Epidemiology of microsporidiosis: sources and modes of transmission

Therapeutic effects of fumaric acid on proteomic expression and gut microbiota composition in Pacific white shrimp (Penaeus vannamei) infected with Ecytonucleospora hepatopenaei (EHP)

Recently, microsporidiosis caused by a microsporidian [Ecytonucleospora (Enterocytozoon) hepatopenaei, EHP] has been found to seriously impact the global shrimp industry. The aim of this study was to evaluate the therapeutic effects of fumaric acid (FA) in EHP-infected Pacific white shrimp (Penaeus vannamei). In the first 2 groups, non-EHP-infected shrimp were fed FA-supplemented (10 g/kg diet) or normal feed (CM+ and CM-, respectively). The other 2 groups of EHP-infected shrimp were also fed FA-supplemented or normal feed (EM+ and EM-, respectively). All the experimental groups were fed for 7 days, and the hepatopancreas and intestine of the shrimp were sampled at 0, 1, 3 and 7 days after application (DAAs). The copy number of EHP in the hepatopancreas of the EM + shrimp was significantly lower than that in the hepatopancreas of the EM-shrimp at 3 and 7 DAAs (P < 0.01). Histopathological investigation revealed that the hepatopancreas of EM + shrimp began healing from microsporidiosis at 3 DAA and had almost completely recovered at 7 DAA. Proteomic analysis also revealed that the levels of immune-related proteins, such as β-1,3-glucan-binding proteins, the tumor suppressor TP53, and protein disulfide isomerase A3, were elevated in the hepatopancreas of the CM + shrimp compared with those in the control shrimp. Microbiome analyses from both LC‒MS/MS data and next-generation sequencing (NGS) of the shrimp intestine revealed that FA supplementation strongly affected the bacterial community in the shrimp gut. Based on the results from this study in the hepatopancreas of shrimp fed a diet of 10 g/kg FA for 7 days, FA strongly affected EHP proliferation; simultaneously, it increased the levels of several key molecules involved in oxidative stress, cellular stress and pattern recognition without harmful negative side effects; and effectively influenced the gut microbiota. This research is the first to show the effectiveness of FA in promoting shrimp health in the context of microsporidiosis in Pacific white shrimp and could be further applied in the global shrimp aquaculture industry.

Digital PCR detection of microsporidia in household pipe water of patients with microsporidial keratitis

This is a prospective non-comparative experimental study aimed to investigate the presence of microsporidia in household pipe water of microsporidial keratitis (MK) patients and to describe the patients' characteristics and behavioral risk factors. This study was conducted at Walailak University Hospital, Thailand, from July 2022 to February 2024. Patients diagnosed with MK were surveyed using a questionnaire to assess personal behaviors and source of household water. Water from faucets of MK patients' houses were collected for laboratory analysis with digital polymerase chain reaction (dPCR) to detect microsporidia in water samples. The study involved 54 MK patients, with 23 households contributing water samples. Utilizing dPCR analysis, we found that all water samples were contaminated with microsporidia. Level of contamination differed depending on the water source, with households that use untreated water in their plumbing system having significantly higher copies of pathogenic microsporidial DNA. Contrary to traditionally perceived risk from soil contact into eyes, our study identifies household water as an unforeseen potential source of MK. This emphasizes the critical importance of water quality management in preventing the infection.

The global prevalence of microsporidia infection in rabbits as a neglected public health concern: A systematic review and meta-analysis

Microsporidia are intracellular parasites with significant impact on both animal and human health. The prevalence of microsporidia infections in rabbits, including the genera Enterocytozoon and Encephalitozoon, underscores the importance of understanding their epidemiology for effective control strategies. This systematic review and meta-analysis estimated the global prevalence of microsporidia infection in rabbits using five databases (Scopus, PubMed, Embase, Web of Science, and Google Scholar) to retrieve articles published between 03 December 2003 and 26 March 2023. The global prevalence was estimated with a 95 % confidence interval. All statistical analyses conducted were based on meta-package of R (version 3.6.1). A p-value lower than 0.05 was interpreted as statistically significant. A total of 71 studies comprising 72 datasets were included, yielding a global pooled prevalence of microsporidia infections in rabbits at 0.312 (0.250-0.378). The prevalence varied significantly by continent with highest observed in North America (0.495, 0.151-0.842). Slovenia had the highest pooled prevalence (0.714, 0.654-0.773). Encephalitozoon cuniculi accounted for the highest prevalence (0.338, 0.271-0.407). The findings highlight the global distribution of microsporidia in rabbit populations, emphasizing the zoonotic potential and public health implications. The predominance of E. cuniculi underscores its importance as a widespread pathogen affecting both animal and human health. The data underscore the need for continued surveillance and monitoring, particularly in regions with high prevalence.

Vinpocetine increases the microsporicidal effect of albendazole on Encephalitozoon intestinalis

Microsporidia are obligate, intracellular, spore-forming eukaryotic fungi that infect humans and animals. In the treatment of disseminated microsporidiosis albendazole is the choice of drug. In recent years, antiparasitic activity of phosphodiesterase (PDE) enzyme inhibitors has been demonstrated against parasites and fungi, however, there is no information on microsporidia. Vinpocetine is currently used as a cerebral vasodilator drug and also as a dietary supplement to improve cognitive functions. Vinpocetine inhibits PDE1, so we aimed to investigate whether vinpocetine alone or in combination with albendazole has any effect on the spore load of Encephalitozoon intestinalis (E. intestinalis)-infected HEK293 cells. After determining the noncytotoxic concentrations of vinpocetine and albendazole on the host cell by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, HEK293 cells were infected with E. intestinalis spores. Then, two different concentrations of vinpocetine, albendazole, and a combination of both drugs were applied to the cells with an interval of 72 h for 15 days. Spore load of the cells was analyzed by real-time PCR. After the last treatment, spore Deoxyribonucleic Acid (DNA) load was significantly reduced only in the group treated with 14 ng/ml albendazole. It was not different from control in groups treated with 7 ng/ml albendazole and 4-20 µM vinpocetine. However, the combination of vinpocetine significantly increased the effect of albendazole at both concentrations. To our knowledge, this is the first study to investigate the microsporicidal activity of vinpocetine as well as its combinations with albendazole. However, further studies are needed to investigate the mechanism of action and also confirm in vivo conditions.

The first evaluation of the in vitro effects of silver(I)-N-heterocyclic carbene complexes on Encephalitozoon intestinalis and Leishmania major promastigotes

Encephalitozoon intestinalis is an opportunistic microsporidian parasite that primarily infects immunocompromised individuals, such as those with HIV/AIDS or undergoing organ transplantation. Leishmaniasis is responsible for parasitic infections, particularly in developing countries. The disease has not been effectively controlled due to the lack of an effective vaccine and affordable treatment options. Current treatment options for E. intestinalis infection and leishmaniasis are limited and often associated with adverse side effects. There is no previous study in the literature on the antimicrosporidial activities of Ag(I)-N-heterocyclic carbene compounds. In this study, the in vitro antimicrosporidial activities of previously synthesized Ag(I)-N-heterocyclic carbene complexes were evaluated using E. intestinalis spores cultured in human renal epithelial cell lines (HEK-293). Inhibition of microsporidian replication was determined by spore counting. In addition, the effects of the compounds on Leishmania major promastigotes were assessed by measuring metabolic activity or cell viability using a tetrazolium reaction. Statistical analysis was performed to determine significant differences between treated and control groups. Our results showed that the growth of E. intestinalis and L. major promastigotes was inhibited by the tested compounds in a concentration-dependent manner. A significant decrease in parasite viability was observed at the highest concentrations. These results suggest that the compounds have potential anti-microsporidial and anti-leishmanial activity. Further research is required to elucidate the underlying mechanisms of action and to evaluate the efficacy of the compounds in animal models or clinical trials.

