Human microsporidial infections

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Characterization of a new insect cell line (NTU-YB) derived from the common grass yellow butterfly, Eurema hecabe (Linnaeus) (Pieridae: Lepidoptera) and its susceptibility to microsporidia

A new lepidopteran cell line, NTU-YB, was derived from pupal tissue of Eurema hecabe (Linnaeus) (Pieridae: Lepidoptera). The doubling time of YB cells in TNM-FH medium supplemented with 8% FBS at 28 degrees C was 26.87h. The chromosome numbers of YB cells varied widely from 21 to 196 with a mean of 86. Compared to other insect cell lines, the YB cells produced distinct esterase, malate dehydrogenase, and lactate dehydrogenase isozyme patterns. Identity of the internal transcribed spacer region-I (ITS-I) of YB cells to E. hecabe larvae was 96% and to Eurema blanda larvae (tissue isolated from head) was 81%. The YB cells were permissive to Nosema sp. isolated from E. blanda and the infected YB cells showed obvious cytopathic effects after 3weeks post inoculation. The highest level of spore production was at 4weeks post inoculation when cells were infected with the Nosema isolate, and spore production was 1.34+/-0.9x10(6)spore/ml. Ultrastructrual studies showed that YB cells can host in vitro propagation of the E. blanda Nosema isolate, and developing stages were observed in the host cell nuclei as observed in the natural host, E. blanda. The NTU-YB cell line is also susceptible to Nosema bombycis.

Sexual transmission of intestinal parasites in men who have sex with men

Direct oral-anal sexual contact is a common practice among men who have sex with men (MSM) and is implicated in the transmission of various enteric pathogens including intestinal parasites. The present study reviewed data on the sexual transmission of intestinal parasites among MSM, and highlighted advances in the diagnosis of such infections. The emergence and spread of intestinal parasites is of public health concern particularly in the homosexual community. Intestinal parasitic infection should be considered in the differential diagnosis of gastrointestinal disease in this population. Combination of traditional diagnostic procedures with implementation of testing based on novel molecular methods in the accurate identification of intestinal parasites is important so that early intervention and control of infection is facilitated.

Fatal Pulmonary Microsporidiosis Due toEncephalitozoon cuniculiFollowing Allogeneic Bone Marrow Transplantation for Acute Myelogenous Leukemia

Microsporidia are ubiquitous obligate eukaryotic intracellular parasites that are now felt to be more akin to degenerate fungi than to protozoa. Microsporidia can be highly pathogenic, causing a broad range of symptoms in humans, especially individuals who are immunocompromised. The vast majority of human cases of microsporidiosis have been reported during the past 20 years, in patients with HIV/AIDS, while only relatively rare cases have been described in immunocompetent individuals. However, microsporidia infections are being increasingly reported in patients following solid-organ transplanation, where the main symptom has been diarrhea. The authors report the first case of pulmonary microsporidial infection in an allogeneic bone marrow transplant recipient in the United States and only the second case in the world. The patient, with a history of Hodgkin disease followed by acute myelogenous leukemia received a T-cell-depleted graft, but succumbed to respiratory failure 63 days post transplantation. An open lung biopsy, taken just before death, was originally thought to show toxoplasmosis. The correct diagnosis of microsporidiosis was made postmortem by light and electron microscopy. DNA polymerase chain reaction analysis confirmed the diagnosis and furthermore revealed it to be the dog strain of the microsporidia species Encephalitozoon cuniculi. Although to date rarely diagnosed, microsporidial infection should also be considered in the differential diagnosis of, e.g., unexplained pulmonary infection in bone marrow transplant patients.

Asymmetrical coexistence of Nosema ceranae and Nosema apis in honey bees

Globalization has provided opportunities for parasites/pathogens to cross geographic boundaries and expand to new hosts. Recent studies showed that Nosema ceranae, originally considered a microsporidian parasite of Eastern honey bees, Apis cerana, is a disease agent of nosemosis in European honey bees, Apis mellifera, along with the resident species, Nosema apis. Further studies indicated that disease caused by N. ceranae in European honey bees is far more prevalent than that caused by N. apis. In order to gain more insight into the epidemiology of Nosema parasitism in honey bees, we conducted studies to investigate infection of Nosema in its original host, Eastern honey bees, using conventional PCR and duplex real time quantitative PCR methods. Our results showed that A. cerana was infected not only with N. ceranae as previously reported [Fries, I., Feng, F., Silva, A.D., Slemenda, S.B., Pieniazek, N.J., 1996. Nosema ceranae n. sp. (Microspora, Nosematidae), morphological and molecular characterization of a microsporidian parasite of the Asian honey bee Apis cerana (Hymenoptera, Apidae). Eur. J. Protistol. 32, 356-365], but also with N. apis. Both microsporidia produced single and mixed infections. Overall and at each location alone, the prevalence of N. ceranae was higher than that of N. apis. In all cases of mixed infections, the number of N. ceranae gene copies (corresponding to the parasite load) significantly out numbered those of N. apis. Phylogenetic analysis based on a variable region of small subunit ribosomal RNA (SSUrRNA) showed four distinct clades of N. apis and five clades of N. ceranae and that geographical distance does not appear to influence the genetic diversity of Nosema populations. The results from this study demonstrated that duplex real-time qPCR assay developed in this study is a valuable tool for quantitative measurement of Nosema and can be used to monitor the progression of microsprodian infections of honey bees in a timely and cost efficient manner.

Cytometric approach for detection of Encephalitozoon intestinalis, an emergent agent

Encephalitozoon intestinalis is responsible for intestinal disease in patients with AIDS and immunocompetent patients. The infectious form is a small spore that is resistant to water treatment procedures. Its detection is very important, but detection is very cumbersome and time-consuming. Our main objective was to develop and optimize a specific flow cytometric (FC) protocol for the detection of E. intestinalis in hospital tap water and human feces. To determine the optimal specific antibody (Microspor-FA) concentration, a known concentration of E. intestinalis spores (Waterborne, Inc.) was suspended in hospital tap water and stool specimens with different concentrations of Microspor-FA, and the tap water and stool specimens were incubated under different conditions. The sensitivity limit and specificity were also evaluated. To study spore infectivity, double staining with propidium iodide (PI) and Microspor-FA was undertaken. Distinct approaches for filtration and centrifugation of the stool specimens were used. E. intestinalis spores stained with 10 microg/ml of Microspor-FA at 25 degrees C overnight provided the best results. The detection limit was 5 x 10(4) spores/ml, and good specificity was demonstrated. Simultaneous staining with Microspor-FA and PI ensured that the E. intestinalis spores were dead and therefore noninfectious. With the stool specimens, better spore recovery was observed with a saturated solution of NaCl and centrifugation at 1,500 x g for 15 min. A new approach for the detection of E. intestinalis from tap water or human feces that ensures that the spores are not viable is now available and represents an important step for the prevention of this threat to public health.

