Diffuse unilateral subacute neuroretinitis. Morphometric, serologic, and epidemiologic support for Baylisascaris as a causative agent

Infectious eye disease in the 21st century-an overview

Infectious diseases affecting the eye often cause unilateral or asymmetric visual loss in children and people of working age. This group of conditions includes viral, bacterial, fungal and parasitic diseases, both common and rare presentations which, in aggregate, may account for a significant portion of the global visual burden. Diagnosis is frequently challenging even in specialist centres, and many disease presentations are highly regional. In an age of globalisation, an understanding of the various modes of transmission and the geographic distribution of infections can be instructive to clinicians. The impact of eye infections on global disability is currently not sufficiently captured in global prevalence studies on visual impairment and blindness, which focus on bilateral disease in the over-50s. Moreover, in many cases it is hard to differentiate between infectious and immune-mediated diseases. Since infectious eye diseases can be preventable and frequently affect younger people, we argue that in future prevalence studies they should be considered as a separate category, including estimates of disability-adjusted life years (DALY) as a measure of overall disease burden. Numbers of ocular infections are uniquely affected by outbreaks as well as endemic transmission, and their control frequently relies on collaborative partnerships that go well beyond the remit of ophthalmology, encompassing domains as various as vaccination, antibiotic development, individual healthcare, vector control, mass drug administration, food supplementation, environmental and food hygiene, epidemiological mapping, and many more. Moreover, the anticipated impacts of global warming, conflict, food poverty, urbanisation and environmental degradation are likely to magnify their importance. While remote telemedicine can be a useful aide in the diagnosis of these conditions in resource-poor areas, enhanced global reporting networks and artificial intelligence systems may ultimately be required for disease surveillance and monitoring.

Cerebral baylisascariosis in a rainbow lorikeet (Trichoglossus moluccanus) in a German Zoo

BACKGROUND

The raccoon roundworm, Baylisascaris procyonis, can cause a meningoencephalitis as neural larva migrans which is known in avian species, including rainbow lorikeets in North America, but has not been described in Old World parrots in Germany yet.

CASE PRESENTATION

A 2-month-old, male rainbow lorikeet from a zoo in Germany was submitted for necropsy. Prior to death the animal had progressive neurological signs like apathy and torticollis. In the cerebrum a focally extensive severe granulomatous to necrotizing encephalitis with an intralesional larval nematode was diagnosed. Based on the clinical and pathological findings, the larval morphology and the epidemiological background, the larva was identified as Baylisascaris procyonis.

CONCLUSIONS

Cerebral baylisascariosis should be considered as a differential diagnosis in zoo and pet birds with neurological signs having contact to racoons or rather racoon faeces in Germany due to the high prevalence of Baylisascaris procyonis in the German raccoon population.

A Worm’s Tale or Why to Avoid the Raccoon Latrine: A Case of Baylisascaris procyonis Meningoencephalitis

The raccoon roundworm Baylisascaris procyonis (B. procyonis) may infect humans to cause severe or fatal meningoencephalitis, as well as ocular and visceral larva migrans. Young children are at greater risk for cerebral larva migrans with severe meningoencephalitis, and early empiric therapy may improve outcomes. Familiarity with characteristic brain imaging findings may prompt earlier diagnosis, particularly in the setting of CSF eosinophilia. We report a case of a 19-month-old boy who presented with truncal ataxia and was found to have peripheral and CSF eosinophilia. MRI demonstrated symmetric, confluent T2 hyperintense signal in the cerebral and cerebellar deep white mater, which helped differentiate B. procyonis meningoencephalitis from other infectious and non-infectious causes of eosinophilic meningoencephalitis. Early recognition and treatment of B. procyonis meningoencephalitis are important for improved outcomes, and careful review of neuroimaging can play a critical role in suggesting the diagnosis.

Is it canine DUSN?: Another view of retinopathies, some acquired, and others possibly "inherited": Another view of retinopathies, some acquired, and others possibly "inherited"

The term retinopathy has been used to group several heterogeneous retinal abnormalities that are clearly acquired or are suspected/proposed to be inherited. Some share characteristic focal/multifocal hyperreflective tapetal lesions with a dark center, and areas of non-tapetal depigmentation suggestive of patchy or diffuse outer retinal atrophy. Progression is variable, and some develop unilateral or bilateral fundus changes resembling the clearly inherited form of retinal degeneration referred to as PRA. In this Commentary and Review, we discuss the role of ocular larva migrans resulting in the entity we refer to as canine DUSN and suggest that it may be responsible for some of the retinal findings grouped under the retinopathy rubric that share this characteristic fundus lesion.

