Microsporidiosis: an emerging and opportunistic infection in humans and animals

The natural symbiotic bacterium Enterococcus faecalis LX10 drives Bombyx mori refractoriness to Nosema bombycis infection via the secretion of enterococcin

BACKGROUND

The microsporidian Nosema bombycis is an obligate intracellular fungal-related parasites of the Bombyx mori, causing the epidemic disease Pebrine and extensive economic losses in the agricultural and sericulture industry. Enterococcus has emerged as one of the predominant gut microorganisms of the major model organism, Bombyx mori. However, the potential interactions mechanism between B. mori, N. bombycis and Enterococcus have not been well demonstrated.

METHODS

To address this gap, we used an insect model, silkworm to examine the potential mechanism of the natural symbiotic bacterium Enterococcus faecalis LX10 drives B. mori refractoriness to N. bombycis infection. E. faecalis LX10 was isolated from the gut of healthy silkworms, and its inhibitory activity against N. bombycis was evaluated at both the cellular and individual levels using posttranslational modifications, gene and protein expression analysis, transfected cells, and in vitro immunofluorescence.

RESULTS

We demonstrated that enterococcin (EntLX), the first antimicrobial protein family in gut commensal bacterium Enterococcus faecalis LX10 of B. mori, contributes to defending against N. bombycis infection resistance depends on the enzyme gelatinase (GelE), disulfide bond and disulfide bond formation proteinA (DsbA). The EntLX protein, abundantly expressed in transgenic BmN cells and gut organs(gut epithelium, peritrophic membrane and contents), can reduce the infection rate of cells and alleviate intestinal damage caused by N. bombycis infection. After simultaneous vaccination with E. faecalis LX10 and N. bombycis, the differentially key metabolites, physiological characteristics(larval mass), or economic traits(cocoon length, cocoon width, whole-cocoon weight, cocoon shell weight, pupation rate and adult emergence rate) showed a certain degrees of recovery and correction compared with those of single N. bombycis inoculation at the individual level.

CONCLUSIONS

This study advances the understanding of the anti-microsporidia activity of enterococci and paves the way for the expression of these molecules as antifungal agents via the genetic transformation of Enterococcus symbionts from disease-transmitting insects.

CLINICAL TRIAL NUMBER

Not applicable.

Molecular Detection of Encephalitozoon cuniculi in Migratory Waterfowl of the Genus Anser (Anseriformes: Anatidae) in Poland

Microsporidiosis is a zoonotic disease that derives from disparate sources. Most of the microsporidial agents are host-specific but some are capable of interspecies transmission, causing disease in various animals including humans. Human microsporidiosis may be caused by 17 species, with Encephalitozoon cuniculi, E. intestinalis and E. hellem mostly being responsible for human infections worldwide. Wildlife and migratory waterfowl can serve as reservoirs of these human-infectious agents and play a significant role in disseminating these pathogens into the environment. The aim of the study was to detect E. cuniculi, E. intestinalis and E. hellem in wild, migratory greater white-fronted geese (Anser albifrons) and other Anatidae members in feacal samples obtained in north-western Poland, using a molecular method. We collected 189 fecal droppings from Anatidae species (75 samples from greater white-fronted geese and 114 from other Anser spp.) during autumn migration. New species specific primers for PCR amplification were used to amplify a fragment of the small subunit ribosomal (SSU) rRNA of E. cuniculi, E. intestinalis and E. hellem. All fecal droppings were negative for E. intestinalis and E. hellem whereas E cuniculi was detected in 6 of 189 fecal samples (3.2%; 95% CI: 1.3-6.3%). In total, 1 of 75 tested fecal samples of greater white-fronted geese was positive (1.3%; 95% CI: 0.08-5.7%) while 5 of 114 (4.4%; 95% CI: 1.6-9.1%) tested fecal samples without exact species affiliation (only Anser sp.) were also positive. The phylogenetic analysis placed the sequences obtained from the birds' droppings in the clade E. cuniculi from various rodents, wild carnivores and humans. Our results provide the first description of the occurrence and genotyping of the microsporidian E. cuniculi in greater white-fronted geese and in other members of the Anserinae Subfamily. Our findings support the results of other authors that E. cuniculi may originate from diverse sources, including common waterfowl. Our results are important in a One Health context, as wild migrating waterfowl may disseminate this zoonotic agent in remote regions through their migratory behaviour. These species should be considered significant sources of zoonotic pathogens, potentially hazardous to domestic and farmed animals as well as humans.

Conserved components of the macroautophagy machinery in Caenorhabditis elegans

Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane autophagosome and its subsequent delivery to lysosomes for degradation and recycling. In Caenorhabditis elegans, autophagy participates in diverse processes such as stress resistance, cell fate specification, tissue remodeling, aging, and adaptive immunity. Genetic screens in C. elegans have identified a set of metazoan-specific autophagy genes that form the basis for our molecular understanding of steps unique to the autophagy pathway in multicellular organisms. Suppressor screens have uncovered multiple mechanisms that modulate autophagy activity under physiological conditions. C. elegans also provides a model to investigate how autophagy activity is coordinately controlled at an organismal level. In this chapter, we will discuss the molecular machinery, regulation, and physiological functions of autophagy, and also methods utilized for monitoring autophagy during C. elegans development.

Macroalgal Biofilm Harbours a Wide Diversity of Parasitic Protists With Distinct Temporal Dynamics

Marine macroalgae surfaces create a nutrient-rich environment that promotes the formation of epiphyte biofilms. Biofilms are complex systems that facilitate ecological interactions within the community, yet parasitism remains largely unexplored. This study describes the diversity and temporal dynamics of the microeukaryotic community in the biofilm of Mediterranean macroalgae during summer, focusing on parasitic groups. Protist diversity was assessed using metabarcoding sequencing of the V4 region of the 18S rDNA gene using primers biased against metazoans. The macroalgal biofilm exhibited dynamic shifts in the microeukaryotic community structure associated to three phases of biofilm formation. Each phase was characterised by the dominance of specific eukaryotic and parasitic groups with clear successions between them. Our study revealed a high diversity of parasitic protists from different lineages in the macroalgal biofilm. These parasites can infect a wide variety of hosts, including the basibiont, species within the biofilm (micro- and macrocolonizers), nearby marine hosts and terrestrial organisms. The highest diversity and abundance of parasites were found in the mature phase of the biofilm, where the complexity and stability of the system seem to favour parasitism. The parasite assemblage was dominated by Apicomplexa, with many corresponding to unknown diversity, demonstrating that biofilms are a hotspot of unknown parasitic interactions. These parasites could potentially affect the dynamics of these communities and facilitate ecological interactions between the biofilm and surrounding organisms, suggesting that parasitism play a key, but still unexplored role, in shaping complex marine biofilms network.

