Risky business: influence of eye flukes on use of risky microhabitats and conspicuousness of a fish host.

A prerequisite for a parasitic manipulation to be considered adaptive is that it confers a fitness benefit to the parasite, such as increased transmission to another host. These manipulations can involve alterations to a wide range of host phenotypic traits, including microhabitat choice. Eye flukes of the trematode family Diplostomidae use fish as intermediate hosts and must be transmitted by predation to a piscivorous bird. In New Zealand, the diplostomid Tylodelphys darbyi infects the eyes of a widespread endemic freshwater fish, the common bully Gobiomorphus cotidianus. Within the eye, T. darbyi metacercariae achieve large sizes and move freely about the aqueous and vitreous humors of the eye. We hypothesized that higher intensities of T. darbyi would (i) cause bullies to show increased activity and spend more time moving about in open space (i.e., more conspicuous, risky microhabitat) and (ii) reduce their ability to compete for shelter with fish harboring lower infection levels. Our experiments showed that heavily infected fish were more active and spent more time in the open, although the effect was age-dependent, with immature fish displaying decreases in activity and time spent in the open with increasing intensities of infection. We also demonstrated that heavily infected female bullies have a lower probability of using shelter, but males show the opposite pattern. It is possible that using more risky microhabitats increases the likelihood of the fish being eaten by the parasite's predatory avian definitive hosts. However, our findings indicate that age- and sex-dependent effects call for a more nuanced interpretation.

Subretinal echinococcosis: a case report.

BACKGROUND: Echinococcosis is a dangerous zoonotic parasitic disease. Ocular echinococcosis is very rare, especially the hydatid cysts in subretinal space. We present a case of subretinal echinococcosis and management. CASE PRESENTATION: A 37-year-old man with subretinal echinococcosis who developed panuveitis and visual impairment. The patient lives on agriculture and animal husbandry, which made him susceptible to parasitic infection. He had severe panuveitis and blurred vision on arrival at hospital. According to his ocular examination and systemic review, the subretinal echinococcosis diagnosis was made. The patient received pars plana lensectomy and pars plana vitrectomy. The lesion underneath his retina was removed, and histopathology examination confirmed the subretinal echinococcosis diagnosis. CONCLUSIONS: Echinococcosis is a dangerous zoonotic parasitic disease in pastoral areas. Ocular echinococcosis is usually secondary to systemic infection. Although the incidence is rare, the disease could lead to destructive visual function impairment.

Toxocara optic neuropathy after ingestion of raw meat products.

PURPOSE: To report Toxocara optic neuropathy in five men with histories of ingestion of raw meat, liver, or blood. CASE REPORT: Five men in their 30s to 60s presented with unilateral visual disturbance. All five had a history of ingesting raw meat, liver, or blood products. All five men presented with optic disc edema and three also showed granulomatous infiltration of the retina. With Goldmann or Humphrey visual field testing, two patients showed central scotomas and two exhibited arcuate defects. Serum eosinophil count and total IgE were elevated in four patients. Serum enzyme-linked immunosorbent assay testing was positive for Toxocara canis IgG in all five cases. CONCLUSIONS: This report shows the variable clinical presentations of Toxocara optic neuropathy and the importance of questioning for a history of eating raw meat and blood products as a risk factor.

Ivermectin for onchocercal eye disease (river blindness).