[Unilateral optic atrophy in a 9-year-old patient]

Ein 9‑jähriger Patient stellte sich aufgrund einer seit 2 Wochen zufällig bemerkten Sehminderung auf dem linken Auge vor. Funduskopisch waren neben einer leichten Vitritis eine blasse Papille, enggestellte Gefäße und eine Reflexvermehrung der Netzhautoberfläche sichtbar. In der Blutuntersuchung waren die Werte bis auf eine Eosinophilie und einen erhöhten Immunglobublin E(IgE)-Antikörpertiter normal.

Multimodal imaging-guided diagnosis, management and follow-up of a case of diffuse unilateral subacute neuroretinitis

A 45-year-old woman presented with diminished vision in the left eye. Visual acuity was 6/9 and fundus showed a very large live nematode near the macula along with inflammatory outer retinal lesions in the periphery. We diagnosed the case as diffuse unilateral subacute neuroretinitis and treated with immediate focal photocoagulation of the worm along with oral antihelminthic drugs and corticosteroids. The report highlights the importance of prompt laser and steroids in achieving good structural as well as the functional outcome, and the added significance of advanced imaging techniques in prognosticating such patients.

Diffuse unilateral subacute neuroretinitis: review article

Diffuse unilateral subacute neuroretinitis (DUSN) is an ocular infectious disease that can lead to severe visual impairment and blindness. It usually occurs in healthy young individuals and depending on the stage of the disease, it may present as vitritis, multifocal gray-white lesions in the outer retina, and derangement of the retinal pigment epithelium, narrowing of the retinal vessels and optic atrophy. Parasites of different sizes and species have been proposed as the etiologic agent of DUSN, including Ancylostoma caninum, Toxocara canis, and others. Thus, it is hypothesized that different infectious worms may be considered as the likely cause of both an autoimmune and toxic form of nematode retinopathy. Because serologic testing is variable, the definitive diagnosis is made when clinical characteristics of DUSN are found in conjunction with an intraocular worm. Ancillary tests can assist in the differential diagnosis when the nematode cannot be visualized, such as fluorescein and indocyanine green angiography, electrophysiological tests, visual field studies, and more recently, optical coherence tomography angiography. Cases in which the worm can be identified, it is defined as confirmed DUSN, and eyes with the typical clinical features but without identification of the worm should be classified as presumed DUSN. In confirmed DUSN, the classic treatment is directly photocoagulation of the worm; however, it can only be visualized in 30% (to 40%) of cases. Treatment of presumed DUSN cases with high-dose oral albendazole has shown encouraging results. However, perhaps due to the disease’s rarity or its underdiagnosis, there are no studies comparing current treatment modalities in both presumed and confirmed DUSN. Due to the possibility of this disease being, in part, autoimmune nematode retinopathy, corticosteroids associated with both albendazole or laser therapy, could be in any way beneficial. Thus, further comparative studies are necessary to elucidate the best treatment for this potentially blinding disease.

Role of PASCAL and optical coherence tomography angiograpgy in the treatment of diffuse unilateral subacute neuroretinitis caused by large live motile worm

A 46-year-old male presented with best corrected visual acuity (BCVA) of 20/125 in his right eye. Fundus showed disc edema, multiple yellow outer retinal crops, macular edema and a live motile worm in the subretinal space. Diagnosis of diffuse unilateral subacute neuroretinitis (DUSN) was made and pattern scanning laser photocoagulation (PSLP) was performed along with administration of oral albendazole, diethylcarbamazine and corticosteroids. Complete disappearance of the worm was observed at 2 weeks. At last follow up, final BCVA improved to 20/30. Herein, we report role of PSLP in the management of DUSN.

Baylisascaris procyonis Central Nervous System Infection in a Four-Month-Old Gordon Setter Dog

A 16 wk old intact female Gordon setter was examined for a 2 wk history of progressive cerebellovestibular ataxia. Eosinophilia was found on complete blood count, and the remaining blood work was normal. A trial treatment with clindamycin and anti-inflammatory prednisone did not result in improvement of clinical signs; therefore, the dog was euthanized. On histopathologic examination, cross sections of a 75 μm wide nematode larva with a 5 μm cuticle, prominent lateral cords, lateral alae, and coeloemyelian musculature were identified in a focally extensive region of cerebellar necrosis. The size and morphology of the parasites was most consistent with Baylisascaris procyonis. This case highlights a rare but important zoonotic disease that should be considered as a differential diagnosis in any dog exhibiting acute, progressive central nervous system signs, and peripheral eosinophilia. The index of suspicion should be elevated in dogs with an unknown deworming history and known or suspected exposure to raccoons. Because most anthelminthics have been shown to be effective against B. procyonis, annual deworming is recommended in the at-risk population to reduce the likelihood of aberrant migration and zoonosis.