Novel zoonotic Enterocytozoon and Encephalitozoon genotypes in domestic pigeons (Columba livia domestica) in Iran: Public health implications

To determine the occurrence of microsporidiosis in domestic pigeons in Iran, privately-owned pigeons presenting weight loss and diarrhea were tested through molecular and histopathological methods. Multiplex-PCR findings showed 57%, 30%, and 14% positivity for Enterocytozoon, Encephalitozoon, and mixed infection in the fecal samples, respectively. A novel Enterocytozoon bieneusi genotype, named IrnEb1, falling into zoonotic group 1 of E. bieneusi, and a novel genotype of Encephalitozoon hellem, named Irn2E, clustering as a sister taxon to genotype 2B were identified in pigeons for the first time using Sanger sequencing and phylogenetic analyses. Histopathological examination revealed the occurrence of non-suppurative enteritis, nephritis, pneumonia, hepatitis, and encephalitis associated with focal necrosis and inflammatory cell infiltration. Data shown herein present a high prevalence of microsporidiosis in pigeons in Iran. Considering that both detected microsporidian species are zoonotic parasites, these findings suggest that the infected pigeons could pose a risk to public health.

Occurrence and Genotypic Identification of Blastocystis spp. and Enterocytozoon bieneusi in Bamaxiang Pigs in Bama Yao Autonomous County of Guangxi Province, China

Blastocystis spp. and Enterocytozoon bieneusi are common intestinal pathogens capable of infecting both humans and animals, which lead to severe diarrhea and other intestinal diseases, posing a threat to public health. The Bamaxiang pig, a specialty of Bama Yao Autonomous County in Guangxi Province, China, is an important local breed in the regional pork market and an excellent model animal for biomedical research. Currently, no data is available on the prevalence or genotype distribution of these pathogens in Bamaxiang pigs. This study aimed to determine the prevalence and genetic characteristics of Blastocystis spp. and E. bieneusi in three Bamaxiang pig farms located in Bama Yao Autonomous County, using molecular techniques based on the small subunit ribosomal RNA (SSU rRNA) gene fragment of Blastocystis spp. and the internal transcribed spacer (ITS) region of E. bieneusi. All positive PCR products from the 311 fecal samples were sequenced to identify the species and genotypes of these organisms. The overall infection rates of Blastocystis spp. and E. bieneusi were 34.08% (106/311) and 18.32% (57/311), respectively. Three subtypes of Blastocystis spp. were detected: ST1 (n = 8), ST3 (n = 3), and ST5 (n = 95). Among them, zoonotic ST5 was the dominant genotype, accounting for 89.62% (95/106) of strains, followed by the genotypes ST1 (7.54%, 8/106) and ST3 (2.83%, 3/106). Two genotypes of E. bieneusi were detected: EbpC (n = 52) and CHG23 (n = 5), with EbpC being the dominant genotype. The human-pathogenic subtypes (ST1, ST3, and ST5) and genotypes (EbpC, CHG23) that were observed in this study indicate a potential threat to public health. Our findings offer basic information for preventing and controlling these zoonotic pathogens in the study area. Additional investigations are necessary to better understand their genetic characteristics and zoonotic potential within Guangxi Province.

Methionine aminopeptidases: Potential therapeutic target for microsporidia and other microbes

Methionine aminopeptidases (MetAPs) have emerged as a target for medicinal chemists in the quest for novel therapeutic agents for treating cancer, obesity, and other disorders. Methionine aminopeptidase is a metalloenzyme with two structurally distinct forms in humans, MetAP-1 and MetAP-2. The MetAP2 inhibitor fumagillin, which was used as an amebicide in the 1950s, has been used for the successful treatment of microsporidiosis in humans; however, it is no longer commercially available. Despite significant efforts and investments by many pharmaceutical companies, no new MetAP inhibitors have been approved for the clinic. Several lead compounds have been designed and synthesized by researchers as potential inhibitors of MetAP and evaluated for their potential activity in a wide range of diseases. MetAP inhibitors such as fumagillin, TNP-470, beloranib, and reversible inhibitors and their analogs guide new prospects for MetAP inhibitor development in the ongoing quest for new pharmacological indications. This perspective provides insights into recent advances related to MetAP, as a potential therapeutic target in drug discovery, bioactive small molecule MetAP2 inhibitors, and data on the role of MetAP-2 as a therapeutic target for microsporidiosis.

Host cell manipulation by microsporidia secreted effectors: Insights into intracellular pathogenesis

Microsporidia are prolific producers of effector molecules, encompassing both proteins and nonproteinaceous effectors, such as toxins, small RNAs, and small peptides. These secreted effectors play a pivotal role in the pathogenicity of microsporidia, enabling them to subvert the host's innate immunity and co-opt metabolic pathways to fuel their own growth and proliferation. However, the genomes of microsporidia, despite falling within the size range of bacteria, exhibit significant reductions in both structural and physiological features, thereby affecting the repertoire of secretory effectors to varying extents. This review focuses on recent advances in understanding how microsporidia modulate host cells through the secretion of effectors, highlighting current challenges and proposed solutions in deciphering the complexities of microsporidial secretory effectors.

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.

Nematocida displodere mechanosensitive ion channel of small conductance 2 assembles into a unique 6-channel super-structure in vitro

Mechanosensitive ion channels play an essential role in reacting to environmental signals and sustaining cell integrity by facilitating ion flux across membranes. For obligate intracellular pathogens like microsporidia, adapting to changes in the host environment is crucial for survival and propagation. Despite representing a eukaryote of extreme genome reduction, microsporidia have expanded the gene family of mechanosensitive ion channels of small conductance (mscS) through repeated gene duplication and horizontal gene transfer. All microsporidian genomes characterized to date contain mscS genes of both eukaryotic and bacterial origin. Here, we investigated the cryo-electron microscopy structure of the bacterially derived mechanosensitive ion channel of small conductance 2 (MscS2) from Nematocida displodere, an intracellular pathogen of Caenorhabditis elegans. MscS2 is the most compact MscS-like channel known and assembles into a unique superstructure in vitro with six heptameric MscS2 channels. Individual MscS2 channels are oriented in a heterogeneous manner to one another, resembling an asymmetric, flexible six-way cross joint. Finally, we show that microsporidian MscS2 still forms a heptameric membrane channel, however the extreme compaction suggests a potential new function of this MscS-like protein.

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.