Investigation of the Infection of Enterocytozoon bieneusi in Sheep and Goats in Jiangsu, China

In order to investigate the infection status and genotypes of Enterocytozoon bieneusi (E. bieneusi) in sheep and goats in Jiangsu Province, a total of 786 fresh fecal samples from 18 farms across five regions in Jiangsu were collected and examined for the presence of E. bieneusi, and the genotype of E. bieneusi was examined using nested-PCR and sequencing of the ribosomal internal transcribed spacer. The results showed that E. bieneusi was detected in the fecal samples of sheep and goats in all regions, with infection rates ranging from 23.65% to 42.81%. The overall infection rate was 36.51% (287/786). The infection rate of E. bieneusi showed no significant difference between sheep and goats, as well as among different ages of animals (p > 0.05), but showed a significant difference in sheep and goats with different health conditions (p < 0.05). The positive products were amplified and cloned and subjected to sequenced analysis. Six genotypes, BEB6, CHG2, CHG3, CHC8, CHG14, and COS-I, were found. Phylogenetic analysis indicated that the six genotypes belonged to Group 2, which had previously been described as a non-zoonotic group.

Genetic diversity of Cryptosporidium spp., Encephalitozoon spp. and Enterocytozoon bieneusi in feral and captive pigeons in Central Europe

Cryptosporidium spp., Enterocytozoon bieneusi and Encephalitozoon spp. are the most common protistan parasites of vertebrates. The results show that pigeon populations in Central Europe are parasitised by different species of Cryptosporidium and genotypes of microsporidia of the genera Enterocytozoon and Encephalitozoon. A total of 634 and 306 faecal samples of captive and feral pigeons (Columba livia f. domestica) from 44 locations in the Czech Republic, Slovakia and Poland were analysed for the presence of parasites by microscopy and PCR/sequence analysis of small subunit ribosomal RNA (18S rDNA), 60 kDa glycoprotein (gp60) and internal transcribed spacer (ITS) of SSU rDNA. Phylogenetic analyses revealed the presence of C. meleagridis, C. baileyi, C. parvum, C. andersoni, C. muris, C. galli and C. ornithophilus, E. hellem genotype 1A and 2B, E. cuniculi genotype I and II and E. bieneusi genotype Peru 6, CHN-F1, D, Peru 8, Type IV, ZY37, E, CHN4, SCF2 and WR4. Captive pigeons were significantly more frequently parasitised with screened parasite than feral pigeons. Cryptosporidium meleagridis IIIa and a new subtype IIIl have been described, the oocysts of which are not infectious to immunodeficient mice, whereas chickens are susceptible. This investigation demonstrates that pigeons can be hosts to numerous species, genotypes and subtypes of the studied parasites. Consequently, they represent a potential source of infection for both livestock and humans.

Opportunistic microsporidiosis unveiled by fine-needle aspiration cytology of cervical lymph node with literature review

Microsporidia are highly specialized obligate intracellular organisms closely related to fungi, traditionally linked to diarrheal diseases in acquired immunodeficiency syndrome patients. Over the past two decades, an increasing incidence of extraintestinal infections affecting various organ systems, especially in immunocompromised individuals, has been observed. The report presents a unique case of lymph node microsporidiosis in a 38-year-old male, positive for human immunodeficiency virus, with coinfections of hepatitis B and C. Fine-needle aspiration cytology (FNAC) from cervical lymph node yielded pus-like, necrotic material with periodic acid-Schiff stained smear uncovering small round to oval spores on microscopy suspicious for microsporidia. Based on polymerase chain reaction and sequencing done with aspiration material, the causative agent was identified as Vittaforma corneae. This rare encounter highlights the significance of recognizing unique morphological characteristics of infectious organisms and employing appropriate ancillary techniques for precise identification. The case underscores the crucial role of FNAC in diagnosing opportunistic infections involving the lymph nodes and the growing significance of molecular tests for specific pathogen confirmation.

Microsporidial keratoconjunctivitis - first outbreak in Japan

BACKGROUND

Most cases of microsporidial keratoconjunctivitis are found in the Southern hemisphere. Our purpose was to investigate the first outbreak of microsporidial keratoconjunctivitis in Japan among healthy, immunocompetent soccer players from the same team during a 1-month period.

CASE PRESENTATION

This study is an observational case series. The medical records were analyzed for five cases with microsporidial keratoconjunctivitis who presented within September 2022. All five cases were males between 28 and 36 years old. These previously healthy individuals belonged to the same football team. Their eyes were considered susceptible to contaminated water or dirt from the turf at game and practice sites. All cases involved unilateral conjunctivitis, with scattered round white lesions that showed positive fluorescein staining in the corneal epithelium. All cases experienced diminution of vision in the affected eye. In three cases, direct smears showed spores of approximately 2-3 μm in diameter. Polymerase chain reaction (PCR) analysis of corneal scrapes revealed partial amplification of microsporidial 18 S ribosomal RNA gene in four cases. Sequences of PCR products from all four cases showed 100% identity with strains of Vittaforma corneae previously reported from an outbreak in Singapore. All cases were treated with topical therapy, including voriconazole, fluorometholone, and levofloxacin. Four eyes underwent corneal scraping. After treatment, all eyes healed without residual opacities.

CONCLUSIONS

Only a few sporadic case reports of this disease have previously been reported in Japan. We detected V. corneae in our case series, representing what appears to be the first outbreak of microsporidial keratoconjunctivitis in Japan. Exposure to contaminated water or soil, in addition to inadequate sanitary facilities, represents a potential source of infection. Further investigations to clarify the characteristics of microsporidia seem warranted.

Microbial Risks Caused by Livestock Excrement: Current Research Status and Prospects

Livestock excrement is a major pollutant yielded from husbandry and it has been constantly imported into various related environments. Livestock excrement comprises a variety of microorganisms including certain units with health risks and these microorganisms are transferred synchronically during the management and utilization processes of livestock excrement. The livestock excrement microbiome is extensively affecting the microbiome of humans and the relevant environments and it could be altered by related environmental factors as well. The zoonotic microorganisms, extremely zoonotic pathogens, and antibiotic-resistant microorganisms are posing threats to human health and environmental safety. In this review, we highlight the main feature of the microbiome of livestock excrement and elucidate the composition and structure of the repertoire of microbes, how these microbes transfer from different spots, and they then affect the microbiomes of related habitants as a whole. Overall, the environmental problems caused by the microbiome of livestock excrement and the potential risks it may cause are summarized from the microbial perspective and the strategies for prediction, prevention, and management are discussed so as to provide a reference for further studies regarding potential microbial risks of livestock excrement microbes.