Update on pathology of ocular parasitic disease

Parasites are a group of eukaryotic organisms that may be free-living or form a symbiotic or parasitic relationship with the hosts. Consisting of over 800,000 recognized species, parasites may be unicellular (Protozoa) or multicellular (helminths and arthropods). The association of parasites with human population started long before the emergence of civilization. Parasitic zoonotic diseases are prevalent worldwide including India. Appropriate epidemiological data are lacking on existing zoonotic parasitic diseases, and newer diseases are emerging in our scenario. Systemic diseases such as cysticercosis, paragonimiasis, hydatidosis, and toxoplasmosis are fairly common. Acquired Toxoplasma infections are rising in immune-deficient individuals. Amongst the ocular parasitic diseases, various protozoas such as Cystoidea, trematodes, tissue flagellates, sporozoas etc. affect humans in general and eyes in particular, in different parts of the world. These zoonoses seem to be a real health related problem globally. Recent intensification of research throughout the world has led to specialization in biological fields, creating a conducive situation for researchers interested in this subject. The basics of parasitology lie in morphology, pathology, and with recent updates in molecular parasitology, the scope has extended further. The current review is to address the recent update in ophthalmic parasites with special reference to pathology and give a glimpse of further research in this field.

Successful Management of Diffuse Unilateral Subacute Neuroretinitis with Anthelmintics, and Intravitreal Triamcinolone followed by Laser Photocoagulation

Purpose:

Diffuse unilateral subacute neuroretinitis (DUSN), a form of posterior uveitis, is secondary to the presence of a highly motile nematode in the intraretinal or subretinal space. Herein, we report a case of DUSN that was successfully managed by an intravitreal injection of triamcinolone and laser therapy.

Case Report:

A middle-aged man with complaint of decreased vision and marked unilateral vitritis and neuroretinitis. Fluorescein angiography revealed disc leakage, vessel wall staining, and diffuse track-like transmission defects of the RPE. Optical coherence tomography confirmed the subretinal location of the worm. The patient received oral thiabendazole and an intravitreal injection of triamcinolone acetonide. After 10 days, media haziness decreased, and a live motile subretinal worm was identified. Direct laser photocoagulation was performed to destroy the worm. After two months, a localized chorioretinal scar developed and no further active inflammation and subretinal worms were detected.

Conclusion:

Intravitreal steroids can be used safely in cases with DUSN and may help detect the causative worm for applying laser photocoagulation.

Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection

Baylisascaris procyonis, the raccoon roundworm, infects a wide range of vertebrate animals, including humans, in which it causes a particularly severe type of larva migrans. It is an important cause of severe neurologic disease (neural larva migrans [NLM]) but also causes ocular disease (OLM; diffuse unilateral subacute neuroretinitis [DUSN]), visceral larva migrans (VLM), and covert/asymptomatic infections. B. procyonis is common and widespread in raccoons, and there is increasing recognition of human disease, making a clinical consideration of baylisascariasis important. This review provides an update for this disease, especially its clinical relevance and diagnosis, and summarizes the clinical cases of human NLM and VLM known to date. Most diagnosed patients have been young children less than 2 years of age, although the number of older patients diagnosed in recent years has been increasing. The recent development of recombinant antigen-based serodiagnostic assays has aided greatly in the early diagnosis of this infection. Patients recovering with fewer severe sequelae have been reported in recent years, reinforcing the current recommendation that early treatment with albendazole and corticosteroids should be initiated at the earliest suspicion of baylisascariasis. Considering the seriousness of this zoonotic infection, greater public and medical awareness is critical for the prevention and early treatment of human cases.

Clinical experience in treatment of diffuse unilateral subretinal neuroretinitis

Purpose

To describe the clinical features, management, and outcomes of patients with diffuse unilateral subacute neuroretinitis (DUSN).

Methods

A noncomparative, consecutive analysis of case series from two tertiary care campuses of LV Prasad Eye Institute, India, between January 2011 and April 2014 was performed. Medical records of the patients presenting with DUSN (early or late stage) were reviewed.