Molecular characterization and phylogenetic analyses of MetAP2 gene and protein of Nosema bombycis isolated from Guangdong, China

Background

Pebrine, caused by microsporidium Nosema bombycis, is a devastating disease that causes serious economic damages to the sericulture industry. Studies on development of therapeutic and diagnostic options for managing pebrine in silkworms are very limited. Methionine aminopeptidase type 2 (MetAP2) of microsporidia is an essential gene for their survival and has been exploited as the cellular target of drugs such as fumagillin and its analogues in several microsporidia spp., including Nosema of honeybees.

Methods

In the present study, using molecular and bioinformatics tools, we performed in-depth characterization and phylogenetic analyses of MetAP2 of Nosema bombycis isolated from Guangdong province of China.

Results

The full length of MetAP2 gene sequence of Nosema bombycis (Guangdong isolate) was found to be 1278 base pairs (bp), including an open reading frame of 1,077 bp, encoding a total of 358 amino acids. The bioinformatics analyses predicted the presence of typical alpha-helix structural elements, and absence of transmembrane domains and signal peptides. Additionally, other characteristics of a stable protein were also predicted. The homology-based 3D models of MetAP2 of Nosema bombycis (Guangdong isolate) with high accuracy and reliability were developed. The MetAP2 protein was expressed and purified. The observed molecular weight of MetAP2 protein was found to be ~43-45 kDa. The phylogenetic analyses showed that MetAP2 gene and amino acids sequences of Nosema bombycis (Guangdong isolate) shared a close evolutionary relationship with Nosema spp. of wild silkworms, but it was divergent from microsporidian spp. of other insects, Aspergillus spp., Saccharomyces cerevisiae, and higher animals including humans. These analyses indicated that the conservation and evolutionary relationships of MetAP2 are closely linked to the species relationships.

Conclusion

This study provides solid foundational information that could be helpful in optimization and development of diagnostic and treatment options for managing the threat of Nosema bombycis infection in sericulture industry of China.

Identification of common human infectious and potentially zoonotic novel genotypes of Enterocytozoon bieneusi in cavernicolous bats in Thailand

Enterocytozoon bieneusi is a common cause of human microsporidiosis and can infect a variety of animal hosts worldwide. In Thailand, previous studies have shown that this parasite is common in domestic animals. However, information on the prevalence and genotypes of this parasite in other synanthropic wildlife, including bats, remains limited. Several pathogens have been previously detected in bats, suggesting that bats may serve as a reservoir for this parasite. In this study, a total of 105 bat guano samples were collected from six different sites throughout Thailand. Of these, 16 from Chonburi (eastern), Ratchaburi (western), and Chiang Rai (northern) provinces tested positive for E. bieneusi, representing an overall prevalence of 15.2%. Based on ITS1 sequence analysis, 12 genotypes were identified, including two known genotypes (D and type IV) frequently detected in humans and ten novel potentially zoonotic genotypes (TBAT01-TBAT10), all belonging to zoonotic group 1. Lyle's flying fox (Pteropus lylei), commonly found in Southeast Asia, was identified as the host in one sample that was also positive for E. bieneusi. Network analysis of E. bieneusi sequences detected in this study and those previously reported in Thailand also revealed intraspecific divergence and recent population expansion, possibly due to adaptive evolution associated with host range expansion. Our data revealed, for the first time, multiple E. bieneusi genotypes of zoonotic significance circulating in Thai bats and demonstrated that bat guano fertilizer may be a vehicle for disease transmission.

Encephalitozoon cuniculi Microsporidia in Cerebrospinal Fluid from Immunocompetent Patients, Czech Republic

We retrospectively analyzed of 211 frozen cerebrospinal fluid samples from immunocompetent persons in the Czech Republic and detected 6 Encephalitozoon cuniculi-positive samples. Microsporidiosis is generally underestimated and patients are not usually tested for microsporidia, but latent infection in immunodeficient and immunocompetent patients can cause serious complications if not detected and treated.

Draft genome of Microsporidia sp. MB-a malaria-blocking microsporidian symbiont of the Anopheles arabiensis

We report the draft whole-genome assembly of Microsporidia sp. MB, a symbiotic malaria-transmission-blocking microsporidian isolated from Anopheles arabiensis in Kenya. The whole-genome sequence of Microsporidia sp. MB has a length of 5,908,979 bp, 2,335 contigs, and an average GC content of 31.12%.

Meta-analysis of the global prevalence and risk factors of Enterocytozoon bieneusi infection in pigs from 1999 to 2021

Enterocytozoon bieneusi (E. bieneusi), which is one of the most common microsporidia, has been identified as an important obligate intracellular pathogen that commonly colonizes in a variety of animal species and humans worldwide, including humans. In this study, the statistical analyses of E. bieneusi infection and prevalence were performed to clarify the relationship between different genotypes in different countries. The databases Chinese National Knowledge Infrastructure (CNKI), VIP Chinese Journal Database, Wanfang Data, PubMed, Web of Science and ScienceDirect were used for data collection. The research data were subjected to subgroup, univariate regression, and correlation, to reveal factors related to the high prevalence of E. bieneusi. A total of, 34 of the 498 articles published before April 2022 met the inclusion criteria. The global prevalence of E. bieneusi in pigs was 37.69% (5175/12672). The prevalence of E. bieneusi in nursery pigs was 58.87% (588/946). In developing countries and Asia, the highest prevalence of E. bieneusi in pigs were 37.62% (4752/11645) and 40.14% (4715/11345), respectively. Moreover, humans and pigs have been found to be infected with the same genotype of E. bieneusi in some cases, as evidenced by the consolidation of genotype information. The results showed that pigs are susceptible to E. bieneusi during the nursery period. The prevalence of E. bieneusi is high in developing countries, and its genotype prevalence varies in each country. Thus, it is essential to strengthen the health inspection of vulnerable groups and customs quarantine inspection.

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.

Microsporidia (Encephalitozoon cuniculi) in Patients with Degenerative Hip and Knee Disease, Czech Republic

Total joint arthroplasty is a commonly used surgical procedure in orthopedics. Revision surgeries are required in >10% of patients mainly because of prosthetic joint infection caused by bacteria or aseptic implant loosening caused by chronic inflammation. Encephalitozoon cuniculi is a microsporidium, an obligate intracellular parasite, capable of exploiting migrating proinflammatory immune cells for dissemination within the host. We used molecular detection methods to evaluate the incidence of E. cuniculi among patients who had total hip or knee arthroplasty revision. Out of 49 patients, E. cuniculi genotypes I, II, or III were confirmed in joint samples from 3 men and 2 women who had implant loosening. Understanding the risks associated with the presence of microsporidia in periprosthetic joint infections is essential for proper management of arthroplasty. Furthermore, E. cuniculi should be considered a potential contributing cause of joint inflammation and arthrosis.

