Encephalitozoon cuniculi and Extraintestinal Microsporidiosis in Bird Owners

We identified Encephalitozoon cuniculi genotype II parasites as a cause of extraintestinal microsporidiosis in 2 owners of birds also infected with E. cuniculi. Patients experienced long-lasting nonspecific symptoms; the disease course was more progressive in a patient with diabetes. Our findings suggest direct bird-to-human transmission of this pathogen.

Triple infection with agamid adenovirus 1, Encephaliton cuniculi-like microsporidium and enteric coccidia in a bearded dragon (Pogona vitticeps)

A 2-month-old juvenile central bearded dragon was presented for anorexia and cachexia. Another specimen from the same cage had died suddenly 2 weeks prior. Fecal analysis revealed a high quantity of Isospora amphiboluri and a few pinworm eggs. Other examinations were not performed and the animal died a few days later despite supportive care. A third individual from the same cage presented with anorexia and a distended cœlom and was euthanized. In this third dragon, histological examination revealed intestinal coccidiosis, basophilic intranuclear inclusions compatible with adenovirus infection, acute hepatic necrosis with intrahepatocytic and intraenteritic organisms typical of microsporidia and renal gout. A PCR confirmed the diagnosis of adenovirosis. Sequencing showed that the PCR product was 100% identical to the corresponding portion of the agamid adenovirus 1 genome. A PCR for the detection of Encephalitozoon (E.) cuniculi was positive. Partial sequencing revealed 100% identity to an E. cuniculi-like organism previously found in bearded dragons. In cases where environmental factors such as poor hygiene or stress can be excluded, the presence of opportunistic pathogens in high numbers can be due to a systemic (viral) infection with temporary immunosuppression.

First report of Enterocytozoon bieneusi and Encephalitozoon intestinalis infection of wild mice in Slovakia

Increased risk of zoonotic transmission of the potential human pathogenic species Enterocytozoon bieneusi, Encephalitozoon intestinalis and Encephalitozoon cuniculi was detected in wild immunocompetent mice (Mus musculus musculus; n=280). Analysis was conducted with the use of PMP1/PMP2 primers and SYBR Green RT-PCR. Using Real Time PCR and comparing the sequences with sequences in the GenBank, E. bieneusi was detected in 3 samples (1.07 %), E. cuniculi in 1 sample (0.35 %) and E. intestinalis in 1 sample (0.35 %). The results of this report document the low host specificity of detected microsporidia species, and imply the importance of synanthropic rodents as a potential source of human microsporidial infection.

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.

Multiplex detection of Enterocytozoon bieneusi and Encephalitozoon spp. in fecal samples using real-time PCR

A multiplex real-time polymerase chain reaction (PCR) method was developed for the simultaneous detection of Enterocytozoon bieneusi (n = 30) and Encephalitozoon spp. (n = 3) in stool samples. The multiplex PCR also included an internal control to detect inhibition of the amplification by fecal constituents in the sample. The assay was performed on species-specific DNA controls (n = 22) and a range of well-defined stool samples (n = 140), and it achieved 100% specificity and sensitivity. The use of this assay in a diagnostic laboratory offers the possibility of introducing DNA detection as a feasible technique in the routine diagnosis of intestinal microsporidian infections.

Disseminated encephalitozoonosis in captive, juvenile, cotton-top (Saguinus oedipus) and neonatal emperor (Saguinus imperator) tamarins in North America

Disseminated encephalitozoonosis was diagnosed in 2 sibling, juvenile, cotton-top tamarins (Saguinus oedipus) and 3 sibling, neonatal, emperor tamarins (S. imperator) by use of histologic examination, histochemical analysis, electron microscopy, and polymerase chain reaction (PCR) analysis with nucleotide sequencing. All tamarins were captive born at zoos in North America and died with no premonitory signs of disease. The main pathologic findings were myocarditis (4/5), hepatitis (3/5), interstitial pneumonia (3/5), skeletal myositis (3/5), meningoencephalitis (2/5), adrenalitis (2/5), tubulointerstitial nephritis (1/5), myelitis (1/5), sympathetic ganglioneuritis (1/5), and retinitis (1/5). Central nervous system lesions were the most prominent findings in cotton-top tamarins. The inflammation was predominantly lymphocytic and suppurative in cotton-top tamarins, whereas emperor tamarins had granulomatous or lymphoplasmacytic lesions. Intralesional periodic acid-Schiff-, gram-, or acid-fast (or all 3)-positive, oval-to-elliptical shaped organisms were found in 1 cotton-top and the 3 emperor tamarins. By electron microscopy, these organisms were consistent with microsporidia of the genus Encephalitozoon. E. cuniculi genotype III was detected by PCR analysis and sequencing in paraffin-embedded brain, lung, and bone marrow specimens from the cotton-top tamarins. Although PCR results were negative for one of the emperor tamarins, their dam was seropositive for E. cuniculi by ELISA and Western blot immunodetection. These findings and recent reports of encephalitozoonosis in tamarins in Europe suggest that E. cuniculi infection may be an emerging disease in callitrichids, causing high neonatal and juvenile mortality in some colonies. The death of 2 less than 1-day-old emperor tamarins from a seropositive dam supports the likelihood of vertical transmission in some of the cases reported here.

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.

