Microsporidial Keratitis: Need for Increased Awareness

Keratic Precipitates: An Overlooked Sign of Microsporidial Stromal Keratitis?

PURPOSE

To elucidate a distinctive clinical feature in cases of microsporidial stromal keratitis (MSK).

METHOD

A retrospective observational study of cases with a histopathological and/or microbiological diagnosis of MSK on corneal biopsy or host corneal button between 2016 and 2022 was conducted.

RESULTS

Eighteen cases with a confirmed histopathological and/or microbiological diagnosis of MSK were detected. Careful review of slit-lamp photographs revealed the presence of pigmented keratic precipitates (KPs) beyond the area of stromal keratitis in five out of eighteen cases (27.7%).

CONCLUSION

The presence of pigmented KPs beyond the area of lesion can alert the clinician to keep microsporidia as a differential cause for stromal keratitis. Management can be tailored accordingly for a better outcome.

Successful Treatment of Microsporidial Keratoconjunctivitis (MKC) With a Combination of Topical Voriconazole 1% and Gatifloxacin 0.5%: A Large Case Series of 29 Patients

OBJECTIVE

This study aims to report the successful treatment of microsporidial keratoconjunctivitis (MKC) with the combination of topical drops of voriconazole (1%) and gatifloxacin (0.5%) in all 29 patients. Demography, clinical profile, and previous treatment history were also analyzed.

METHODS

A retrospective, non-comparative case series of all Gram stain-proven MKC from September 2021 to October 2022 was included in this study. Patients were given antimicrobials such as topical drops of voriconazole 1%, gatifloxacin 0.5%, or a combination of both in 29 patients based on the treatment response. Topical steroids were added to 31 patients for corneal haziness.

RESULTS

A total of 33 patients were found to be positive for microsporidiosis confirmed by Gram staining. Twenty-four (72.7%) were men and nine (27.3%) were women. The mean age was 34.45±12. The presenting symptoms were mainly redness in 30 patients (90.9%), followed by watering in 13 (39.4%), foreign body sensation in 10 (30.3%), etc. Among the 23 patients (69%), a history of risk factors was identified, with 17 patients (51.5%) specifically reporting dust exposure as a major cause. MKCs were successfully treated with antimicrobials such as voriconazole 1% in three patients, gatifloxacin 0.5% in one patient, and a combination of both in 29 patients. Topical steroids were added to 31 patients for corneal haziness. At the last follow-up, a visually insignificant nummular corneal scar was noted in six patients. No drop in vision was noted in any of these patients at the end of the follow-up. No cases progressed to stromal keratitis and no surgical intervention was required in any cases.

CONCLUSIONS

We successfully treated all 29 cases with a combination of voriconazole and gatifloxacin without requiring any surgical intervention or encountering stromal complications. This successful treatment in all 29 cases offers valuable insights into the potential of this drug combination, possibly attributable to its additive action or broad-spectrum coverage across various species.

Microsporidial keratoconjunctivitis - first outbreak in Japan

BACKGROUND

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

CASE PRESENTATION

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

CONCLUSIONS

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

Microsporidia-Associated Anterior Uveitis After Keratoconjunctivitis

OBJECTIVE

The aim of this study was to describe the clinical features and management of uveitis associated with microsporidial keratoconjunctivitis (MKC).

METHODS

The medical records of clinically diagnosed or microbiologically proven patients with MKC between July 2016 and August 2021 were reviewed. Patients with documented evidence of keratic precipitates (KPs) or anterior chamber cells were analyzed for their demography, clinical features, and treatment. Patients with microsporidial stromal keratitis and herpes simplex virus keratouveitis were excluded from the study.

RESULTS

Of the 2212 patients reviewed within the study period 171 of 172 eyes (7.7%) had documented evidence of KPs and/or anterior chamber cells. The patients' mean age was 43.8 ± 13.8 years, and there were more men (n = 120). The mean duration of appearance of KPs was 6.9 ± 5.5 days, and 28% (n = 48 of 171) appeared on the day of presentation. Superficial punctate keratitis was central and diffuse in 48 and 49 patients, respectively. The treatment was either lubricant alone (45.3%; 78 eyes) or combined with topical steroids (54.7%; 94 eyes). The mean duration of the resolution was longer in the "corticosteroid" than "no corticosteroid" group: KPs: 15.3 ± 6.5 days versus 12.3 ± 5.8 days ( P = 0.007) and superficial punctate keratitises: 15.4 ± 9.4 days versus 11.7 ± 6.2 days ( P = 0.01). The presenting visual acuity with a pinhole was 0.26 ± 0.26 (logMAR) and it improved to 0.03 ± 0.07 on resolution ( P < 0.0001, paired t test).

CONCLUSIONS

Uveitis after MKC is a self-limiting entity that often resolves without corticosteroid. One must exercise caution in using steroids in the presence of active corneal lesions.