Global prevalence and risk factors of Enterocytozoon bieneusi infection in humans: a systematic review and meta-analysis

Enterocytozoon bieneusi is one of the most important zoonotic pathogens. In this study, we present a systematic review and meta-analysis of the prevalence of human E. bieneusi infection in endemic regions and analyze the various potential risk factors. A total of 75 studies were included. Among 31,644 individuals tested, 2,291 (6.59%) were E. bieneusi-positive. The highest prevalence of E. bieneusi in the male population was 5.50%. The prevalence of E. bieneusi in different age groups was varied, with 10.97% in teenagers. The prevalence of E. bieneusi in asymptomatic patients (6.49%) is significantly lower than that in HIV-infected patients (11.49%), and in patients with diarrheal symptoms (16.45%). Rural areas had a higher rate (7.58%) than urban ones. The prevalence of E. bieneusi in humans was the highest (6.42%) at altitudes <10 m. Moreover, the temperate zone marine climate (13.55%) had the highest prevalence. A total of 69 genotypes of E. bieneusi have been found in humans. This is the first global study regarding E. bieneusi prevalence in humans. Not only people with low immunity (such as the elderly, children, people with HIV, etc.), but also people in Europe in temperate marine climates should exercise caution to prevent infection with E. bieneusi during contact process with animals.

Treatment of Microsporidium Nosema bombycis Spores with the New Antiseptic M250 Helps to Avoid Bacterial and Fungal Contamination of Infected Cultures without Affecting Parasite Polar Tube Extrusion

Microsporidia are a group of widespread eukaryotic spore-forming intracellular parasites of great economic and scientific importance. Since microsporidia cannot be cultured outside of a host cell, the search for new antimicrosporidian drugs requires an effective antiseptic to sterilize microsporidian spores to infect cell lines. Here, we show that a new polyhexamethylene guanidine derivative M250, which is active against fungi and bacteria at a concentration of 0.5-1 mg/L, is more than 1000 times less effective against spores of the microsporidium Nosema bombycis, a highly virulent pathogen of the silkworm Bombyx mori (LC50 is 0.173%). Treatment of N. bombycis spores that were isolated non-sterilely from silkworm caterpillars with 0.1% M250 solution does not reduce the rate of spore polar tube extrusion. However, it completely prevents contamination of the Sf-900 III cell culture medium by microorganisms in the presence of antibiotics. The addition of untreated spores to the medium results in contamination, whether antibiotics are present or not. Since 0.1% M250 does not affect spore discharging, this compound may be promising for preventing bacterial and fungal contamination of microsporidia-infected cell cultures.

Functional annotation of a divergent genome using sequence and structure-based similarity

BACKGROUND

Microsporidia are a large taxon of intracellular pathogens characterized by extraordinarily streamlined genomes with unusually high sequence divergence and many species-specific adaptations. These unique factors pose challenges for traditional genome annotation methods based on sequence similarity. As a result, many of the microsporidian genomes sequenced to date contain numerous genes of unknown function. Recent innovations in rapid and accurate structure prediction and comparison, together with the growing amount of data in structural databases, provide new opportunities to assist in the functional annotation of newly sequenced genomes.

RESULTS

In this study, we established a workflow that combines sequence and structure-based functional gene annotation approaches employing a ChimeraX plugin named ANNOTEX (Annotation Extension for ChimeraX), allowing for visual inspection and manual curation. We employed this workflow on a high-quality telomere-to-telomere sequenced tetraploid genome of Vairimorpha necatrix. First, the 3080 predicted protein-coding DNA sequences, of which 89% were confirmed with RNA sequencing data, were used as input. Next, ColabFold was used to create protein structure predictions, followed by a Foldseek search for structural matching to the PDB and AlphaFold databases. The subsequent manual curation, using sequence and structure-based hits, increased the accuracy and quality of the functional genome annotation compared to results using only traditional annotation tools. Our workflow resulted in a comprehensive description of the V. necatrix genome, along with a structural summary of the most prevalent protein groups, such as the ricin B lectin family. In addition, and to test our tool, we identified the functions of several previously uncharacterized Encephalitozoon cuniculi genes.

CONCLUSION

We provide a new functional annotation tool for divergent organisms and employ it on a newly sequenced, high-quality microsporidian genome to shed light on this uncharacterized intracellular pathogen of Lepidoptera. The addition of a structure-based annotation approach can serve as a valuable template for studying other microsporidian or similarly divergent species.

Screening of the Pandemic Response Box identifies anti-microsporidia compounds

Microsporidia are fungal obligate intracellular pathogens, which infect most animals and cause microsporidiosis. Despite the serious threat that microsporidia pose to humans and agricultural animals, few drugs are available for the treatment and control of microsporidia. To identify novel inhibitors, we took advantage of the model organism Caenorhabditis elegans infected with its natural microsporidian Nematocida parisii. We used this system to screen the Pandemic Response Box, a collection of 400 diverse compounds with known antimicrobial activity. After testing these compounds in a 96-well format at high (100 μM) and low (40 μM) concentrations, we identified four inhibitors that restored the ability of C. elegans to produce progeny in the presence of N. parisii. All four compounds reduced the pathogen load of both N. parisii and Pancytospora epiphaga, a C. elegans-infecting microsporidia related to human-infecting species. One of these compounds, a known inhibitor of a viral protease, MMV1006203, inhibited invasion and prevented the firing of spores. A bis-indole derivative, MMV1593539, decreased spore viability. An albendazole analog, MMV1782387, inhibited proliferation of N. parisii. We tested albendazole as well as 5 other analogs and observed that MMV1782387 was amongst the strongest inhibitors of N. parisii and displayed the least host toxicity. Our study further demonstrates the effectiveness of the C. elegans-N. parisii system for discovering microsporidia inhibitors and the compounds we identified provide potential scaffolds for anti-microsporidia drug development.

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.

Non-coding RNAs identification and regulatory networks in pathogen-host interaction in the microsporidia congenital infection

BACKGROUND

The interaction networks between coding and non-coding RNAs (ncRNAs) including long non-coding RNA (lncRNA), covalently closed circular RNA (circRNA) and miRNA are significant to elucidate molecular processes of biological activities and interactions between host and pathogen. Congenital infection caused by vertical transmission of microsporidia N. bombycis can result in severe economic losses in the silkworm-feeding industry. However, little is known about ncRNAs that take place in the microsporidia congenital infection. Here we conducted whole-transcriptome RNA-Seq analyses to identify ncRNAs and regulatory networks for both N. bombycis and host including silkworm embryos and larvae during the microsporidia congenital infection.

