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.

Case Report: Microsporidial Endophthalmitis after Penetrating Eye Trauma

SIGNIFICANCE

In the recent past, there are increasing publications on microsporidia affecting the cornea in Asian population. However, microsporidia-causing endophthalmitis has been rarely reported. This report intends to draw the attention of eye care professionals to consider microsporidia as a differential diagnosis in cases of keratitis or endophthalmitis after ocular trauma.

PURPOSE

The purpose of this study was to report a case of microsporidial endophthalmitis after corneal tear in an otherwise healthy patient.

CASE REPORT

A 62-year-old healthy gentleman sustained injury to the left eye cornea with the tip of a soiled and wet screw driver. Two days after the corneal tear suturing, he complained of pain. On examination, circumcorneal congestion with hypopyon of 2 mm in height was present. Vitreous tap and intravitreal antibiotics were injected. Vitreous tap showed microsporidia. Pars plana vitrectomy was performed. His vision improved to 6/12.

CONCLUSIONS

Microsporidia are an emerging cause of stromal keratitis. In the recent past, there has been an increase in microsporidial keratitis in both immunocompetent and immunocompromised individuals. History of trauma especially in rainy season and exposure to soil are reported risk factors. This is a case report on microsporidia-causing endophthalmitis after corneal tear repair. Ophthalmologists and optometrists should be aware of the possibility of microsporidia as a potential pathogen causing stromal keratitis or endophthalmitis in a setting of ocular trauma. Early treatment can result in good visual recovery.

Two parasites in one host: spatiotemporal dynamics and co-occurrence of Microsporidia and Rickettsia in an amphipod host

Biological interactions can greatly influence the abundance of species. This is also true for parasitic species that share the same host. Microsporidia and Rickettsia are widespread intracellular parasites in populations of Paracalliope fluviatilis, the most common freshwater amphipods in New Zealand. Although both parasites coexist in many populations, it is unclear whether they interact with each other. Here, we investigated spatial−temporal dynamics and co-occurrence of the two parasites, Microsporidia and Rickettsia in P. fluviatilis hosts, across one annual cycle and in three different locations. Prevalence of both Microsporidia and Rickettsia changed over time. However, while the prevalence of Rickettsia varied significantly between sampling times, that of Microsporidia did not change significantly and remained relatively low. The two parasites therefore followed different temporal patterns. Also, the prevalence of both parasites differed among locations, though the two species reached their highest prevalence in different locations. Lastly, there was no evidence for positive or negative associations between the two parasite species; the presence of one parasite in an individual host does not appear to influence the probability of infection by the other parasite. Their respective prevalence may follow different patterns among populations on a larger spatial scale due to environmental heterogeneity across locations.

Temporal trend of microsporidial keratoconjunctivitis and correlation with environmental and air pollution factors in India

Purpose:

The aim of this study was to describe the correlation between the temporal pattern of presentation of acute microsporidial keratoconjunctivitis (MKC) with meteorological parameters such as environmental temperature, rainfall, humidity, windspeed, and air pollution.

Methods:

This cross-sectional hospital-based study included 182,789 patients presenting between January 2016 and December 2019 hailing from the district of Hyderabad. Patients with a clinical diagnosis of MKC in at least one eye with an acute onset (≤1 week) of presentation were included as cases. Correlation analysis was performed with the local environmental temperature, rainfall, humidity, and windspeed (Telangana State Development and Planning Society) and air pollution (Central Pollution Control Board, Government of India).

Results:

Overall, 84 (0.05%) patients were diagnosed with acute onset MKC from the district of Hyderabad. The mean monthly prevalence in this cohort was 0.05% with peak prevalence in the months of July (0.08%), August (0.09%), September (0.12%), and October (0.08%). The environmental parameters of rainfall (r² = 0.87/P = < 0.0001), humidity (r² = 0.78/P = 0.0001), windspeed (r² = 0.38/P = 0.0321) were significantly positively correlated and the air pollution parameters such as ground level ozone (r² = 0.89/P = < 0.0001), particulate matter PM₁₀ (r² = 0.65/P = 0.0013), PM_2.5 (r² = 0.50/P = 0.0095), nitrogen dioxide (r² = 0.53/P = 0.0071), and carbon monoxide (r² = 0.69/P = 0.0008) were significantly negatively correlated with the temporal pattern of MKC in the population.

Conclusion:

Parasitic infections like MKC show a distinct temporal trend peaking during the monsoon season in the population. An increase in humidity, wind speed, and especially rainfall contributes to a higher prevalence of MKC cases during the year. An increase in ground-level ozone seems to be protective against infection.

