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We describe a multiannual outbreak of keratoconjunctivitis caused by the microsporidium Vittaforma corneae in the Sea of Galilee, Israel. Patients had multifocal punctate corneal infiltrates and reduced visual acuity, confirmed by locally-developed pathogen-specific real-time PCR. Topical chlorhexidine, rather than traditional antimicrobial drugs, proved an effective and safe primary treatment.

Cryptosporidium spp. and Enterocytozoon bieneusi are two well-known protist pathogens which can result in diarrhea in humans and animals. To examine the occurrence and genetic characteristics of Cryptosporidium spp. and E. bieneusi in pet red squirrels (Sciurus vulgaris), 314 fecal specimens were collected from red squirrels from four pet shops and owners in Sichuan province, China. Cryptosporidium spp. and E. bieneusi were examined by nested PCR targeting the partial small subunit rRNA (SSU rRNA) gene and the ribosomal internal transcribed spacer (ITS) gene respectively. The infection rates were 8.6% (27/314) for Cryptosporidium spp. and 19.4% (61/314) for E. bieneusi. Five Cryptosporidium species/genotypes were identified by DNA sequence analysis: Cryptosporidium rat genotype II (n = 8), Cryptosporidium ferret genotype (n = 8), Cryptosporidium chipmunk genotype III (n = 5), Cryptosporidium rat genotype I (n = 4), and Cryptosporidium parvum (n = 2). Additionally, a total of five E. bieneusi genotypes were revealed, including three known genotypes (D, SCC-2, and SCC-3) and two novel genotypes (RS01 and RS02). Phylogenetic analysis revealed that genotype D fell into group 1, whereas the remaining genotypes clustered into group 10. To our knowledge, this is the first study to report Cryptosporidium spp. and E. bieneusi in pet red squirrels in China. Moreover, C. parvum and genotype D of E. bieneusi, previously identified in humans, were also found in red squirrels, suggesting that red squirrels may give rise to cryptosporidiosis and microsporidiosis in humans through zoonotic transmissions. These results provide preliminary reference data for monitoring Cryptosporidium spp. and E. bieneusi infections in pet red squirrels and humans.

Hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) is an important disease of cultivated shrimp. Heavy infections may lead to retarded growth and unprofitable harvests. Existing PCR detection methods target the EHP small subunit ribosomal RNA (SSU rRNA) gene (SSU-PCR). However, we discovered that they can give false positive test results due to cross reactivity of the SSU-PCR primers with DNA from closely related microsporidia that infect other aquatic organisms. This is problematic for investigating and monitoring EHP infection pathways. To overcome this problem, a sensitive and specific nested PCR method was developed for detection of the spore wall protein (SWP) gene of EHP (SWP-PCR). The new SWP-PCR method did not produce false positive results from closely related microsporidia. The first PCR step of the SWP-PCR method was 100 times (104 plasmid copies per reaction vial) more sensitive than that of the existing SSU-PCR method (106 copies) but sensitivity was equal for both in the nested step (10 copies). Since the hepatopancreas of cultivated shrimp is not currently known to be infected with microsporidia other than EHP, the SSU-PCR methods are still valid for analyzing hepatopancreatic samples despite the lower sensitivity than the SWP-PCR method. However, due to its greater specificity and sensitivity, we recommend that the SWP-PCR method be used to screen for EHP in feces, feed and environmental samples for potential EHP carriers.

Research conducted on model organisms may be biased due to undetected pathogen infections. Recently, screening studies discovered high prevalence of the microsporidium Pseudoloma neurophilia in zebrafish ( Danio rerio ) facilities. This spore-forming unicellular parasite aggregates in brain regions associated with motor function and anxiety, and despite its high occurrence little is known about how sub-clinical infection affects behaviour. Here, we assessed how P. neurophilia infection alters the zebrafish´s response to four commonly used neurobehavioral tests, namely: mirror biting, open field, light/dark preference and social preference, used to quantify aggression, exploration, anxiety, and sociability. Although sociability and aggression remained unaltered, infected hosts exhibited reduced activity, elevated rates of freezing behaviour, and sex-specific effects on exploration. These results indicate that caution is warranted in the interpretation of zebrafish behaviour, particularly since in most cases infection status is unknown. This highlights the importance of comprehensive monitoring procedures to detect sub-clinical infections in laboratory animals.