BACKGROUND: It is believed that ivermectin (a microfilaricide) could prevent blindness due to onchocerciasis. However, when given to everyone in communities where onchocerciasis is common, the effects of ivermectin on lesions affecting the eye are uncertain and data on whether the drug prevents visual loss are unclear. OBJECTIVES: The aim of this review was to assess the effectiveness of ivermectin in preventing visual impairment and visual field loss in onchocercal eye disease. The secondary aim was to assess the effects of ivermectin on lesions affecting the eye in onchocerciasis. SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 3), MEDLINE (January 1950 to April 2012), EMBASE (January 1980 to April 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 2 April 2012. SELECTION CRITERIA: We included randomised controlled trials with at least one year of follow-up comparing ivermectin with placebo or no treatment. Participants in the trials were people normally resident in endemic onchocercal communities with or without one or more characteristic signs of ocular onchocerciasis. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed trial quality. We contacted study authors for additional information. As trials varied in design and setting, we were unable to perform a meta-analysis. MAIN RESULTS: The review included four trials: two small studies (n = 398) in which people with onchocercal infection were given one dose of ivermectin or placebo and followed up for one year; and two larger community-based studies (n = 4941) whereby all individuals in selected communities were treated every six or 12 months with ivermectin or placebo, whether or not they were infected, and followed for two to three years. The studies provide evidence that treating people who have onchocerciasis with ivermectin reduces the number of microfilariae in their skin and eye(s) and reduces the number of punctate opacities. There was weaker evidence that ivermectin reduced the risk of chorioretinitis. The studies were too small and of too short a duration to provide evidence for an effect on sclerosing keratitis, iridocyclitis, optic nerve disease or visual loss. One community-based study in communities mesoendemic for the savannah strain of O.volvulus provided evidence that annual mass treatment with ivermectin reduces the risk of new cases of optic nerve disease and visual field loss. The other community-based study of mass biannual treatment of ivermectin in communities affected by the forest strain of O.volvulus demonstrated reductions in microfilarial load, punctate keratitis and iridocyclitis but not sclerosing keratitis, chorioretinitis, optic atrophy or visual impairment. The study was underpowered to estimate the effect of ivermectin on visual impairment and other less frequent clinical signs. The studies included in this review reported some adverse effects, in particular an increased risk of postural hypotension in people treated with ivermectin. AUTHORS' CONCLUSIONS: The lack of evidence for prevention of visual impairment and blindness should not be interpreted to mean that ivermectin is not effective, however, clearly this is a key question that remains unanswered. The main evidence for a protective effect of mass treatment with ivermectin on visual field loss and optic nerve disease comes from communities mesoendemic for the savannah strain of O.volvulus. Whether these findings can be applied to communities with different endemicity and affected by the forest strain is unclear. Serious adverse effects were rarely reported. None of the studies, however, were conducted in areas where people are infected with Loa loa (loiasis).

Ocular toxocariasis--United States, 2009-2010.

Ocular toxocariasis (OT) is caused by the zoonotic parasites Toxocara canis and Toxocara cati, roundworms of dogs and cats. Persons become infected with Toxocara when they unintentionally ingest embryonated eggs that have been shed in the feces of infected animals. Although OT is uncommon, it most often affects young children and can cause debilitating ophthalmologic disease, including blindness. Previous studies of OT in the United States have been conducted in single institutions. This report describes the results of a web-based survey distributed to uveitis, retinal, and pediatric ophthalmology specialists nationwide to collect epidemiologic, demographic, and clinical information on patients with OT. A total of 68 patients were newly diagnosed with OT from September 2009 through September 2010. Among the 44 patients for whom demographic information was available, the median patient age was 8.5 years (range: 1-60 years), and 25 patients (57%) lived in the South at the time of diagnosis. Among 30 patients with reported clinical data, the most common symptom was vision loss, reported by 25 (83%) patients; of these, 17 (68%) suffered permanent vision loss. The results of this first national level survey demonstrate that OT transmission continues to occur in the United States, frequently affecting children and causing permanent vision loss in the majority of reported patients. Good hygiene practices, timely disposal of pet feces, and routine deworming of pets are strategies necessary to reduce OT in humans.

Occlusion of the central retinal artery in Plasmodium falciparum malaria.

A 40-year-old woman presented with sudden painless diminution of vision in left eye. The best corrected visual acuity was 20/20 in the right eye and 20/400 in the left eye. The vision loss occurred 3 days after the onset of fever with chills and rigour. Rapid diagnostic test and peripheral blood smear examination revealed Plasmodium falciparum malaria. The left eye fundus showed a pale disc with marked attenuation of arterioles. A detailed systemic evaluation including cardiovascular, haematological and angiographic assessments was performed which did not reveal any abnormality. A diagnosis of central retinal artery occlusion (CRAO) associated with uncomplicated P. falciparum malaria was made. In this communication, we report that acute loss of vision in a patient with P. falciparum malaria, CRAO needs to be ruled out.

Comparative Brain Morphology of the Greenland and Pacific Sleeper Sharks and its Functional Implications.

In cartilaginous fishes, variability in the size of the brain and its major regions is often associated with primary habitat and/or specific behavior patterns, which may allow for predictions on the relative importance of different sensory modalities. The Greenland (Somniosus microcephalus) and Pacific sleeper (S. pacificus) sharks are the only non-lamnid shark species found in the Arctic and are among the longest living vertebrates ever described. Despite a presumed visual impairment caused by the regular presence of parasitic ocular lesions, coupled with the fact that locomotory muscle power is often depressed at cold temperatures, these sharks remain capable of capturing active prey, including pinnipeds. Using magnetic resonance imaging (MRI), brain organization of S. microcephalus and S. pacificus was assessed in the context of up to 117 other cartilaginous fish species, using phylogenetic comparative techniques. Notably, the region of the brain responsible for motor control (cerebellum) is small and lacking foliation, a characteristic not yet described for any other large-bodied (>3 m) shark. Further, the development of the optic tectum is relatively reduced, while olfactory brain regions are among the largest of any shark species described to date, suggestive of an olfactory-mediated rather than a visually-mediated lifestyle.