Results

The current study included 13 patients. The majority (10/13, 76.92%) of the patients were aged 20 years or less. All patients had unilateral eye involvement. Visual acuity at presentation was 20/200 or worse in 9/13 (69.23%) patients. A delay in diagnosis occurred in 6/13 patients, and initial diagnosis in these patients included retinitis pigmentosa (4 patients) and posterior uveitis (2 patients). Clinical features included early presentation (prominent vitritis, localized retinitis, and vasculitis) in 7/13 (53.85%) patients and late presentation (attenuation of vessels, retinal pigment epithelium atrophic changes, and optic atrophy) in 6/13 (46.15%) patients. Worm could not be identified in any of the cases. All the patients received laser photocoagulation of retina and oral albendazole treatment for a period of 30 days. With treatment, visual acuity improved in seven patients (six early stage, one late stage) and remained unchanged in six patients. Mean follow-up period was 8.69 months (range, 1–21 months). The mean central foveal thickness in the affected eye, done by optical coherence tomography, during the late stage of the disease was 188.20±40 µm (range, 111–242 µm), which was significantly thinner than the fellow eye, 238.70±36.90 µm (range, 186–319 µm), P=0.008.

Conclusion

DUSN is a serious vision threatening disease, which may progress to profound vision loss in the later stage of the disease. Visualization of subretinal worm is usually not possible. Treatment with high-dose albendazole therapy and laser photocoagulation may alter the blood–retinal barrier and may be useful in achieving visual recovery.

Diffuse unilateral subacute neuroretinitis in a healthy Korean male: the first case report in Korea

A 52-yr-old male was referred for progressive visual loss in the left eye. The decimal best-corrected visual acuity (BCVA) was 0.01. Fundus examination revealed diffuse retinal pigment epithelial degeneration, focal yellow-white, infiltrative subretinal lesion with fuzzy border and a live nematode within the retina. Diffuse unilateral subacute neuroretinitis (DUSN) was diagnosed and the direct laser photocoagulation was performed to destroy the live nematode. During eight months after treatment, BCVA gradually improved to 0.2 along with the gradual restoration of outer retinal layers on SD-OCT. We report on the first case of DUSN in Korea. DUSN should be included in the differential diagnosis of unexplained unilateral visual loss in otherwise healthy subjects.

Baylisascaris larva migrans

Baylisascaris procyonis is a roundworm of the raccoon found primarily in North America but also known to occur in other parts of the world including South America, Europe, and Japan. Migration of the larvae of this parasite is recognized as a cause of clinical neural larva migrans (NLM) in humans, primarily children. It is manifested as meningoencephalitis associated with marked eosinophilia of the cerebrospinal fluid and peripheral blood. Diagnosis is made by recovering and identifying larvae in or from the tissues, epidemiological history, serology, and imaging of the central nervous system. Treatment is with albendazole and steroids, although the prognosis is generally poor. This parasite can also cause ocular larva migrans (OLM) which usually presents as diffuse unilateral subacute neuroretinitis (DUSN). The ocular diagnosis can be made by visualizing the larva in the eye and by serology. Intraocular larvae can be destroyed by photocoagulation although albendazole and steroids may also be used. However, once visual disturbance is established the prognosis for improved vision is poor. Related Baylisascaris species occur in skunks, badgers, and certain other carnivores, although most cases of NLM are caused by B. procyonis. Baylisascaris procyonis has also been found in kinkajous in the USA and South America and may also occur in related procyonids (coatis, olingos, etc.).

Baylisascariosis--infections of animals and humans with 'unusual' roundworms

The nematode genus Baylisascaris (order Ascaridida, superfamily Ascaridoidea) contains nine relatively host-specific, parasite species of carnivores, omnivores, herbivores, carnivorous marsupials or rodents. They have a facultative heteroxenous life cycle, at least under experimental conditions. Eggs passed in faeces embryonate in the environment and the second-stage larva infective for both definitive and intermediate hosts develops. In intermediate hosts larvae migrate extensively through tissues, where they grow and moult to the third-stage, causing extensive damage. All Baylisascaris spp. are considered a potential cause of visceral, ocular and/or neural larval migrans in mammals including humans and in birds. This paper summarises our current knowledge on the prevalence, biology, pathogenicity and zoonotic significance of three Baylisascaris species: B. transfuga, B. schroederi and B. procyonis which have as definitive hosts bears, giant pandas and raccoons (occasionally dogs), respectively.