Genetically unique microsporidian Encephalitozoon cuniculi strain type III isolated from squirrel monkeys

Microsporidian spores were isolated from two squirrel monkeys (Saimiri sciureus) that had been bred at an animal-breeding colony in Japan. The spores were identified as Encephalitozoon cuniculi on the basis of nucleotide sequence analysis of the small-subunit (SSU) rRNA gene. The internal transcribed spacer (ITS) gene sequence revealed that these isolates were classified into genotype III because it contained tetrarepeats of 5'-GTTT-3'. However, the sequences of the polar tube protein (PTP) gene of the monkey isolates were not identical to a reported sequence of genotype III but were quite similar to a reported sequence of genotype II. On the other hand, sequence analysis of the spore wall protein 1 (SWP-1) gene revealed that the monkey isolates did not belong to any of genotypes I, II and III. These results suggest that the present E. cuniculi isolates of squirrel monkey origin are a new subtype of E. cuniculi ITS genotype III that can cause a disseminated infection.

Microsporidiosis in travel-associated chronic diarrhea in immune-competent patients

We analyzed retrospectively 21 immune-competent travelers with chronic traveler's diarrhea (3-6 weeks) after returning from recreational travel to the tropics with stool samples positive for microsporidia. Nine patients had been treated with albendazole and 12 patients had been treated symptomatically. Diarrhea resolved in 8 of 9 and 12 of 12 patients, respectively. In the albendazole group, Encephalitozoon intestinalis was cleared in 4 of 4 patients and Enterocytozoon bieneusi persisted in 7 of 7 patients (2 patients were lost to follow-up). In the symptomatic treated group microsporidia persisted in stool samples of all patients. We conclude that there is only a transient correlation between detection of microsporidia in stool and gastrointestinal symptoms, and suggest that microsporidia infection may cause clinical symptoms during the early stages of infection that resolve even though the microsporidia may persist.

Intraocular microsporidiosis due to Encephalitozoon cuniculi in a patient with idiopathic CD4+ T-lymphocytopenia

Encephalitozoon cuniculi was documented to cause disseminated microsporidial infection including an iris tumor and endophthalmitis in an adolescent with idiopathic CD4+ T-lymphocytopenia. The diagnosis was established by microscopic, serologic and molecular methods. E. cuniculi (rabbit strain) was identified from the iris tumor, as well as from urine, conjunctival, corneal, and nasal swabs. Treatment with oral albendazole led to rapid improvement. This case raises the possibility of disseminated microsporidial infection in the context of idiopathic CD4+ T-lymphocytopenia and possibly advanced human immunodeficiency virus (HIV) infection, and above all the possibility of intraocular infection with E. cuniculi in humans.

Quantitation of microsporidia in cultured cells by flow cytometry

BACKGROUND

Microsporidia are obligate intracellular protozoan parasites that emerged as major opportunistic pathogens in humans since the onset of the AIDS pandemic. In the present study, we investigated whether FCM is a useful method for the quantitation of intracellular microsporidian spores in cultured cells.

METHODS

Microsporidia (Encephalitozoon cuniculi) were grown in cell cultures and various cell-lines were coincubated with microsporidian spores at different multiplicities of infection, as well as for different periods of time. After permeabilization of the cells, intracellular spores were stained with a polyclonal anti-E. cuniculi serum and a FITC-labeled secondary antibody. Stained cells were analyzed on a flow cytometer and results were compared with those of fluorescence microscopy.

RESULTS

Noninfected cells showed a lower fluorescence, while the relative fluorescence observed for infected cells was significantly higher. The cell population with the more intense fluorescence, representing cells with internalized microsporidian spores, increased with the multiplicity of infection as well as over time. Results of FCM and fluorescence microscopy were in excellent agreement for all experiments.

CONCLUSIONS

We have developed a flow cytometric assay to detect and quantify cells with intracellular microsporidian spores. This method is easy to use, highly reproducible, and should be useful for future research.

Susceptibility of IFN-gamma or IL-12 knock-out and SCID mice to infection with two microsporidian species, Encephalitozoon cuniculi and E. intestinalis

Susceptibility of three strains of immunodeficient mice to two related microsporidian species Encephalitozoon cuniculi Levaditi, Nicolau et Schoen, 1923 and Encephalitozoon intestinalis (Cali, Kotler et Orenstein, 1993) was compared. While both, severe combined immunodeficient (SCID) and interferon-gamma knock-out (IFN-gamma KO) mice, succumbed to either intraperitoneal (i.p.) or peroral (p.o.) (natural) infection with both parasites, only i.p. infection with E. cuniculi killed interleukin-12 knock-out (IL-12 KO) mice. IFN-gamma KO mice died earlier than SCID mice. Adoptive transfer of naive splenocytes from IFN-gamma KO mice did not protect the SCID mice from a lethal infection with either of the Encephalitozoon species. However, reconstituted mice survived significantly longer (P<0.05), thus indicating the role of IFN-gamma produced by host NK cells in the development of mechanisms of anti-microsporidial protective immunity. Non-lethal outcome of the infection always correlated with the increase in CD8+ T lymphocyte subpopulation. Both E. intestinalis-infected IFN-gamma KO and IL-12 KO mice produced comparable levels of specific antibodies, suggesting that antibodies did not protect IFN-gamma KO mice from lethal infection.