Identification of Encephalitozoon cuniculi genotype III and two novel genotypes of Enterocytozoon bieneusi in swine

Samples of intestinal content from thirty fattened pigs of six farms slaughtered at an abattoir in North-Western Germany, and faecal samples of four pigs kept as laboratory animals at the Federal Institute for Risk Assessment (BfR, Berlin, Germany) were investigated for the occurrence of microsporidia by light microscopy, PCR and sequencing. A modified Webers trichrome staining and the immunohistochemistry (the Avidin-Biotin-Peroxidase-Complex technique with a polyclonal anti-Encephalitozoon cuniculi-serum and monoclonal antibodies against Encephalitozoon intestinalis and Enterocytozoon bieneusi) was used as a screening method for the light microscopical detection of these pathogenic eukaryotes. By this light microscopically methods microsporidia suspected organisms were found in all samples (100%). By the use of PCR, microsporidia were identified in fourteen samples (41.2%). The prevalence of microsporidia infections among the farms diversifies from 0 to 80% as considered by PCR. E. bieneusi was the most prevalent species and was identified in twelve fattened pigs (40%) from five of the six tested farms (83.3%) and in two of the four laboratory animals (50%). Three of the E. bieneusi species belonged to the genotype O, one to the genotype E, and one to the genotype F. Two isolates were identified as novel genotypes and two samples showed a mixed infection of different genotypes. In three faecal samples of the pigs from two farms E. cuniculi genotype III was identified. One sample contained both microsporidia species. To our knowledge, this is the first time that the genotype III of E. cuniculi was identified in swine.

Environmentally Transmitted Pathogens

Pathogenic microorganisms usually originate from an infected host or directly from the environment; however, only a small proportion of these microbes cause infection. This chapter discusses the pathogens that are transmitted through the environment such as bacteria, viruses, and protozoa. Many human pathogens can be transmitted only by direct or close contact with an infected person or animal such as herpesvirus. Virus transmission by the airborne route may be both direct and indirect inhalation of infectious droplets or through contact with contaminated fomites. Water-borne diseases—such as yellow fever, dengue, filariasis, malaria, onchocerciasis, and sleeping sicknessare transmitted by insects that breed in water or live near water. The common bacterial pathogens transmitted through water include Salmonella, Escherichia coli, Shigella, Campylobacter, Yersinia, Vibrio, Helicobacter, and Legionella. Opportunistic pathogens are also numerous in the environment, and the most important opportunistic pathogen is Pseudomonas aeruginosa. Viruses are a leading cause of gastroenteritis and water-borne outbreaks may be caused by norovirus, hepatitis A virus, Coxsackie virus, echovirus, and adenoviruses. Respiratory diseases are also associated with a large number of viruses such as rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus (RSV), influenza virus, and adenovirus. Generally, viral and protozoan pathogens survive longer in the environment than enteric bacterial pathogens.

Morphological and molecular studies of a microsporidium (Nosema sp.) isolated from the thee spot grass yellow butterfly, Eurema blanda arsakia (Lepidoptera: Pieridae)

A microsporidium possessing molecular and morphological characteristics of the genus Nosema was isolated from larvae of the thee-spot grass yellow butterfly, Eurema blanda arsakia. The complete rRNA gene sequences of the E. blanda isolate contained 4,428 base pairs (GenBank Accession No. EU338534). The organization of the rRNA genes is LSU rRNA-ITS-SSU rRNA-IGS-5S, which corresponds with that of Nosema species closely related to Nosema bombycis. Phylogenetic analysis based on rRNA gene sequences show that this isolate is closely related to Nosema bombycis, Nosema plutellae, Nosema spodopterae, and Nosema antheraeae. The ultrastructure of all developmental stages of this microsporidium confirmed its placement in the genus Nosema. The isolate was successfully propagated in cell lines IPLB-LD652Y (Lymantria dispar) and NTU-LY (Lymantria xylina) and, in the in vitro system, it was frequently found to develop in the nuclei of the host cells, a circumstance that seldom occurs in other Nosema species. An extra-cellular vegetative stage of this microsporidium was also observed in the culture medium after 14 days of infection. The ECMDFs might be released from disrupted host cells.

Encephalitozoon cuniculi-associated placentitis and perinatal death in an alpaca (Lama pacos)

Placentitis, premature birth, and perinatal death were associated with Encephalitozoon cuniculi infection in an alpaca. Histologically, chorionic trophoblasts contained many Gram-positive, period acid-Schiff positive, variably acid-fast spores. Multifocal necrosis and infiltration by lymphocytes, eosinophils, and neutrophils were scattered throughout the chorionic membrane. Spores in trophoblasts were approximately 1 microm x 2 microm, thick-walled, and contained polar filaments and polar vacuoles consistent with microsporidia. The presence of E. cuniculi DNA was confirmed by sequencing the polymerase chain reaction amplicon from frozen placental tissue. A few glial nodules were scattered throughout the cerebrum, and mild lymphocytic inflammation was present in the heart, liver, and lung. No organisms were detected in tissues other than the placenta. This is the first reported case of E. cuniculi infection in an alpaca.

Efficacy of gamma interferon and specific antibody for treatment of microsporidiosis caused by Encephalitozoon cuniculi in SCID mice

Microsporidia are eukaryotic, obligate, intracellular protists that are emerging pathogens in immunocompromised hosts, including AIDS patients and organ transplant recipients. The efficacy of gamma interferon (IFN-gamma) for the treatment of microsporidiosis caused by Encephalitozoon cuniculi was studied by means of adoptive transfer and IFN-gamma administration in SCID mice. While the adoptive transfer of CD4(+) T cells from immunocompetent mice prolonged survival of SCID mice infected perorally with E. cuniculi, survival was not improved by adoptive transfer of CD4(+) T lymphocytes from IFN-gamma-deficient mice. The protective effect of IFN-gamma was confirmed in cytokine therapy experiments in which SCID mice receiving IFN-gamma survived significantly longer than mice receiving mock injections. The administration of serum containing specific antibodies against E. cuniculi was found to prolong the survival of concurrently IFN-gamma-treated SCID mice. The data presented in this study suggest that IFN-gamma is potentially useful as a cytokine therapy for microsporidiosis, especially in CD4(+) T-cell-deficient patients.