Baylisascaris procyonis in raccoons (Procyon lotor) from North Carolina and current status of the parasite in the USA

Baylisascaris procyonis is an intestinal nematode of raccoons (Procyon lotor) that can cause fatal larva migrans in numerous species of birds and mammals, including humans. Historically, this parasite has been rare in the southeastern USA but recently has been reported in eastern Tennessee and isolated parts of Georgia and Florida. The objective of the current study was to investigate the distribution and prevalence of B. procyonis in raccoons from North Carolina. In western North Carolina, in counties bordering Tennessee, B. procyonis was detected in nine of 74 (12 %) raccoons sampled in 2010-2011. In general, worm burdens (average 20 worms) were low, but one raccoon had 122 adult worms. No difference was noted in prevalence by year or age, but significantly more males were infected compared with females. Sequences of the internal transcribed spacer 2 region from three samples were identical to B. procyonis. In central North Carolina (Guilford County), all 34 raccoons and 49 fecal samples tested were negative. Collation of data from previous studies conducted in the Southeast indicates that B. procyonis has been reported from numerous counties, but surveillance has been patchy and many negative results are >30 years old. These results indicate that B. procyonis is established in North Carolina and given the zoonotic and wildlife health implications of this parasite, additional surveillance in North Carolina and other southeastern states is warranted.

Letter to the editor. Diffuse unilateral subacute neuroretinitis (DUSN)

PURPOSE

To show that diffuse unilateral subacute neuroretinitis (DUSN) may masquerade as multiple evanescent white dot syndrome, and to describe structural and functional recovery following treatment in DUSN.

DESIGN

Case report.

METHODS

Baseline and serial optical coherence tomography (OCT) and perimetry following photocoagulation of nematode.

RESULTS

After laser treatment, the inner segment-outer segment (IS-OS) junction was restored and the visual field was improved.

CONCLUSIONS

DUSN, early on, can be mistaken for other inflammatory white dot syndromes. OCT and perimetry, in combination, provide strong support for success of treatment with photocoagulation.

Zoonoses of procyonids and nondomestic felids

There are several important zoonotic diseases which can be acquired from procyonids, and nondomestic felids. Baylisascaris procyonis, the raccoon roundworm, is a common parasite of raccoons and can cause visceral, ocular, or neural larval migrans in people. Neural larval migrans can cause severe signs in individuals. Dermatophytosis and enteric pathogens are the most important zoonotic agents found in nondomestic felids. Microsporum canis infections can be spread from nondomestic felids to owners and veterinarians. Toxoplasma gondii can be potentially shed by infected felids, and human infections occurring during pregnancy can cause blindness in the fetus.

Spectral domain optical coherence tomography in diffuse unilateral subacute neuroretinitis

Purpose. To describe the SD-OCT findings in patients with diffuse unilateral subacute neuroretinitis (DUSN) and evaluate CRT and RNFL thickness. Methods. Patients with clinical diagnosis of DUSN who were submitted to SD-OCT were included in the study. Complete ophthalmologic examination and SD-OCT were performed. Cirrus scan strategy protocols used were 200 × 200 macular cube, optic nerve head cube, and HD-5 line raster. Results. Eight patients with DUSN were included. Mean RNFL thickness was 80.25 μm and 104.75 μm for affected and normal eyes, respectively. Late stage had mean RNFL thickness of 74.83 μm compared to 96.5 μm in early stage. Mean CMT was 205.5 μm for affected eyes and 255.13 μm for normal fellow eyes. Conclusion. RNFL and CMT were thinner in DUSN eyes compared to normal eyes. Late-stage disease had more pronounced thinning compared to early-stage patients. This thinning in RNFL and CMT may reflect the low visual acuity in patients with DUSN.

Zoonotic helminths affecting the human eye

Nowaday, zoonoses are an important cause of human parasitic diseases worldwide and a major threat to the socio-economic development, mainly in developing countries. Importantly, zoonotic helminths that affect human eyes (HIE) may cause blindness with severe socio-economic consequences to human communities. These infections include nematodes, cestodes and trematodes, which may be transmitted by vectors (dirofilariasis, onchocerciasis, thelaziasis), food consumption (sparganosis, trichinellosis) and those acquired indirectly from the environment (ascariasis, echinococcosis, fascioliasis). Adult and/or larval stages of HIE may localize into human ocular tissues externally (i.e., lachrymal glands, eyelids, conjunctival sacs) or into the ocular globe (i.e., intravitreous retina, anterior and or posterior chamber) causing symptoms due to the parasitic localization in the eyes or to the immune reaction they elicit in the host. Unfortunately, data on HIE are scant and mostly limited to case reports from different countries. The biology and epidemiology of the most frequently reported HIE are discussed as well as clinical description of the diseases, diagnostic considerations and video clips on their presentation and surgical treatment.

