma cells. Five of 18 patients (28%) had flattening of the mucosa associated with a prominent neutrophilic infiltrate. The intensity of infection in patients with villous flattening as measured from biopsy specimens and stool was significantly higher than in those without flattening (92% vs. 12% mucosa occupied with organisms; 738 x 10(3) vs. 199 x 10(3) oocyst/mL stool) (P < 0.004 in both cases).

CONCLUSIONS

Most patients with intestinal Cryptosporidium infection had normal duodenal villous architecture. Severe duodenal morphological abnormalities, including flattening of the villi, were associated with high-intensity infections.

Characterization and immunolocalization of a Cryptosporidium protein containing repeated amino acid motifs

The oocyst wall is one of the components that permits cryptosporidia both to survive in the environment and to retain infectivity. With the aim of identifying Cryptosporidium proteins specifically expressed at the oocyst stage, we screened lambda gt11 genomic libraries of Cryptosporidium parvum with both an oocyst antiserum and a specific genetic probe. We isolated, from distinct libraries, two overlapping clones containing an open reading frame encoding a 1,252-amino-acid polypeptide. The analysis of the deduced amino acid sequence revealed unusually high contents of cysteine, proline, and histidine. The sequence was also characterized by two distinct amino acid motifs, each repeated several times. The DNA sequences coding for the amino acid repeats showed a high frequency of synonymous mutations, a result suggesting that the repeated motifs may be functionally and/or structurally important to the parasite. Antisera and monoclonal antibodies developed against a recombinant polypeptide encompassing the first 786 amino acids revealed that the corresponding protein in C. parvum had an apparent molecular weight of 190,000. Moreover, confocal microscopy analysis with immunofluorescence indicated that the protein was localized on the oocyst wall as a uniform stain and within the oocyst itself as bright granules in close association with the residual body.

Cryptosporidium: different behaviour in calves of isolates of human origin

The behaviour in calves of 3 Cryptosporidium human isolates was analysed in comparison with a bovine isolate. Twenty-four neonatal calves were infected. An isolate from a patient infected with human immunodeficiency virus (HIV) and showing mild cryptosporidiosis caused severe diarrhoea with a high production of oocysts in neonatal calves, as did a bovine isolate (group 1). Two human isolates, obtained from HIV patients with severe cryptosporidiosis, caused mild diarrhoea with low oocyst production in neonatal calves (group 2). The difference between the 2 groups in numbers of oocysts shed in calves was statistically significant (P = 0.005), as was the duration of oocyst shedding (P = 0.0004). Oocysts of group 2 isolates were less resistant to storage in 2% potassium dichromate at 4 degrees C than were oocysts of group 1. The biological and epidemiological implications are discussed.

Treatment of diarrhoea in human immunodeficiency virus-infected patients with immunoglobulins from bovine colostrum

Diarrhoea and weight loss are found in more than 50% of patients with the acquired immunodeficiency syndrome (AIDS). In some patients the symptoms can be very severe, leading to death even in the absence of opportunistic infections. In 30% of these patients, enteric pathogens cannot be identified, and approximately only half of the identifiable aetiologic agents of diarrhoea in patients infected with the human immunodeficiency virus (HIV) were treatable with antibiotics. Immunoglobulins from bovine colostrum (Lactobin, Biotest, Dreieich, FRG) contain high titers of antibodies against a wide range of bacterial, viral and protozoal pathogens as well as against various bacterial toxins. Lactobin (LIG) is quite resistant to 24-h incubation with gastric juice. In a multi-center pilot study 37 immunodeficiency patients with chronic diarrhoea [29 HIV-infected patients, 2 patients with common variable immunodeficiency (CVID), one unidentified immunodeficiency, five patients with graft versus host disease (GvHD) following bone marrow transplantation] were treated with oral LIG (10 g/day for 10 days). Good therapeutic effects were observed. Out of 31 treatment periods in 29 HIV-infected patients 21 gave good results leading to transient (10 days) or long-lasting (more than 4 weeks) normalisation of the stool frequency. The mean daily stool frequency decreased from 7.4 to 2.2 at the end of the treatment. Eight HIV-infected patients showed no response. The diarrhoea recurred in 12 patients within 4 weeks (32.4%), while 19 patients were free of diarrhoea for at least 4 weeks (51.3%). In 5 patients intestinal cryptosporidiosis disappeared following oral LIG treatment. LIG treatment was also beneficial in 4 out of 5 GvHD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Swimming-associated cryptosporidiosis

In July and August 1988, an outbreak of gastroenteritis affected 44 of 60 (73%) persons from 5 separate swimming groups who had used the same swimming pool in Los Angeles. Cryptosporidium was identified in 5 of 8 (63%) stool specimens, and the clinical picture was consistent with Cryptosporidium infection. Resistance of Cryptosporidium to chlorine, an inadequately maintained pool filtration system, repeated exposure to pool water, and possible continuing pool contamination may have contributed to ongoing transmission. Cryptosporidium should be considered a potential etiologic agent of gastroenteritis associated with recreational water use.