Occurrence and genotypic characteristics of Enterocytozoon bieneusi in pigs with diarrhea

There is limited information available on the association between Enterocytozoon bieneusi and diseases in animals or on the characteristics of the strains involved. This study examined the occurrence of E. bieneusi in piglets with and without diarrhea to determine its involvement. Among 472 fecal samples from 472 piglets (237 with diarrhea and 235 without) up to 7 weeks of age, 67 (approximately 14%) were polymerase chain reaction (PCR) positive for E. bieneusi. Of the 237 piglets with diarrhea, 38 (approximately 16%) tested positive for E. bieneusi. Of the 235 healthy piglets, 29 (approximately 12%) tested positive for E. bieneusi. This species was detected only in the younger group of piglets with diarrhea, particularly those aged less than 1 week and between 1 and 2 weeks. This suggests that E. bieneusi is a possible cause of diarrhea in piglets. This organism, however, produced asymptomatic infections in the older piglets, as there was no significant difference in the rates of occurrence between the diarrheic and nondiarrheic older piglets (aged older than 4 weeks). The internal transcribed spacer (ITS) region of the ribosomal ribonucleic acid gene of the ten E. bieneusi-positive samples was amplified using nested PCR and subsequently sequenced. Genetic polymorphisms, which were represented by five distinct genotypes (PEbA-PEbE), were found among the E. bieneusi isolates. The five genotypes identified in this study differed from each other by two to six single-nucleotide polymorphisms. Nine isolates from four genotypes (PEbA-PEbD) were homologous to previously known types that had originally been isolated from pigs. However, one isolate from the PEbE genotype was identical to type CAF1, which was originally isolated from humans. In addition, the phylogenetic relationships determined by the neighbor-joining analysis of the ITS sequences indicated this genotype to be more distant from the other pig-specific genotypes. Thus, this isolate from pigs may be distantly related to the pig-specific genotypes and may be capable of infecting humans.

Detection of Encephalitozoon cuniculi in a new host--cockateel (Nymphicus hollandicus) using molecular methods

A total of 123 avian faecal specimens randomly collected in Bohemian commercial aviaries, Zoo parks and countryside were screened for the presence of human pathogenic microsporidia by both calcofluor M2R staining and polymerase chain reaction. Of these, no positive sample was detected using microscopical examination, and one isolate was detected by polymerase chain reaction and identified as Encephalitozoon cuniculi. Cockateel (Nymphicus hollandicus) represents a new avian host of this microsporidian.

Detection of the intranuclear microsporidium Nucleospora salmonis in naturally and experimentally exposed Chinook salmon Oncorhynchus tshawytscha by in situ hybridization

Nucleospora salmonis, an intranuclear microsporidian parasite of salmonid fish, is often difficult to observe in histological sections or wet mount preparations from lightly infected tissues because of its small size and location within the nuclei of lymphoblast-type cells. Diagnosis of infections by conventional light microscopy is directly dependent upon distinguishing different stages of the parasite from host cell nuclear material or vacuoles. To assist detection of stages of the parasite in tissues of its primary host, the Chinook salmon (Oncorhynchus tshawytscha), we developed a nonradioactive in situ hybridization (ISH) method. The new method was then used to detect N. salmonis among Chinook salmon after both natural and experimental exposures to the parasite. Probes derived from the small subunit ribosomal DNA (ssu-rDNA) sequence of the microsporidium were labeled with digoxigenin deoxyuridine triphosphate (DIG-dUTP) and hybridized to parasite DNA present in infected tissues. The ISH procedure effectively identified merogonic and spore stages of N. salmonis in paraffin-embedded tissues of clinically and subclinically infected fish. A Nucleospora-like microsporidium was also detected by ISH in tissues of a nonsalmonid fish, the English sole (Pleuronectes vetulus), using probes designed to a region of the ssu-rDNA of N. salmonis.

Study on the prevalence of Toxoplasma gondii and Neospora caninum and molecular evidence of Encephalitozoon cuniculi and Encephalitozoon (Septata) intestinalis infections in red foxes (Vulpes vulpes) in rural Ireland

Thoracic fluid (pleural fluid and clotted blood) from 206 foxes were examined for antibodies to Toxoplasma gondii and 220 thoracic fluid samples were tested for Neospora caninum antibodies using indirect immunofluorescent antibody tests (IFAT). A total of 115 (56%) and six (3%) foxes had antibodies to T. gondii and N. caninum, respectively. The brains from 148 foxes were examined for histological lesions and pathological changes suggestive of parasitic encephalitis were observed in 33 (22%). Two thirds of these foxes had antibodies to T. gondii and one fox had antibodies to both T. gondii and N. caninum. PCR assays carried out on DNA extracted from the 33 brains with histological lesions were negative for N. caninum but one of the brains was positive for T. gondii. Microsporidian DNA was also amplified from the brains of two of these foxes. Sequencing these amplicons revealed 100% homology with Encephalitozoon (Septata) intestinalis in one fox and Encephalitozoon cuniculi in the second fox. This is the first report of Encephalitozoon infections in wildlife in Ireland.

Pure CD4+ T lymphocytes fail to protect perorally infected SCID mice from lethal microsporidiosis caused by Encephalitozoon cuniculi

The role of CD4+ and CD8+ T lymphocytes in the protection against intraperitoneally (i.p.) or perorally (p.o.) acquired Encephalitozoon cuniculi (Levaditi et al., C R Soc Biol Paris 89:984-986, 1923) infection was studied by means of reconstitution of severe combined immunodeficiency (SCID) mice with well-defined populations of naive CD8+ or CD4+ T lymphocytes. Adoptive transfer of pure CD8+ T lymphocyte subpopulation protects SCID mice against a lethal microsporidiosis caused by E. cuniculi. The protective effect of CD8+ T lymphocytes is manifested in both i.p. and p.o. infection. On the contrary, the host defense against peroral infection does not require CD8+ T cells. The protective role is not mediated by CD4+ T lymphocytes only. SCID mice reconstitution with pure CD4+ T cell subpopulation led to prolonged survival of perorally infected mice. However, these mice died due to lethal encephalitozoonosis caused by i.p. infection.

Microsporidiosis in South Africa: PCR detection in stool samples of HIV-positive and HIV-negative individuals and school children in Vhembe district, Limpopo Province

Microsporidia were initially recognized as pathogens of insects and fish but have recently emerged as an important group of human pathogens, especially in immune-compromised individuals, such as those with HIV infection. In this study, we used a PCR-RFLP assay confirmed by quantitative real-time PCR and trichrome staining to determine the prevalence of microsporidian infections among hospital patients and school children in Vhembe region. Enterocytozoon bieneusi was the only microsporidian species detected in these stool samples. It was found in 33 (12.9%) of 255 samples from the hospitals and in 3 (4.5%) of 67 samples from primary school children and was significantly associated (P=0.039) with diarrhea in HIV-positive patients (21.6%) compared to HIV-negative individuals (9%). However, microsporidian infections were not associated with intestinal inflammation as indicated by the lactoferrin test. These results suggest that microsporidia might be a cause of secretory diarrhea in HIV-positive patients. To our knowledge, this is the first report of E. bieneusi in the Vhembe region of South Africa. Further investigations are needed in order to clarify the pathogenesis of E. bieneusi in HIV-positive patients.