Molecular cloning of an immunogenic protein of Baylisascaris procyonis and expression in Escherichia coli for use in developing improved serodiagnostic assays

Larva migrans caused by Baylisascaris procyonis is an important zoonotic disease. Current serological diagnostic assays for this disease depend on the use of the parasite's larval excretory-secretory (ES) antigens. In order to identify genes encoding ES antigens and to generate recombinant antigens for use in diagnostic assays, construction and immunoscreening of a B. procyonis third-stage larva cDNA expression library was performed and resulted in identification of a partial-length cDNA clone encoding an ES antigen, designated repeat antigen 1 (RAG1). The full-length rag1 cDNA contained a 753-bp open reading frame that encoded a protein of 250 amino acids with 12 tandem repeats of a 12-amino-acid long sequence. The rag1 genomic DNA revealed a single intron of 837 bp that separated the 753-bp coding sequence into two exons delimited by canonical splice sites. No nucleotide or amino acid sequences present in the GenBank databases had significant similarity with those of RAG1. We have cloned, expressed, and purified the recombinant RAG1 (rRAG1) and analyzed its diagnostic potential by enzyme-linked immunosorbent assay. Anti-Baylisascaris species-specific rabbit serum showed strong reactivity to rRAG1, while only minimal to no reactivity was observed with sera against the related ascarids Toxocara canis and Ascaris suum, strongly suggesting the specificity of rRAG1. On the basis of these results, the identified RAG1 appears to be a promising diagnostic antigen for the development of serological assays for specific detection of B. procyonis larva migrans.

Baylisascaris Procyonis Induced Diffuse Unilateral Subacute Neuroretinitis in New York City

Diffuse unilateral subacute neuroretinitis (DUSN) secondary to raccoon roundworm (Baylisascaris procyonis) infection has been reported in rural and suburban areas of North America and Europe with extant raccoon populations. Here, we present a case of Baylisascaris-induced DUSN from the densely populated borough of Brooklyn in New York City and alert urban ophthalmologists to consider this etiology even in areas not typically thought to be associated with endemic risk factors. Infected raccoons also occur in urban settings, and urban patients may be exposed in surrounding areas. Most patients with Baylisascaris ocular larva migrans-DUSN will not have concomitant neurologic disease; this fact and larval neurotropism are both misconceptions regarding this infection.

The negative ERG: clinical phenotypes and disease mechanisms of inner retinal dysfunction

Inner retinal dysfunction is encountered in a number of retinal disorders, either inherited or acquired, as a primary or predominant defect. Fundus examination is rarely diagnostic in these disorders, although some show characteristic features, and careful electrophysiological assessment of retinal function is needed for accurate diagnosis. The ERG in inner retinal dysfunction typically shows a negative waveform with a preserved a-wave and a selectively reduced b-wave. Advances in retinal physiology and molecular genetics have led to a greater understanding of the pathogenesis of these disorders. This review summarizes current knowledge on normal retinal physiology, the investigative techniques used and the range of clinical disorders in which there is predominantly inner retinal dysfunction.

Diffuse unilateral subacute neuroretinitis: report of a case from the Indian subcontinent and the importance of immediate photocoagulation

PURPOSE

To report a case of DUSN from the Indian subcontinent and emphasize the importance of immediate photocoagulation.

METHOD

Review of case record.

RESULT

The referring ophthalmologist had photographed the subretinal worm but had not undertaken laser photocoagulation. On presentation to us the patient had features typical of DUSN but no worm could be detected despite repeated examinations. Failure to localize the worm at subsequent examinations resulted in only partial recovery of vision.

CONCLUSION

Whenever the nematode is detected, immediate laser photocoagulation of the worm is necessary as the migratory worm may be difficult to identify later on. This is necessary to prevent the otherwise natural decline in vision.

Central nervous system and eye manifestations of infection with Baylisascaris procyonis

Baylisascaris procyonis, a parasitic infection of raccoons, causes severe neurologic and ocular disease in humans when infectious eggs from raccoon feces are ingested. In the absence of a serologic test, definitive diagnosis is challenging but can be made by isolation of larvae in brain biopsy, direct visualization of the worm in the eye, or exclusion of other potential causes of eosinophilic meningoencephalitis. Currently, no effective treatment has been identified, making preventive efforts critical.

Late-stage diffuse unilateral subacute neuroretinitis: photocoagulation of the worm does not improve the visual acuity of affected patients

BACKGROUND AND OBJECTIVE

To evaluate the visual outcome following direct laser photocoagulation of the worm in patients with late-stage diffuse unilateral subacute neuroretinitis (DUSN).

PATIENTS AND METHODS

The study reports on 22 DUSN patients diagnosed in its late stage, in whom the worm was identified and subsequently destroyed by laser photocoagulation. Information gathered included initial and final visual acuities and length of follow-up. Statistical analysis was performed with the Paired Student's t-Test. A p value of less than 0.05 was considered significant.