A comparison of homologous genes encoding aminopeptidases among bird and human Encephalitozoon hellem isolates and a rabbit E. cuniculi isolate

Encephalitozoon cuniculi and E. hellem are often recognized as the agents of human microsporidiosis, but less than optimal therapy is available for treatment. The identification of enzymes critical to the parasitic life cycle is an important step in finding targets for potential drug development. Aminopeptidase gene sequences were obtained from cDNA and gDNA from avian and human E. hellem isolates and from a rabbit E. cuniculi isolate. At the amino acid level, the aminopeptidase sequences from the E. hellem human and bird isolates share >99% identity and are nearly 70% identical with the E. cuniculi sequence. Conserved HEXXH and GAMEN motifs classify the predicted aminopeptidase in the MA clan of the M1 family. The obtained aminopeptidase gene sequences are likely homologous to the previously reported E. cuniculi glutamyl aminopeptidase. The conservation of this aminopeptidase between species and divergence from mammalian aminopeptidases indicate that this enzyme may be a valid target for drug therapy.

Serodiagnostic studies in an immunocompetent individual infected with Encephalitozoon cuniculi

Little is known about the prevalence and clinical significance of infection with Encephalitozoon species in immunocompetent individuals. In the present study, by using indirect immunofluorescence technique (IFAT), Western blot, and recombinant antigens of the spore wall (SWP1) and polar tube (PTP1, PTP2, and PTP3 ), we analyzed the IgG antibody response of a laboratory worker who was infected with Encephalitozoon cuniculi. Serum samples were analyzed 1, 20, 32, and 38 months after infection. After 1 month, by use of IFAT, only spore-wall antigens were recognized, an antibody reaction that changed toward both the spore wall and polar tube in the following months. By use of Western blot analysis, a characteristic pattern that recognized multiple bands was noticed. Reaction against SWP1 was present in all 4 serum samples. The IgG response against PTP1, PTP2, and PTP3 was not detectable 1 month after infection, but became evident in the follow-up serum samples. Serum samples showed cross-reactivity with the spore wall of Encephalitozoon hellem and Encephalitozoon intestinalis, but only little cross-reactivity with the polar tube of these parasites. This is the first study to our knowledge that provides full details about the antibody response against a specified Encephalitozoon species in an immunocompetent person. The results strongly encourage the development and use of reliable serodiagnostic methods, which will provide information about the prevalence and clinical significance of Encephalitozoon species infection in humans.

Disseminated lethal Encephalitozoon cuniculi (genotype III) infections in cotton-top tamarins (Oedipomidas oedipus)--a case report

For the first time, Encephalitozoon (E.) cuniculi genotype III ('dog strain') was verified in two cotton-top tamarins (Oedipomidas oedipus) by light microscopy, immunohistochemistry, electron microscopy, PCR and sequencing. The animals had a disseminated lethal infection with this protist. In earlier reports, genotype III had been found only in domestic dogs, man, emperor tamarins (Saguinus imperator) and golden lion tamarins (Leontopithecus rosalia). This investigation establishes now that the 'dog strain' can occur in cotton-top tamarins too. This is further evidence for the zoonotic potential of E. cuniculi. Furthermore, free E. cuniculi spores were identified also in blood vessels of several tissues. These findings indicate that during a disseminated infection E. cuniculi spores can occur in peripheral blood, too. We propose that blood should also be included in the investigations for the detection of microsporidia, so that a possible disseminated course of an infection can be detected.

Prevalence of antibodies to Encephalitozoon cuniculi in horses in the Israel

Infection with the intracellular microsporidium Encephalitozoon cuniculi can cause a serious disease--encephalitozoonosis in various animals and people. Several species of mammals, including the horse, were seem to be potential sources of encephalitozoonosis for animal as well as human hosts. The disease diagnosis is based on clinical signs, pathological findings, and the detection of E. cuniculi or circulating antibodies directed against the parasite. This study investigates the seroconversion to E. cuniculi in horses admitted to the Veterinary Teaching Hospital of the Hebrew University of Jerusalem and 3 different private horse-riding farms across Israel. Antibodies to E. cuniculi were determined using the IFA test in the sera from 102 horses. Of 72 asymptomatic horses, 60% were seropositive and 19% of the positive samples showed a titter of 1:512. Of 30 horses with various clinical signs, 80% were seropositive and 68% of the positive samples showed a titer of 1:512. High titers were associated with colic and neurological signs. This could prove to be interesting if the high percentages of prevalence of antibodies level in horses are an indication of health risk in humans.

Microsporidial keratoconjunctivitis in a HIV-seronegative patient treated with debridement and oral itraconazole

PURPOSE

To report a case of microsporidial keratoconjunctivitis in an HIV-seronegative.

METHODS

We report on a 40-year-old woman who presented with acute symptoms of 4 days' duration. Visual acuity was 6/6 in the right eye and 6/6 partial in the left eye. In the left eye, there was diffuse conjunctival congestion with papillary changes. There were multiple raised epithelial lesions in the cornea.

RESULTS

Corneal scrapings stained with potassium hydroxide and calcofluor white showed Microsporidium spores in large numbers. These spores with polar staining were also confirmed in Gram stain. One month after initiation of itraconazole, the left eye was quiet. She had a visual acuity of 6/6 in that eye, with faint corneal haze.