Trachipleistophora hominis: molecular characterization of a rare pathogen causing microsporidial stromal keratitis

The authors report the clinical and microbiological findings of a unique case of stromal keratitis caused by a rare microsporidium, Trachipleistophora hominis. This case of stromal keratitis was in a 49-year-old male with a history of COVID-19 infection and diabetes mellitus. Corneal scraping specimens revealed numerous microsporidia spores upon microscopic examination. PCR of the corneal button revealed the presence of T. hominis infection, which could be controlled by penetrating keratoplasty surgery. The graft was clear with no recurrence of infection until the last follow-up 6 weeks postsurgery. This is the first case of human stromal keratitis caused by this organism in a post-COVID infection, confirmed by molecular diagnosis.

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.

Coexistence of Fungal Keratitis in Bilateral Sequential Microsporidial Keratitis - A Rare Case Presentation

AIM

To report a case of bilateral microsporidiosis with coexisting fungal infection in one eye.

METHOD

Retrospective interventional case report.

RESULTS

A 61-year-old man with uncontrolled diabetes presented with clinical and microbiological features of non-resolving fungal keratitis in the right eye since 3 months and underwent therapeutic penetrating keratoplasty (TPK) for the same. Fungal filaments along with oval bodies suspicious of microconidia were noted on calcofluor stain. A week following TPK, the patient presented with features of viral keratouveitis in the left eye which on microbiology was confirmed as microsporidiosis. Retrospectively, the right eye microbiology slides were reassessed, which confirmed the coexistence of fungus with microsporidiosis by acid-fast stain and polymerase chain reaction.

CONCLUSION

Structural resemblance of microconidia with microsporidial spores can be misleading, thus creating a need for awareness regarding the possible coexistence along with a need to suspect microsporidiosis in nonresponding clinically resembling viral keratitis.

Bilateral microsporidial keratoconjunctivitis in a clinically healthy female receiving intravitreal steroid injections: Associations and potential risk factors

Purpose

To present a unique case of bilateral microsporidial keratoconjunctivitis in a clinically healthy female receiving intravitreal steroid injections, and explore several associations and potential risk factors.

Observations

A 75-year-old woman with chronic idiopathic anterior uveitis was receiving regular intravitreal steroid in both eyes for secondary cystoid macular edema. Flare-ups of iritis were usually treated with topical non-steroidal anti-inflammatory drops, but in the left eye the patient also received a few limited courses of topical corticosteroid. The patient regularly instilled topical cyclosporine 0.05% for dry eyes. She was otherwise clinically healthy but had low serum Immunoglobulin (Ig) M levels. There was no history of trauma or exposure to contamination. In her course of treatment, she developed a bilateral punctate keratitis. Corneal scrapings were diagnostic of Microsporidia. Topical voriconazole and moxifloxacin, as well as corneal debridement, were effective in resolving the infection.

Conclusions and importance

We propose that the factors and associations described in this case--intravitreal steroid, topical steroid, topical cyclosporine, and IgM deficiency--contributed variably to create relative, local, immunologic suppression in our patient. Among these potential risk factors, we believe that intravitreal steroid exposure may be prominent. In aggregate, they facilitated development of her opportunistic microsporidial corneal infection. Eye care specialists should have a high index of suspicion for microsporidial keratitis, if they observe an atypical chronic punctate keratitis in patients with similar clinical associations.

Microsporidial Endotheliitis Mimicking Graft Rejection After Deep Anterior Lamellar Keratoplasty

PURPOSE

The purpose of this study was to report a case of microsporidial endotheliitis masquerading as graft rejection after deep anterior lamellar keratoplasty (DALK).

METHODS

A 36-year-old man visited the clinic with complaints of blurred vision, redness, pain, watering, and whitish appearance of the black portion of his left eye. On evaluation, there was diffuse stromal edema with epithelial defect and hypopyon. Microbial keratitis resolved with macular grade scar. He underwent DALK. After 3 years, he presented with complaints of sudden diminution of vision in the same eye for 10 days. His unaided visual acuity was counting finger 1 meter. The clinical findings were circumcorneal congestion, diffuse graft edema, Descemet membrane folds, and diffuse keratic precipitates. A presumptive diagnosis of left eye graft rejection was made. Topical steroids were administered. There was significant improvement within a week. However, at 1 month, there was an increase in graft edema after the steroids were tapered. At this point, a diagnosis of endotheliitis of viral origin was made. He was then administered oral antivirals and steroids. There were 2 such waxing and waning episodes of graft edema before the graft failed. Patient underwent penetrating keratoplasty with cataract extraction with intraocular lens implantation.

RESULTS

The previous donor and host Descemet endothelium complex was sent for histopathology and polymerase chain reaction. Both histology and polymerase chain reaction were positive for microsporidia.

CONCLUSIONS

Microsporidial endotheliitis may present as graft rejection. There should be a suspicion of microsporidial infection in cases of features mimicking as endothelial rejection after DALK.