Human-virulent microsporidian spores in solid waste landfill leachate and sewage sludge, and effects of sanitization treatments on their inactivation

Solid waste landfill leachate and sewage sludge samples were quantitatively tested for viable Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, and Encephalitozoon cuniculi spores by the multiplexed fluorescence in situ hybridization (FISH) assay. The landfill leachate samples tested positive for E. bieneusi and the sludge samples for E. bieneusi and E. intestinalis. The effects of four sanitization treatments on the inactivation of these pathogens were assessed. Depending on the variations utilized in the ultrasound disintegration, sonication reduced the load of human-virulent microsporidian spores to nondetectable levels in 19 out of 27 samples (70.4%). Quicklime stabilization was 100% effective, whereas microwave energy disintegration was 100% ineffective against the spores of E. bieneusi and E. intestinalis. Top-soil stabilization treatment gradually reduced the load of both pathogens, consistent with the serial dilution of sewage sludge with the soil substrate. This study demonstrated that sewage sludge and landfill leachate contained high numbers of viable, human-virulent microsporidian spores, and that sonication and quicklime stabilization were the most effective treatments for the sanitization of sewage sludge and solid waste landfill leachates. Multiplexed FISH assay is a reliable quantitative molecular fluorescence microscopy method for the simultaneous identification of E. bieneusi, E. intestinalis, E. hellem, and E. cuniculi spores in environmental samples.

Prevalence and molecular characteristics of Enterocytozoon bieneusi in cattle in Korea

Enterocytozoon bieneusi is the most common microsporidium associated with AIDS patients. Moreover, its detection in increasing numbers of immunocompetent patients has made it an emerging pathogen. This organism was also identified in a wide range of animals, and the zoonotic potential of human infections is of particular interest. In this study, 538 fecal samples from cattle in Korea were analyzed for the presence of E. bieneusi by PCR. Approximately 15% were found to be positive, with higher rates being detected over the summer months. The internal transcribed spacer (ITS) regions of the rRNA gene of ten E. bieneusi positive samples were amplified using nested PCR and sequenced. Genetic polymorphisms, which were represented by six distinct genotypes (CEbA-CEbF), were found among the E. bieneusi isolates. Five isolates from this study had identical ribosomal ITS to the previously known E. bieneusi genotype ITSs in cattle and other animals. Four isolates were previously unreported but were quite similar to the previously known genotypes of E. bieneusi from cattle and other animals. One isolate was identical to the human E. bieneusi type D, which indicated some E. bieneusi isolates from cattle in the country may be of public health importance. To the best of my knowledge, this is the first report of E. bieneusi study in cattle in Asia.

Retrospective species identification of microsporidian spores in diarrheic fecal samples from human immunodeficiency virus/AIDS patients by multiplexed fluorescence in situ hybridization

In order to assess the applicability of multiplexed fluorescence in situ hybridization (FISH) assay for the clinical setting, we conducted retrospective analysis of 110 formalin-stored diarrheic stool samples from human immunodeficiency virus (HIV)/AIDS patients with intestinal microsporidiosis collected between 1992 and 2003. The multiplexed FISH assay identified microsporidian spores in 94 of 110 (85.5%) samples: 49 (52.1%) were positive for Enterocytozoon bieneusi, 43 (45.8%) were positive for Encephalitozoon intestinalis, 2 (2.1%) were positive for Encephalitozoon hellem, and 9 samples (9.6%) contained both E. bieneusi and E. intestinalis spores. Quantitative spore counts per ml of stool yielded concentration values from 3.5 x 10(3) to 4.4 x 10(5) for E. bieneusi (mean, 8.8 x 10(4)/ml), 2.3 x 10(2) to 7.8 x 10(4) (mean, 1.5 x 10(4)/ml) for E. intestinalis, and 1.8 x 10(2) to 3.6 x 10(2) for E. hellem (mean, 2.7 x 10(2)/ml). Identification of microsporidian spores by multiplex FISH assay was more sensitive than both Chromotrope-2R and CalcoFluor White M2R stains; 85.5% versus 72.7 and 70.9%, respectively. The study demonstrated that microsporidian coinfection in HIV/AIDS patients with intestinal microsporidiosis is not uncommon and that formalin-stored fecal samples older than 10 years may not be suitable for retrospective analysis by techniques targeting rRNA. Multiplexed FISH assay is a reliable, quantitative fluorescence microscopy method for the simultaneous identification of E. bieneusi, E. intestinalis, and E. hellem, as well as Encephalitozoon cuniculi, spores in fecal samples and is a useful tool for assessing spore shedding intensity in intestinal microsporidiosis. The method can be used for epidemiological investigations and applied in clinical settings.

Induction of host chemotactic response by Encephalitozoon spp

Microsporidians are a group of emerging pathogens typically associated with chronic diarrhea in immunocompromised individuals. The number of reports of infections with these organisms and the disseminated pathology is growing as diagnostic tools become more readily available. However, little is known about the innate immune response induced by and generated against these parasites. Using a coculture chemotaxis system, primary human macrophages were infected with Encephalitozoon cuniculi or Encephalitozoon intestinalis, and the recruitment of naïve monocytes was monitored. Encephalitozoon spp. induced an average threefold increase in migration of naïve cells 48 h postinfection, which corresponded to optimal infection of monocyte-derived-macrophages. A limited microarray analysis of infected macrophages revealed several chemokines involved in the inflammatory responses whose expression was upregulated, including CCL1, CCL2, CCL3, CCL4, CCL7, CCL15, CCL20, CXCL1, CXCL2, CXCL3, CXCL5, and CXCL8. The levels of 6 of 11 chemokines also present in the microarray were confirmed to be elevated by protein profiling. Kinetic studies confirmed that secreted CCL2, CCL3, and CCL4 were expressed as early as 6 h postinfection, with peak expression at 12 to 24 h and expression remaining until 48 h postinfection. Neutralization of these chemokines, specifically CCL4, significantly reduced the number of migrating cells in vitro, indicating their role in the induction of monocyte migration. This mechanism of recruitment not only supports the evidence that in vivo cellular infiltration occurs but also provides new hosts for the parasites, which escape macrophages by rupturing the host cell. To our knowledge, this is the first documentation that chemokine production is induced by microsporidian infections in human macrophages.

