A microsporidian isolated from an AIDS patient corresponds to Encephalitozoon cuniculi III, originally isolated from domestic dogs

Encephalitozoon spp. as a potential human pathogen

Encephalitzoon spp. are microsporidia, and intracellular opportunistic pathogens. The hosts of these pathogens include vertebrates, invertebrates, and certain protozoa. In people microsporidia may be opportunistic pathogens for immunocompromised patients (with AIDS or after organ transplantation). Infection with these microorganisms was also described in persons with diarrhea and corneal diseases.

The species causing rare infections in humans, Encephalitozooncuniculi, had previously been described from animal hosts. However, several new microsporidial species, including E. intestinalis and E. hellem, have been discovered in humans, raising the question of their natural origin. Vertebrate animals are now identified as hosts for all three microsporidial species infecting humans, implying a zoonotic nature of these microorganisms. 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 to present the zoonotic potential of E. intestinalis, E. cuniculi, and E. hellem.

Microsporidiosis in Humans

Microsporidia are obligate intracellular pathogens identified ∼150 years ago as the cause of pébrine, an economically important infection in silkworms. There are about 220 genera and 1,700 species of microsporidia, which are classified based on their ultrastructural features, developmental cycle, host-parasite relationship, and molecular analysis. Phylogenetic analysis suggests that microsporidia are related to the fungi, being grouped with the Cryptomycota as a basal branch or sister group to the fungi. Microsporidia can be transmitted by food and water and are likely zoonotic, as they parasitize a wide range of invertebrate and vertebrate hosts. Infection in humans occurs in both immunocompetent and immunodeficient hosts, e.g., in patients with organ transplantation, patients with advanced human immunodeficiency virus (HIV) infection, and patients receiving immune modulatory therapy such as anti-tumor necrosis factor alpha antibody. Clusters of infections due to latent infection in transplanted organs have also been demonstrated. Gastrointestinal infection is the most common manifestation; however, microsporidia can infect virtually any organ system, and infection has resulted in keratitis, myositis, cholecystitis, sinusitis, and encephalitis. Both albendazole and fumagillin have efficacy for the treatment of various species of microsporidia; however, albendazole has limited efficacy for the treatment of Enterocytozoon bieneusi. In addition, immune restoration can lead to resolution of infection. While the prevalence rate of microsporidiosis in patients with AIDS has fallen in the United States, due to the widespread use of combination antiretroviral therapy (cART), infection continues to occur throughout the world and is still seen in the United States in the setting of cART if a low CD4 count persists.

The opportunistic pathogen Encephalitozoon cuniculi in wild living Murinae and Arvicolinae in Central Europe

Encephalitozoon spp. is an obligate intracellular microsporidian parasite that infects a wide range of mammalian hosts, including humans. This study was conducted to determine the prevalence of Encephalitozoon spp. in wild living rodents from Poland, the Czech Republic and Slovakia. Faecal and spleen samples were collected from individuals of Apodemus agrarius, Apodemus flavicollis, Apodemus sylvaticus, and Myodes glareolus (n = 465) and used for DNA extraction. PCR, targeting the ITS region of the rRNA gene was performed. The overall prevalence of microsporidia was 15.1%. The occurrence of Encephalitozoon cuniculi in the abovementioned host species of rodents has been presented for the first time, with the highest infection rate recorded for A. flavicollis. Sequence analysis showed that the most frequent species was E. cuniculi genotype II (92.5%). E. cuniculi genotypes I (1.5%) and III (6.0%) were also identified.

Serological survey of Encephalitozoon cuniculi infection in cats in Japan

Antibodies to Encephalitozoon cuniculi (E. cuniculi) were examined by enzyme-linked immunosorbent assay using E. cuniculi PTP2 recombinant protein from serum samples that had been collected from a total of 295 cats in Japan. Of these samples, 6.1% (18/295) had antibodies against E. cuniculi, which included 6.3% (6/96) of the male cats and 6.0% (12/199) of the female cats. The incidence was slightly higher in feral cats (8.3%, 11/132) compared to domesticated cats (4.3%, 7/163). This suggests the possibility that the cats of our country have become a reservoir of E. cuniculi. This study is the first to demonstrate the prevalence of E. cuniculi infection in cats in Japan.