High Prevalence of Microsporidia in the North African Hedgehog (Atelerix algirus) in the Canary Islands, Spain

Microsporidia are unicellular eukaryotic obligate intracellular parasites with a wide range of hosts reported worldwide; however, little is known about the epidemiological data on microsporidia infection in animals from the Canary Islands. Since data on microsporidia infection in hedgehog species are scarce, the aim of this study was to analyze the presence and identity of microsporidia in a group of North African hedgehogs (Atelerix algirus) using microscopic and molecular methods. From December 2020 to September 2021, a total of 36 fecal samples were collected from naturally deceased hedgehogs from Tenerife and Gran Canaria. All samples showed spore-compatible structures (100%; 36/36) under microscopic analysis, of which 61.1% (22/36) were amplified via the nested-polymerase chain reaction (PCR) targeting the partial sequence of the 16S rRNA gene, the internal transcribed spacer (ITS) region, and the partial sequence of the 5.8S rRNA gene. After Sanger sequencing and ITS analysis, Enterocytozoon bieneusi was detected in 47.2% (17/36) of the samples, identifying two novel genotypes (AAE1 and AAE2), followed by the detection of an undetermined species in 8.3% (3/36) and Encephalitozoon cuniculi genotype I in 5.6% (2/36) of the samples. This study constitutes the first report of microsporidia species in Atelerix algirus worldwide, highlighting the high prevalence of zoonotic species.

Past, present, and prospects in microsporidial keratoconjunctivitis- A review

Ocular microsporidiosis comprises two entirely different spectra of disease as keratoconjunctivitis and stromal keratitis. Microsporidial keratoconjunctivitis (MKC) has been increasingly reported in the past two decades, probably due to raised awareness, simpler diagnostic procedures, and a better understanding of the clinical presentation. It is characterized by the presence of raised, coarse, punctate, multifocal, round to oval, greyish-white corneal epithelial lesions which usually evolve into nummular scars before resolution. Conjunctivitis seen is non-purulent and of mild-moderate intensity, with mixed papillary-follicular reaction. The mode of transmission and pathogenesis is poorly understood. Despite lack of inflammatory response, uncommon associations reported were- endotheliitis, corneal edema, limbitis, uveitis, and sub-epithelial infiltrates. There has been no consensus on the management of MKC. It varies from the use of multiple antimicrobial agents to simple lubricants. The majority of the disease goes underdiagnosed or misdiagnosed and treated as adenoviral keratoconjunctivitis, with topical steroids or anti-virals empirically. Changing trends have been noticed in the pattern of infection, possibly with increasing evidence of Vittaforma corneae as causative organisms, previously reported to cause stromal keratitis. An elaborate review of the past and present literature on MKC is provided in this review article, along with gaps in knowledge, and future directions of research.

A mouse ear skin model to study the dynamics of innate immune responses against the microsporidian Encephalitozoon cuniculi

Microsporidia are obligate intracellular parasites related to fungi that cause severe infections in immunocompromised individuals. Encephalitozoon cuniculi is a microsporidian species capable of infecting mammals, including human and rodents. In response to microsporidian infection, innate immune system serves as the first line of defense and allows a partial clearance of the parasite via the innate immune cells, namely macrophages, neutrophils, dendritic cells, and Natural Killer cells. According to the literature, microsporidia bypass this response in vitro by modulating the response of macrophages. In order to study host-parasites interactions in vivo, we developed a model using the mouse ear pinna in combination with an intravital imaging approach. Fluorescent E. cuniculi spores were inoculated into the skin tissue to follow for the first time in real time in an in vivo model the recruitment dynamics of EGFP + phagocytic cells in response to the parasite. The results show that parasites induce an important inflammatory recruitment of phagocytes, with alterations of their motility properties (speed, displacement length, straightness). This cellular response persists in the injection zone, with spores detected inside the phagocytes up to 72 h post-infection. Immunostainings performed on ear tissue cryosections evoke the presence of developing infectious foci from 5 days post-infection, in favor of parasite proliferation in this tissue. Overall, the newly set up mice ear pinna model will increase our understanding of the immunobiology of microsporidia and in particular, to know how they can bypass and hijack the host immune system of an immunocompetent or immunosuppressed host.

Nosemosis Prevention and Control

Nosemosis is a serious microsporidian disease of adult European honey bees caused by the spore-forming unicellular fungi Nosema apis and Nosema ceranae. In this paper we describe the currently known techniques for nosemosis prevention and control including Good Beekeeping Practices (GBPs) and biosecurity measures (BMBs). Topics such as queen renewal, nosema-resistant bees and hygienic and control methods are described. Strong efforts are currently provided to find more a sustainable solution than the use of antibiotics. So far, it seems that the best way to approach nosemosis is given by an “integrated pest management strategy”, which foresees the contemporary application of different, specific GBPs and BMBs.

Intestinal microsporidiosis among HIV/AIDS patients receiving antiretroviral therapy in Sana'a city, Yemen: first report on prevalence and predictors

Background

Intestinal microsporidiosis is an opportunistic infection associated with persistent diarrhea among HIV/AIDS patients. In Yemen, however, its epidemiology is unknown. Therefore, this study determined its prevalence and predictors among HIV/AIDS patients receiving antiretroviral therapy (ART) in Sana’a city, the capital of Yemen.

Methods

This cross-sectional study included 402 patients receiving ART at Al-Jomhori Educational Hospital in Sana’a from November 2019 to December 2020. Data about demographics, clinical characteristics and risk factors were collected using a pre-designed questionnaire. Stool samples were collected and examined for microsporidian spores using the Gram-chromotrope Kinyoun staining. Blood samples were also collected and used for CD4 cell counting by flow cytometry. Univariate analysis was used to test the association of patients’ characteristics and risk factors with intestinal microsporidiosis. Multivariable logistic regression was then used to identify the independent predictors of infection. Statistical significance was considered at P-values < 0.05.

Results

Intestinal microsporidiosis was prevalent among 14.2% (57/402) of HIV/AIDS patients and was significantly associated with diarrhea (OR 3.4, 95% CI 1.7–6.6; P = 0.001). The significant independent predictors of infection were < 200 CD4 cells/µl (AOR 3.2, 95% CI 1.5–6.9; P = 0.003), not washing hands after contacting soil (AOR 2.5, 95% CI 1.1–5.4; P = 0.026) and before eating (AOR 3.1, 95% CI 1.5–6.4; P = 0.003), eating unwashed raw produce (AOR 2.5, 95% CI 1.2–5.3; P = 0.017) and absence of indoor latrines (AOR 6.2, 95% CI 1.5–25.9; P = 0.012).

Conclusions

The prevalence of intestinal microsporidiosis among HIV/AIDS patients in Sana'a is high and comparable to that reported from several other countries, being prevalent among approximately 14.0% of patients and significantly associated with diarrhea. It could be predicted among patients who have < 200 CD4 cells/µl, have poor hand hygiene after contacting soil and before eating, usually eat unwashed raw produce, or do not possess indoor latrines. Large-scale studies on its epidemiology and predictors among HIV/AIDS patients across the country are warranted.

A Perspective on the Molecular Identification, Classification, and Epidemiology of Enterocytozoon bieneusi of Animals

The microsporidian Enterocytozoon bieneusi is an obligate intracellular pathogen that causes enteric disease (microsporidiosis) in humans and has been recorded in a wide range of animal species worldwide. The transmission of E. bieneusi is direct and likely occurs from person to person and from animal to person via the ingestion of spores in water, food, or the environment. The identification of E. bieneusi is usually accomplished by molecular means, typically using the sequence of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. Currently, ~820 distinct genotypes of E. bieneusi have been recorded in at least 210 species of vertebrates (mammals, birds, reptiles, and amphibians) or invertebrates (insects and mussels) in more than 50 countries. In this chapter, we provide a perspective on (1) clinical aspects of human microsporidiosis; (2) the genome and DNA markers for E. bieneusi as well as molecular methods for the specific and genotypic identification of E. bieneusi; (3) epidemiological aspects of E. bieneusi of animals and humans, with an emphasis on the genotypes proposed to be zoonotic, human-specific, and animal-specific; and (4) future research directions to underpin expanded molecular studies to better understand E. bieneusi and microsporidiosis.