RESULTS

A total of 4,171 mRNAs, 403 lncRNA, 62 circRNAs, and 284 miRNAs encoded by N. bombycis were identified, among which some differentially expressed genes formed cross-talk and are involved in N. bombycis proliferation and infection. For instance, a lncRNA/circRNA competing endogenous RNA (ceRNA) network including 18 lncRNAs, one circRNA, and 20 miRNAs was constructed to describe 14 key parasites genes regulation, such as polar tube protein 3 (PTP3), ricin-B-lectin, spore wall protein 4 (SWP4), and heat shock protein 90 (HSP90). Regarding host silkworm upon N. bombycis congenital infection, a total of 14,889 mRNAs, 3,038 lncRNAs, 19,039 circRNAs, and 3,413 miRNAs were predicted based on silkworm genome with many differentially expressed coding and non-coding genes during distinct developmental stages. Different species of RNAs form interacting network to modulate silkworm biological processes, such as growth, metamorphosis and immune responses. Furthermore, a lncRNA/circRNA ceRNA network consisting of 140 lncRNAs, five circRNA, and seven miRNAs are constructed hypothetically to describe eight key host genes regulation, such as Toll-6, Serpin-6, inducible nitric oxide synthase (iNOS) and Caspase-8. Notably, cross-species analyses indicate that parasite and host miRNAs play a vital role in pathogen-host interaction in the microsporidia congenital infection.

CONCLUSION

This is the first comprehensive pan-transcriptome study inclusive of both N. bombycis and its host silkworm with a specific focus on the microsporidia congenital infection, and show that ncRNA-mediated regulation plays a vital role in the microsporidia congenital infection, which provides a new insight into understanding the basic biology of microsporidia and pathogen-host interaction.

Prevalence of Encephalitozoon cuniculi Infection in Guinea Pigs (Cavia porcellus) in Poland with Different Clinical Disorders-A Pilot Study

Encephalitozoonosis is a disease caused by E. cuniculi. It is diagnosed primarily in rabbits but is less frequently so in other animal species. E. cuniculi is classified among Microsporidia-fungi frequently found in the environment, that are resistant to numerous external factors. Apart from rabbits, rodents form the next group of animals most exposed to infection with these pathogens. The objective of the study was to analyze the prevalence of E. cuniculi infection in guinea pigs with different clinical disorders. The study included 67 animals with E. cuniculi infection confirmed via real-time PCR. The infected animals most frequently exhibited nervous and urinary system symptoms, as well as issues with vision organs, while several animals were also recorded as having problems with the respiratory system and thyroid gland dysfunction. The study shows that encephalitozoonosis constitutes a significant problem in rodents kept as domestic animals, which in turn may be a source of infection for humans.

[Ophthalmic findings caused by Encephalitozoon cuniculi (strain III) in a dog]

A 2-year-old female mixed-breed canine patient from Namibia presented originally with chronic uveitis. A serum antibody titer and a PCR test performed on the aqueous humor were positive for encephalitozoon cuniculi. The left eye showed an immature anterior focal cortical cataract in the periphery with suspected lens capsule rupture and signs of chronic uveitis. An incipient anterior focal cortical cataract was also perceivable in the patient's right eye. Despite local treatment as well as systemic administration of carprofen, prednisolone, and fenbendazol recurrent uveitis occurred. The patient then underwent bilateral extracapsular lensextraction via phacoemulsification. A PCR test of the lens material was positive for encephalitozoon cuniculi strain III. Recurring uveitis and secondary glaucoma 10 months post-op resulted in permanent blindness of the left eye. The patient then continued to receive local anti-inflammatory treatment. The last recheck examination of both eyes, 31 month post-op, revealed no signs of uveitis. This is the first case reported of a cataract in a canine patient caused by encephalitozoon cuniculi strain III.

Enterocytozoon bieneusi in fecal samples from calves and cows in Austria

Enterocytozoon bieneusi is an obligate intracellular pathogen that infects livestock, companion animals, and wildlife and has the potential to cause severe diarrhea especially in immunocompromised humans. In the underlying study, fecal samples from 177 calves with diarrhea and 174 adult cows originating from 70 and 18 farms, respectively, in Austria were examined for the presence of E. bieneusi by polymerase chain reaction targeting the Internal Transcribed Spacer 1 (ITS1) region. All positive samples were further sequenced for genotype determination. Overall, sixteen of the 351 (4.6%) samples were positive for E. bieneusi, two of the 174 samples from cows (1.2%) and 14 of the 177 samples from calves (7.9%). In total, four genotypes, J (n = 2), I (n = 12), BEB4 (n = 3), and BEB8 (n = 1), were identified. The uncorrected p-distance between the four ITS1 lineages (344 bp) ranges from 0.3% to 2.9%. The lineages differ by 1 bp (I and J), 2 bp (J and BEB4), and 3 bp (I and BEB4), respectively, and BEB8 differs by 7 to 10 bp from the latter three lineages. Two of the E. bieneusi-positive calves showed an infection with two different genotypes. E. bieneusi occurred significantly more often in calves > 3 weeks (8/59) than in calves ≤ 3 weeks (6/118), respectively (p = 0.049). Calves with a known history of antimicrobial treatment (50 of 177 calves) shed E. bieneusi significantly more often than untreated calves (p = 0.012). There was no statistically significant difference in E. bieneusi shedding in calves with or without a medical history of antiparasitic treatment (p = 0.881). Calves showing a co-infection with Eimeria spp. shed E. bieneusi significantly more often than uninfected calves (p = 0.003). To our knowledge, this is the first report of E. bieneusi in cattle in Austria. Cattle should be considered as a reservoir for human infection since potentially zoonotic E. bieneusi genotypes were detected.

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.

Microsporidia as a Potential Threat to the Iberian Lynx (Lynx pardinus)

Simple Summary

The Iberian lynx, which inhabits the Iberian Peninsula, is one of the most endangered felines in the world. Wild Iberian lynx populations have suffered a constant regression over the past century, with a rapid decline of 90% in the last 20 years. Infectious diseases are one of the most critical threats that cause the population decline of these animals, either in the wild or captivity. Different studies have revealed positive seroprevalence against various pathogens, confirming contact and exposure to bacteria, viruses, and parasites. In this sense, searching for pathogens related to the depopulation of the Iberian lynx is vital for conserving and maintaining this threatened species. The present work confirmed the presence of microsporidia, opportunistic intracellular parasites recently related to fungi, in the lynx environment. Also, different species of microsporidia were determined for the first time in the urine, feces, and tissue samples of Lynx pardinus. Further studies are needed to establish the impact of microsporidia infection on the survival of the Iberian lynx. These studies would contribute to the endurance and conservation of this feline by implementing new prevention strategies.