Chlorhexidine in the treatment of microsporidial stromal keratitis and the effect of host immunity: A case series and literature review

Microsporidial stromal keratitis is an increasingly well-known vision-threatening disease. A large proportion of cases are initially misdiagnosed as herpes simplex keratitis and treated with topical steroids. In most of such cases, medical treatment failed, and corneal transplantation was required. This study reported the results of 0.02% topical chlorhexidine used to treat three cases of microsporidial stromal keratitis and reviewed the literature on the outcomes of microsporidial stromal keratitis treatment. In the first case, histopathology of a specimen from penetrating keratoplasty (PK) revealed severe chronic inflammation involving the entire stromal layer but no microorganism activity after the application of topical chlorhexidine for 10 months. The second case exhibited complete resolution of keratitis after topical chlorhexidine. The patient in the third case did not respond to medical treatment, and therapeutic PK was performed. Histopathological examination revealed numerous microsporidial spores that had colonized in the mid and deep stroma, where few inflammatory cells were observed. These findings explain the variable microsporidial susceptibility to chlorhexidine, suggesting the crucial role of host immunity. In cases of host immunity, topical chlorhexidine may represent a promising option for the treatment of microsporidial stromal keratitis.

Microsporidia-induced stromal keratitis: a new cause of presumed immune stromal (interstitial) keratitis

BACKGROUND AND OBJECTIVE

To describe the clinical features, diagnosis and management of immune stromal keratitis/interstitial keratitis (IK) associated with microsporidial epithelial keratitis.

METHODS

Between October 2020 and January 2021, medical records of IK patients microbiologically proven as microsporidia from samples collected from corneal epithelium on smear examination, and/ or molecular analysis were reviewed. Demography, clinical profile and treatment were analysed. Real-time PCR (RT-PCR) for adenovirus (ADV), Epstein-Barr virus (EBV), herpes simplex virus (HSV) and varicella-zoster virus (VZV) was done.

RESULTS

Twenty of 152 (13%) microbiologically proven cases of microsporidial keratitis were diagnosed as IK during the study period, the mean age and duration of symptoms were 35.7±11.4 years and 46.3±27.7 days, respectively. Half had predisposing risk factors, like trauma; and 30% had prior recurrences. One-fourth of patients were using antivirals on presentation. Characteristic presentations included disciform keratitis(n=12), incomplete/complete ring(n=5), and combination(n=3), along with variable subepithelial infiltrates (n=14). All cases had stromal oedema, with an intact epithelium and fine pigment dusting on endothelium. Corneal epithelial scrapings had scanty microsporidia spores in smears of 17/20 (85%), and pan-microsporidial DNA was identified in 14/20 (70%), with Vittaforma corneae by sequencing in 11/20 (55%). Other viruses detected were ADV (14,70%), VZV (2,10%), EBV (1,5%) and HSV (1,5%). Rapid resolution of inflammation and oedema within 2 weeks of starting steroids was seen in all cases.

CONCLUSION

Microsporidia epithelial keratitis induced stromal inflammatory keratitis; is distinguished from microsporidial keratoconjunctivitis and stromal keratitis, by characteristic clinical features, and response to topical steroids.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Corneal Involvement in HIV-infected Individuals

Corneal involvement in HIV-infected individuals may be broadly classified into two categories, namely, infectious and noninfectious with the vast majority of manifestations occurring in the former. In this article, we shall focus on these two categories and strive to highlight those presentations that should alert the clinician to suspect underlying HIV infection. Infectious group mainly consists of Herpitic group of viral infections. Bacterial causes may be due to Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeroginosa, alpha hemolytic Streptococcus, Micrococcus and Bacillus. Fungalf keratitis in HIV-infected individuals depends on the geographic locations from which patient comes. Microsporidia and Acanthamoeba are common Protozoal causes. Non-infective inflammatory causes include peripheral ulcerative keratitis, keratoconjunctivitis sicca, and squamous cell carcinoma of the conjunctiva. Severity which is abnormally severe or very minimally reactive makes the clinician suspect of immunosuppression.

Microsporidiosis in Humans

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

Microsporidial Keratitis Related to Water Exposure: A Case Series

The objective of this retrospective study was to present a series of cases involving the rare ocular disease of microsporidia keratitis treated at a private practice clinic and describe the details regarding specific water exposure, clinical course, voriconazole treatment, and increased prevalence of this infection in Augusta, Georgia, USA. Our analysis was based on the accumulated data from all patients (n=15) diagnosed with microsporidia keratitis at our private practice clinic; the clinical course of three cases is discussed in detail in this article. Specific environmental exposures were documented in 10 patients. All patients self-reported that they had no acquired immunodeficiency. In all cases, patients had complete resolution of active symptoms after receiving treatment with 1-2% topical voriconazole, with an approximate average primary treatment duration of 40.1 ± 17.1 days (median: 40 days, range: 14-70 days). None of the patients reported any clinically significant adverse effects from therapy.

There have been increasing reports about this emerging infectious pathogen, particularly in Asia. However, there is limited data in the literature on the etiology, pathogenesis, and treatment of microsporidia-caused ophthalmic diseases. In this case series, we highlight the strong correlation of our patients' condition with specific types of water exposure in the USA as well as the complete resolution of active disease in all our patients as a result of monotherapy with topical voriconazole.