Cryptosporidiosis: Pathogenesis and immunology

Cryptosporidium parvum is an increasingly recognized agent of intestinal infection in normal and immunocompromised humans, and in many other animals. The intraepithelial cell infection results in villous atrophy, mild submucosal inflammation, reduction of brush-border enzymes and a characteristic persistent watery diarrhea. The infection is self-limiting in immunocompetent hosts, probably because of specific acquired immunity; specific serum and secretory antibody responses develop that may be required for clearance and protection against reinfection. Passive milk antibody, especially i f in high titers, may be partially protective but severe, persistent infection in athymic rodents and humans with AIDS demonstrate that T cells are essential for controlling the infection. Specific anti-bodies and lymphocyte extracts have been tested in cases of cryptosporidiosis but the interpretation of the results remains controversial. Here, Shu-Xian Zu, Guo-Dong Fang, Ronald Foyer and Richard Guerrant emphasize that effective treatment and prevention remain dependent on advances in our understanding of the host cell-parasite relationship.

Ultrastructural pathology of human immunodeficiency virus infection

The electron microscope has been used with great skill in many aspects of the acquired immunodeficiency syndrome. It has played a critical role in classifying the human immunodeficiency virus, in characterizing the morphogenesis and gene products of the virus, and in elucidating the host cell targets and interactions. With the aid of the electron microscope, new opportunistic pathogens are being identified, and particularly difficult diagnoses are being made. Extrapolations from observations made at the ultrastructural level to the light microscopic level have provided criteria for the diagnosis of several infectious agents. As with any powerful scientific tool, observations must be interpreted with great care by scientists experienced in electron microscopy.

Cryptosporidiosis--an educational experience

Eleven children aged 7 to 8 years from one school class developed diarrhoea and vomiting after an educational visit to a dairy farm. Three required hospital admission and intravenous fluid replacement for dehydration. Cryptosporidium oocytes were found in the faeces of these three children and from one classmate when the remainder of the class was tested between 16 and 21 days after the visit. At the farm some children tasted pelleted cow feed, silage and dried milk powder. A case-control study showed a significant correlation between diarrhoea and the tasting of silage and pelleted feed. Guidance on the safe conduct of educational visits to farms is given.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.

Small-intestinal brushing cytology in the diagnosis of cryptosporidiosis in AIDS

We report the cytologic findings of small intestinal brushing material showing cryptosporidiosis in two patients with acquired immunodeficiency syndrome (AIDS). Cryptosporidia measuring approximately 2-4 mu were aligned along the surface of the glandular cells, although many freely dispersed organisms were also present. The differential diagnoses of other structures that could be confused with cryptosporidia are also presented in this article. Small-intestinal brushing cytology may complement endoscopic biopsy in the workup of diarrheal diseases in AIDS, especially in patients with thrombocytopenia, since the bleeding disorder may be a contraindication for endoscopic biopsy.

Resistance of calves to Cryptosporidium parvum: effects of age and previous exposure

Cryptosporidium parvum is a coccidian parasite that causes diarrheal disease in many vertebrate species, including young (less than or equal to 1 month old) calves. Older calves and adult cattle are resistant to infection. In this study, newborn calves were raised in isolation from C. parvum for 1 week to 3 months before experimental challenge with the parasite. Calves orally challenged with C. parvum at 1 week of age shed oocysts in their feces and had diarrhea after challenge exposure. When these calves were rechallenged at 1 and 3 months of age, they neither shed oocysts nor had diarrhea. There was no significant increase in the mean anticryptosporidium enzyme-linked immunosorbent assay serum antibody titer in these calves following any of the challenge exposures. Calves orally inoculated with C. parvum for the first time at 1 month of age shed oocysts, had diarrhea after challenge exposure, and were resistant to rechallenge at 3 months of age. These calves had a twofold increase in serum antibody titer after the first challenge and no increase after the second challenge. Calves orally inoculated with C. parvum for the first time at 3 months of age shed oocysts, and two of seven animals had diarrhea. These calves had a 10-fold increase in serum antibody to C. parvum after exposure. This study demonstrates that calves raised in isolation from C. parvum remain susceptible to challenge until at least 3 months of age. Furthermore, within this time period, initial exposure and recovery renders calves resistant to further challenge with the parasite. The data also suggest that exposure of young calves to C. parvum may inhibit the development of a serum antibody response to the parasite.