Microsporidial Stromal Keratitis: Epidemiological Features, Slit-Lamp Biomicroscopic Characteristics, and Therapy

PURPOSE

Microsporidial stromal keratitis is a rare form of infectious keratitis, with only 7 cases reported in the United States to date. This study was performed to evaluate risk factors, clinical features, and response to therapy.

METHODS

A retrospective review of the medical records of all patients diagnosed with microsporidial stromal keratitis seen in the practices of the authors between 1999 and 2020 was performed. Diagnosis was determined by cytology or histopathology in corneal specimens. Risk factors, presence or absence of distinctive clinical features, and response to medical and surgical therapies were recorded.

RESULTS

Nine patients-7M:2F, aged 7 to 99 years-with microsporidial stromal keratitis were identified. Exposures to recreational water and hymenopteran insect bites, both epidemiologically linked risk factors for systemic microsporidial infection, were identified in our patients. Presence of stromal edema with features of disciform keratitis and a distinctive granular keratitis were observed in 6 of 9 and 5 of 9 patients, respectively. Poor response to medical therapy was noted. Penetrating keratoplasty was effective in curing the infection. Final visual acuity was 20/40 or better in 6 of 9 patients.

CONCLUSIONS

In patients with slowly progressive keratitis, history of exposure to recreational water or hymenopteran insects should be sought. In patients with corneal edema consistent with disciform keratitis, with evolution to a granular keratitis, microsporidia should be considered in the differential diagnosis. In cases of established microsporidial stromal keratitis, penetrating keratoplasty should be considered if prompt response to medical therapy is not noted.

Incubation period, spore shedding duration, and symptoms of Enterocytozoon bieneusi genotype C infection in a foodborne outbreak in Denmark, 2020

Background

Microsporidia are rarely reported to cause outbreaks of diarrhea. We describe a foodborne outbreak of microsporidiosis from a workplace canteen in November 2020 in Denmark.

Methods

A probable case was defined as any person using the canteen between 4 November and 13 December 2020, reporting at least one gastrointestinal symptom, whereas a confirmed case also had an Enterocytozoon bieneusi positive stool sample. A web-based questionnaire was used to collect clinical, epidemiological, and food exposure data. We performed a retrospective cohort study and tested stool samples from affected individuals for bacterial, viral, and parasitic pathogens, including E. bieneusi.

Results

Altogether, 195 individuals completed the questionnaire. We identified 52 cases (65% male; median age 45 years [range 25–65]). Diarrhea (90%), fatigue (83%), and abdominal pain (79%) were the most commonly reported symptoms. Eight cases were laboratory-confirmed and had E. bieneusi genotype C. The incubation period was between 5 and 12 days, and polymerase chain reaction (PCR)-detectable spore shedding occurred up to 43 days after symptom onset. Disease was associated with consuming food from the workplace canteen on 4 November 2020 (relative risk [RR[, 2.8 [95% confidence interval [CI]: 1.4 – 5.4]) and lunchboxes containing open sandwiches (RR, 3.2 [95% CI: 1.4 – 7.2]) served that day.

Conclusions

This is the second documented foodborne outbreak of E. bieneusi genotype C-associated diarrhea worldwide. Epidemiological findings advocated an open sandwiches lunchbox from 4 November 2020, as a likely source. E. bieneusi may be an under-reported cause of outbreaks of diarrhea, and testing for it might be useful in foodborne outbreak investigations.

First Identification and Genotyping of Enterocytozoon bieneusi and Prevalence of Encephalitozoon intestinalis in Patients with Acute Diarrhea in the Republic of Korea

Encephalitozoon intestinalis and Enterocytozoon bieneusi can cause diarrhea in humans, especially severe diarrhea in immunocompromised patients. However, there have been few studies on Enc. intestinalis and Ent. bieneusi in patients with acute diarrhea in the Republic of Korea (ROK). In this study, fecal samples were collected from 1241 patients with acute diarrhea in 2020. Among these, 24 cases of Enc. intestinalis and one case of Ent. bieneusi were detected via PCR amplification of small subunit ribosomal RNA. Genotyping of the internal transcribed spacer region sequence revealed that the detected Ent. bieneusi genotype was in Group 1. This study provides the first evidence that Ent. bieneusi exists in humans in addition to animals in the ROK. To identify the causative agent, continuous monitoring of Enc. intestinalis and Ent. bieneusi is necessary for patients with acute diarrhea in the ROK.

Molecular Identification of Encephalitozoon hellem from Companion Birds Kept in Pet Shops, Japan

To evaluate the role of companion birds as a reservoir of Encephalitozoon hellem infection in humans, the present study determined the prevalence and genotypes of E. hellem from 269 birds in 4 pet shops using polymerase chain reaction (PCR) assay. E. hellem was identified in 4.8% (13/269) of the birds and was detected in all pet shops. Every positive sample corresponded to zoonotic genotype 1A. Considering the low prevalence of E. hellem infection, it is likely that the risk of zoonotic transmission from companion birds kept in pet shops to humans is low in Japan.

Parasitic zoonoses in the Roma population

Roma people are the largest minority group in Europe. The vast majority live in substandard conditions in segregated settlements, overcrowded with people and animals that predispose them to various, especially zoonotic diseases. Parasitic zoonotic diseases remain a challenge in this vulnerable population group, especially among Roma children. PubMed was searched using the keywords Roma with combination of names of different parasites to get all available studies on prevalence of parasitic zoonoses among European Roma, published between years 2000 and 2020. After application of exclusion criteria, data were extracted from the studies that made the final sample. Parasitic zoonoses are common among Roma. Cryptosporidium, Toxoplasma gondii, soil-transmitted helminths and Giardia spp. are more common in Roma children compared to non-Roma children, and Toxoplasma gondii and soil-transmitted helminths are also more common in Roma adults compared to non-Roma adults. Data on prevalence of trichinellosis, echinococcosis, and taeniasis among Roma show that they do not affect Roma more often compared to the general population. Roma people, particularly children, are more susceptible to parasitic zoonoses. Substandard sanitary conditions and close contact with infected animals are important risk factors in this population and should be aimed with preventive measures.

Epidemiological and clinical study of microsporidiosis in French kidney transplant recipients from 2005 to 2019: TRANS-SPORE registry

INTRODUCTION

Microsporidiosis is an emerging opportunistic infection in renal transplantation (RT) recipients. We aimed to describe its clinical presentation and treatment.

MATERIALS AND METHODS

We collected microsporidiosis cases identified in RT recipients between 2005 and 2019 in six French centers from the Crystal, Divat and Astre prospective databases.

RESULTS

We report 68 RT recipients with intestinal microsporidiosis; the patients were predominantly male (61.8%), with a median age of 58 (46-69) years. Infection occurred at a median time of 3 (0.8-6.8) years posttransplant. Only Enterocytozoon bieneusi was found. Microsporidiosis manifested as diarrhea (98.5% of patients) with weight loss (72.1%) and acute renal injury (57.4%) without inflammatory biological parameters. The therapeutic approaches were no treatment (N = 9), reduction of the immunosuppressive regimen (∆IS) (N = 22), fumagillin alone (N = 9), fumagillin and ∆IS (N = 19), and albendazole or nitazoxanide and ∆IS (N = 9). Overall clinical remission was observed in 60 patients (88.2%). We observed no acute kidney rejection, renal transplant failure, or death within 6 months after microsporidiosis.