Microsporidiosis in Vertebrate Companion Exotic Animals

Veterinarians caring for companion animals may encounter microsporidia in various host species, and diagnosis and treatment of these fungal organisms can be particularly challenging. Fourteen microsporidial species have been reported to infect humans and some of them are zoonotic; however, to date, direct zoonotic transmission is difficult to document versus transit through the digestive tract. In this context, summarizing information available about microsporidiosis of companion exotic animals is relevant due to the proximity of these animals to their owners. Diagnostic modalities and therapeutic challenges are reviewed by taxa. Further studies are needed to better assess risks associated with animal microsporidia for immunosuppressed owners and to improve detection and treatment of infected companion animals.

Seroprevalence of Encephalitozoon cuniculi in Humans and Rabbits in China

BACKGROUND

Encephalitozoon cuniculi is a microsporidian parasite commonly found in rabbits that can infect humans, causing encephalitozoonosis. Our objective in this study was to evaluate the seroprevalence of this parasite in rabbits and humans in China.

METHODS

Overall, 300 serum samples each from clinically healthy rabbit and human were collected from three regions of China (Sichuan Province, Chongqing Municipality and Jilin Province) from January to September 2013 and tested for anti-E. Cuniculi antibodies using an ELISA.

RESULTS

An overall seroprevalence of E. cuniculi was recorded as 56/300 (18.76%) and 29/300 (9.76%) in rabbit and human sera, respectively. The seropositivity of rabbit samples collected from Jilin province was 41%, which was significantly higher (P<0.01) than Sichuan Province (9%) and Chongqing Municipality (6%). Three breeds of rabbit were used in the present study and antibody detection in Rex Rabbit was significantly (P<0.01) higher than Japanese White and New Zealand Rabbit. In human, Jilin province was more prevalent (18%) followed by Sichuan Province (6%) and Chongqing Municipality (5%).

CONCLUSIONS

The E. cuniculi was present and widespread among healthy rabbits and humans in China.

Evaluation of spore wall protein 1 as an alternative antigen for the diagnosis of Encephalitozoon cuniculi infection of farmed foxes using an enzyme-linked immunosorbent assay

The sequence encoding SWP1 was cloned from the genome of Encephalitozoon cuniculi. Recombinant SWP1 (rSWP1) was expressed in Escherichia coli and used to detect E. cuniculi infections in farmed foxes and dogs with an indirect enzyme-linked immunosorbent assay (ELISA) in the present study. The sera of foxes infected with E. cuniculi could be distinguished from the sera of foxes infected with Toxoplasma gondii, Neospora caninum, and Cryptosporidium parvum using the ELISA. In total, 198 fox samples collected in Liaoning were used to determine the prevalence of antibodies against this disease. The results showed that 16.7% of the fox serum samples were positive according to the ELISA using rSWP1, which agreed with the ELISA results based on recombinant PTP2 (rPTP2). The sensitivity and specificity of the ELISA based on rSWP1 suggest that this could be an alternative method for the diagnosis of E. cuniculi infections in foxes. In addition, 298 dog samples collected in Beijing, Shanghai, and Hunan were also detected in this study, of which six dog samples (2%) were positive according to the ELISA using rSWP1. To the best of our knowledge, this is the first study to demonstrate the serological prevalence of E. cuniculi infections in dogs and foxes in China.

Microsporidiosis acquired through solid organ transplantation: a public health investigation

BACKGROUND

Encephalitozoon cuniculi, a microsporidial species most commonly recognized as a cause of renal, respiratory, and central nervous system infections in immunosuppressed patients, was identified as the cause of a temporally associated cluster of febrile illness among 3 solid organ transplant recipients from a common donor.

OBJECTIVE

To confirm the source of the illness, assess donor and recipient risk factors, and provide therapy recommendations for ill recipients.

DESIGN

Public health investigation.

SETTING

Two transplant hospitals and community interview with the deceased donor's family.

PATIENTS

Three transplant recipients and the organ donor.

MEASUREMENTS

Specimens were tested for microsporidia by using culture, immunofluorescent antibody, polymerase chain reaction,immunohistochemistry, and electron microscopy. Donor medical records were reviewed and a questionnaire was developed to assess for microsporidial infection.

RESULTS

Kidneys and lungs were procured from the deceased donor and transplanted to 3 recipients who became ill with fever 7 to 10 weeks after the transplant. Results of urine culture, serologic,and polymerase chain reaction testing were positive for E. cuniculi of genotype III in each recipient; the organism was also identified in biopsy or autopsy specimens in all recipients. The donor had positive serologic test results for E. cuniculi. Surviving recipients received albendazole. Donor assessment did not identify factors for suspected E. cuniculi infection.