CONCLUSIONS

We report a rare case of microsporidial keratoconjunctivitis in a HIV-seronegative patient who was treated by debridement and oral itraconazole. Microsporidium should be suspected even in an immunocompetent individual if the corneal examination revealed showed multiple raised epithelial lesions.

Humoral immune response in adult blue foxes (Alopex lagopus) after oral infection with Encephalitozoon cuniculi spores

Encephalitozoon cuniculi causes severe diseases in blue fox puppies. When pregnant vixens are infected, parasites are transmitted over the placenta to the unborn that subsequently develop encephalitozoonosis. Adult foxes themselves do not have signs of disease, but show antibody titres to E. cuniculi. The purpose of the present study was to gain information on the immune response in adult foxes after experimental infection. Sixteen foxes were infected orally with E. cuniculi spores, eight of them twice and 28 days apart. The two groups of animals showed elevated serological values in both the carbon immunoassay and in the ELISA. Elevated serological levels were recorded up to 1 year after the infection took place. The control group (n=8) remained serologically negative throughout the trial. The results of the study showed that blue foxes could be seropositive for at least a year after oral infection with E. cuniculi.

Encephalitozoon cuniculi in pet rabbits

The results of a serological test for Encephalitozoon cuniculi in 125 pet rabbits are reviewed, together with follow-up studies of clinical cases. Blood samples were taken from 38 asymptomatic rabbits and 87 rabbits showing neurological, renal or ocular signs suggestive of encephalitozoonosis. In the asymptomatic group, six of 26 (23 per cent) apparently healthy rabbits, sampled as part of a health screen, were seropositive; of the remaining 12 asymptomatic rabbits, sampled because they lived with seropositive companions, eight (66 per cent) were seropositive. Fifty-eight of the rabbits with clinical disease showed neurological signs, including head tilt, seizures, ataxia and swaying; three of them also showed renal signs and two showed ocular signs, and these five rabbits were all seropositive. Head tilt was the most common neurological sign in 21 of 23 (91 per cent) of the seropositive cases. All nine rabbits with ocular lesions were seropositive. In follow-up studies of clinical cases, the rabbits showed variable responses to treatment with albendazole, fenbendazole, antibiotics or corticosteroids, and some cases recovered without treatment.

Development of a real-time PCR assay for quantitative detection of Encephalitozoon intestinalis DNA

A new real-time PCR assay for quantitation of Encephalitozoon intestinalis DNA was developed which used a TaqMan fluorescent probe for specific detection. Serial dilutions of E. intestinalis spore suspensions obtained from tissue culture were used as external standards. The detection limit of the technique was 20 spores per ml, with a good interassay reproducibility (coefficient of variation of 7.1% for the suspension containing 20 spores/ml, 5.0% for the suspension containing 75 spores/ml and below 3.5% for higher concentrations). Quantitative detection of E. intestinalis DNA was similar whether the serial dilutions of spores were made in distilled water or in a stool suspension, allowing the use of the assay for stool specimens. The assay was then applied to 14 clinical specimens from 8 immunocompromised patients with proven E. intestinalis infection. The quantitation of the parasitic burden was achieved in stools, blood, urine, tissue biopsies, and bronchopulmonary specimens. The highest parasitic burdens were noted in stools, urine, and bronchopulmonary specimens, reaching 10(5) to 10(6) spores/g or ml. Dissemination of the infection was also evidenced in some patients by demonstration of E. intestinalis DNA in blood and serum. We conclude that real-time PCR is a valuable tool for quantitation of E. intestinalis burden in clinical specimens.

Development and optimization of a quantitative cell culture infectivity assay for the microsporidium Encephalitozoon intestinalis and application to ultraviolet light inactivation

Microsporidia are unique parasites recognized as a major cause of intestinal illness among immunocompromised patients and occasionally in otherwise healthy hosts. These organisms have been detected in water and are likely transmitted by the fecal-oral route. The most common human pathogenic microsporidia for which cell culture methods have been established is Encephalitozoon intestinalis. This study describes the development of a quantitative cell culture infectivity assay for E. intestinalis and its application to assess inactivation by ultraviolet (UV) light irradiation. The method described here employs calcofluor white, a fluorescent brightener that targets the chitin spore wall, to visualize groups of developing spores in order to confirm infectivity. Serial dilutions of the spore suspension were seeded into tissue culture well slides containing RK-13 cells. Slides were then rinsed, fixed in methanol and stained with calcofluor white and examined microscopically. Large masses of developing spores were easily visible on infected cell monolayers. Positive and negative wells at each dilution step were used to quantify the number of infectious spores in the original suspension using a most-probable-number (MPN) statistical analysis. This assay was used to evaluate the disinfecting potential of ultraviolet light on E. intestinalis spores in water. The ultraviolet dose required for a 3-log(10) or 99.9% reduction in the number of infective spores was determined to be 8.43 mW s/cm(2).