CONCLUSION

E. bieneusi is an underestimated opportunistic pathogen in RT recipients, and infection with E. bieneusi leads to diarrhea with important dehydration and acute renal injury. The treatment is based on the reduction of the immunosuppressive regimen and the administration of fumagillin if available.

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.

Presumptive neural microsporidiosis in a young adult German Shepherd dog from rural Australia

CASE REPORT

A 1-year-old, neutered male German Shepherd was presented with a 5-month history of episodic lethargy, intermittent fever, weight loss and a hunched posture. The dog was diagnosed with presumptive microsporidian meningoencephalitis based on cytological findings on cerebrospinal fluid analysis and a positive PCR test. The dog initially responded favourably to a 4-week course of trimethoprim-sulfadiazine, pyrimethamine and fenbendazole, and remained well for 12 weeks following cessation of treatment. Disease then recurred, and despite an initial positive response to treatment, he deteriorated and was euthanased 11 weeks later, 7.5 months after definitive diagnosis and 13 months after clinical signs were first reported.

CONCLUSION

To the authors knowledge, this is the first case of canine microsporidiosis in Australia.

The largest meta-analysis on the global prevalence of microsporidia in mammals, avian and water provides insights into the epidemic features of these ubiquitous pathogens

BACKGROUND

Microsporidia are obligate intracellular parasites that can infect nearly all invertebrates and vertebrates, posing a threat to public health and causing large economic losses to animal industries such as those of honeybees, silkworms and shrimp. However, the global epidemiology of these pathogens is far from illuminated.

METHODS

Publications on microsporidian infections were obtained from PubMed, Science Direct and Web of Science and filtered according to the Newcastle-Ottawa Quality Assessment Scale. Infection data about pathogens, hosts, geography and sampling dates were manually retrieved from the publications and screened for high quality. Prevalence rates and risk factors for different pathogens and hosts were analyzed by conducting a meta-analysis. The geographic distribution and seasonal prevalence of microsporidian infections were drawn and summarized according to sampling locations and date, respectively.

RESULTS

Altogether, 287 out of 4129 publications up to 31 January 2020 were obtained and met the requirements, from which 385 epidemiological data records were retrieved and effective. The overall prevalence rates in humans, pigs, dogs, cats, cattle, sheep, nonhuman primates and fowl were 10.2% [2429/30,354; 95% confidence interval (CI) 9.2-11.2%], 39.3% (2709/5105; 95% CI 28.5-50.1%), 8.8% (228/2890; 95% CI 5.1-10.1%), 8.1% (112/1226; 95% CI 5.5-10.8%), 16.6% (2216/12,175; 95% CI 13.5-19.8%), 24.9% (1142/5967; 95% CI 18.6-31.1%), 18.5% (1388/7009; 95% CI 13.1-23.8%) and 7.8% (725/9243; 95% CI 6.4-9.2%), respectively. The higher prevalence in pigs suggests that routine detection of microsporidia in animals should be given more attention, considering their potential roles in zoonotic disease. The highest rate was detected in water, 58.5% (869/1351; 95% CI 41.6-75.5%), indicating that water is an important source of infections. Univariate regression analysis showed that CD4+ T cell counts and the living environment are significant risk factors for humans and nonhuman primates, respectively. Geographically, microsporidia have been widely found in 92 countries, among which Northern Europe and South Africa have the highest prevalence. In terms of seasonality, the most prevalent taxa, Enterocytozoon bieneusi and Encephalitozoon, display different prevalence trends, but no significant difference between seasons was observed. In addition to having a high prevalence, microsporidia are extremely divergent because 728 genotypes have been identified in 7 species. Although less investigated, microsporidia coinfections are more common with human immunodeficiency virus and Cryptosporidium than with other pathogens.

CONCLUSIONS

This study provides the largest-scale meta-analysis to date on microsporidia prevalence in mammals, birds and water worldwide. The results suggest that microsporidia are highly divergent, widespread and prevalent in some animals and water and should be further investigated to better understand their epidemic features.

Global prevalence of microsporidia infection in cats: A systematic review and meta-analysis of an emerging zoonotic pathogen

Microsporidiosis in pet and stray cats is an emerging zoonotic threat with public health significance worldwide. However, the epidemiological patterns of feline microsporidiosis is still neglected around the world. Hence, current systematic review and meta-analysis aimed at characterizing the prevalence estimates and genotypes of microsporidian parasites among cats of the world. Several databases (PubMed, Web of Science, Scopus, and Google scholar) were systematically explored to find relevant studies. Evaluation of the weighted prevalences among included studies was done using random-effects model. Totally, 30 studies (34 datasets) reported from 19 countries were included in the present work. Microsporidia infection demonstrated higher prevalence rates using microscopy 29.7 % (19.7-42.2 %), followed by serology and molecular techniques with 11 % (4.6-24.2 %) and 8.2 % (5.9-11.4 %), respectively. Moreover, molecular data showed Enterocytozoon bieneusi as the most dominant reported species with 7.4 % (5.1-10.5 %). Also, investigations (11 studies) mostly isolated D genotype among all E. bieneusi genotypes. These results highlight cats as a potential reservoir for acquisition of microsporidia infection in humans, and surveillance programs should be implemented in high-risk areas.

Enterocytozoon bieneusi of animals-With an 'Australian twist'

Enterocytozoon bieneusi is a microsporidian microorganism that causes intestinal disease in animals including humans. E. bieneusi is an obligate intracellular pathogen, typically causing severe or chronic diarrhoea, malabsorption and/or wasting. Currently, E. bieneusi is recognised as a fungus, although its exact classification remains contentious. The transmission of E. bieneusi can occur from person to person and/or animals to people. Transmission is usually via the faecal-oral route through E. bieneusi spore-contaminated water, environment or food, or direct contact with infected individuals. Enterocytozoon bieneusi genotypes are usually identified and classified by PCR-based sequencing of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA. To date, ~600 distinct genotypes of E. bieneusi have been recorded in ~170 species of animals, including various orders of mammals and reptiles as well as insects in >40 countries. Moreover, E. bieneusi has also been found in recreational water, irrigation water, and treated raw- and waste-waters. Although many studies have been conducted on the epidemiology of E. bieneusi, prevalence surveys of animals and humans are scant in some countries, such as Australia, and transmission routes of individual genotypes and related risk factors are poorly understood. This article/chapter reviews aspects of the taxonomy, biology and epidemiology of E. bieneusi; the diagnosis, treatment and prevention of microsporidiosis; critically appraises the naming system for E. bieneusi genotypes as well as the phylogenetic relationships of these genotypes; provides new insights into the prevalence and genetic composition of E. bieneusi populations in animals in parts of Australia using molecular epidemiological tools; and proposes some areas for future research in the E. bieneusi/microsporidiosis field.