RESULTS

After a mean follow-up of 13.1 months, visual acuity improved in 2 patients, remained unchanged in 19 patients and decreased in one patient. Comparison of the visual outcome before and after laser treatment was not statistically significant (p = 0.302).

CONCLUSION

Destruction of the worm by laser photocoagulation in eyes with late-stage DUSN does not improve the visual acuity of affected patients.

Diffuse unilateral subacute neuroretinitis in Africa

PURPOSE

Diffuse unilateral subacute neuroretinitis (DUSN) is well known in endemic areas of the southeastern United States, South America, and the northern Midwestern United States. Two different categories of nematodes, according to their length, are related to endemic areas. We report the first case of DUSN caused by a small nematode in Africa.

METHODS

We describe the case of a 12-year-old Senegalese girl who presented a long-standing diffuse unilateral subacute neuroretinitis and in whom the worm could be localized.

RESULTS

The length of the unidentified worm measured using the software of the fundus camera was approximately 600 microm. This measurement corresponds to the smaller nematode usually found in patients from the southeastern United States and South America.

CONCLUSION

Diffuse unilateral subacute neuroretinitis can also be observed in patients living in Africa.

Baylisascariasis

The raccoon roundworm, Baylisascaris procyonis, is the most common and widespread cause of clinical larva migrans in animals. In addition, it is increasingly recognized as a cause of devastating or fatal neural larva migrans in infants and young children and ocular larva migrans in adults. Humans become infected by accidentally ingesting infective B. procyonis eggs from raccoon latrines or articles contaminated with their feces. Two features distinguish B. procyonis from other helminthes that cause larva migrans: (i) its aggressive somatic migration and invasion of the central nervous system and (ii) the continued growth of larvae to a large size within the central nervous system. Typically, B. procyonis neural larva migrans presents as acute fulminant eosinophilic meningoencephalitis. Once invasion of the central nervous system has occurred, the prognosis is grave with or without treatment. To date, despite anthelmintic treatment of cases of B. procyonis neural larva migrans, there are no documented neurologically intact survivors. Epidemiologic study of human cases of neural larva migrans demonstrate that contact with raccoon feces or an environment contaminated by infective eggs and geophagia or pica are the most important risk factors for infection. In many regions of the United States, increasingly large populations of raccoons, with high rates of B. procyonis infection, live in close proximity to humans. Although documented cases of human baylisascariasis remain relatively uncommon, widespread contamination of the domestic environment by infected raccoons suggests that the risk of exposure and human infection is probably substantial. In the absence of early diagnosis or effective treatment, prevention of infection is the most important public health measure.

Clinical features and outcomes of patients with diffuse unilateral subacute neuroretinitis treated with oral albendazole

PURPOSE

To investigate the clinical features, visual function outcomes, and adverse events in patients with diffuse unilateral subacute neuroretinitis (DUSN) treated with high-dose oral albendazole.

DESIGN

Interventional case series.

METHODS

Twelve Brazilian patients, aged 7 through 36 years, with active DUSN in the early or late clinical stage, were recruited for this study between 1999 and 2001. A small variant motile worm was found in 4 (33.3%) of these cases. All patients were treated exclusively with high-dose oral albendazole (400 mg/d) for 30 days.

RESULTS

Improvement of visual acuity, visual field, and active ocular inflammatory signs was observed in all patients after 4 weeks of treatment (median follow-up: 3 years). Also, during the first weeks of treatment, evidence of worm inactivation was documented for the four patients with visible worms. No adverse drug side effects were observed in any of our cases during follow-up.

CONCLUSION

High-dose oral albendazole seems to be safe and beneficial for patients with DUSN.

Fatal Baylisascaris Larva Migrans in a Colony of Japanese Macaques Kept by a Safari-Style Zoo in Japan

A colony of Japanese macaques (Macaca fuscata fuscata) kept by a safari-style zoo in Japan experienced 9 sporadic cases of fatal neurological diseases, such as epilepsy and posterior paralysis, during the 12 yr from 1989 to 2001. This macaque colony consisted of approximately 30 animals, on average, during this period, and the macaques shared their living space with II American black bears (Ursus americanus) harboring zoonotic roundworms (Baylisascaris transfuga). Close to this enclosure, a cote for 2-3 raccoons (Procyon lotor) was placed, and raw sewage from this cote ran into a shallow drain in the area for macaques and bears. However, fecal examinations in recent years did not detect the infection of raccoons with zoonotic roundworms (Baylisascaris procyonis). Postmortem histological examination of the latest 2 ill macaques detected multifocal malacia in the brain; 2 ascarid larvae of 60 microm maximum width were encapsulated in the cerebrum and lungs of 1 of the animals. To determine the causative ascarid species of the fatal larva migrans, we analyzed 2 additional encapsulated Baylisascaris larvae collected from formalin-fixed lungs by morphological and molecular approaches. This sporadic outbreak is the second record of Baylisascaris larva migrans in animals in Japan.