Sequelae of microsporidial keratoconjunctivitis and its management

Purpose:

To characterize the sequelae of microsporidia keratoconjunctivitis (MKC) and outline its management.

Methods:

Retrospective analysis of microbiologically proven MKC returned with persistent disease between January 2015 and December 2019 was done. Demographics, clinical features, management, and outcome were analyzed.

Results:

Sixteen patients (21 eyes) of 332 treated for MKC returned with the persisting disease. The mean age of 11 males (68.7%), and 5 females was 35.1 ± 12.2 years. Three-quarter of them did not have a known predisposing risk factor and one-quarter of them were referred for chronic conjunctivitis. Past medications included topical antivirals (n = 8) and topical corticosteroid (n = 6). Three predominant presentations were persistent (>3 weeks) superficial punctate keratitis (SPKs, n = 7), sub-epithelial infiltrates (SEIs, n = 13), and uveitis (n = 2). The lesions recurred in eight eyes (SPK and SEI 4 each) after a disease-free interval of 60.4 ± 40.6 days; there were 13 episodes of recurrence. Topical low potent corticosteroids (loteprednol/fluorometholone), and tacrolimus ointment 0.03% were used in 17 (80.9%) and 8 (38%) eyes, respectively, for a mean duration of 44.8 ± 31.6 and 226.8 ± 180.5 days, respectively. At follow-up, 172.3 ± 183.6 days, visual recovery was statistically significant in persistent eyes (BCVA 0.07 ± 0.07 logMAR; P < 0.00001) but, not in recurrent eyes (BCVA 0.16 ± 0.08 logMAR; P = 0.07). Five of 21 eyes were left with residual significant scar.

Conclusion:

The sequelae of microsporidial keratoconjunctivitis are not uncommon. Topical 0.03% tacrolimus ointment appeared to be an effective corticosteroid-sparing agent for the treatment of SEIs and prevention of recurrence.

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.

"A prospective study on the clinical course and proposed morphological classification scheme of microsporidial keratoconjunctivitis."

Background and objective: To describe the clinical course and propose a morphological classification scheme of microsporidial keratoconjunctivitis. Methods: This is a prospective study at L V Prasad Eye Institute, Odisha, between August-January (2017-19). Patients of any age or sex, microbiologically proven as microsporidial keratoconjunctivitis were included. Demographic parameters, history, clinical course, and visual outcome were analysed. All received artificial tear substitutes till resolution and topical immunosuppressants used in cases of persisting sub-epithelial infiltrates (SEI) beyond 2 weeks. Results: Fifty-three eyes of 47 cases were included with males, 72.3%. Corneal lesions were classified into 3 morphological types- coarse, ring, and flat-topped (Type1, 2 & 3). Depending upon the location, Type 1 was further sub-divided into peripheral, paracentral, central, and diffuse (Type 1a, b, c & d). The mean age was highest in Type 3(p = .026). Risk factors and prior steroid use were most common in Type 1d. The mean duration of symptom before presentation was longest in Type 3(11.6 ± 3.65) days. Severe conjunctival congestion at presentation in more than half of the eyes were seen in Type 1a, 1b and 1d, with moderate congestion at Day14 persisting in 66.7% and 40% of eyes belonging to Type 1c and 1d, respectively. Keratic precipitates were most common in Type 2. The mean duration of resolution was longest in Type 1d (38 ± 15.87) days and shortest in type 1b (7.88 ± 2.47) days (p = .022). Persistent SEIs beyond Day 90 were seen in total of 6 (11.3%) (Type 1c & 1d- 3 each) eyes and recurrent SEIs in 7(13.2%) (Type 1c-2 & 1d- 5) eyes. The mean duration of topical steroids use was longest in Type 1d (49.3 ± 22.3) days, followed by Type 1c (28 ± 0) days. Conclusion: Microsporidial keratoconjunctivitis can have a variable clinical presentation, the course of each being different depending on the host and ocular surface factors. Though considered as a self-limiting disease, central and diffuse coarse variety (Type1c&1d) required long-term topical immunosuppressants and follow-up.

Microsporidial stromal keratitis in an immunocompromised patient: Successful management with medical therapy

Microsporidial stromal keratitis is refractory to topical drugs and is classically described in immunocompetent hosts. A 55-year-old patient with renal transplant and oral immunosuppressants, presented with a 15-day history of redness, pain, and diminution of vision in the right eye. Slit-lamp examination revealed epithelial defect and mid-stromal infiltrate. On corneal scraping, microsporidial spores were observed. The patient was started on topical 0.02% polyhexamethylene biguanide (PHMB) and the infiltrate resolved after 6 weeks of initiation of topical therapy.

Clinical Profile of Bilateral Microsporidial Keratoconjunctivitis in Healthy Individuals-A Case Series With Long-term Follow-up

PURPOSE

To describe bilateral microsporidial keratoconjunctivitis in healthy individuals with long-term follow-up.