LIMITATION

Inability to detect organism by culture or polymerase chain reaction in donor due to lack of autopsy specimens.

CONCLUSION

Microsporidiosis is now recognized as an emerging transplant-associated disease and should be considered in febrile transplant recipients when tests for routinely encountered agents are unrevealing. Donor-derived disease is critical to assess when multiple recipients from a common donor are ill.

In vitro growth of the microsporidian Heterosporis saurida in the eel kidney EK-1 cell line

Heterosporis saurida is an intracellular microsporidian that infects lizardfish Saurida undosquamis. Although some attempts have been introduced to clarify microsporidian host-pathogen interactions, development of novel strategies to combat fish diseases is still needed. Here we present an in vitro cultivation model for fish microsporidia based on an eel kidney cell line (EK-1), which is susceptible to infection by H. saurida. Spores were isolated from infected lizardfish and used to inoculate EK-1 cells. H. saurida were propagated in the eel kidney EK-1 cell line and detected by immunofluorescence. Developmental stages of H. saurida were seen in EK-1 cells by transmission electron microscopy. Identity of the parasite was confirmed by partial sequencing of the 16S rDNA gene. Our cell culture model provides a valuable means to explore molecular and immunological events and will facilitate development of effective treatment strategies.

Seroprevalence of Encephalitozoon cuniculi in wild rodents, foxes and domestic cats in three sites in the United Kingdom

Encephalitozoon cuniculi is an obligate intracellular microsporidian that is the causal agent of encephalitozoonosis, an important and emerging disease in both humans and animals. Little is known about its occurrence in wildlife. In this study, serum samples from 793 wild rodents [178 bank voles (BV), 312 field voles (FV) and 303 wood mice (WM)], 96 foxes and 27 domestic cats from three study areas in the UK were tested for the presence of antibodies to E. cuniculi using a direct agglutination test (DAT). Seroprevalence in the wild rodents ranged from 1.00% to 10.67% depending on species (overall 5.31%) and was significantly higher in foxes [49.50% (50/96)]. None of the 27 cats sampled were found to be seropositive. This is the first report of seroprevalence to E. cuniculi in BV, FV, WM, foxes and cats in the UK and provides some evidence that foxes could act as sentinels for the presence of E. cuniculi in rodents. The study demonstrates that wildlife species could be significant reservoirs of infection for both domestic animals and humans.

Microsporidia as emerging pathogens and the implication for public health: a 10-year study on HIV-positive and -negative patients

Despite recent advances in the understanding and diagnosis of emerging microsporidian pathogens, more research is necessary to elucidate their complex epidemiology. In fact, studies that reflect true human-infecting microsporidian prevalence are still inadequate. The present 10-year study was undertaken to examine the occurrence of Microsporidia in 1989 stools, 69 urine and 200 pulmonary specimens from HIV-positive and HIV-negative patients using PCR and DNA sequencing. In stools, 12.0% were Microsporidia-positive. Prevalences of 13.9% and 8.5% were observed for HIV+ and HIV- samples, respectively. The percentage of children that were Microsporidia-positive (18.8%) was significantly higher than that of adults (10.2%). In stools, Enterocytozoon bieneusi (6.3%) and Vittaforma-like parasites (6.8%) were identified. Based on the internal transcribed spacer (ITS) region of E. bieneusi, Type IV (37.5%), Peru 6 (29.2%), D (12.5%), A (8.3%), C (6.3%) and PtEb II (6.3%) genotypes were identified. Microsporidia were detected in 1.5% and 1.0% of urine and pulmonary specimens, respectively. Encephalitozoonintestinalis was detected in urine. In pulmonary specimens, Encephalitozoon cuniculi and Vittaforma-like parasites were identified. An immunosuppressive condition and youth (children) appear to be risk factors for microsporidian infection. Microsporidia seems to have an important impact on public health in Portugal, highlighting the need to implement routine diagnosis.

Encephalitozoon cuniculi genotype I as a causative agent of brain abscess in an immunocompetent patient

A brain abscess caused by Encephalitozoon cuniculi genotype I together with Streptococcus intermedius occurred in a patient without major immunocompromise and with diabetes. The distinguishing clinical signs were hemiparesis and epilepsy. The microsporidium was observed in the abscess aspirate, and its specific DNA was also detected in stool and urine. The patient was successfully treated with albendazole and mebendazole.