Severe and fatal central nervous system disease in humans caused by Baylisascaris procyonis, the common roundworm of raccoons: a review of current literature

Baylisascaris procyonis, a parasitic infection of raccoons, causes severe neurologic disease in humans when infective eggs from raccoon feces are ingested. Definitive diagnosis is challenging, but can be made by isolation of larvae in brain biopsy or exclusion of other potential causes of eosinophilic meningoencephalitis. Prevention efforts are critical due to the lack of effective treatment.

Raccoon roundworm encephalitis

The raccoon roundworm, Baylisascaris procyonis, is increasingly recognized as a cause of zoonotic visceral, ocular, and neural larva migrans and, in particular, of devastating encephalitis in young children. Exposure occurs mainly at raccoon latrines, where large numbers of infective eggs may be accidentally ingested. Risk factors for infection include contact with raccoon latrines, pica/geophagia, age of <4 years, and male sex. The severity of central nervous system (CNS) disease depends on the number of eggs ingested, the extent and location of larval migration, and the severity of ensuing inflammation and necrosis. Diagnosis of Baylisascaris encephalitis is based on clinical CNS disease, peripheral and cerebrospinal fluid eosinophilia, deep white matter lesions visible by magnetic resonance imaging, and positive results of serologic tests. Treatment efficacy in clinical cases is poor, but albendazole prevents disease if given promptly after infection. Considering the seriousness of this disease and limitations of diagnosis and treatment, prevention of infection with eggs is of utmost importance.

Early-stage diffuse unilateral subacute neuroretinitis: improvement of vision after photocoagulation of the worm

PURPOSE

To evaluate the visual outcome after direct laser photocoagulation of the worm in patients with early-stage diffuse unilateral subacute neuroretinitis (DUSN).

METHODS

We report on four patients with DUSN diagnosed in its early stage, in whom the worm was identified and destroyed by laser photocoagulation.

RESULTS

In all the four cases, resolution of the inflammatory multifocal lesions was achieved within 1 month of treatment. After that period and during follow-up (mean 11.5 months), visual acuity improved in three eyes and remained unchanged in one eye.

CONCLUSION

The diagnosis of DUSN in its early stage followed by prompt location and destruction of the worm by photocoagulation may improve vision of affected patients.

Larva migrans by Baylisascaris transfuga: fatal neurological diseases in Mongolian jirds, but not in mice

Raccoon roundworms (Baylisascaris procyonis) and other Baylisascaris species cause patent or latent larva migrans (LM) in a variety of mammals and birds, including humans. It is not clear whether LM by Baylisascaris transfuga, roundworms of bears, is associated with clinical neurological disorders. To clarify this issue, ICR and BALB/c mice as well as Mongolian jirds (Meriones unguiculatus) were orally inoculated with 2,000-5,000 embryonated eggs of B. transfuga. In mice, the ascarid caused symptomatic LM of limited extent and duration, whereas the infection was fatal in jirds; i.e., they exhibited general signs such as severe depression and emaciation on days 8-11 postinfection (PI) and died, or they developed progressive and fatal neurological disorders after day 14 PI. Histological examination showed B. transfuga larvae in the brain of all mice and jirds examined, and the larvae collected from them developed to a size comparable with that of B. procyonis. There existed, however, critical differences in host reactions against larvae localized in the brain of mice and jirds; B. transfuga larvae found in mice were surrounded by granulomatous reactions and immobilized, whereas larvae found in jirds were free from any host reaction and mobile, causing extensive malacia.

Raccoon roundworm eggs near homes and risk for larva migrans disease, California communities

The raccoon roundworm, Baylisascaris procyonis, is increasingly recognized as a cause of serious or fatal larva migrans disease in humans and animals. We assessed the potential for infection in three northern California communities by determining the density and distribution of raccoon latrines, where transmission primarily occurs, and the prevalence of eggs at private residences. We collected fecal samples from 215 latrines and found that 44%-53% of the latrines contained B. procyonis eggs and that 16%-32% contained infective eggs. Among the properties surveyed, 28%-49% harbored at least one latrine that was positive for B. procyonis eggs. The latrine densities in these communities were higher than any previously reported. The presence of B. procyonis eggs in raccoon latrines was common, widespread, and closely associated with human habitation. Where raccoon densities are high, education of the public and removal of raccoons may be necessary.