METHODS

Six cases of smear-positive bilateral microsporidial keratoconjunctivitis were diagnosed and followed up during the study period August 2017 to January 2019. Associated risk factors, clinical features, coexistence with adenovirus, clinical course, and recurrence were studied.

RESULTS

The mean age was 36.6 years (range: 10-65 years). The mean duration of symptoms was 13.6 days (range: 7-60 days). Predisposing risk factors were present in 4 of 6 cases. The best-corrected visual acuity at presentation was ≥20/30 in all eyes except in one. Typical microsporidial epithelial lesions were seen in only one case. Persistent lesions, clinically resembling Thygeson superficial punctate keratitis in both eyes, were observed in 3 cases. The lesions in 5 eyes resolved with topical lubricants, and the remaining 7 eyes were treated with topical steroids and tacrolimus 0.03%. Complete resolution was seen in 5 eyes at the end of 1 month, and superficial scarring at the last follow-up was seen in 5 eyes. The best-corrected visual acuity was ≤20/30 in 3 eyes at the last follow-up. The mean duration of follow-up was 7.3 months (range: 3-12 mo).

CONCLUSIONS

Bilateral microsporidial keratoconjunctivitis in healthy patients has an atypical presentation with prolonged course. Microsporidia could be implicated as potential candidates in the etiopathogenesis of Thygeson superficial punctate keratitis.

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

Background

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

Methods

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

Results

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

Conclusions

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

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04700-x.

Vittaforma Corneae keratoconjunctivitis: An emerging pathology among travelers returning from Southeast Asia

Microsporidium keratoconjunctivitis is an very rare disease. It is related to outbreaks in Asia due to exposure to contaminated water or soil. Microsporidium keratoconjunctivitis is a a self-limited disease, but it could have long term courses. We present the case of a 29 year old woman who started with pain, redness and blurred vision after a holiday in Singapore and did not respond to conjunctivitis treatment. PCR sequencing and PAS staining of corneal epithelial biopsy identified Vittaforma corneae as the causative organism. Treatment was initiated with corneal debridement, oral albendazol, and intensive topical voriconazole, levofloxacin and propamidine, but the conjunctival and corneal disease was only resolved 5 months later with the introduction of topical steroids to treat her severe limbitis. Suspicion of Microsporidium keratoconjunctivitis should be raised amongst ophthalmologists in unilateral keratitis with mild conjunctivitis in travelers from Asia.

Parasitic keratitis - An under-reported entity

Parasitic keratitis (PK) is unique entity among parasitic infections where corneal involvement could result from direct inoculation of the parasite via exogenous environment or spread via endogenous neighboring organs or as a result of immune-mediated damage secondary to a systemic parasitic infection. Most cases of PK are caused by Acanthamoeba spp. and Microsporidia spp. though few other parasitic agents can also lead to corneal involvement. Mimicking as other infectious and non-infectious causes of keratitis, PK often escapes detection. This review summarizes the predominant causes of PK along with the epidemiological, clinical and microbiological details of each. Though several gaps exist in our understanding of the prevalence of PK, the one thing for sure is that PK is on the rise. With advanced diagnostic modalities and enough literature on optimal management of cases of PK, it is now imperative that a strong clinical suspicion of PK is kept when examining a case of corneal pathology and adequate investigations are ordered.

Molecular identification of microsporidian species in patients with epithelial keratitis

Introduction. Ocular microsporidiosis is a significant emerging infectious disease reported in immunocompromised patients and immunocompetent persons throughout the world.Aim. To identify the pathogens responsible for human keratitis, via corneal scrapings.Methodology. Thirty-three hospitalized patients with epithelial keratitis were examined using staining and DNA sequencing. DNA was extracted from corneal samples and the small-subunit ribosomal RNA gene was amplified by polymerase chain reaction (PCR) and sequenced.Results. Twenty-one samples were positive by staining while PCR generated amplicons in 18 cases. Of the 18 sequences, 16 were identical with, or very similar to, those of Vittaforma corneae (99-100 % similarity) and the remaining two sequences were similar to that of unidentified Microsporidium species deposited in the GenBank.Conclusion. This study has reconfirmed that V. corneae causes epithelial keratitis in humans and that a newly detected Microsporidium species is also involved in microsporidial keratitis as one of the emerging pathogens in Thailand. Ophthalomologists should be aware of microsporidial keratitis in people from Thailand and those from neighbouring countries.

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.

Acute stromal keratitis in clinics - are we missing microsporidia?

Purpose: To report 3 cases of microsporidial stromal keratitis presenting as a diagnostic dilemma to a tertiary eye care center in north India.

Methods: Three eyes of 3 patients underwent therapeutic keratoplasty for microsporidial stromal keratitis. A decision for early surgery was taken as the patients were not responding to conventional medical management and were worsening clinically. The diagnosis of microsporidia was made by corneal scraping and confirmed on histopathological evaluation of the corneal button.

Results: Out of the 3 patients, one maintained a clear graft, one had a recurrence and one had graft rejection, 6 months postoperatively. The patients were not started on steroids in the postoperative period and were given topical antibiotics and polyhexamethylene biguanide (PHMD). Oral Albendazole 400 mg was also given twice a day for a month.