Swimming Pool-Associated Vittaforma-Like Microsporidia Linked to Microsporidial Keratoconjunctivitis Outbreak, Taiwan

We analyzed 2 batches of environmental samples after a microsporidial keratoconjunctivitis outbreak in Taiwan. Results indicated a transmission route from a parking lot to a foot washing pool to a swimming pool and suggested that accumulation of mud in the foot washing pool during the rainy season might be a risk factor.

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.

Outbreak of Microsporidial Keratoconjunctivitis Associated With Water Contamination in Swimming Pools in Taiwan

PURPOSE

To report an outbreak of microsporidial keratoconjunctivitis resulting from a swimming pool in Taiwan.

DESIGN

Retrospective case series.

METHODS

The records of 13 teenagers (15 eyes) contracting microsporidial keratoconjunctivitis after swimming in a local swimming pool were reviewed. Corneal scrapings were collected in all eyes at a tertiary referred hospital in June 2017. Gram stain, modified Kinyoun acid-fast stain, polymerase chain reaction (PCR), and gene analysis of the microsporidian 16S ribosomal RNA (rRNA) were examined in all 15 cases.

RESULTS

Symptoms occurred 1-12 days after the water contact. At presentation, all eyes showed nonpurulent conjunctivitis and small, plaque-like epithelial lesions peripherally (n = 6), centrally (n = 3), both peripherally and centrally (n = 5), or centrally with superficial punctate keratopathy (n = 1). During the follow-up period, 10 eyes developed central superficial punctate keratopathy (n = 6) or subepithelial haze or infiltrates, which were distributed centrally (n = 2) or peripherally (n = 3), following development of plaque-like epithelial lesions. The results of Gram stain and modified Kinyoun's acid-fast stain were confirmatory in 10 cases (67%). All 15 cases yielded positive PCR results and were all identified to be Vittaforma corneae. All followed-up eyes healed without sequelae using topical levofloxacin and betamethasone eye drops.

CONCLUSIONS

Microsporidial keratoconjunctivitis can develop from contact with swimming pool water. The clinical course initially manifested as rapidly resolving conjunctivitis and peripheral plaque-like epithelial lesions, followed by paracentral or central plaque-like epithelial lesions, which evolved into subepithelial haze or infiltrates.

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.

Case Report: Ocular Microsporidiosis: Case in a Patient Returning from India and Review of the Literature

Microsporidia are protists close to the kingdom of fungi that may cause eye infections. Most cases are reported in Asia and affect both immunocompromised and immunocompetent patients. Here, we report a rare case of microsporidial keratoconjunctivitis in an immunocompetent French patient 3 weeks after returning from India. In our patient, Weber trichrome staining of conjunctival scrapings revealed rounded elements approximately 1-3 μm in size. Conventional polymerase chain reaction analysis by ribosomal RNA subunit sequencing showed 100% identity with Vittaforma corneae. Treatment by corneal debridement combined with fluoroquinolone eye drops allowed complete resolution of the lesions. Although rare, ocular microsporidiosis should be investigated in a patient who is native to Asia or has returned from an endemic area and presents with keratoconjunctivitis of undetermined etiology.

Microsporidial Stromal Keratitis: Clinical Features, Unique Diagnostic Criteria, and Treatment Outcomes in a Large Case Series

PURPOSE

To describe the history, clinical features, and outcomes of a large case series of microsporidial stromal keratitis with emphasis on probable predictors of the etiology in this rare and unspecified form of keratitis.

METHODS

Retrospective analysis of cases seen between January, 2002, and December, 2013, diagnosed at LV Prasad Eye Institute as having microsporidial stromal keratitis based on clinical, microbiology, and histopathology examination. Outcomes of medical and surgical management with visual recovery were documented.

RESULTS

There were 34 cases of microsporidial stromal keratitis with a mean age of 43.3 years (range 2-77 years) and male preponderance. The duration of symptoms was chronic in most cases (mean duration of 288 days). Nearly half of the cases had a history of trauma, in the age group of 20 to 50 years. The most common clinical misdiagnosis was herpes simplex virus keratitis (26.5%) followed by fungal keratitis (17.6%). This could be attributed to the nonspecific clinical picture of diffuse multifocal stromal lesions in 82.4% of cases. The organisms were detected in microbiological evaluation of corneal scrapings in 47% cases, and histopathological detection of the organisms showed a positivity rate of 92.3%. Surgical management was necessary in the majority of the cases (73.5% of patients).

CONCLUSIONS

The typical history of trauma with a smoldering, diffuse form of keratitis refractory to conventional medical therapy, responding to surgical removal for recovery is clearly demonstrated as a recurring feature in the majority of the cases. Patients presenting with this characteristic clinical picture should be suspected to harbor this rare pathogen, and early surgical interventions should be considered.