Encephalitozoon cuniculi placentitis and abortion in a quarterhorse mare

Encephalitozoon cuniculi is a microsporidial parasite, which has rarely been reported to cause placentitis in animals. A late-term aborted fetus and placenta from a Quarterhorse were presented to the Livestock Disease Diagnostic Center, University of Kentucky, for diagnostic examination. There was a necrotizing placentitis, with distension of many chorionic epithelial cells by intracytoplasmic vacuoles containing 1-2-microm-diameter, elongated, gram-positive organisms. The organisms were identified as E. cuniculi by electron microscopy and by polymerase chain reaction using primers to microsporidial ribosomal DNA. Joints of the fetus were swollen, with gross and microscopic lesions of synovitis; however, E. cuniculi DNA was not detected.

Real-time PCR method for detection of Encephalitozoon intestinalis from stool specimens

The prevalence of microsporidiosis is likely underestimated due to the labor-intensive, insensitive, and nonspecific clinical laboratory methods used for the diagnosis of this disease. A real-time PCR assay was designed to assess DNA extraction methods and to detect three Encephalitozoon species in feces. Modifications of the MagNA Pure LC DNA isolation kit protocol (Roche Applied Sciences, Indianapolis, Ind.) were compared by using the automated MagNA Pure LC instrument (Roche) and fecal specimens spiked with Encephalitozoon intestinalis spores. Extracted DNA was amplified by the LightCycler (Roche) PCR assay. Assay sensitivity, reproducibility, and efficiency were assessed by comparing threshold crossover values achieved with different extraction and storage conditions (fresh, refrigerated, frozen, and preserved specimens). Optimal extraction conditions were achieved by using a commercial buffer, tissue lysis buffer (Roche), as the specimen diluent. LightCycler PCR results were compared to those obtained from routine stool microscopy with trichrome blue stain. The lower limit of detection for the LightCycler PCR assay varied by storage conditions from 10(2) to 10(4) spores/ml of feces, a value which represented a significant improvement over that achieved by staining (> or =1.0 x 10(6) spores/ml). Melting temperature analysis of the amplicons allowed for the differentiation of three Encephalitozoon species (E. intestinalis, E. cuniculi, and E. hellem). The assay is readily adaptable to the clinical laboratory and represents the first real-time PCR assay designed to detect Encephalitozoon species.

A single genotype of Encephalitozoon intestinalis infects free-ranging gorillas and people sharing their habitats in Uganda

Microsporidian spores have been detected by Chromotrope 2R and calcofluor stains in fecal samples of three free-ranging human-habituated mountain gorillas in Uganda and in two people who share gorilla habitats. All spore isolates have been identified by PCR with species-specific primers and fluorescent in situ hybridization with a species-specific oligonucleotide probe to be Encephalitozoon intestinalis. Sequencing analyses of the full length SSUrRNA amplified from all spore isolates were identical with Enc. intestinalis SSUrRNA GenBank SIU09929. Sequences generated from a fragment containing the internal transcribed spacer of these isolates were identical to GenBank sequence Y11611, i.e., Enc. intestinalis of anthroponotic origin. A single pathogen genotype in two genetically distant but geographically united host groups indicates anthropozoonotic transmission of Enc. intestinalis. It is highly unlikely that these two identical Enc. intestinalis genotypes were acquired independently by gorillas and people; it is much more probable that one group initiated infection of the other.

Fox encephalitozoonosis: isolation of the agent from an outbreak in farmed blue foxes (Alopex lagopus) in Finland and some hitherto unreported pathologic lesions

The farmed blue fox (Alopex lagopus) is particularly susceptible to congenital infections of the microsporidian species Encephalitozoon cuniculi. This report is based on an outbreak of the disease in Finland with high mortality. Five pups (four males and one female) with prolonged disease were examined. The pups had moderate pathological alterations in the kidneys and mild lesions were found in the brains, hearts, salivary and prostatic glands. Diagnosis of E. cuniculi infection was made from serological tests (ELISA, CIA, IFAT), and by in vitro isolation of the parasite from the brain of all five pups investigated. The identity was confirmed by molecular means as E. cuniculi strain II ('mouse strain'). Novel histopathological lesions not described as yet in fox encephalitozoonosis are presented. These include cerebral infarction and necrotizing inflammation of the renal pelvis. The sources and mechanisms of spreading of E. cuniculi to blue foxes are discussed.

First isolation and characterisation of Encephalitozoon cuniculi from a free-ranging rat (Rattus norvegicus)

The microsporidian species Encephalitozoon cuniculi can infect a wide variety of mammals including man. It is a common parasite in rabbits and several sporadic infections in laboratory rats have been described. Based on molecular data three E. cuniculi strains have been identified. Here we describe the first in vitro propagation of E. cuniculi, which was isolated from a free-ranging rat (Rattus norvegicus). The rat was one of three seropositive animals among 23 rats captured in the city of Zurich. The new isolate was further characterised as strain II ("mouse"-strain) based on the rDNA internal transcribed spacer sequence. Western blot analysis of this isolate revealed slight differences to other available strain II isolates originating from laboratory mice and farmed blue foxes. The new isolate caused disseminated infection in liver and lung upon oral inoculation of Brown Norway (BN) rats and was transmitted to sentinel rats. This rat-adapted isolate will be valuable to study the pathogenesis of Encephalitozoon infections in the rat model.