Conclusion: Many questions remained unanswered about the management protocol of stromal keratitis caused by microsporidia. The role of topical steroids, antifungal agents, oral Albendazole needs to be discussed. Clinicians should be aware of recurrences which may mimic as rejections. There needs to be more awareness regarding microsporidia as a cause of acute stromal keratitis, so that its not overlooked or underdiagnosed.

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.

Demographic and clinical profile of microspodial keratitis in North India: an underreported entity

Ocular microsporidiosis was first described in immunocompromised subjects but recent reports have also shown cases in immunocompetent hosts. The database of existing clinical studies is very limited. The aim of present study was to analyse demographic profile, clinical features, microbiological profile, treatment and outcome of ocular microsporidiosis in northern India. The present study was carried out in the Department of Medical Parasitology, Advanced Eye Center, Postgraduate Institute of Medical Education and Research, and Bharat Vikas Parishad Charitable trust, Chandigarh. A total of 250 patients during year 2013-17 and suspected of microsporidial keratitis (either clinically or after exclusion of bacterial, viral or fungal agents). Corneal scraping were taken and subjected for various staining methods and PCR. 8 patients of microsporidial keratitis were confirmed, based on positivity by at least any two of the above mentioned techniques. None of the patients had history of contact lens wear or exposure to swimming pool. All these patients were systemically healthy and HIV serology was negative except one had history of diabetes mellitus. This study is a reminder to clinicians that when multifocal diffuse epithelial keratitis and culture-negative keratoconjunctivitis not responding to medical therapy, regardless of immune status are found in patients with symptoms suggesting an infectious keratitis, microsporidial keratoconjunctivitis should be included in the differential diagnosis.

Microsporidial keratitis retrospectively diagnosed by ultrastructural study of formalin-fixed paraffin-embedded corneal tissue: a case report

Background

The utility of formalin-fixed paraffin-embedded (FFPE) corneal tissue specimens for retrospective diagnosis of microsporidial keratitis was evaluated by transmission electron microscopy (TEM) analysis and the possible second case of microsporidial keratitis after Descemet stripping automated endothelial keratoplasty (DSAEK) was described.

Case presentation

A 68-year-old man presented with multiple crystalline opacities in the corneal stroma that progressed extremely slowly after DSAEK. Fungiflora Y staining of corneal scrapings from the affected regions revealed an oval microorganism. Topical voriconazole administration was ineffective and penetrating keratoplasty was performed. Histological and molecular analyses were carried out on the excised cornea. Ziehl–Neelsen staining revealed an acid-fast, oval organism that was visible by ultraviolet illumination after Fungiflora Y and Uvitex 2B staining, whereas periodic acid-Schiff and Grocott’s staining did not yield any significant findings. Microsporidium was detected by TEM of FFPE tissue. Nosema or Vittaforma sp. was suspected as the causative microorganism by PCR of FFPE tissue and by the fact that those species are known to cause eye infection. The corneal graft has maintained transparency at 1 year and half postoperatively.

Conclusions

This is the first known case of microsporidial keratitis diagnosed retrospectively by molecular and ultrastructural study of FFPE tissue, and the possible second case of microsporidial keratitis after DSAEK. Microsporidial keratitis should be considered when corneal opacity refractory to conventionally known therapy would occur after DSAEK. Our findings suggest that more microsporidial keratitis cases than have been reported to date can be identified by TEM or PCR examination of FFPE corneal specimens.

Importance of clinical signs leading to the diagnosis in a case of microbiological smear negative ocular microsporidiosis

A 28-year-old patient presented to us with multifocal coarse raised epithelial lesions in the left eye associated with pain watering redness and blurred vision with a visual acuity of 20/40 in the left eye. The patient had been managed elsewhere with a course of topical moxifloxacin eye-drops four times a day and topical steroids (prednisolone acetate) 1% three times a day for 2 weeks without any resolution, which was stopped 2 days ago prior to presentation at our centre. Gram stain was negative for bacteria as well as microsporidial spores. 10% KOH was negative for fungal hyphae. Based on strong clinical signs of corneal microsporidiosis, in spite of the negative microbiology smear, the patient was started on voriconazole eye-drops five times a day. The lesions started resolving in 5 days and completely healed after 17 days of therapy. No relevant history pertaining to exposure of contaminated water, swimming or history of trauma could be elicited.

Exotic Tourist Destinations and Transmission of Infections by Swimming Pools and Hot Springs-A Literature Review

A growing number of people undertake international travel, and yet faster growth of such travel is expected in the tropics. Information on the hazards presented by pool and hot spring waters in tropical countries is very limited. This review aims to collate available information on pool water quality, alongside data on cases and outbreaks associated with swimming in pools in tropical regions affecting both local populations and travellers. Bacteria species commonly causing cases and outbreaks in the tropics as well as elsewhere in the world were excluded, and the review focuses on studies related to pathogens that, with the exception of Cryptosporidium, are unusual in more temperate climates. Studies concerning subtropical countries were included in the light of climate change. Diseases transmitted by vectors breeding in poorly maintained, neglected or abandoned pools were also included. 83 studies dealing with Microsporidia, Leptospira spp., Schistosomas spp., Cryptosporidium spp., Acanthamoeba spp., Naegleria spp., Clostridium trachomatis, viruses, and vectors breeding in swimming pool and hot tub waters, and fulfilling predefined criteria, have been included in our survey of the literature. In conclusion, prevention strategies for pool safety in the tropics are imperative. Public health authorities need to provide guidance to westerners travelling to exotic destinations on how to protect their health in swimming pools.