Cryptosporidiosis and AIDS

Cryptosporidiosis in patients with AIDS presents as a chronic enteritis, with biliary complications in about 10% of sufferers. The disease is persistent and progressively fatal. Due to the widespread prevalence of the parasite in the community and amongst domesticated animals, persons with AIDS are constantly at risk. Treatment is extremely difficult in view of the apparent lack of a specific anticryptosporidial drug. Methods of immunomodulation are worth considering, but the main recourse may have to be a prolonged regimen of rehydration and parenteral nutrition. However, if T helper cell function improves, the disease may go into remission or the parasite could be eliminated. Vaccination of those at risk is not feasible at present.

Intestinal microsporidiosis as a cause of diarrhea in human immunodeficiency virus-infected patients: a report of 20 cases

Chronic diarrhea accompanied by weight loss is a common and often debilitating problem associated with human immunodeficiency virus (HIV) infection. Enterocytozoon bieneusi, a newly identified species of the phylum of protozoa, Microspora, has been reported associated with chronic diarrhea and wasting in 11 acquired immunodeficiency syndrome (AIDS) patients in the United States, Europe, and Africa. Diagnosis has been based solely on the ultrastructural identification of this small, intracellular parasite in bowel biopsies. Seventy-one small bowel biopsies from 67 homosexual AIDS and AIDS-related complex patients with chronic diarrhea and with no pathogens identified by light microscopy on paraffin sections, were embedded in plastic and studied by light and transmission electron microscopy. Enterocytozoon bieneusi microsporidiosis was diagnosed by electron microscopy in 20 (22 biopsies) of the patients. More jejunal biopsies (16 of 36) were positive than duodenal biopsies (six of 35). Parasites and spores were clearly visible at the light microscopic level in the semi-thin plastic sections from 17 and 21 of the biopsies, respectively. In retrospect, parasites could be identified by light microscopy in standard hematoxylin and eosin-stained paraffin sections. Infection was confined to enterocytes covering the villi, especially the tips, and was associated with villous atrophy and cell degeneration, necrosis, and sloughing. Release of spores into the bowel lumen was evident. Colorectal biopsies from two of the patients with small bowel microsporidiosis were negative for microsporidia. Enterocytozoon bieneusi infection of the small bowel may be an important cause of diarrhea in HIV-infected persons.

Epidemiological aspects of human cryptosporidiosis

The coccidian protozoan parasiteCryptosporidiumhas been described in many host species since its discovery in the early part of the century, but it remained obscure until the recognition by veterinary workers in the 1970s of its importance as a cause of scours in young livestock animals [1–4].

Parasite infections in AIDS

'Illnesses no one's got' was the epidemiological clue that led to the identification of AIDS as a new disease in 1981 when a rare infectious organism Pneumocystis carinii was seen in previously healthy homosexuals. Since then a wide range of parasite infections has been recognized in AIDS patients. However, these patients are not susceptible to just any passing parasite. The human immunodeficiency virus (HIV) produces a specific immune defect and only parasites that can exploit that defect will be able to flourish. In this review Diana Lockwood and Jonathan Weber explore the spectrum of parasite diseases recognized in AIDS and also consider those parasites that occur infrequently in AIDS. Analysis of parasitic infections that AIDS patients do not suffer from will yield valuable information about immune recognition and handling of these parasites.

Pulmonary excretion of H2 in calves with Cryptosporidium-induced malabsorption

Pulmonary hydrogen gas (H2) concentrations were used to assess the malabsorption of dietary nutrients in preruminating calves inoculated with Cryptosporidium sp. Normal values were established in five control calves and seven calves (principals) were inoculated with 1.0 x 10(8) Cryptosporidium sp. oocysts. Hydrogen concentrations and wet fecal weights were measured at three stages: before Cryptosporidium sp. inoculation (stage 1), three days after the onset of diarrhea (stage 2), and after the resolution of diarrhea (stage 3). Mean end-breath and total-breath H2 concentrations in the principal calves were higher (P less than 0.025 and P less than 0.05) for stage 2, when compared to control values. Both end-breath and total-breath H2 concentrations were increased (P less than 0.001 and P less than 0.025, respectively) in the principal calves during stage 2 when compared to values obtained for stages 1 and 3. Concurrently, Cryptosporidium sp. infection was associated with increased (P = 0.06) fecal output during stage 2, only. The increased H2 concentrations and cumulative fecal output show that Cryptosporidium sp. caused malabsorption of fermentable nutrients.