Zoonotic Microsporidia in Wild Lagomorphs in Southern Spain

Microsporidia are obligate intracellular protist-like fungal pathogens that infect a broad range of animal species, including humans. This study aimed to assess the presence of zoonotic microsporidia (Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, and Encephalitozoon cuniculi) in organ meats of European wild rabbit (Oryctolagus cuniculus) and Iberian hare (Lepus granatensis) consumed by humans in Spain. Between July 2015 and December 2018, kidney samples from 383 wild rabbits and kidney and brain tissues from 79 Iberian hares in southern Spain were tested by species-specific PCR for the detection of microsporidia DNA. Enterocytozoon bieneusi infection was confirmed in three wild rabbits (0.8%; 95% CI: 0.0-1.7%) but not in hares (0.0%; 95% CI: 0.0-4.6%), whereas E. intestinalis DNA was found in one wild rabbit (0.3%; 95% CI: 0.0-0.8%) and three Iberian hares (3.8%; 95% CI: 0.0-8.0%). Neither E. hellem nor E. cuniculi infection were detected in the 462 (0.0%; 95% CI: 0.0-0.8%) lagomorphs analyzed. The absence of E. hellem and E. cuniculi infection suggests a low risk of zoonotic foodborne transmission from these wild lagomorph species in southern Spain. To the authors' knowledge, this is the first report of E. intestinalis infection in wild rabbits and Iberian hares. The presence of E. bieneusi and E. intestinalis in organ meats from wild lagomorphs can be of public health concern. Additional studies are required to determine the real prevalence of these parasites in European wild rabbit and Iberian hare.

Encephalitozoon cuniculi Genotype II Concentrates in Inflammation Foci

Background

Microsporidia of the genus Encephalitozoon are generally connected with severe infections with lethal outcome in immunodeficient hosts. In immunocompetent hosts, microsporidiosis typically establishes a balanced host–parasite relationship that produces minimal clinically overt disease. Although the alimentary tract represents one of the main primary target tissues, the mechanisms of reaching other tissues during systemic microsporidian infections remain unclear.

Methods

In the present study, we tested the relation between inflammation induction in immunocompetent and immunodeficient mice and the presence of spores of E. cuniculi genotype II in selected organs and in fecal specimens by using molecular and histology methods.

Results

We reported the positive connection between inflammation induction and the significant increase of E. cuniculi genotype II occurrence in inflammation foci in both immunocompetent BALB/c and immunodeficient severe combined immunodeficient (SCID) mice in the acute phase of infection and the re-activation of latent microsporidial infection following inflammation induction in immunocompetent mice.

Conclusion

The results imply possible involvement of immune cells serving as vehicles transporting E. cuniculi genotype II purposefully across the whole host body towards inflammation. With increasing number of records of infections, it is necessary to reconsider microsporidia as agents responsible for various pathologies. The elucidation of possible connection with pro-inflammatory immune responses represents an important challenge with consequences for human health and development of therapeutic strategies.

A systematic review and meta-analysis on the global prevalence of microsporidia infection among dogs: a zoonotic concern

Background

Microsporidiosis is an emerging zoonotic disease that is considered a global public health concern. Dogs are suggested as one of potential reservoirs for transmitting the microsporidia infection to humans. However, there is little data on distribution of microsporidia in dogs. The current study aimed to evaluate the global prevalence and genetic diversity of microsporidia infection among the dog population.

Methods

We searched four major databases for studies reporting the prevalence of microsporidia in dogs until 30 May 2020. A random-effects model was used to estimate the overall and the subgroup-pooled prevalence of microsporidia across studies.

Result

Finally, a total of 32 studies (including 37 datasets) from 17 countries were included in this meta-analysis. The overall prevalence (95% CI) of microsporidia infection was estimated at 23.1% (13.5–36.8%) using microscopic methods, 20.9% (14.6–29%) using serological methods, and 8.4% (6.1–11.5%) using molecular methods. Molecular methods showed that the highest number of reports was related to Enterocytozoon bieneusi with a pooled prevalence of 6.5% (4.9–8.7%). Considering E. bieneusi genotypes, most studies reported the PtEb IX (10 studies) and the D (eight studies) genotypes.

Conclusion

These results emphasize the role of a dog as a reservoir host for human-infecting microsporidia. In addition, monitoring programs for human-infecting microsporidia in animals with close contact to humans should be considered.

Complete genome of a unicellular parasite (Antonospora locustae) and transcriptional interactions with its host locust

Microsporidia are a large group of unicellular parasites that infect insects and mammals. The simpler life cycle of microsporidia in insects provides a model system for understanding their evolution and molecular interactions with their hosts. However, no complete genome is available for insect-parasitic microsporidian species. The complete genome of Antonospora locustae, a microsporidian parasite that obligately infects insects, is reported here. The genome size of A. locustae is 3 170 203 nucleotides, composed of 17 chromosomes onto which a total of 1857 annotated genes have been mapped and detailed. A unique feature of the A. locustae genome is the presence of an ultra-low GC region of approximately 25 kb on 16 of the 17 chromosomes, in which the average GC content is only 20 %. Transcription profiling indicated that the ultra-low GC region of the parasite could be associated with differential regulation of host defences in the fat body to promote the parasite's survival and propagation. Phylogenetic gene analysis showed that A. locustae, and the microsporidian family in general, is likely at an evolutionarily transitional position between prokaryotes and eukaryotes, and that it evolved independently. Transcriptomic analysis showed that A. locustae can systematically inhibit the locust phenoloxidase PPO, TCA and glyoxylate cycles, and PPAR pathways to escape melanization, and can activate host energy transfer pathways to support its reproduction in the fat body, which is an insect energy-producing organ. Our study provides a platform and model for studies of the molecular mechanisms of microsporidium-host interactions in an energy-producing organ and for understanding the evolution of microsporidia.

Molecular detection and genotyping of microsporidia species in chickens in Turkey

Microsporidia are obligate intracellular pathogens that infect various hosts including invertebrates and vertebrates. Despite the importance, knowledge on the prevalence and molecular characteristics of microsporidia in chickens is limited, and no data are available for Turkey. A total of 300 fecal samples from chickens in the Central Anatolia Region of Turkey were analyzed by using a nested polymerase chain reaction assay targeting the rRNA internal transcribed spacer (ITS) region for the common microsporidia species. Corresponding PCR amplicons from the positive samples were sequenced for genotyping. Enterocytozoon bieneusi was identified in 22 (7.3 %) samples, whereas Encephalitozoon spp. was not detected. The prevalence of E. bieneusi was 63.6 % in Kayseri and 36.4 % in Nevsehir provinces, and 8.8 % in soft fecal samples and 9.7 % in diarrhoeic samples. No infections were found in Kirsehir Province. Significant differences were found for the distribution of E. bieneusi among provinces and fecal conditions. Infections were found only in free-range chickens. As a result of ITS region sequencing, two genotypes were characterized. The novel genotype ERUNT1 (n = 21), belonging to zoonotic group 1, was the most common genotype throughout the study area. The other known genotype, ERUSS1 (n = 1), had a restricted distribution and was previously detected in cattle and sheep in the same region. Our study provides the first data on microsporidia species from chickens in Turkey. None of these genotypes have been reported in humans; thus, the risk potential for public health is limited but needs further investigation.

Microsporidia infection in patients with autoimmune diseases

Purpose

Microsporidium is a spore-forming intracellular parasite that affects a wide range of hosts including humans. The tumor necrosis factor alpha (TNF-α) plays a key role in the immunity to infection with microsporidia. Recently, the TNF-α antagonists have proven successful in treating variable autoimmune diseases. In the current study, we aimed to investigate the impact of using TNF-α antagonists as a therapeutic regimen in the prevalence of infections with microsporidia.

Materials and Methods

Diarrheal patients with distinct autoimmune diseases (n = 100) were assigned to the study. Patients taking anti-TNF-α medications (n = 60) were allocated to Group 1A and those undergoing non-TNF-α inhibitor treatment (n = 40) to Group 1B. Furthermore, patients with diarrhea without autoimmune disorders (n = 20) were allocated as controls. Stool specimens, 3 per patient, were collected and microscopically examined for microsporidia spores. A microsporidia-specific stool polymerase chain reaction was used to confirm the microscopic findings.