Abstract

Lynx pardinus is one of the world’s most endangered felines inhabiting the Iberian Peninsula. The present study was performed to identify the presence of microsporidia due to the mortality increase in lynxes. Samples of urine (n = 124), feces (n = 52), and tissues [spleen (n = 13), brain (n = 9), liver (n = 11), and kidney (n = 10)] from 140 lynxes were studied. The determination of microsporidia was evaluated using Weber’s chromotrope stain and Real Time-PCR. Of the lynxes analyzed, stains showed 10.48% and 50% positivity in urine and feces samples, respectively. PCR confirmed that 7.69% and 65.38% belonged to microsporidia species. The imprints of the tissues showed positive results in the spleen (38.46%), brain (22.22%), and liver (27.27%), but negative results in the kidneys. PCR confirmed positive microsporidia results in 61.53%, 55.55%, 45.45%, and 50%, respectively. Seroprevalence against Encephalitozoon cuniculi was also studied in 138 serum samples with a positivity of 55.8%. For the first time, the results presented different species of microsporidia in the urine, feces, and tissue samples of Lynx pardinus. The high titers of anti-E. cuniculi antibodies in lynx sera confirmed the presence of microsporidia in the lynx environment. New studies are needed to establish the impact of microsporidia infection on the survival of the Iberian lynx.

A multidisciplinary review about Encephalitozoon cuniculi in a One Health perspective

Encephalitozoon cuniculi is a microsporidian parasite mostly associated with its natural host, the rabbit (Oryctolagus cuniculus). However, other animals can be infected, like other mammals, birds, and even humans. Although it usually causes subclinical infection, it can also lead to encephalitozoonosis, a clinical disease characterized by neurological, ocular, and/or renal signs that can be even fatal, especially in immunocompromised individuals. Therefore, this multidisciplinary review contributes with updated information about the E. cuniculi, deepening in its molecular and genetic characterization, its mechanisms of infection and transmission, and its prevalence among different species and geographic locations, in a One Health perspective. Recent information about the diagnostic and therapeutic approach in the main host species and the prophylaxis and infection control measures currently suggested are also discussed.

Microsporidia, a Highly Adaptive Organism and Its Host Expansion to Humans

Emerging infectious disease has become the center of attention since the outbreak of COVID-19. For the coronavirus, bats are suspected to be the origin of the pandemic. Consequently, the spotlight has fallen on zoonotic diseases, and the focus now expands to organisms other than viruses. Microsporidia is a single-cell organism that can infect a wide range of hosts such as insects, mammals, and humans. Its pathogenicity differs among species, and host immunological status plays an important role in infectivity and disease severity. Disseminated disease from microsporidiosis can be fatal, especially among patients with a defective immune system. Recently, there were two Trachipleistophora hominis, a microsporidia species which can survive in insects, case reports in Thailand, one patient had disseminated microsporidiosis. This review gathered data of disseminated microsporidiosis and T. hominis infections in humans covering the biological and clinical aspects. There was a total of 22 cases of disseminated microsporidiosis reports worldwide. Ten microsporidia species were identified. Maximum likelihood tree results showed some possible correlations with zoonotic transmissions. For T. hominis, there are currently eight case reports in humans, seven of which had Human Immunodeficiency Virus (HIV) infection. It is observed that risks are higher for the immunocompromised to acquire such infections, however, future studies should look into the entire life cycle, to identify the route of transmission and establish preventive measures, especially among the high-risk groups.

Occurrence and molecular characterization of Enterocytozoon bieneusi in water buffaloes (Bubalus bubalis) in Turkey

Microsporidia are obligate intracellular fungus-like parasites that infect humans and animals worldwide. However, there is limited epidemiological data on the occurrence and molecular diversity of microsporidia in buffaloes worldwide. In the present study, fecal samples of 300 water buffaloes (Bubalus bubalis) in Kayseri, Sivas, and Samsun provinces of Turkey were investigated using two nested PCR assays targeting the rRNA of E. bieneusi and Encephalitozoon spp. All the fecal samples from water buffalo were found to be negative for Encephalitozoon spp. PCR positive isolates of E. bieneusi were bidirectionally sequenced for genotyping and phylogenetic analyses. Enterocytozoon bieneusi was the only microsporidian species identified in 8 water buffaloes with an overall molecular prevalence of 2.7%. Two known genotypes, YNDCEB-90 (n = 5) and J (n = 3) were identified by ITS sequence analysis. The YNDCEB-90 and J genotypes fall into zoonotic Group 1 and 2 of E. bieneusi in the phylogenetic tree, respectively. These findings suggested that water buffalo in Turkey are harbouring zoonotic genotypes of E. bieneusi and may have a significant risk for zoonotic transmission to humans. This is the first report of detecting E. bieneusi genotypes J and YNDCEB-90 in water buffaloes. Further insight into the epidemiology of E. bieneusi in water buffaloes in different geographical areas in Turkey will be highly important to have determined the public health significance of this pathogen.

Molecular Epidemiology and Genetic Diversity of Enterocytozoon bieneusi in Cervids from Milu Park in Beijing, China

Simple Summary

Enterocytozoon bieneusi is the most prevalent microsporidian species that can cause significant intestinal diseases in both humans and animals worldwide. This study investigated the overall E. bieneusi prevalence of 21.9% (47/215) in captive and free-ranging deer species in Beijing, China. Thirteen E. bieneusi genotypes including six known and seven novel genotypes were identified. These resources will provide the insights to understand the veterinary and public health and the transmission dynamics between animal environments and human ones.

Abstract

Enterocytozoon bieneusi is the most prevalent microsporidian species that can cause zoonotic diseases in humans and animals. Despite receiving increasing attention in relation to domestic animals, there has been limited information on the infection burden of E. bieneusi in cervids. Altogether, 215 fecal samples collected from four deer species in Beijing, China were examined by nested- Polymerase Chain Reaction (PCR)targeting the internal transcribed spacer (ITS) region. The overall prevalence of E. bieneusi in deer was 21.9% (47/215), with 30.0% (24/80) in Pere David’s deer, 27.3% (15/55) in fallow deer, 12.5% (5/40) in sika deer, and 7.5% (3/40) in Chinese water deer. Thirteen E. bieneusi genotypes were identified, including six known (HLJD-V, MWC_d1, BEB6, CGC2, JLD-XV, and HND-I) and seven novel genotypes (BJED-I to BJED-V, BJFD, and BJCWD). A phylogenetic analysis showed that 38.3% of the isolates belonged to zoonotic Group 1. In addition, E. bieneusi infection was first detected in fallow deer and Chinese water deer, which could act as potential zoonotic reservoirs. Our findings suggest that E. bieneusi circulates in deer and might be of importance to public health.