Emerging microsporidian infections in Russian HIV-infected patients

Microsporidia were identified in stool specimens by histochemistry and PCR of 30 (18.9%) of 159 HIV-infected patients presenting to the S. P. Botkin Memorial Clinical Hospital of Infectious Diseases, St. Petersburg, Russia. The higher prevalence of Encephalitozoon intestinalis, in 21 (12.8%) patients, than of Enterocytozoon bieneusi, in 2 patients (1.2%), was unexpected. Encephalitozoon cuniculi was detected in three patients: one with strain I and two with strain II. Encephalitozoon hellem was detected in one patient, and two patients were identified as being infected by Microsporidium species. One patient was infected with both E. intestinalis and E. cuniculi. In two patients, the microsporidian species were not identifiable. No statistically significant differences in gender, age, and stage of AIDS were observed between the microsporidian-positive and -negative HIV-infected patients. HIV-infected patients diagnosed with microsporidian infection, however, were significantly more likely to exhibit ≤ 100 CD4(+) T cells/μl blood (20/30 patients [67%]; odds ratio [OR], 3.150; 95% confidence interval [CI(95)], 1.280 to 7.750; P = 0.0116) and weight loss of >10% of the baseline (19/30 patients [63%]; odds ratio, 2.995; CI(95), 1.100 to 8.158; P = 0.0352) than HIV-infected patients not diagnosed with microsporidian infection. In summary, this is the first report describing the diagnosis of microsporidian infection of HIV-infected patients in Russia and the first detection of E. cuniculi strain II in a human.

Serological survey of Encephalitozoon cuniculi infection in Japanese dogs

Antibodies to Encephalitozoon cuniculi were examined by enzyme-linked immunosorbent assay using E. cuniculi PTP2 recombinant protein and by Western blot analysis on a total of 472 dog serum samples that had been collected in Japan. Of these samples, 21.8% (103/472) had antibodies against E. cuniculi. Each of 5 serum samples that showed high (>1.0) or low (<0.1) OD value was selected randomly and further examined by Western blot using E. cuniculi-native antigens. All samples with high OD values reacted with specific E. cuniculi proteins, including an antigen of approximately 35 kDa corresponding with PTP2; sera with low OD values did not recognize this E. cuniculi band. This study is the first to demonstrate the prevalence of E. cuniculi infection in dogs in Japan.

Encephalitozoon cuniculi infections in dogs: a case series

Encephalitozoon (E.) cuniculi has been occasionally identified as a cause of neurological or renal disease in dogs, but cases are not well documented in the United States. The medical records from a state veterinary diagnostic laboratory for 19 cases of fatal encephalitozoonosis in puppies were reviewed. Clinical histories included depression, inappetence, and progressive neurological signs of short duration. Histopathological evaluation showed brain and renal lesions typical of encephalitis and nephritis, respectively. Molecular analyses of parasites from 13 cases confirmed the identity of the organisms as E. cuniculi strain III. This parasite may be an underdiagnosed cause of fatal canine neurological or renal disease.

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.

Systenostrema alba Larsson 1988 (Microsporidia, Thelohaniidae) in the Dragonfly Aeshna viridis (Odonata, Aeshnidae) from South Siberia: morphology and molecular characterization

An octospore microsporidium was found in the nymphs of Aeshna viridis, collected in intermittent streams near Novosibirsk, Siberia, Russia in 2003. Spores were uninucleate and measured 6.1+/-0.07 x 3.0+/-0.04 microm on fresh smears. The polar filament was anisofilar having 10-11 anterior coils (thicker filament diam.) and 10-11 posterior (thinner filament diam.) coils. Sporophorous vesicles were persistent and measured 12.3+/-0.23 x 11.9+/-0.20 microm. The infection was restricted to the adipose tissue and caused the formation of whitish "cysts" containing mature octospores. Based on ultrastructural similarity we consider this Siberian isolate to be Systenostrema alba, a species described from Aeshna grandis collected in Sweden (Larsson 1988). Maximum likelihood, neighbor joining, and maximum parsimony analyses of the small subunit rDNA all placed Systenostrema alba (Accession no. AY953292) as the sister taxon to a clade consisting of Thelohania solenopsae, Tubulinosema ratisbonensis, and Tubulinosema acridophagus.