Results

Microsporidia infection was identified in 28.3% (17/60), 10% (4/40), and in 5% (1/20) of patients in Group 1A, Group 1B, and in the control group, respectively. Overall, infection was significantly high in cases compared to the controls and in patients receiving TNF-α antagonists compared to patients not given TNF-α inhibitors (P < 0.05). Finally, infection was significantly higher in cases treated with TNF-α antagonists for ≥2 months compared to cases treated for <2 months of duration (P < 0.05).

Conclusion

There was a significant increase in microsporidia infection in autoimmune disease patients undergoing treatment with TNF-α antagonists, and the duration of treatment is one of the risk factors. The study highlights the importance of microsporidia testing in immunocompromised patients, particularly those undergoing treatment with anti-TNF-α drugs and emphasises the need for awareness among clinicians regarding this opportunistic parasite.

First identification and genotyping of Enterocytozoon bieneusi and Encephalitozoon spp. in pet rabbits in China

Background

Microsporidia are common opportunistic parasites in humans and animals, including rabbits. However, only limited epidemiology data concern about the prevalence and molecular characterization of Enterocytozoon bieneusi and Encephalitozoon spp. in rabbits. This study is the first detection and genotyping of Microsporidia in pet rabbits in China.

Results

A total of 584 faecal specimens were collected from rabbits in pet shops from four cities in Sichuan province, China. The overall prevalence of microsporidia infection was 24.8% by nested PCR targeting the internal transcribed spacer (ITS) region of E. bieneusi and Encephalitozoon spp. respectively. E. bieneusi was the most common species (n = 90, 15.4%), followed by Encephalitozoon cuniculi (n = 34, 5.8%) and Encephalitozoon intestinalis (n = 16, 2.7%). Mixed infections (E. bieneusi and E. cuniculi) were detected in five another rabbits (0.9%). Statistically significant differences in the prevalence of microsporidia were observed among different cities (χ² = 38.376, df = 3, P < 0.01) and the rabbits older than 1 year were more likely to harbour microsporidia infections (χ² = 9.018, df = 2, P < 0.05). Eleven distinct genotypes of E. bieneusi were obtained, including five known (SC02, I, N, J, CHY1) and six novel genotypes (SCR01, SCR02, SCR04 to SCR07). SC02 was the most prevalent genotype in all tested cities (43.3%, 39/90). Phylogenetic analysis showed that these genotypes were clustered into group 1–3 and group 10. Meanwhile, two genotypes (I and II) were identified by sequence analysis of the ITS region of E. cuniculi.

Conclusion

To the best of our knowledge, this is the first report of microsporidia infection in pet rabbits in China. Genotype SC02 and four novel genotypes were classified into potential zoonotic group 1, suggesting that pet rabbits may cause microsporidiosis in humans through zoonotic transmissions. These findings provide preliminary reference data for monitoring microsporidia infections in pet rabbits and humans.

Characterization of humoral and cell-mediated immunity in rabbits orally infected with Encephalitozoon cuniculi

Encephalitozoonosis is a common infectious disease widely spread among rabbits. Encephalitozoon cuniculi, is considered as a zoonotic and emerging pathogen capable of infecting both immunocompetent and immunocompromised hosts. The aim of the study was to describe in detail the spread of the E. cuniculi in a rabbit organism after experimental infection and the host humoral and cellular immune response including cytokine production. For that purpose, healthy immunocompetent rabbits were infected orally in order to simulate the natural route of infection and euthanised at 2, 4, 6 and 8-weeks post-infection. Dissemination of E. cuniculi in the body of the rabbit was more rapid than previously reported. As early as 2 weeks post-infection, E. cuniculi was detected using immunohistochemistry not only in the intestine, mesenteric lymph nodes, spleen, liver, kidneys, lungs and heart, but also in nervous tissues, especially in medulla oblongata, cerebellum, and leptomeninges. Based on flow cytometry, no conspicuous changes in lymphocyte subpopulations were detected in the examined lymphoid organs of infected rabbits. Cell-mediated immunity was characterized by ability of both CD4⁺ and CD8⁺ T cells to proliferate after stimulation with specific antigens. Th1 polarization of immune response with a predominance of IFN-γ expression was detected in spleen, mesenteric lymph nodes and Peyer’s patches. The increased expression of IL-4 and IL-10 mRNA in mixed samples from the small intestine is indicative of balanced control of IFN-γ, which prevents tissue damage. On the other hand, it can enable E. cuniculi to survive and persist in the host organism in a balanced host-parasite relationship. The Th17 immunity lineage seems to play only a minor role in E. cuniculi infection in rabbits.

Encephalitozoon cuniculi Genotype III Evinces a Resistance to Albendazole Treatment in both Immunodeficient and Immunocompetent Mice

Of four genotypes of Encephalitozoon cuniculi, E. cuniculi genotype II is considered to represent a parasite that occurs in many host species in a latent asymptomatic form, whereas E. cuniculi genotype III seems to be more aggressive, and infections caused by this strain can lead to the death of even immunocompetent hosts. Although albendazole has been considered suitable for treatment of Encephalitozoon species, its failure in control of E. cuniculi genotype III infection has been reported. This study determined the effect of a 100× recommended daily dose of albendazole on an Encephalitozoon cuniculi genotype III course of infection in immunocompetent and immunodeficient mice and compared the results with those from experiments performed with a lower dose of albendazole and E. cuniculi genotype II. The administration of the regular dose of abendazole during the acute phase of infection reduced the number of affected organs in all strains of mice and absolute counts of spores in screened organs. However, the effect on genotype III was minor. Surprisingly, no substantial effect was recorded after the use of a 100× dose of albendazole, with larger reductions seen only in the number of affected organs and absolute counts of spores in all strains of mice, implying variations in albendazole resistance between these Encephalitozoon cuniculi genotypes. These results imply that differences in the course of infection and the response to treatment depend not only on the immunological status of the host but also on the genotype causing the infection. Understanding how microsporidia survive in hosts despite targeted antimicrosporidial treatment could significantly contribute to research related to human health.

A Narrative Review of Microsporidial Infections of the Cornea

Microsporidia are a rare and commonly misdiagnosed cause of corneal infection, accounting for approximately 0.4% of cases of microbial keratitis in some populations. Ocular microsporidiosis most often presents as either microsporidial keratoconjunctivitis (MKC) or microsporidial stromal keratitis (MSK). Though these two clinical entities exhibit similar symptomology, they are distinguished from one another by the time course for disease progression, findings on slit-lamp examination, and response to medical therapy. This review summarizes the current literature on the etiology and clinical presentation of microsporidial infections of the cornea and highlights ongoing developments in available diagnostic modalities and treatment regimens.

Screening of opportunistic Encephalitozoon intestinalis and Enterocytozoon bieneusi in immunocompromised patients in Slovakia

OBJECTIVE

In recent years new infectious diseases, i.e. emerging or re-emerging diseases, have been coming to the forefront. Currently, microsporidia, considered to be a major cause of emerging and opportunistic infections particularly in immunocompromised individuals, are also included in this group. Therefore, the aim of our study was to map the prevalence of Encephalitozoon intestinalis and Enterocytozoon bieneusi infection in a group of patients and to compare it with the occurrence of specific antigens in immunocompetent people.

METHODS

Detection of spores of both pathogens in faecal samples was performed by an immunofluorescence test using species-specific monoclonal antibodies.