Disseminated microsporidiosis caused by Encephalitozoon cuniculi III (dog type) in an Italian AIDS patient: a retrospective study

We report a case of disseminated microsporidiosis in an Italian woman with AIDS. This study was done retrospectively using formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy. Microsporidia spores were found in the necrotic lesions of the liver, kidney, and adrenal gland and in ovary, brain, heart, spleen, lung, and lymph nodes. The infecting agent was identified as belonging to the genus Encephalitozoon based on transmission electron microscopy and indirect immunofluorescence. Additional molecular studies, including sequence of the rDNA internal transcribed spacer region, identified the agent as E. cuniculi, Genotype III. We believe that this is the first report of a human case of disseminated microsporidial infection involving the ovary.

In vitro activities of two antimitotic compounds, pancratistatin and 7-deoxynarciclasine, against Encephalitozoon intestinalis, a microsporidium causing infections in humans

The antiparasitic effect of a collection of compounds with antimitotic activity has been tested on a mammalian cell line infected with Encephalitozoon intestinalis, a microsporidian causing intestinal and systemic infection in immunocompromised patients. The antiparasitic effect was evaluated by counting the number of parasitophorous vacuoles detected by immunofluorescence. Out of 526 compounds tested, 2 (pancratistatin and 7-deoxynarciclasine) inhibited the infection without affecting the host cell. The 50% inhibitory concentrations (IC(50)s) of pancratistatin and 7-deoxynarciclasine for E. intestinalis were 0.18 microM and 0.2 microM, respectively, approximately eightfold lower than the IC(50)s of these same compounds against the host cells. Electron microscopy confirmed the gradual decrease in the number of parasitophorous vacuoles and showed that of the two life cycle phases, sporogony was more sensitive to the inhibitors than merogony. Furthermore, the persistence of meronts in some cells apparently devoid of sporonts and spores indicated that the inhibitors block development rather than entry of the parasite into the host cell. The occurrence of binucleate sporoblasts and spores suggests that these inhibitors blocked a specific phase of cell division.

Developmental expression of two spore wall proteins during maturation of the microsporidian Encephalitozoon intestinalis

Microsporidia are intracellular eukaryotes that infect many animals and cause opportunistic infections in AIDS patients. The disease is transmitted via environmentally resistant spores. Two spore wall constituents from the microsporidian Encephalitozoon intestinalis were characterized. Spore wall protein 1 (SWP1), a 50-kDa glycoprotein recognized by monoclonal antibody (MAb) 11B2, was detected in developing sporonts and at low levels on the surfaces of mature spores. In contrast, SWP2, a 150-kDa glycoprotein recognized by MAb 7G7, was detected on fully formed sporonts and was more abundant on mature spores than SWP1. Nevertheless, the SWPs appeared to be complexed on the surfaces of mature spores. SWP1 and SWP2 are similar at the DNA and protein levels and have 10 conserved cysteines in the N-terminal domain, suggesting similar secondary structures. The C-terminal domain of SWP2 has a unique region containing 50 repeating 12- or 15-amino-acid units that lacks homology to known protein motifs. Antibodies from mice infected with E. intestinalis recognized SWP1 and SWP2. The characterization of two immunogenic SWPs from E. intestinalis will allow the study of exospore structure and function and may lead to the development of useful tools in the diagnosis and treatment of microsporidiosis.

Genotyping Encephalitozoon cuniculi by multilocus analyses of genes with repetitive sequences

Encephalitozoon cuniculi infects a wide range of mammalian hosts. Three genotypes based on the number of GTTT repeats in the internal transcribed spacer (ITS) of the rRNA have been described, of which genotypes I and III have been identified in humans. In this study, the genetic diversity of E. cuniculi was examined at the polar tube protein (PTP) and spore wall protein I (SWP-1) loci. Nucleotide sequence analysis of the PTP gene divided 11 E. cuniculi isolates into three genotypes in congruence with the result of analysis of the ITS of the rRNA gene. The three PTP genotypes differed from one another by the copy number of the 78-bp central repeat as well as point mutations. These E. cuniculi isolates also differed from one another in the number of 15- and 36-bp repeats in the SWP-1 gene. In addition, some E. cuniculi isolates had heterogeneous copies of the SWP-1 gene with various numbers of repeats. Intragenotypic variation was also observed at the SWP-1 locus. Based on the length polymorphism and sequence diversities of the PTP and SWP-1 genes, two simple PCR tests were developed to differentiate E. cuniculi in clinical samples.

Genotyping Encephalitozoon hellem isolates by analysis of the polar tube protein gene

To develop an alternative genotyping tool, the genetic diversity of Encephalitozoon hellem was examined at the polar tube protein (PTP) locus. Nucleotide sequence analysis of the PTP gene divided 24 E. hellem isolates into four genotypes, compared to two genotypes identified by analysis of the internal transcribed spacer of the rRNA gene. The four PTP genotypes differed from each other by the copy number of the 60-bp central repeat as well as by point mutations. A simple PCR test was developed to differentiate E. hellem genotypes based on the difference in the size of PTP PCR products, which should facilitate the genotyping of E. hellem in clinical samples.

In vitro culture, ultrastructure, antigenic, and molecular characterization of Encephalitozoon cuniculi isolated from urine and sputum samples from a Spanish patient with AIDS

In this report we describe the cultivation of two isolates of microsporidia, one from urine and the other from sputum samples from a Spanish AIDS patient. We identified them as Encephalitozoon cuniculi, type strain III (the dog genotype), based on ultrastructure, antigenic characteristics, PCR, and the sequence of the ribosomal DNA internal transcribed spacer region.