ITS1 sequence variabilities correlate with 18S rDNA sequence types in the genus Acanthamoeba (Protozoa: Amoebozoa)

The subgenus classification of the ubiquitously spread and potentially pathogenic acanthamoebae still poses a great challenge. Fifteen 18S rDNA sequence types (T1-T15) have been established, but the vast majority of isolates fall into sequence type T4, and so far, there is no means to reliably differentiate within T4. In this study, the first internal transcribed spacer (ITS1), a more variable region than the 18S rRNA gene, was sequenced, and the sequences of 15 different Acanthamoeba isolates were compared to reveal if ITS1 sequence variability correlates with 18S rDNA sequence typing and if the ITS1 sequencing allows a differentiation within T4. It was shown that the variability in ITS1 is tenfold higher than in the 18S rDNA, and that ITS1 clusters correlate with the 18S rDNA clusters and thus corroborate the Acanthamoeba sequence type system. Moreover, high sequence dissimilarities and distinctive microsatellite patterns could enable a more detailed differentiation within T4.

Enterocytozoon bieneusi (microsporidia) in clinical samples from immunocompetent individuals in Tenerife, Canary Islands, Spain

Microsporidia are newly emerging pathogens of humans and animals, with Enterocytozoon bieneusi being the most common causal agent in human microsporidiosis. To determine the presence of E. bieneusi, 273 clinical samples (40 urine, 156 stools, 37 sputum, 9 bronchial aspirates, 5 bronchial washes and 26 pleural fluids) from immunocompetent patients, mainly suffering diarrhoea or pneumonia, in Tenerife, Canary Islands, Spain were analysed using light microscopy after staining with Weber's chromotrope and by PCR/hybridisation with a specific probe designed to increase the sensitivity of the identification. In this study, detection of E. bieneusi after PCR/hybridisation is reported in 18 (11.54%) of 156 stool samples, 1 (2.5%) of 40 urine samples and 6 (16.22%) of 37 sputum samples. To our knowledge, these are the first reports of E. bieneusi in this subtropical region, showing the increased importance of these parasites as emerging pathogens worldwide.

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.

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.

Molecular phylogeny of the Microsporidia: ecological, ultrastructural and taxonomic considerations

The Microsporidia are a group of obligate intracellular parasites, now thought to be derived fungi. Presented here is a comparative small subunit rDNA (ssrDNA) analysis of 125 species of Microsporidia (sequences obtained from GenBank). This analysis shows that groups or clades are formed based largely on habitat and host. This result is supported by comparative molecular analyses of the past decade, and indicates that structural and ultrastructural characters are unreliable for distinguishing among higher-level microsporidian taxa. Our findings indicate the presence of five major clades of Microsporidia which group according to habitat. We present three new classes of Microsporidia based on natural phylogenetic groupings as illustrated by the ssrDNA analysis: Aquasporidia, Marinosporidia and Terresporidia. The names of the proposed classes reflect the habitat of each group. The class Aquasporidia, found primarily in freshwater habitats, is a paraphyletic group consisting of three clades. The Marinosporidia are found in hosts of marine origin and the Terresporidia are primarily from terrestrial environments.

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.

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.

Intraspecies genotype variability of the microsporidian parasite Encephalitozoon hellem

Seven isolates of Encephalitozoon hellem from human immunodeficiency virus-positive patients were genotyped through a series of markers: the internal transcribed spacer (ITS) of ribosomal DNA, the polar tube protein (PTP) gene, and two intergenic spacers (IGS-TH and IGS-HZ) whose polymorphism is newly reported. The genome markers were all analyzed at three levels: PCR amplification followed by polyacrylamide gel electrophoresis, single-strand conformation analysis (SSCA), and DNA sequencing. The polymorphisms detected involve insertions/deletions and point mutations. SSCA can distinguish any pair of sequences, even those differing by a single base pair. The different isolates studied fit into the previously described ITS genotype 1A, except one which seems to be a 2A derivative variant (2D). When PTP and the new markers IGS-TH and IGS-HZ were analyzed, most of the isolates displayed different genotypes, demonstrating that E. hellem has a strong intraspecies variability. A set of markers such as those used here may be very useful in genotyping of clinical samples and in the assessment of epidemiological relationships among E. hellem strains.