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.

Temporal variations of Microsporidia diversity and discovery of new host-parasite interactions in a lake ecosystem

Microsporidia are a large group of obligate intracellular eukaryotic parasites related to Fungi. Recent studies suggest that their diversity has been greatly underestimated and little is known about their hosts other than metazoans, and thus about their impact on the communities at the base of the food web. In this work, we therefore studied the diversity of Microsporidia over one year and identified potential new hosts in small-sized fractions (<150 μm) in a lake ecosystem using a metabarcoding approach coupled with co-occurrence networks and tyramide signal amplification-fluorescent in situ hybridization. Our analysis shows a great Microsporidia diversity (1 472 OTUs), with an important part of this diversity being unknown. Temporal variations of this diversity have been observed, which might follow temporal variations of their potential hosts such as protists and microzooplankton. New hosts among them were identified as well as associations with phytoplankton. Indeed, repeated infections were observed in Kellicottia (rotifers) with a prevalence of 38% (infected individuals). Microsporidia inside a Stentor (ciliate) were also observed. Finally, potential infections of the diatom Asterionella were identified (prevalence <0.1%). The microsporidian host spectrum could be therefore even more important than previously described, and their role in the functioning of lake ecosystems is undoubtedly largely unknown.

More than seven decades of Acta Tropica: Looking back to move into the future

Acta Tropica is an international, peer-reviewed journal advancing scientific research in the fields of tropical medicine and parasitology. This article elucidates the rich history of the journal and speculates about its future. Acta Tropica was launched in 1944 and formed an integral part of the establishment and running of the Swiss Tropical Institute in Basel. After two distinct periods of relatively small publication activities (1944-1976 and 1977-1988), in 1989, Acta Tropica was transferred to the Dutch publisher Elsevier. Subsequently, the annual number of publications steadily increased and the scope of the journal broadened to the biology of pathogens and their vectors, to genetics, host-parasite relationships, mechanisms of pathogenicity, diagnostics, and treatment of tropical diseases. The body of published articles contributed to an improved understanding of the prevention, surveillance, control, and elimination of diseases that are intimately linked to poverty, such as malaria and neglected tropical diseases. In recent years, the scope of Acta Tropica was widening to target emerging and re-emerging infectious diseases, epidemics and pandemics, interrelations of microbes, viruses, and parasites, co-dependencies of epidemiology, ecology, environment, and climate change. Importantly, non-communicable diseases are gaining interest in low- and middle-income countries due to urbanization, globalization, and rapidly changing life styles, and hence, these issues receive growing prominence. Acta Tropica continues to embrace inter- and, indeed, transdisciplinary research to address pressing global health issues and sustainable development.

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.

Immune Response to Microsporidia

Microsporidia are a group of pathogens, which can pose severe risks to the immunocompromised population, such as HIV-infected individuals or organ transplant recipients. Adaptive immunity has been reported to be critical for protection, and mice depleted of T cells are unable to control these infections. In a mouse model of infection, CD8 T cells have been found to be the primary effector cells and are responsible for protecting the infected host. Also, as infection is acquired via a peroral route, CD8 T cells in the gut compartment act as a first line of defense against these pathogens. Thus, generation of a robust CD8 T-cell response exhibiting polyfunctional ability is critical for host survival. In this chapter, we describe the effector CD8 T cells generated during microsporidia infection and the factors that may be essential for generating protective immunity against these understudied but significant pathogens. Overall, this chapter will highlight the necessity for a better understanding of the development of CD8 T-cell responses in gut-associated lymphoid tissue (GALT) and provide some insights into therapies that may be used to restore defective CD8 T-cell functionality in an immunocompromised situation.

Investigation of the relationship between lymphocyte subsets and intestinal parasites

We analyzed the peripheral blood lymphocyte subsets of cancer patients infected with intestinal parasites, with an aim to find out the relationship between the levels of different types of lymphocytes with the prognosis of patients. 201 cancer patients aged 18 and over were included. Stool samples of the patients were examined using native-lugol, trichrome, modified trichrome (Weber's Trichrome stain), and modified Ziehl-Neelsen staining methods. Microsporidia and Cryptosporidium parvum were investigated at the genus and species levels using PCR. Lymphocyte subsets were determined by flow cytometry in blood samples. One or more parasite species were detected in 115 (56.7%) patients. The most common parasite species were Microsporidia, Blastocystis and Entamoeba coli, respectively. The frequency of parasites was high in patients with low lymphocyte percentage, CD3⁺ T cell and CD3⁺ CD4⁺ T (Th) cell levels in blood samples studied by flow cytometry. Microsporidia infection was significantly higher in patients with low lymphocyte percentage and Th cell levels. Similarly, C. parvum infection was found to be significantly higher in patients with low T lymphocyte percentage and Th cell level. Finally, Blastocystis infection was significantly higher in patients with low lymphocyte percentage and CD4/CD8 ratio higher than 1. The decrease in lymphocyte percentage, CD3⁺ T cell and Th cell count, and low CD4/CD8 ratio in cancer patients increase the frequency of intestinal parasitic infections. Based on these results, lymphocyte subsets may help identify cancer patients at high risk of opportunistic parasites. We suggest that opportunistic parasitic infections affecting the clinical course of the disease should be considered by clinicians during the follow-up and treatment of patients.

Chronic Infections in Mammals Due to Microsporidia

Microsporidia are pathogenic organism related to fungi. They cause infections in a wide variety of mammals as well as in avian, amphibian, and reptilian hosts. Many microsporidia species play an important role in the development of serious diseases that have significant implications in human and veterinary medicine. While microsporidia were originally considered to be opportunistic pathogens in humans, it is now understood that infections also occur in immune competent humans. Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Enterocytozoon bieneusi are primarily mammalian pathogens. However, many other species of microsporidia that have some other primary host that is not a mammal have been reported to cause sporadic mammalian infections. Experimental models and observations in natural infections have demonstrated that microsporidia can cause a latent infection in mammalian hosts. This chapter reviews the published studies on mammalian microsporidiosis and the data on chronic infections due to these enigmatic pathogens.

Myositis Caused by Trachipleistophora hominis in a Person With Human Immunodeficiency Virus: The First Case in Thailand

Background

To date, cases of extraintestinal micro-sporidiosis have been increasingly reported in both otherwise healthy and immunocompromised individuals. Among them, microsporidial myositis is very rare. To the best of our knowledge, this is the first report of microsporidial myositis caused by Trachipleistophora hominis in a patient with human immunodeficiency virus (HIV) in Thailand.