Therapeutic targets for the treatment of microsporidiosis in humans

INTRODUCTION

Microsporidia have been increasingly reported to infect humans. The most common presentation of microsporidiosis is chronic diarrhea, a significant mortality risk in immune-compromised patients. Albendazole, which inhibits tubulin, and fumagillin, which inhibits methionine aminopeptidase type 2 (MetAP2), are the two main therapeutic agents used for treatment of microsporidiosis. In addition, to their role as emerging pathogens in humans, microsporidia are important pathogens in insects, aquaculture, and veterinary medicine. New therapeutic targets and therapies have become a recent focus of attention for medicine, veterinary, and agricultural use. Areas covered: Herein, we discuss the detection and symptoms of microsporidiosis in humans and the therapeutic targets that have been utilized for the design of new drugs for the treatment of this infection, including triosephosphate isomerase, tubulin, MetAP2, topoisomerase IV, chitin synthases, and polyamines. Expert opinion: Enterocytozoon bieneusi is the most common microsporidia in human infection. Fumagillin has a broader anti-microsporidian activity than albendazole and is active against both Ent. bieneusi and Encephaliozoonidae. Microsporidia lack methionine aminopeptidase type 1 and are, therefore, dependent on MetAP2, while mammalian cells have both enzymes. Thus, MetAP2 is an essential enzyme in microsporidia and new inhibitors of this pathway have significant promise as therapeutic agents.

Opportunistic ocular infections in the setting of HIV

PURPOSE OF REVIEW

The aim of this review is to highlight recent changes in opportunistic ocular infections (OOIs) in the era of modern combination antiretroviral therapy (cART), in the setting of HIV-infected patients.

RECENT FINDINGS

Improvements in modern cART has led to a progressive decline in the incidence of OOIs and mortality among patients with AIDS. Not only has there been a decreasing incidence of cytomegalovirus (CMV) retinitis, but there also has been a decline in progression of such retinitis when it does occur in AIDS patients, since the introduction of cART. Nevertheless, CMV retinitis remains the major cause of vision loss in AIDS patients. Although the incidence of CMV retinitis has declined overall, the incidence of ocular syphilis has increased during the cART era. Moreover, the impact of having HIV plays a role with respect to multidrug-resistant (MDR) tuberculosis and has resulted in a high prevalence of presumed ocular tuberculosis in HIV/MDR-TB co-infected patients. Although immune reconstitution uveitis (IRU) has been an important cause of visual deficits in developed countries, OOIs remain an important cause of blindness in the developing world.

SUMMARY

Reconstituting the immune system with effective cART while increasing accessibility of screening examinations is key to the success of blindness prevent in HIV-infected individuals, particularly in developing countries.

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.

A DNA dot hybridization model for molecular diagnosis of parasitic keratitis

Purpose

Developing a DNA dot hybridization model for diagnosing parasitic keratitis.

Methods

Newly designed oligonucleotide probes for detecting Acanthamoeba and microsporidia were tested with target reference strains of Acanthamoeba (n = 20) and microsporidia (n = 3), and non-target microorganisms, including bacteria (n = 20) and fungi (n = 20). These probes, which had passed the preliminary tests, were then assembled as a parasite dot hybridization (PDH) model for assessing 33 clinical samples from patients with clinically suspected Acanthamoeba and microsporidia keratitis, including eight positives for Acanthamoeba, 13 positives for microsporidia, and 12 negatives for both pathogens.

Results

Two probes for detecting Acanthamoeba and two for detecting microsporidia passed the tests using target and non-target strains and then were assembled in the PDH model. For clinical samples, one Acanthamoeba-positive sample (proved with pathology) was falsely negative according to the PDH assay. The sensitivity and specificity of the PDH assay for diagnosing Acanthamoeba keratitis were 87.5% and 100%, respectively, while the sensitivity and specificity for diagnosing microsporidia keratitis were 100%. The infectious agent of all clinical samples of microsporidia keratitis was identified as Vittaforma corneae with DNA sequencing, while those of Acanthamoeba keratitis were caused by four species of Acanthamoeba, with Acanthamoeba castellanii found in four samples (50%, 4/8).

Conclusions

The PDH model has the potential to be a molecular assay for diagnosing Acanthamoeba and microsporidia keratitis. However, a prospective clinical study might be needed before the model is adopted in routine clinical practice.