Multiple infections are common in honey bees, Apis mellifera , but the possible role of nutrition in this regard is poorly understood. Microsporidian infections, which are promoted by protein-fed, can negatively correlate with virus infections, but the role of protein nutrition for the microsporidian-virus interface is unknown. Here, we challenged naturally deformed wing virus - B (DWV-B) infected adult honey bee workers fed with or without pollen ( = protein) in hoarding cages, with the microsporidian Nosema ceranae . Bee mortality was recorded for 14 days and N. ceranae spore loads and DWV-B titers were quantified. Amongst the groups inoculated with N. ceranae , more spores were counted in protein-fed bees. However, N. ceranae infected bees without protein-diet had reduced longevity compared to all other groups. N. ceranae infection had no effect on protein-fed bee’s longevity, whereas bees supplied only with sugar-water showed reduced survival. Our data also support that protein-feeding can have a significant negative impact on virus infections in insects. The negative correlation between N. ceranae spore loads and DWV-B titers was stronger expressed in protein-fed hosts. Proteins not only enhance survival of infected hosts, but also significantly shape the microsporidian-virus interface, probably due to increased spore production and enhanced host immunity.

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

Microsporidia, as opportunistic parasitic pathogens, constitute a formidable threat to human health. Although the regulatory circuitry of the nucleus-targeted effector EnP1 remains highly intricate and only partially characterized, our study identifies histone H2A as a novel binding partner of EnP1. Furthermore, we demonstrate that both EnP1 overexpression and microsporidia infection induce monoubiquitination of H2A (H2Aub) through downregulation of BAP1 expression. Subsequent mechanistic analyses revealed that elevated H2Aub levels positively correlate with enhanced microsporidian proliferation, whereas attenuation of H2Aub markedly suppresses pathogen expansion. Furthermore, EnP1 orchestrates the enrichment of H2Aub at the SLC7A11 promoter, driving its transcriptional upregulation. Collectively, these findings underscore that EnP1 modulates the ferroptosis state of host cells through H2Aub-mediated epigenetic reprogramming, ultimately facilitating pathogen propagation. This study endeavors to elucidate the critical survival strategies of microsporidia within host cells mediated by EnP1 and to unravel the multifaceted interplay between these pathogens and their hosts.

Giardia duodenalis , Enterocytozoon bieneusi and Cyclospora cayetanensis are usually classified as Neglected Tropical Diseases, causing giardiasis, microsporidiosis and cyclosporiasis, respectively, which significantly contributed to food- and water-transmitted intestinal illnesses in both humans and animals. In this study, we conducted on the prevalence and molecular characterization of Giardia , E. bieneusi and C. cayetanensis of diarrheal outpatients from three areas in the Yangtze River Delta, China. A total of 2 720 fecal samples were collected and nested PCR was used to identify and describe the genetic characteristic of Giardia , E. bieneusi and C. cayetanensis . The overall prevalence of the three pathogens was 2.54% (69/2 720), with 1.03% for E. bieneusi (28/2 720), 0.8% for G. duodenalis (22/2 720), and 0.7% for C. cayetanensis (19/2 720), respectively. 9 E. bieneusi genotypes, together with two known genotypes A ( n  = 20) and D ( n  = 1), and 7 novel genotypes named JDFY-1 to JDFY-7 were identified. All the genotypes were clustered into zoonotic potential Group 1. In addition, 22 G. intestinalis -positive samples were genotyped as assemblages A ( n  = 4), B ( n  = 17) and E ( n  = 1). 19 stool samples were identified to be C. cayetanensis and two new sequences were found. Therefore, our results underscored the existence and importance of E. bieneusi , Giardia and C. cayetanensis in diarrheal outpatients. Furthermore, the findings of E. bieneusi genotypes and new sequences of Giardia and C. cayetanensis indicates a high zoonotic potential of these pathogens in diarrheal outpatients. A broader range of investigations should be conducted on human, animal, and environmental sources to better understand the real transmission routes of the three enteric zoonotic protozoan.

Although brought to the forefront in the 1980s with the AIDS pandemic, microsporidia infecting humans are still little known. , by far the most frequent microsporidia species causing diseases in humans, is responsible for intestinal illness in both non- and immunocompromised patients. This species presents an astonishing genetic diversity with more than 500 genotypes described, some of which have a strong zoonotic potential. Indeed, infects a broad array of hosts, from wild to domestic animals. This emerging eukaryotic pathogen has thus been associated with foodborne/waterborne outbreaks. Several molecular assays have been developed to enhance its diagnosis or for epidemiological purposes, providing valuable new data. Here, we propose an overview of the current knowledge on this major species among the microsporidia, so far rather neglected in human medicine.