Climate and season: the effects on ophthalmic diseases

Seasonal changes and climate have a significant impact on human health. Diseases influenced by temperature and climate conditions are likely to undergo dynamic pattern shifts with consequent impact on human health. A number of infectious and non-infectious ophthalmic diseases are influenced by temperature and seasonality. Awareness of this is important from public and global health perspective in addition to resource allocation strategies. We examine the evidence for a seasonal pattern to ophthalmic diseases and assess the possible impact of climate change.

Microsporidial stromal keratitis and endophthalmitis in an immunocompetent patient

Purpose

The purpose of this study is to report a case of microsporidial endophthalmitis after penetrating keratoplasty in a healthy patient and discuss the management.

Methods

This is a case report.

Results

A 69-year-old healthy male underwent penetrating keratoplasty for corneal scar secondary to herpes stromal keratitis. He presented with features of acute graft rejection 3 years later. After failure of medical management, a repeat full thickness keratoplasty was performed. Pathologic examination of the corneal specimen showed microsporidia. The patient then developed a chronic endophthalmitis, and a vitreous tap and injection followed by pars plana vitrectomy were performed. Pathologic examination of tissue showed microsporidia.

Conclusions

Microsporidia are being increasingly identified as the cause of stromal keratitis. This is the first report of microsporidial endophthalmitis in a patient without underlying systemic illness.

A study of microsporidiosis in corneal scrapings of keratitis patients referring to Farabi Eye Hospital, Tehran, Iran in 2013-14

Background and Purpose:

Microsporidiosis is one of the emerging and opportunistic infections, which causing various clinical symptoms in humans. The prevalence of this infection varies, depending on the infected organ, diagnostic methods, and geographical conditions. In the present study, we aimed to investigate microsporidial keratitis in patients referring to Farabi Eye Hospital Tehran, Iran in 2013-14.

Materials and Methods:

Two scraping samples were collected from 91 keratitis patients, five cases had prior history of receiving immune suppressive drugs. One of the two collected samples from each participant was used for Vero cell culture and the other was used for the preparation of Giemsa and Gram staining slides. After 30 days, the cells were scrapped and used for DNA extraction; afterwards, nested polymerase chain reaction (PCR) detection method was applied. Primer pairs of small-subunit ribosomal RNA gene were designed by CLC Genomics workbench software to amplify all major microsporidian pathogens, as well as E. bieneusi , which was used as the positive control in this study.

Results:

The nested PCR showed negative results regarding the presence of microsporidia in the samples. Similarly, Giemsa and Gram staining slides did not detect any spores.

Conclusion:

The prevalence of human microsporidiosis ranges between 0% and 50%, worldwide. Based on all the negative samples in the present study, we can conclude that the prevalence of this infection among Iranian patients falls in the lower quartile. By gathering further evidence, researchers can take a step forward in this area and open new doors for the assessment of AIDS patients and users of immunosuppressive drugs.

Clinical Features, Risk Factors, and Treatments of Microsporidial Epithelial Keratitis

OBJECTIVE

To report the clinical manifestations, risk factors, and treatments of microsporidial epithelial keratitis in Thailand.

METHODS

Twenty eyes of 19 patients were diagnosed and the clinical presentations, risk factors, and management were analyzed.

RESULTS

Of 19 patients, six patients (32%) had no apparent risk factors. Predisposing factors included soil exposure (6/19, 32%), water contamination (6/19, 32%), and eye liner (1/19, 4%). Twelve cases (63%) were detected in the rainy season. All cases presented with disseminated, punctated, elevated, epithelial keratitis. Corneal scrapings with Gram-chromotrope staining were positive in all patients. Moxifloxacin 0.5% eye drops were given and all 16 patients experienced complete resolution. Three recurrent cases were resolved with only topical moxifloxacin without corneal scraping or swabbing.

CONCLUSIONS

Predisposing factors were not found in some patients; thus, corneal scraping with staining should be considered in cases having a high index of suspicion. The incidence is increased during the rainy season; therefore, clinicians should have more awareness during these times. Debridement with topical moxifloxacin eye drops, without any systemic medication, may be an effective treatment. Corneal scraping or swabbing may not be required in recurrences.