Isolation of Encephalitozoon cuniculi using primary tissue culture techniques from a rabbit in a colony showing encephalitozoonosis

Encephalitozoon spores were isolated in a primary tissue culture of the kidneys from an encephalitozoonosis-suspected rabbit in a municipal zoo in Hokkaido. The isolated spores were morphologically characteristic of microsporidial ones in chromotrope stain, and proven to be E. cuniculi by a polymerase chain reaction (PCR) with a species-specific primer set and by direct DNA sequencing of the PCR products.

Dissemination of Encephalitozoon intestinalis, a causative agent of human microsporidiosis, in IFN-gamma receptor knockout mice

The dissemination of Encephalitozoon intestinalis, a microsporidium causing intestinal diseases and systemic infection in humans, was investigated in IFN-gamma Ro/o mice. Although lesions were seen in organs of autopsied animals, the parasites were rarely detected using histological examination. Nevertheless, infection of the duodenum, liver, kidneys and lungs was demonstrated by polymerase chain reaction. This method also enabled the detection of the parasite in the brain and the heart. The development of E. intestinalis in RK13 cell cultures to which cell suspensions from liver, kidney, lung or brain of infected IFN-gamma Ro/o mice were added, confirmed the spread of intestinal microsporidiosis to these organs. No dissemination was observed in wild-type mice. These results confirm those of previous studies and emphasize the low morbidity of the infection in IFN-gamma Ro/o mice and confirm the role of IFN-gamma in the control of E. intestinalis infection. These mice infected with E. intestinalis offer important information about this interesting and important parasitic disease of man and animals.

Microsporidial AIDS cholangiopathy due to Encephalitozoon intestinalis: case report and review

Microsporidia are increasingly recognized as opportunistic infections in immunodeficient patients, predominantly patients with AIDS. The two microsporidia most commonly associated with disease in AIDS patients are Enterocytozoon bieneusi and Encephalitozoon intestinalis (previously known as Septata intestinalis). The most common clinical presentation of microsporidiosis in AIDS patients is diarrhea, most commonly caused by the Enterocytozoon bieneusi species. Encephalitozoon intestinalis is a recently described species that has been reported to cause disseminated human infection including cholangitis. We report a case of AIDS cholangiopathy that presented with abdominal pain and cholestatic liver tests. Ultrasound examination and ERCP revealed a picture of sclerosing cholangitis. Bile samples obtained at ERCP were negative for microsporidia; stool studies for microsporidia and cryptosporidia were also negative. No organisms were identified on routine light microscopy of the biopsy specimens from the duodenum, ampulla, and bile duct. E. intestinalis spores were demonstrated in the bile duct biopsies, by methylene blue and azure 11 staining and confirmed by electron microscopy. Albendazole therapy was successful in eradicating E. intestinalis with clinical improvement and improvement in CD4 count. However, the cholangiographic picture did not improve and repeat cholangiography revealed progressive bile duct injury. Albendazole therapy was delayed and may have been too late to prevent bile duct damage; the drug had to be approved by the US Food and Drug Administration for compassionate use. This is an unusual case of sclerosing cholangitis caused by an unusual organism and requiring biliary sphincterotomy and stent placement for progressive stricturing despite eradication of the infection.

Isolation and characterization of an avian isolate of Encephalitozoon hellem

Members of the phylum Microspora are a group of unusual, obligate intracellular eukaryotic parasites that infect a wide range of hosts. However, there are a limited number of microsporidial infections reported in avian hosts, and no parasite species has been defined as an avian pathogen. A microsporidian organism was recovered from the droppings of a clinically normal peach-faced lovebird (Agapornis roseicollis) and established in in vitro culture. Intermittent parasite spore shedding was documented over a 2-month period using calcofluor M2R staining of cloacal swabs. The organism was identified as Encephalitozoon hellem based on protein and antigenic profiles and molecular sequencing of the small subunit and internal transcribed spacer regions of the ribosomal RNA gene.

Microsporidia: emerging advances in understanding the basic biology of these unique organisms

Microsporidia are long-known parasites of a wide variety of invertebrate and vertebrate hosts. The emergence of these obligate intracellular organisms as important opportunistic pathogens during the AIDS pandemic and the discovery of new species in humans renewed interest in this unique group of organisms. This review summarises recent advances in the field of molecular biology of microsporidia which (i) contributed to the understanding of the natural origin of human-infecting microsporidia, (ii) revealed unique genetic features of their dramatically reduced genome and (iii) resulted in the correction of their phylogenetic placement among eukaryotes from primitive protozoans to highly evolved organisms related to fungi. Microsporidia might serve as new intracellular model organisms in the future given that gene transfer systems will be developed.

Genetic homology among thirteen Encephalitozoon intestinalis isolates obtained from human immunodeficiency virus-infected patients with intestinal microsporidiosis

The ribosomal DNA internal transcribed spacer sequences of 13 unrelated Encephalitozoon intestinalis isolates obtained from human immunodeficiency virus (HIV)-infected patients with intestinal microsporidiosis were analyzed by gene amplification and DNA sequencing. Among these isolates, we found only one genetic lineage which suggests that E. intestinalis may have a clonal distribution in HIV-infected patients.