RESULTS

Positivity to E. intestinalis in 91 examined immunosuppressed patients reached 33% (30/91), while only 4.3% (3/70) of the control group samples were found to be positive (relative risk 7.7, p < 0.001). In case of E. bieneusi 14.3% (13/91) of immunocompromised patients were positive, as were 5.7% (4/70) of people from the control group (relative risk 2.5, p = 0.095).

CONCLUSION

In case of development of any opportunistic infection, the infection is detected and removed in most cases at an early stage. The incidence of clinically manifested microsporidiosis in patients with immunodeficiency is rare as they are under constant medical supervision. However, we must not forget about opportunistic infections, and in case of any non-specific symptoms it is necessary to exclude or confirm the diagnosis for immediate treatment.

Immunohistochemical Detection of Encephalitozoon cuniculi in Ocular Structures of Immunocompetent Rabbits

Encephalitozoonosis is a common infectious disease widely spread among rabbits. Its causative agent, Encephalitozoon cuniculi, is considered as a zoonotic and emerging pathogen capable of infecting both immunocompetent and immunocompromised hosts, including humans. In rabbits, clinical signs include neurological, kidney and ocular disease. The aim of this study was to detect E. cuniculi in ocular structures in immunocompetent rabbits after experimental oral infection using immunohistochemistry. In infected animals, E. cuniculi spores were present in periocular connective tissue, sclera, cornea, choroidea, iris, retina and lens, as a round to ovoid organism reacting with a specific anti-E. cuniculi monoclonal antibody as early as 2 weeks after infection. There were no signs of inflammatory lesions in any of the ocular tissues examined at 2, 4, 6 and 8 weeks after infection. In the present study, E. cuniculi was also detected in the lenses of adult rabbits, which indicates that ways of lens infection other than intrauterine and haematogenic are possible.

Multilocus Sequence Typing and Population Genetic Analysis of Enterocytozoon bieneusi: Host Specificity and Its Impacts on Public Health

Microsporidia comprise a large class of unicellular eukaryotic pathogens that are medically and agriculturally important, but poorly understood. There have been nearly 1,500 microsporidian species described thus far, which are variable in biology, genetics, genomics, and host specificity. Among those, Enterocytozoon bieneusi is the well-known species responsible for the most recorded cases of human microsporidian affections. The pathogen can colonize a broad range of mammals and birds and most of the animals surveyed share some genotypes with humans, posing a threat to public health. Based on DNA sequence analysis of the ribosomal internal transcribed spacer (ITS) and phylogenetic analysis, several hundreds of E. bieneusi genotypes have been defined and clustered into different genetic groups with varied levels of host specificity. However, single locus-based typing using ITS might have insufficient resolution to discriminate among E. bieneusi isolates with complex genetic or hereditary characteristics and to assess the elusive reproduction or transmission modes of the organism, highlighting the need for exploration and application of multilocus sequence typing (MLST) and population genetic tools. The present review begins with a primer on microsporidia and major microsporidian species, briefly introduces the recent advances on E. bieneusi ITS genotyping and phylogeny, summarizes recent MLST and population genetic data, analyzes the inter- and intragroup host specificity at the MLST level, and interprets the public health implications of host specificity in zoonotic or cross-species transmission of this ubiquitous fungus.

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.

Evolutionary Genomics of Metchnikovella incurvata (Metchnikovellidae): An Early Branching Microsporidium

Metchnikovellids are highly specialized hyperparasites, which infect and reproduce inside gregarines (Apicomplexa) inhabiting marine invertebrates. Their phylogenetic affiliation was under constant discussion until recently, when analysis of the first near-complete metchnikovellid genome, that of Amphiamblys sp., placed it in a basal position with respect to most Microsporidia. Microsporidia are a highly diversified lineage of extremely reduced parasites related to Rozellida (Rozellosporidia = Rozellomycota = Cryptomycota) within the Holomycota clade of Opisthokonta. By sequencing DNA from a single-isolated infected gregarine cell we obtained an almost complete genome of a second metchnikovellid species, and the first one of a taxonomically described and well-documented species, Metchnikovella incurvata. Our phylogenomic analyses show that, despite being considerably divergent from each other, M. incurvata forms a monophyletic group with Amphiamplys sp., and confirm that metchnikovellids are one of the deep branches of Microsporidia. Comparative genomic analysis demonstrates that, like most Microsporidia, metchnikovellids lack mitochondrial genes involved in energy transduction and are thus incapable of synthesizing their own ATP via mitochondrial oxidative phosphorylation. They also lack the horizontally acquired ATP transporters widespread in most Microsporidia. We hypothesize that a family of mitochondrial carrier proteins evolved to transport ATP from the host into the metchnikovellid cell. We observe the progressive reduction of genes involved in DNA repair pathways along the evolutionary path of Microsporidia, which might explain, at least partly, the extremely high evolutionary rate of the most derived species. Our data also suggest that genome reduction and acquisition of novel genes co-occurred during the adaptation of Microsporidia to their hosts.

Isolation of Encephalitozoon intestinalis from crows living in urban parks of Tehran, Iran: an investigation with zoonotic aspect

Microsporidia are eukaryotic, intracellular obligate parasites that widely involve many organisms including insects, fish, birds, and mammals. One of the genera of Microsporidia is Encephalitozoon, which contains several opportunistic pathogens. Since Encephalitozoon spp. are zoonotic and opportunistic pathogens, it is important to find their reservoir hosts; hence, the current study aimed at isolating and identifying Encephalitozoon spp. in the crows by the light microscopy observations and molecular methods. For this purpose, 36 samples were collected by the dropping method; however, due to the low volume of samples, the total samples were collected in a sterile stool container and the polymerase chain reaction (PCR) was performed to detect Encephalitozoon spp. Accordingly, 300-bp bands, specific to Encephalitozoon spp., were observed and by sequencing E. intestinalis was identified. Crows can be considered as the hosts of E. intestinalis.

Molecular surveillance of Vittaforma-like microsporidia by a small-volume procedure in drinking water source in Taiwan: evidence for diverse and emergent pathogens

Vittaforma corneae belongs to microsporidia, which include over 1500 species of opportunistic obligate intracellular fungi infecting almost all known animal taxa. Although outbreaks of ocular infections caused by waterborne V. corneae have been reported in recent years, little is known about the occurrence of this pathogen in aquatic environments. In this study, 50 water samples from rivers and reservoirs around Taiwan in two seasons were analyzed to explore the presence of this pathogen in natural aquatic environments. A high detection rate of Vittaforma-like amplicons (94%; 47/50) was observed in the water samples when examined by nested PCR with primer pairs specific to the small ribosomal subunit (SSU) rRNA gene. After electrophoresis, many lanes showed multiband patterns with expected molecular weights. After confirmation by DNA sequencing and by sequence alignment in the NCBI database, we identified a variety of Vittaforma-like microsporidia with weak sequence similarity, with approximately 85% identity to V. corneae, thus indicating high diversity of microsporidia in aquatic environments. Phylogenetic analysis showed clear-cut microsporidian clade classification and indicated that the most Vittaforma-like microsporidia in this study belong to clade IV and cluster into four major groups. The first group is similar to the microsporidia associated with ocular microsporidiosis. The second group is associated with the diarrheal pathogens, whereas the third and fourth groups are a novel group and a zoonotic group, respectively. This study provides abundant sequencing information, which will be useful for future molecular biological studies on microsporidia. Because microsporidia are important pathogens of animals and humans, it is urgently necessary to determine via a survey whether there are species with potential threats that have not yet been revealed.