Microsporidia infection of the cornea--a unique and challenging disease

Microsporidia are a diverse group of obligate, intracellular, eukaryotic, spore-forming parasites. Traditionally, these were considered as protozoans but recently have been reclassified as fungi. Microsporidia behave as opportunistic pathogens causing systemic infections. In the eye, Microsporidia cause keratoconjunctivitis, corneal stromal keratitis, scleritis, and endophthalmitis. This review shares our experiences with anterior segment infections caused by this pathogen. Keratoconjunctivitis is a common form of ocular infection caused by the parasite. Although early reports described it as occurring only in immunosuppressed individuals, it can also occur in immunocompetent individuals. The disease shows a seasonal pattern with a peak incidence during the rainy season. Although several drugs have been considered, our experience suggests that keratoconjunctivitis is a self-limiting disease. In contrast to keratoconjunctivitis, stromal keratitis is an ill-defined disease. We collected 30 cases and analyzed the various aspects of this disease. Stromal keratitis is characterized by a slowly progressive course. The corneal picture resembles herpes simplex virus stromal keratitis or fungal keratitis cases, and is characterized by deep stromal infiltrates with overlying and surrounding stromal edema and keratic precipitates. The diagnosis of Microsporidia infection is confirmed by a microscopic examination of smears from patients with ulcerative keratitis or by a histopathological examination of corneal tissues. Definitive genus identification requires the examination of specimens by electron microscopy or by molecular methods. In the absence of a definitive medical treatment, nearly all patients require surgical treatment. The confusion regarding Microsporidia is not only limited to their classification but also extends to various aspects of the corneal disease caused by them.

Outbreak of microsporidial keratoconjunctivitis with rugby sport due to soil exposure

AIMS

To investigate a cluster of microsporidial keratoconjunctivitis in 33 eyes of 25 previously healthy paediatric and teenage individuals after a rugby match.

METHODS

An observational case series was reported. Analysis of medical record of patients with microsporidial keratoconjunctivitis, who presented within May 2012, was performed. All patients were treated by a single ophthalmologist with a standardized topical regime, including a fluoroquinolone (moxifloxacin) and an antiseptic (Brolene or Desomedine). Five eyes received corneal scrapings.

RESULTS

The mean age was 13.36 years (range 5-16). All patients have participated in a rugby match on 21-22 April 2012. The onset of symptoms ranged from 10 to 30 days post exposure. All eyes had multiple superficial coarse punctate keratitis. Four (12%) eyes presented with keratic precipitates. One (3%) eye had intraocular pressure of 27 mm Hg. Microscopic examination of corneal scrapings with modified trichrome or calcofluor white (CFW) fluorescent staining was unremarkable but subsequent PCR test was positive for the small subunit rRNA gene of Vittaforma corneae in three out of five eyes. Sequencing of the PCR product of 1150 bp showed 96-100% identity with the Indian or Singaporean strains of V. corneae. After treatment, all eyes healed without sequel.

CONCLUSIONS

The first outbreak of microsporidial keratoconjunctivitis in paediatric and teenage individuals with a rugby match is reported. A standardized topical regime, including a fluoroquinolone (moxifloxacin) and an antiseptic (Brolene or Desomedine), seems to be safe and effective, and requires validation in future treatment trials.

Methods to assess seasonal effects in epidemiological studies of infectious diseases--exemplified by application to the occurrence of meningococcal disease

Seasonal variation in occurrence is a common feature of many diseases, especially those of infectious origin. Studies of seasonal variation contribute to healthcare planning and to the understanding of the aetiology of infections. In this article, we provide an overview of statistical methods for the assessment and quantification of seasonality of infectious diseases, as exemplified by their application to meningococcal disease in Denmark in 1995-2011. Additionally, we discuss the conditions under which seasonality should be considered as a covariate in studies of infectious diseases. The methods considered range from the simplest comparison of disease occurrence between the extremes of summer and winter, through modelling of the intensity of seasonal patterns by use of a sine curve, to more advanced generalized linear models. All three classes of method have advantages and disadvantages. The choice among analytical approaches should ideally reflect the research question of interest. Simple methods are compelling, but may overlook important seasonal peaks that would have been identified if more advanced methods had been applied. For most studies, we suggest the use of methods that allow estimation of the magnitude and timing of seasonal peaks and valleys, ideally with a measure of the intensity of seasonality, such as the peak-to-low ratio. Seasonality may be a confounder in studies of infectious disease occurrence when it fulfils the three primary criteria for being a confounder, i.e. when both the disease occurrence and the exposure vary seasonally without seasonality being a step in the causal pathway. In these situations, confounding by seasonality should be controlled as for any confounder.

Microsporidial keratitis in patients with hot springs exposure

This retrospective study included 10 eyes of 9 patients diagnosed with microsporidial keratitis. All of them were known to contract this disease after taking baths in hot springs. The disease was diagnosed based on detecting microsporidia in corneal scrapings using Gram stain and the modified Kinyoun's acid-fast stain. The specimens from the last six patients were subjected to PCR and then sequencing. All of them revealed that the microorganism identified has a high similarity to Vittaforma corneae. Repeated debridement of the epithelial lesions successfully eradicated the microsporidial infection in all nine patients.