A spore counting method and cell culture model for chlorine disinfection studies of Encephalitozoon syn. Septata intestinalis

The microsporidia have recently been recognized as a group of pathogens that have potential for waterborne transmission; however, little is known about the effects of routine disinfection on microsporidian spore viability. In this study, in vitro growth of Encephalitozoon syn. Septata intestinalis, a microsporidium found in the human gut, was used as a model to assess the effect of chlorine on the infectivity and viability of microsporidian spores. Spore inoculum concentrations were determined by using spectrophotometric measurements (percent transmittance at 625 nm) and by traditional hemacytometer counting. To determine quantitative dose-response data for spore infectivity, we optimized a rabbit kidney cell culture system in 24-well plates, which facilitated calculation of a 50% tissue culture infective dose (TCID(50)) and a minimal infective dose (MID) for E. intestinalis. The TCID(50) is a quantitative measure of infectivity and growth and is the number of organisms that must be present to infect 50% of the cell culture wells tested. The MID is as a measure of a system's permissiveness to infection and a measure of spore infectivity. A standardized MID and a standardized TCID(50) have not been reported previously for any microsporidian species. Both types of doses are reported in this paper, and the values were used to evaluate the effects of chlorine disinfection on the in vitro growth of microsporidia. Spores were treated with chlorine at concentrations of 0, 1, 2, 5, and 10 mg/liter. The exposure times ranged from 0 to 80 min at 25 degrees C and pH 7. MID data for E. intestinalis were compared before and after chlorine disinfection. A 3-log reduction (99.9% inhibition) in the E. intestinalis MID was observed at a chlorine concentration of 2 mg/liter after a minimum exposure time of 16 min. The log(10) reduction results based on percent transmittance-derived spore counts were equivalent to the results based on hemacytometer-derived spore counts. Our data suggest that chlorine treatment may be an effective water treatment for E. intestinalis and that spectrophotometric methods may be substituted for labor-intensive hemacytometer methods when spores are counted in laboratory-based chlorine disinfection studies.

Actin mediates Encephalitozoon intestinalis entry into the human enterocyte-like cell line, Caco-2

Microsporidia are spore-forming obligate intracellular eucaryotes that parasitize eukaryotic cells. Encephalitozoon intestinalis (formerly Septata intestinalis) is a microsporidian species of emerging medical importance, responsible for chronic diarrhoea in immunocompetent patients and enteritis and systemic infections in HIV-1 infected patients. Infection of host enterocytes has been demonstrated in HIV-1-infected patients. However, the mechanisms of entry of E. intestinalis into host enterocytes have not been studied and remain hypothetically based on diacytosis, a model involving the injection of microsporidian sporoplasm through the polar tubule into the host cell. An electron microscopy based study recently challenged this hypothesis. We studied the entry of E. intestinalis into intestinal epithelial cells by infecting the human enterocyte-like cell line Caco-2. Entry was mediated by directed phagocytosis, as suggested by the inhibiting effect of cytochalasin D on E. intestinalis uptake, colocalization of E. intestinalis and F-actin and engulfment of E. intestinalis into Caco-2 cell protrusions. Confocal- and electron microscopy observations also suggested that after initial contacts through the posterior pole of the microsporidian spore, the basolateral surface of Caco-2 cells may be the portal of entry for E. intestinalis sporoplasm. Our observations allowed us to propose a new, actin-based model to describe the entry of microsporidia into enterocytes.

Identification of proteins in Encephalitozoon intestinalis, a microsporidian pathogen of immunocompromised humans: an immunoblotting and immunocytochemical study

Microsporidia are unicellular and obligate intracellular spore-forming parasites. The spore inoculates the host cell with its non-motile infectious content, the sporoplasm, by way of the polar tube--the typical invasive apparatus of the microsporidian spore. Molecules involved in host cell invasion were investigated in Encephalitozoon intestinalis. Mouse polyclonal and monoclonal antibodies were raised against spore proteins and their reactivity was tested by Western-blotting and immunolocalization techniques, including electron and confocal microscopy. The antibodies thus generated could be divided into two major groups. One group reacted to the surface of the parasite at different developmental stages, mostly presporous stages and mature spores, whereas the other group recognized the polar tube. Of the antibodies reacting to the spore wall, one identified an exospore protein at 125 kDa while all others recognized a major doublet at 55-60 kDa, and minor proteins present at the surface of sporogonic stages and in the endospore. All antibodies recognizing spore wall proteins reacted also to the material forming septa in the parasitophorous vacuole. A major polar tube protein at 60 kDa was identified by another group of antibodies.

Encephalitozoon cuniculi strain III is a cause of encephalitozoonosis in both humans and dogs

Microsporidia are obligate intracellular eukaryotic organisms found in a wide range of vertebrate and invertebrate hosts. Encephalitozoon cuniculi is commonly found in domestic rabbits and rodents and also occurs in dogs, other canids, and primates, including humans. DNA sequencing of the ribosomal RNA genes has been used to identify these parasites to a species level and to define E. cuniculi strains I, II, and III. Eight new dog isolates were characterized as E. cuniculi strain III by use of molecular methods. This strain has also been identified in isolates from immunocompromised humans, suggesting the zoonotic potential of this parasite species. Prolonged microsporidial spore shedding from asymptomatic dogs is also reported.