The immunology of parasite infections in immunocompromised hosts

Immune compromise can modify the severity and manifestation of some parasitic infections. More widespread use of newer immnosuppressive therapies, the growing population of individuals with immunocompromised states as well as the prolonged survival of these patients have altered the pattern of parasitic infection. This review article discusses the burden and immunology of parasitic infections in patients who are immunocompromised secondary to congenital immunodeficiency, malnutrition, malignancy, and immunosuppressive medications. This review does not address the literature on parasitic infections in the setting of HIV-1 infection.

Diagnóstico laboratorial de enteroparasitoses oportunistas, com ênfase nas microsporidioses humanas, em Goiânia-GO

Os microsporídios são protozoários, emergentes e oportunistas, responsáveis por patologias de alta morbi-mortalidade, principalmente em indivíduos com distúrbios imunes. Este estudo visa determinar o perfil clínico-laboratorial destes agentes. No total, foram avaliados 723 pacientes divididos em dois grupos: I) Indivíduos imunodeprimidos/imunossuprimidos; II) Indivíduos aparentemente imunocompetentes. Estes, após livre e esclarecido consentimento, foram entrevistados e cederam amostras fecais, sendo todas submetidas a técnicas de HPJ, Rugai, Faust e colorações específicas para coccídios e microsporídios. A freqüência de microsporídios foi 1,3% (5/393) no grupo I, enquanto no outro grupo foi quatro vezes menor. A ocorrência de outras enteroparasitoses oportunistas também foi maior no grupo I. Conclui-se, por um lado, que estes agentes estão em nosso meio, e por outro, necessitamos aprimorar o diagnóstico clínico e laboratorial, para definir a distribuição geográfica destes agentes no Estado de Goiás e no Brasil.

Factors contributing to spontaneous Enterocytozoon bieneusi infection in simian immunodeficiency virus-infected macaques

BACKGROUND

A cohort of SIV-infected macaques had been used to investigate the effect of dietary supplement, immune status, SIV/AIDS disease progression and serum micronutrients levels on spontaneous acquisition of Enterocytozoon bieneusi infection in SIV-infected macaques.

METHODS

Twenty-four SIV-infected macaques were randomized into 2 groups. One group received a vitamin/mineral supplementation and a second group received a placebo. Both groups were examined for E. bieneusi infection.

RESULTS

SIV-infected macaques were more prone to acquire E. bieneusi with the progression of SIV/AIDS, and the increased shedding of infectious spores was directly associated with decreased CD4 lymphocyte and increased circulating SIV, in both supplemented and unsupplemented groups of animals. Dietary supplementation, body composition factors and serum micronutrients levels however had no association with the acquisition of E. bieneusi infection in these animals.

CONCLUSIONS

Acquisition of E. bieneusi infection is related to SIV disease progression, CD4 counts and viral load but independent of changes in body composition and serum micronutrient levels.

Cryptosporidium, Giardia and Enterocytozoon bieneusi in cats from Bogota (Colombia) and genotyping of isolates

The prevalence of Cryptosporidium, Giardia, and Enterocytozoon bieneusi in cats from Bogota (Colombia) was determined from fecal specimens and scrapings of duodenal and ileal mucosa screened by PCR. All PCR-positive specimens were sequenced to determine the genotype(s) present. Of 46 cats, 6 (13%) were positive for Cryptosporidium, 5 (11%) were infected with C. felis and one (2%) with C. muris. Three (6.5%) cats were infected with Giardia duodenalis Assemblage F. Eight (17%) cats were infected with four genotypes of E. bieneusi: genotype D-like (9%), K (4%), Peru 10 (2%), and Peru 5 (2%). This is the first report on the presence of zoonotic species/genotypes of Cryptosporidium and E. bieneusi in cats in Colombia.

Diagnosis and manifestation of encephalitozoonosis in mice after experimental infection with different species and application of dexamethasone

Twenty-eight BALB/c mice were infected with different strains of Encephalitozoon species (Encephalitozoon cuniculi II - mouse type, E. cuniculi III - dog type, Encephalitozoon hellem, Encephalitozoon intestinalis). Five of them were infected with E. cuniculi II (mouse type) and simultaneously immunosuppressed with dexamethasone. Clinical signs of encephalitozoonosis were not remarkable. Ascites was found in two mice of dexamethasone-treated group 14 days post-infection (p.i.). The histopathological changes were found mainly in spleen and liver in the form of lymphoepithelioid granuloma. Spores were found in faeces since day 14 p.i. and visualized by Calcoflour White M2R. After cultivation on cellular cultures (VERO E6 - monkey kidney cells, RK-13 - rabbit kidney fibroblasts), the species differentiation was performed by PCR using panmicrosporidial primers (PMP1, PMP2) and specific primers (ECUN-F, ECUN-R, V1, SI-500). The differences were recorded in the immune response of immunocompetent and immunosuppressed mice. At day 60 p.i., the titres of specific antibodies measured by indirect immunofluorescence antibody test were lower (1:4096) in dexamethasone-treated mice when compared with non-immunosuppressed animals (1:8196). The significant increases of antibody titres were recorded in particular infected groups within the experiment (P < 0.01 between day 14 p.i. and day 30 p.i., P < 0.001 between day 14 p.i. and day 60 p.i.). Experimental encephalitozoonosis in non-immunosuppressed and immunosuppressed mice provides a useful model for the study of immune response and lesions associated with these protozoans.

Augmentation of microsporidia adherence and host cell infection by divalent cations

The infection process of intracellular opportunistic microsporidia involves the forcible eversion of a coiled hollow polar filament that pierces the host cell membrane, allowing the passage of infectious sporoplasm into the host cell cytoplasm. Although the exact mechanism of spore activation leading to polar filament discharge is unknown, we have shown that spore adherence to host cells, which is mediated by sulfated glycosaminoglycans, may play a vital role. When adherence is inhibited, host cell infection decreases, indicating a direct link between adherence and infection. The goal of this study was to evaluate the effects of exogenous divalent cations on microsporidia spore adherence and infection. Data generated using an in vitro spore adherence assay show that spore adherence is augmented by manganese (Mn2+) and magnesium (Mg2+), but not by calcium (Ca2+). However, each of the three divalent cations contributed to increased host cell infection when included in the assay. Finally, we show that Mn2+ and Mg2+ may activate a constituent on the microsporidia spore, not on the host cell, leading to higher infection efficiency. This report further supports recent evidence that spore adherence to the host cell surface is an important aspect of the microsporidial infection process.