Surveillance of Vittaforma corneae in hot springs by a small-volume procedure

Vittaforma corneae is an obligate intracellular fungus and can cause human ocular microsporidiosis. Although accumulating reports of V. corneae causing keratoconjunctivitis in both healthy and immunocompromised persons have been published, little is known about the organism's occurrence in aquatic environments. Limitations in detection sensitivity have meant a large sampling volume is required to detect the pathogen up to now, which is problematic. A recent study in Taiwan has shown that some individuals suffering from microsporidial keratitis (MK) were infected after exposure to the pathogen at a hot spring. As a consequence of this, a survey and analysis of environmental V. corneae present in hot springs became an urgent need. In this study, sixty water samples from six hot spring recreation areas around Taiwan were analyzed. One liter of water from each sample site was filtered to harvest the fungi. The positive samples were detected using a modified nested PCR approach followed by sequencing using specific SSU rRNA gene primer pairs for V. corneae. In total fifteen V. corneae-like isolates were identified (25.0% of sites). Among them, six isolates, which were collected from recreational areas B, C and D, were highly similar to known V. corneae keratitis strains from Taiwan and other countries. Furthermore, five isolates, which were collected from recreation areas A, C, E and F, were very similar to Vittaforma-like diarrhea strains isolated in Portugal. Cold spring water tubs and public foot bath pools had the highest detection rate (50%), suggesting that hot springs might be contaminated via untreated water sources. Comparing the detection rate across different regions of Taiwan, Taitung, which is in the east of the island, gave the highest positive rate (37.5%). Statistical analysis showed that outdoor/soil exposure and a high heterotrophic plate count (HPC) were risk factors for the occurrence of V. corneae. Our findings provide empirical evidence supporting the need for proper control and regulations at hot spring recreational waters in order to avoid health risks from this pathogen. Finally, we have developed a small volume procedure for detecting V. corneae in water samples and this has proved to be very useful.

Microsporidial Stromal Keratitis: Successful Treatment with Topical Voriconazole and Oral Itraconazole

We report a case of microsporidial stromal keratitis successfully treated with topical voriconazole and oral itraconazole. A 30-year-old Hispanic male construction worker who wears contacts lenses presented with left eye erythematous, epiphora, and mild pain increasing over few days after failing previous antibiotics treatment. His best corrected visual acuity in the left eye was count fingers at three feet, and the slit lamp examination showed 3+ conjunctival injection, a circular central corneal ulcer 3.2 mm in diameter, stromal thinning, and an anterior chamber with white cells, flair, and 0.1 mm hypopyon. A cornea punch biopsy identified microsporidial organisms with some features suggestive of Vittaforma corneae. After treatment with topical voriconazole and oral itraconazole for eight weeks, the patient had complete resolution with no recurrence for over 12 months of follow-up. To our knowledge, this is the first reported case of successful treatment of microsporidial stromal keratitis with antifungals.

Ocular parasitoses: A comprehensive review

Parasitic infections of the eyes are a major cause of ocular diseases across the globe. The causative agents range from simple organisms such as unicellular protozoans to complex metazoan helminths. The disease spectrum varies depending on the geographic location, prevailing hygiene, living and eating habits of the inhabitants, and the type of animals that surround them. They cause enormous ocular morbidity and mortality not because they are untreatable, but largely due to late or misdiagnosis, often from unfamiliarity with the diseases produced. We provide an up-to-date comprehensive overview of the ophthalmic parasitoses. Each section describes the causative agent, mode of transmission, geographic distribution, ocular pathologies, and their management for common parasites with brief mention of the ones that are rare.

Microsporidia - Emergent Pathogens in the Global Food Chain

Intensification of food production has the potential to drive increased disease prevalence in food plants and animals. Microsporidia are diversely distributed, opportunistic, and density-dependent parasites infecting hosts from almost all known animal taxa. They are frequent in highly managed aquatic and terrestrial hosts, many of which are vulnerable to epizootics, and all of which are crucial for the stability of the animal-human food chain. Mass rearing and changes in global climate may exacerbate disease and more efficient transmission of parasites in stressed or immune-deficient hosts. Further, human microsporidiosis appears to be adventitious and primarily associated with an increasing community of immune-deficient individuals. Taken together, strong evidence exists for an increasing prevalence of microsporidiosis in animals and humans, and for sharing of pathogens across hosts and biomes.

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.

Microsporidial stromal keratitis masquerading as acute graft rejection

PURPOSE

To describe the clinical features, disease course, management, and visual outcome of stromal microsporidial keratitis involving the corneal graft in an immunocompetent patient.

METHODS

Case report.

RESULTS

We report the case of a 21-year-old immunocompetent woman, who underwent penetrating keratoplasty for advanced keratoconus in her right eye and presented with features of acute graft rejection after 15 months. Standard treatment using topical and systemic steroids failed to reverse the graft rejection. A regraft was performed in that eye. Histopathology of the donor corneal button revealed microsporidiosis involving the deep stroma.

CONCLUSIONS

Microsporidiosis is rarely encountered in a corneal graft and masquerades as acute graft rejection. Histopathology could help in making a final diagnosis.