Case report

A Thai man with HIV presented with fever and muscle pain at both anterior thighs and left arm for 3 months. Muscle biopsy was performed, and pathology exhibited neutrophil infiltration and focal aggregations of microsporidial spores. The 18S ribosomal RNA sequence revealed the species of this microsporidium as T hominis, and albendazole of 800mg/day was initiated. He gradually improved, and was discharged home 6 weeks after hospitalization.

Conclusions

To the best of our knowledge, this is the first report of microsporidial myositis caused by Trachipleistophora hominis in a person with HIV in Thailand.

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.

Molecular-Based Detection of Enterocytozoon bieneusi in Farmed Masked Palm Civets (Paguma larvata) in Hainan, China: A High-Prevalence, Specificity, and Zoonotic Potential of ITS Genotypes

Enterocytozoon bieneusi is a microsporidian and zoonotic species. This study investigated the prevalence and distribution of E. bieneusi genotypes in farmed masked palm civets using nested PCR, as well as assessed their zoonotic potential by phylogenetic analysis of the ITS region of the rRNA region. Here, we collected 251 fecal specimens from farmed masked palm civets (Paguma larvata) from the Hainan Island, China. In total, 128 of 251 samples were positive for E. bieneusi, with an average infection rate of 51.0%. Seventeen genotypes were identified including 12 known genotypes—HNR-VI (n = 56), SHR1 (n = 45), SHW7 (n = 6), KIN-1 (n = 3), D (n = 3), New1 (n = 3), EbpC (n = 2), CHC5 (n = 1), CHG19 (n = 1), CHN4 (n = 1), EbpA (n = 1), and Henan-III (n = 1)—and five novel genotypes (HNPL-I to HNPL-II; one each). Phylogenetic analysis categorized these genotypes into two groups. Thirteen of them were members of the zoonotic group 1, and the remaining four genotypes were in group 12. This study has shown that the infection rates of E. bieneusi in masked palm civets from Hainan were relatively high and provide baseline data to control and prevent microsporidiosis in farm-related communities. Therefore, infections in masked palm civets with zoonotic genotypes D, EbpC, CHN4, EbpA, KIN-1, and Henan-III should be considered potential threats to public health.

Enterocytozoon Bieneusi Infects Children With Inflammatory Bowel Disease Undergoing Immunosuppressive Treatment

Objectives: Patients with inflammatory bowel disease (IBD) are susceptible to intestinal opportunistic infections due to both defective mucosal immunity and altered immune response resulting from immunosuppressive treatment. Microsporidia infecting the gastrointestinal tract and causing diarrhoea can potentially affect the course of IBD.

Methods: Stool samples (90 IBD children and 121 healthy age-matched controls) were screened for Encephalitozoon spp. and Enterocytozoon bieneusi by microscopy and polymerase chain reaction followed by sequencing.

Results:E. bieneusi genotype D was found in seven out of 90 (7.8%) IBD children. No children from the control group were infected, making the pathogen prevalence in the IBD group significant (P = 0.002). Furthermore, infection was confirmed only in patients receiving immunosuppressive treatment (P = 0.013).

Conclusions: Children with IBD are at risk of intestinal E. bieneusi infection, especially when receiving immunosuppressive treatment. Therefore, microsporidia should be considered as a significant infectious agent in this group of patients.

The global molecular epidemiology of microsporidia infection in sheep and goats with focus on Enterocytozoon bieneusi: a systematic review and meta-analysis

BACKGROUND

Microsporidia is a zoonotic pathogen with health consequences in immunocompromised patients. Small ruminants are a potential reservoir of microsporidia for humans in their vicinity. Hence, we aimed to evaluate the molecular prevalence of microsporidian infections with emphasis on Enterocytozoon bieneusi genotypes among sheep and goats at a global scale through systematic review and meta-analysis approach.

METHODS

The standard protocol of preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed. Eligible prevalence studies on small ruminant microsporidiosis, published from 1 January 2000 until 15 April 2021 were gathered using systematic literature search in PubMed, Scopus, Web of Science and Google Scholar databases. Inclusion and exclusion criteria were applied. The point estimates and 95% confidence intervals were calculated using a random-effects model. The variance between studies (heterogeneity) was quantified by I2 index.

RESULTS

In total, 25 articles (including 34 datasets) were included for final meta-analysis. The pooled molecular prevalence of microsporidia in sheep and goats was estimated to be 17.4% (95% CI: 11.8-25%) and 16% (95% CI: 11.2-22.4%), respectively. Likewise, the overall prevalence of E. bieneusi was estimated to be 17.4% (95% CI: 11.8-25%) for sheep and 16.3% (95% CI: 11.3-22.8%) for goats. According to internal transcribed spacer (ITS) gene analysis, E. bieneusi with genotypes BEB6 (15 studies) and COS-1 (nine studies) in sheep, and CHG3 (six studies) and BEB6 (five studies) in goats were the highest reported genotypes.

CONCLUSION

The present results highlight the role of sheep and goats as reservoir hosts for human-infecting microsporidia. Therefore, this global estimate could be beneficial on preventive and control measures.

Sparse Evidence for Giardia intestinalis, Cryptosporidium spp. and Microsporidia Infections in Humans, Domesticated Animals and Wild Nonhuman Primates Sharing a Farm-Forest Mosaic Landscape in Western Uganda

Zoonotic pathogen transmission is considered a leading threat to the survival of non-human primates and public health in shared landscapes. Giardia spp., Cryptosporidium spp. and Microsporidia are unicellular parasites spread by the fecal-oral route by environmentally resistant stages and can infect humans, livestock, and wildlife including non-human primates. Using immunoassay diagnostic kits and amplification/sequencing of the region of the triosephosphate isomerase, small ribosomal subunit rRNA and the internal transcribed spacer genes, we investigated Giardia, Cryptosporidium, and microsporidia infections, respectively, among humans, domesticated animals (livestock, poultry, and dogs), and wild nonhuman primates (eastern chimpanzees and black and white colobus monkeys) in Bulindi, Uganda, an area of remarkably high human-animal contact and spatial overlap. We analyzed 137 fecal samples and revealed the presence of G. intestinalis assemblage B in two human isolates, G. intestinalis assemblage E in one cow isolate, and Encephalitozoon cuniculi genotype II in two humans and one goat isolate. None of the chimpanzee and colobus monkey samples were positive for any of the screened parasites. Regular distribution of antiparasitic treatment in both humans and domestic animals in Bulindi could have reduced the occurrence of the screened parasites and decreased potential circulation of these pathogens among host species.