Microsporidian species known to infect humans are present in aquatic birds: implications for transmission via water?

Human microsporidiosis, a serious disease of immunocompetent and immunosuppressed people, can be due to zoonotic and environmental transmission of microsporidian spores. A survey utilizing conventional and molecular techniques for examining feces from 570 free-ranging, captive, and livestock birds demonstrated that 21 animals shed microsporidian spores of species known to infect humans, including Encephalitozoon hellem (20 birds; 3.5%) and Encephalitozoon intestinalis (1 bird; 0.2%). Of 11 avian species that shed E. hellem and E. intestinalis, 8 were aquatic birds (i.e., common waterfowl). The prevalence of microsporidian infections in waterfowl (8.6%) was significantly higher than the prevalence of microsporidian infections in other birds (1.1%) (P < 0.03); waterfowl fecal droppings contained significantly more spores (mean, 3.6 x 10(5) spores/g) than nonaquatic bird droppings contained (mean, 4.4 x 10(4) spores/g) (P < 0.003); and the presence of microsporidian spores of species known to infect humans in fecal samples was statistically associated with the aquatic status of the avian host (P < 0.001). We demonstrated that a single visit of a waterfowl flock can introduce into the surface water approximately 9.1 x 10(8) microsporidian spores of species known to infect humans. Our findings demonstrate that waterborne microsporidian spores of species that infect people can originate from common waterfowl, which usually occur in large numbers and have unlimited access to surface waters, including waters used for production of drinking water.

Histopathological evaluation of ocular microsporidiosis by different stains

Background

There is limited data on comparing stains in the detection of microsporidia in corneal biopsies. Hence we wanted to evaluate various stains for their ability to detect microsporidia in corneal tissue sections.

Methods

Four cases diagnosed with microsporidiosis on Hematoxylin and Eosin and Periodic Acid Schiff's stained sections of the corneal button between January 2002 and December 2004, were included. Further sections were prospectively stained with calcofluor white, Gram, Giemsa, Masson's trichrome, acridine orange, Gomori's methenamine silver, Gram's chromotrope and modified acid fast stain. The stained sections were analyzed for the spore characteristics in terms of size, shape, color contrast, cell wall morphology, waist band in cytoplasm and ease of detection.

Results

All sections showed microsporidial spores as 3 – 5 μm, oval bodies. 1% acid fast, Gram's chromotrope and GMS stains provided a reliable diagnosis of microsporidia as diagnostic waist band could be identified and good contrast helped distinguish the spores from inflammatory debris.

Conclusion

Considering the ease of performance, cost effectiveness and rapidity of the technique, 1% acid fast stain and Gram's chromotrope stain are ideal for the detection of microsporidia.

Antiparasitic activity of flavonoids and isoflavones againstCryptosporidium parvumandEncephalitozoon intestinalis

Flavonoids, polyphenolic compounds found in plants, have demonstrated activity against several parasites and can augment the efficacy of other drugs by either increasing the uptake or decreasing the efflux of these drugs. We evaluated 11 of these compounds alone or in combination in order to test the hypothesis that flavonoids are effective against Cryptosporidium parvum and Encephalitozoon intestinalis. Using in vitro cell culture assays, HCT-8 cells or E6 cells were infected with C. parvum and E. intestinalis, respectively, and treated with compounds at doses ranging from 1 to 200 microM. We found that six compounds were active against C. parvum. Naringenin and genistein had the greatest activities with EC(50) of 15 and 25 microM, respectively. Two compounds, quercetin and apigenin, had activity against E. intestinalis at EC(50) of 15 and 50 microM, respectively. The EC(50) of trifluralin, a dinitroaniline compound, was decreased significantly when combined with genistein in an in vitro assay, suggesting that compounds may be used alone on in combination with other moderately active drugs to increase efficacy. In addition, induction of apoptosis by these compounds was studied but not observed to be a significant mechanism of action.

Recovery, bioaccumulation, and inactivation of human waterborne pathogens by the Chesapeake Bay nonnative oyster, Crassostrea ariakensis

The introduction of nonnative oysters (i.e., Crassostrea ariakensis) into the Chesapeake Bay has been proposed as necessary for the restoration of the oyster industry; however, nothing is known about the public health risks related to contamination of these oysters with human pathogens. Commercial market-size C. ariakensis triploids were maintained in large marine tanks with water of low (8-ppt), medium (12-ppt), and high (20-ppt) salinities spiked with 1.0 x 10(5) transmissive stages of the following human pathogens: Cryptosporidium parvum oocysts, Giardia lamblia cysts, and microsporidian spores (i.e., Encephalitozoon intestinalis, Encephalitozoon hellem, and Enterocytozoon bieneusi). Viable oocysts and spores were still detected in oysters on day 33 post-water inoculation (pwi), and cysts were detected on day 14 pwi. The recovery, bioaccumulation, depuration, and inactivation rates of human waterborne pathogens by C. ariakensis triploids were driven by salinity and were optimal in medium- and high-salinity water. The concentration of human pathogens from ambient water by C. ariakensis and the retention of these pathogens without (or with minimal) inactivation and a very low depuration rate provide evidence that these oysters may present a public health threat upon entering the human food chain, if harvested from polluted water. This conclusion is reinforced by the concentration of waterborne pathogens used in the present study, which was representative of levels of infectious agents in surface waters, including the Chesapeake Bay. Aquacultures of nonnative oysters in the Chesapeake Bay will provide excellent ecological services in regard to efficient cleaning of human-infectious agents from the estuarine waters.

Use of different stains for microscopic evaluation of corneal scrapings for diagnosis of microsporidial keratitis

Retrospective evaluation of potassium hydroxide plus calcofluor white (KOH+CFW), Gram, Giemsa, and modified Ziehl-Neelsen (1% H(2)SO(4), cold) stains for the detection of microsporidia in corneal scrapings from 30 patients showed KOH+CFW and acid-fast stains to be most efficient (29/30 [96.7%] and 28/30 [93.3%], respectively) in the diagnosis of microsporidial keratitis.

Clinical and Microbiological Profile of Microsporidial Keratoconjunctivitis in Southern India

PURPOSE

To report the clinical and microbiological profile of microsporidial keratoconjunctivitis in immunocompetent individuals in southern India.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Nineteen cases of microsporidial keratoconjunctivitis diagnosed between January 2002 and December 2004 were studied.