Overt fatal and chronic subclinical Encephalitozoon cuniculi microsporidiosis in a colony of captive emperor tamarins (Saguinus imperator)

The course of an infection with the microsporidian Encephalitozoon cuniculi in a colony of captive emperor tamarins (Saguinus imperator) is described. In two litters, the infection was associated with overt disease and death of all infants. Immunohistochemistry for E. cuniculi showed generalized infections, and histopathologic evaluation revealed systemic vasculitis and disseminated mixed inflammatory cell infiltration with and without necrosis in several organs. Serologically, some of the juvenile animals presented with high titres for Encephalitozoon, while the adults had low titres. The E. cuniculi "dog strain" was identified by molecular means for the first time in Europe. The origin of the infection appeared to be a pair of breeding adults that originated from the US. Our data suggest that the organism persisted over years in the colony, and that subclinically infected animals most likely were involved in perpetuating the infection. Efforts should be made to ascertain if this microorganism is present in other captive populations of this endangered monkey species and to prevent its further spreading.

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).

Inter-strain variability of insertion/deletion events in the Encephalitozoon cuniculi genome: a comparative KARD-PFGE analysis

We applied a two-dimensional pulsed-field gel electrophoresis procedure to the genomes of two karyotype variants assigned to two different strains of the microsporidian Encephalitozoon cuniculi, termed D (strain III) and F (strain II). Data obtained for BssHII and MluI restriction fragment length polymorphisms in each chromosome are compiled and compared to the reference strain I variant A. Six Insertion/Deletion (InDels) are found in subterminal position, some of these being characteristic of either D or F. Like in strain 1, the terminal fragments extending between each telomere and rDNA locus are conserved in length for each chromosome. They are however smaller than in reference variant. This size reduction is estimated to be 2.5 kbp for the strain III isolate and 3.5 kbp for the strain II isolate. We hypothesize that for the three E. cuniculi strains, all chromosome extremities are prone to a constant process of sequence homogenization through mitotic recombination between conserved regions.

Enterocytozoon bieneusi (microsporidia) in faecal samples from domestic animals from Galicia, Spain

In this survey we examined 87 domestic animal stool samples in order to detect the possible presence of microsporidia in animals in close contact with humans in Galicia (NW, Spain). The detection of Enterocytozoon bieneusi spores was confirmed in faecal samples from two dogs and one goat by polymerase chain reaction. None of the positive samples for microsporidia in the staining method were amplified with species-specific primers for Encephalitozoon intestinalis, E. hellem and E. cuniculi. Four rabbits faecal samples reacted with anti-E. cuniculi serum. Our results could indicate the importance of domestic animals as zoonotic reservoirs of microsporidial human infections.

Disseminated microsporidiosis in a renal transplant recipient

Disseminated microsporidiosis is diagnosed uncommonly in patients not infected with human immunodeficiency virus (HIV). We present a case of disseminated microsporidiosis in a renal transplant recipient who was seronegative for HIV. Chromotrope-based stains were positive for microsporidia in urine, stools, sputum, and conjunctival scrapings. Electron microscopy, immunofluorescence, polymerase chain reaction, and cultures of renal tissue identified the organism as Encephalitozoon cuniculi. The patient was treated with oral albendazole and topical fumagillin with clinical improvement. In addition, she underwent a transplant nephrectomy and immunosuppressive therapy was withdrawn. Follow-up samples were negative for microsporidia. However, the patient developed central nervous system manifestations and died. An autopsy brain tissue specimen demonstrated E. cuniculi by immunofluorescent staining. Disseminated microsporidiosis must be considered in the differential diagnosis of multiorgan involvement in renal allograft recipients.

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.

Microsporidia and acquired immunodeficiency syndrome

Microsporidia is a common term that has been used to refer to a group of eukaryotic, obligate intracellular protozoan parasites belonging to the phylum Microspora. They are important agricultural parasites, contaminating commercial insects; they are also important by infecting laboratory rodents, rabbits and primates. Ever since the early cases found by Magarino Torres, who reported the presence of Encephalitozoon in a patient suffering of a meningoencephalomyelitis, some human pathology caused by microsporidia has been described. However, only after the acquired immunodeficiency syndrome outbreak have these organisms appeared as significant etiological agents in different pathologies. Even so, they remain underestimated. In the present article, the importance of microsporidia for the human pathology in immunocompromised host has been stressed.