METHODS

All medical and laboratory records of patients with infectious keratitis during the study period were reviewed. In all cases, after relevant history recording and slit-lamp examination, corneal/conjunctival scrapings were collected. Multiple scrapings were taken from the lesions and examined by fluorescence or light microscopy after staining with potassium hydroxide and calcofluor white (KOH + CFW), Gram's stain, Kinyoun's, and Giemsa stain. In some cases, the serum was tested for human immunodeficiency virus antibody by enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Clinical course, demographic features, predisposing factors, microbiological profile, treatment, and final outcome.

RESULTS

Of 4822 cases of suspected microbial keratitis seen during the period, 19 (0.4%) were identified as microbiologically proven microsporidial keratitis. All patients were apparently healthy; 8 had a history of ocular trauma, and 3 mentioned bathing in unclean river water. All but 2 had unilateral involvement. The mean age of the patients was 38.4+/-13.7 years (range, 23-73). The duration of symptoms ranged from 1 day to 2 years, with 11 of 19 (58%) presenting within a week of onset of symptoms. Slit-lamp examination revealed multifocal, coarse, punctate, raised epithelial lesions in all patients. A mild to moderate nonpurulent conjunctivitis was present in all cases, with papillary and/or follicular reaction in 14. Corneal/conjunctival scrapings demonstrated microsporidial spores by KOH + CFW in 16 of 17 cases tested, whereas the diagnosis was made by Giemsa stain in 2 cases and by Gram's stain in one. Kinyoun's (1% acid fast) stain was confirmatory in all cases. In all patients, treatment was started after debridement and included oral and/or topical antimicrobial agents. At last follow-up, 15 of 19 achieved a visual acuity of 20/20.

CONCLUSIONS

Microsporidial keratoconjunctivitis should be considered in the differential diagnosis of atypical punctate epithelial keratitis associated with conjunctivitis and can be diagnosed by routine microbiological methods. The disease can occur in healthy individuals, and the outcome of treatment is often satisfactory.

Morphological and molecular characterization of a new microsporidian (Protozoa: Microsporidia) isolated from Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

A microsporidium was isolated from larvae of Spodoptera litura (Fabricius) collected from Tamil Nadu, India. This microsporidian species is monomorphic, disporous and develops in direct contact with the cytoplasm of the host cell. The nuclear configuration of merogonic and sporogonic stages was diplokaryotic. The merogonic proliferative stage was unusual that normal development with 1, 2 and 4 binucleated forms were common, while large multinucleate meronts containing 8 and 12 small compact horseshoe-like diplokaryotic nuclei were also observed. The fresh spores were typically ovocylindrical in shape, with a mean size of 3.91 x 1.91 microm and the polar filament length was approximately 90 microm. Infection was systemic with mature spores produced in the midgut, nervous tissue, muscles, labial glands, gonads, tracheae, epidermis, Malpighian tubules and, most extensively, fat body tissues. The new isolate was highly pathogenic to S. litura larvae. Host specificity tests performed on 37 non-target hosts of 5 different insect orders revealed that the new isolate is pathogenic only to lepidopteran insects. We sequenced the 16S small subunit rRNA (SSU rRNA) gene of the isolate and compared it with 72 non-redundant microsporidian sequences from the GenBank. Based on the light microscopic studies and phylogenetic analyses, the new isolate is assigned to the genus Nosema. Significant differences in the SSU rRNA sequence were identified when compared with the type species Nosema bombycis and other closely related species viz., Nosema spodopterae. Structural differences were also observed in the 16S SSU rRNA between the new isolate and the two above-mentioned microsporidian pathogens. We conclude that the microsporidian isolate reported here is distinctly different from the other known species and is likely to be a new species.

Variability in Infection Efficiency In Vitro of Different Strains of the Microsporidian Encephalitozoon hellem

The infection efficiency of different strains of Encephalitozoon hellem of human origin was tested in Vero E6 cell cultures, scoring the number of infection foci (NIF) after 9, 14, 20, and 24 days of inoculation. The results revealed a strong interaction of the strain type with time: different strains showed different proliferative dynamics. Number of infection foci was lower on the first sampling day for CDC: V257, EHVS-96, and PV6-96, with a subsequent increase at a higher rate for the first strain and lower for the latter. In contrast, PV7-96 showed the highest NIF at the first sampling, followed by a slight decrease. Since these strains were selected by their genotype for the polar tube protein (PTP)-1A, 1B, 1C, and 2C, respectively, it is tempting to suggest a major role of this protein in the differences detected, although the influence of other genes that hypothetically may also differ among the strains employed cannot be discarded. The different in vitro infection efficiencies raise the possibility that some strains of E. hellem will also produce more aggressive features in infected patients.

Parasitic central nervous system infections in immunocompromised hosts: malaria, microsporidiosis, leishmaniasis, and African trypanosomiasis

Immunosuppression associated with HIV infection or following transplantation increases susceptibility to central nervous system (CNS) infections. Because of increasing international travel, parasites that were previously limited to tropical regions pose an increasing infectious threat to populations at risk for acquiring opportunistic infection, especially people with HIV infection or individuals who have received a solid organ or bone marrow transplant. Although long-term immunosuppression caused by medications such as prednisone likely also increases the risk for acquiring infection and for developing CNS manifestations, little published information is available to support this hypothesis. In an earlier article published in Clinical Infectious Diseases, we described the neurologic manifestations of some of the more common parasitic CNS infections. This review will discuss the presentation, diagnosis, and treatment of the following additional parasitic CNS infections: malaria, microsporidiosis, leishmaniasis, and African trypanosomiasis.

Monoclonal antibodies against Enterocytozoon bieneusi of human origin

Enterocytozoon bieneusi is clinically the most significant among the microsporidia infecting humans, causing chronic diarrhea, wasting, and cholangitis in individuals with human immunodeficiency virus/AIDS. The lack of immune reagents is largely due to the absence of methods for laboratory propagation of E. bieneusi. We recently described a procedure for the concentration and purification of spores from diarrheic stool of infected humans. Purified spores were used to immunize mice for production and screening of monoclonal antibodies (MAbs) against E. bieneusi. The eight immunoglobulin M MAbs generated and fully characterized did not cross-react with other human microsporidia or with other microorganisms normally present in stool. One of the MAbs, 2G4, reacted with E. bieneusi spores in stools from monkeys and humans, without background fluorescence, which makes it an ideal diagnostic reagent. It also recognizes intracellular stages of the parasite and will be suitable for determining tissue distribution of E. bieneusi in infected hosts. At least two immunodominant antigens of E. bieneusi of 33,000 and 35,000 Da exist, which were recognized by rabbit and mouse antisera. The availability of MAbs against E. bieneusi will simplify considerably the diagnosis of this infection in humans and will provide tools for epidemiologic investigations regarding the true prevalence of the infection in various human and mammalian populations and the environmental sources of infection.

Transport of microsporidium Encephalitozoon intestinales spores in sandy porous media

The retention and transport of microsporidium Encephalitozoon intestinales spores in two water-saturated sandy porous media was investigated in this study. The initial breakthrough of the spores in the column effluent occurred essentially simultaneously with that of a non-reactive tracer, indicating no significant velocity enhancement. A large fraction (45-73%) of the spores injected into the columns was not recovered in the effluent, indicating removal from solution through colloid retention processes of attachment and/or straining. The relative significance of attachment and straining to total retention was evaluated in additional experiments. An experiment was conducted with a sieved coarse fraction of porous media for which straining is unlikely to be of significance based on the relative diameters of the spores and porous-medium pores. The spore recovery for this experiment was similar to the recoveries obtained for microsporidia transport in the un-sieved parent porous medium. An additional experiment was conducted with a subsample of the coarse fraction that was acid-washed to reduce potential surface attachment sites. Spore recovery was complete for this experiment. These results suggest surface deposition was the primary removal mechanism in our system. This conclusion is supported by the results of an experiment wherein deionized water was flushed through a column that was previously flushed with electrolyte solution. The effluent spore concentrations were observed to increase upon injection of deionized water, indicating re-mobilization of spores upon a change in water chemistry. The measured data were successfully simulated using a mathematical model incorporating colloid filtration. The results of this study suggest that the transport of microspordia in sandy porous media is governed by established colloid-transport processes.

Is microsporidial keratitis an emerging cause of stromal keratitis? A case series study

Background

Microsporidial keratitis is a rare cause of stromal keratitis. We present a series of five cases of microsporidial keratitis from a single centre in southern India with microbiologic and histopathologic features.

Case presentation

Patient charts of five cases of microsporidial stromal keratitis diagnosed between January 2002 and June 2004 were reviewed retrospectively for clinical data, microbiologic and histopathologic data. The presence of microsporidia was confirmed by special stains on corneal scrapings and/or corneal tissues, and electron microscopy. All patients were immunocompetent with a preceding history of trauma in three. Four patients presented with unilateral, small, persisting deep stromal infiltrates, of uncertain etiology, in the cornea, which were not responding to conventional antimicrobial treatment and required penetrating keratoplasty in three. Fifth case was unsuspected and underwent keratoplasty for post-traumatic scar. Three of five cases were diagnosed on corneal scrapings, prior to keratoplasty, while two were diagnosed only on histology. The microsporidia appeared as oval well defined bodies with dense staining at one pole. None of the patients showed recurrence following keratoplasty.

Conclusion

Microsporidia, though rare, should be suspected in chronic culture-negative stromal keratitis. Organisms could lie dormant without associated inflammation.

First detection and genotyping of human-associated microsporidia in pigeons from urban parks

Microsporidia are ubiquitous opportunistic parasites in nature infecting all animal phyla, and the zoonotic potential of this parasitosis is under discussion. Fecal samples from 124 pigeons from seven parks of Murcia (Spain) were analyzed. Thirty-six of them (29.0%) showed structures compatible with microsporidia spores by staining methods. The DNA isolated from 26 fecal samples (20.9%) of microsporidia-positive pigeons was amplified with specific primers for the four most frequent human microsporidia. Twelve pigeons were positive for only Enterocytozoon bieneusi (9.7%), 5 for Encephalitozoon intestinalis (4%), and one for Encephalitozoon hellem (0.8%). Coinfections were detected in eight additional pigeons: E. bieneusi and E. hellem were detected in six animals (4.8%); E. bieneusi was associated with E. intestinalis in one case (0.8%); and E. hellem and E. intestinalis coexisted in one pigeon. No positive samples for Encephalitozoon cuniculi were detected. The internally transcribed spacer genotype could be completed for one E. hellem-positive pigeon; the result was identical to the genotype A1 previously characterized in an E. hellem Spanish strain of human origin. To our knowledge, this is the first time that human-related microsporidia have been identified in urban park pigeons. Moreover, we can conclude that there is no barrier to microsporidia transmission between park pigeons and humans for E. intestinalis and E. hellem. This study is of environmental and sanitary interest, because children and elderly people constitute the main visitors of parks and they are populations at risk for microsporidiosis. It should also contribute to the better design of appropriate prophylactic measures for populations at risk for opportunistic infections.

Inhibitory activity of human immunodeficiency virus aspartyl protease inhibitors against Encephalitozoon intestinalis evaluated by cell culture-quantitative PCR assay

Immune reconstitution might not be the only factor contributing to the low prevalence of microsporidiosis in human immunodeficiency virus (HIV)-infected patients treated with protease inhibitors, as these drugs may exert a direct inhibitory effect against fungi and protozoa. In this study, we developed a cell culture-quantitative PCR assay to quantify Encephalitozoon intestinalis growth in U-373-MG human glioblastoma cells and used this assay to evaluate the activities of six HIV aspartyl protease inhibitors against E. intestinalis. A real-time quantitative PCR assay targeted the E. intestinalis small-subunit rRNA gene. HIV aspartyl protease inhibitors were tested over serial concentrations ranging from 0.2 to 10 mg/liter, with albendazole used as a control. Ritonavir, lopinavir, and saquinavir were able to inhibit E. intestinalis growth, with 50% inhibitory concentrations of 1.5, 2.2, and 4.6 mg/liter, respectively, whereas amprenavir, indinavir, and nelfinavir had no inhibitory effect. Pepstatin A, a reference aspartyl protease inhibitor, could also inhibit E. intestinalis growth, suggesting that HIV protease inhibitors may act through the inhibition of an E. intestinalis-encoded aspartyl protease. These results showed that some HIV protease inhibitors can inhibit E. intestinalis growth at concentrations that are achievable in vivo and that the real-time quantitative PCR assay that we used is a valuable tool for the in vitro assessment of the activities of drugs against E. intestinalis.

Zoonotic potential of the microsporidia

Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans.

Spore shedding pattern of Enterocytozoon bieneusi in asymptomatic children

Stool samples from seven human immunodeficiency virus (HIV)-negative and two HIV-positive children with asymptomatic Enterocytozoon bieneusi infections were daily examined to quantify spore shedding using Gram-chromotrope staining under light microscopy. The spore shedding pattern and intensity in these children was variable. Mean spore concentrations in the stool samples from these children ranged from 2.4 x 10(2) to 1.2 x 10(5) spores per gram. Light microscopy could detect spores in stool specimens for 9-33 days, while PCR was able to detect E. bieneusi in stool specimens for 3-40 days longer. This suggests that light microscopy may not detect low levels of spore shedding. Considering that the asymptomatic group are a potential source of infection, detection methods with a higher sensitivity should be used.