Detection of microsporidia in surface water: a one-year follow-up study

In order to estimate the rate and seasonal variation of Enterocytozoon bieneusi contamination of surface water, sequential samples of water from the River Seine in France were collected during a 1-year period. Each sample (300-600 l) was submitted to sequential filtrations, and the filters were then examined for microsporidia using light microscopy and nested polymerase chain reaction (PCR) for E. bieneusi. Amplified products were hybridized with a E. bieneusi-specific probe. Twenty-five samples of water were analyzed during 1 year. Microscopic examination of stained filters proved unreliable for the identification of spores. Using nested PCR, 16 of 25 specimens were positive (64%). Unexpectedly, E. bieneusi was identified in only one sample by specific hybridization underlining the lack of specificity of ours primers. Nevertheless, using DNA sequence analysis, unknown microsporidia species were identified in eight cases, which had highest scores of homology with Vittaforma corneae or Pleistophora sp. This study shows a low rate of water contamination by E. bieneusi suggesting that the risk of waterborne transmission to humans is limited.

Disseminated infection due to Encephalitozoon cuniculi in a patient with AIDS: case report and review

OBJECTIVE AND METHODS

Infections due to microsporidia are increasingly recognized as opportunistic infections in patients with AIDS. We describe here a case of disseminated infection due to Encephalitozoon cuniculi and review the literature on this microsporidial infection.

RESULTS

All 12 patients reported in the literature had AIDS and nine presented with disseminated infection involving the kidneys, sinuses, lungs, brain and conjunctiva. Asymptomatic infection was seen in three patients. Microsporidia were detected by light microscopy examination of urine samples in all the cases. Species identification was performed by various genotypic methods or transmission electron microscopy. Eight of 12 patients who received albendazole therapy experienced clinical improvement with documented clearance of spores in five of these eight patients. Two patients relapsed.

CONCLUSIONS

E. cuniculi infection should be considered in severely immunocompromised HIV-infected patients with multi-organ involvement and fever, especially when renal failure is present. Microsporidial spores are usually seen in urine samples and in the involved organ. Albendazole therapy seems to be effective.

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.

Mammalian microsporidiosis

The phylum Microspora contains a diverse group of single-celled, obligate intracellular protozoa sharing a unique organelle, the polar filament, and parasitizing a wide variety of invertebrate and vertebrate animals, including insects, fish, birds, and mammals. Encephalitozoon cuniculi is the classic microsporidial parasite of mammals, and encephalitozoonosis in rabbits and rodents has been and continues to be recognized as a confounding variable in animal-based biomedical research. Although contemporary research colonies are screened for infection with this parasite, E. cuniculi remains a cause of morbidity and mortality in pet and conventionally raised rabbits. In addition, E. cuniculi is a potential pathogen of immature domestic dogs and farm-raised foxes. The recent discovery and identification of Encephalitozoon intestinalis, Encephalitozoon hellem, and Enterocytozoon bieneusi, in addition to E. cuniculi, as opportunistic pathogens of humans have renewed interest in the Microspora. Veterinary pathologists, trained in the comparative anatomy of multiple animal species and infectious disease processes, are in a unique position to contribute to the diagnosis and knowledge of the pathogenesis of these parasitic diseases. This review article covers the life cycle, ultrastructure, and biology of mammalian microsporaidia and the clinical disease and lesions seen in laboratory and domestic animals, particularly as they relate to Encephalitozoon species. Human microsporidial disease and animal models of human infection are also addressed. Often thought of as rabbit pathogens of historical importance, E. cuniculi and the related mammalian microsporidia are emerging as significant opportunistic pathogens of immunocompromised individuals.

Human microsporidial infection and possible animal sources

Sources of human microsporidial infection remain speculative, but possible animal reservoirs are emerging. Of the common human microsporidial infections, Enterocytozoon bieneusi has now been identified in non-human primates, pigs, dogs and a cat; Encephalitozoon intestinalis in dogs, pigs, cows, goats and donkeys and Encephalitozoon hellem in budgerigars and parrots. Evidence of species heterogeneity is also emerging suggesting that some animal isolates may be distinctive. Further molecular epidemiological studies need to be undertaken to clarify which animal genotypes can also infect humans. Some of the less common microsporidial infections found in humans, such as those involving Pleistophora-like species, may be the result of infrequent accidental exposure (for example, inadequately cooked infected fish muscle) and establishment, particularly if the individual is severely immunocompromised.