Tie2 activation promotes choriocapillary regeneration for alleviating neovascular age-related macular degeneration.

Choriocapillary loss is a major cause of neovascular age-related macular degeneration (NV-AMD). Although vascular endothelial growth factor (VEGF) blockade for NV-AMD has shown beneficial outcomes, unmet medical needs for patients refractory or tachyphylactic to anti-VEGF therapy exist. In addition, the treatment could exacerbate choriocapillary rarefaction, necessitating advanced treatment for fundamental recovery from NV-AMD. In this study, Tie2 activation by angiopoietin-2-binding and Tie2-activating antibody (ABTAA) presents a therapeutic strategy for NV-AMD. Conditional Tie2 deletion impeded choriocapillary maintenance, rendering eyes susceptible to NV-AMD development. Moreover, in a NV-AMD mouse model, ABTAA not only suppressed choroidal neovascularization (CNV) and vascular leakage but also regenerated the choriocapillaris and relieved hypoxia. Conversely, VEGF blockade degenerated the choriocapillaris and exacerbated hypoxia, although it suppressed CNV and vascular leakage. Together, we establish that angiopoietin-Tie2 signaling is critical for choriocapillary maintenance and that ABTAA represents an alternative, combinative therapeutic strategy for NV-AMD by alleviating anti-VEGF adverse effects.

Intraocular angiostrongyliasis: clinical findings, treatments and outcomes.

Ocular angiostrongyliasis, diagnosed by identification of Angiostrongylus cantonensis in any part of the eye, is a very rare manifestation. We report seven cases of intraocular angiostrongyliasis in Srinagarind Hospital, Khon Kaen University, Thailand. From a total of 654 cases of angiostrongyliasis diagnosed between January 1995 and April 2005, 7 cases (1.1%) with ocular manifestations were found. Four men and three women were diagnosed, with a mean age of 32.1 years (range 21-46 years). All of the patients lived in the northeast of Thailand and acquired the infection by eating raw Pila spp. snails, the intermediate host of A. cantonensis. The incubation period lasted from 2 weeks to 2 months. The most common symptom, blurred vision without eosinophilic meningitis, occurred as a presenting symptom in five cases. The other two cases presented with eosinophilic meningitis prior to development of poor visual acuity. Both cases had papilloedema, neck stiffness and eosinophilia without fever. The visual acuity of the patient was mostly lower than 2/60 and, evidently, visual impairment in all patients was caused by retinal pigment epithelial defects. All cases had only one immature A. cantonensis worm in the eye, with the most common site being the intravitreous area. Several treatments, including oral prednisolone, topical prednisolone, argon laser, diode laser, Nd:YAG laser, surgical removal of the parasite and combination therapy, were used. There is no evidence that surgical and laser interventions improve the course of the disease, and both have associated risks. Visual outcome depends on the initial visual defects.

Visual function in human ocular toxoplasmosis.

AIM: To assess functional impairment in terms of visual acuity reduction and visual field defects in inactive ocular toxoplasmosis. METHODS: 61 patients with known ocular toxoplasmosis in a quiescent state were included in this prospective, cross-sectional study. A complete ophthalmic examination, retinal photodocumentation and standard automated perimetry (Octopus perimeter, program G2) were performed. Visual acuity was classified on the basis of the World Health Organization definition of visual impairment and blindness: normal (> or =20/25), mild (20/25 to 20/60), moderate (20/60 to 20/400) and severe (<20/400). Visual field damage was correspondingly graded as mild (mean defect <4 dB), moderate (mean defect 4-12 dB) or severe (mean defect >12 dB). RESULTS: 8 (13%) patients presented with bilateral ocular toxoplasmosis. Thus, a total of 69 eyes was evaluated. Visual field damage was encountered in 65 (94%) eyes, whereas only 28 (41%) eyes had reduced visual acuity, showing perimetric findings to be more sensitive in detecting chorioretinal damage (p<0.001). Correlation with the clinical localisation of chorioretinal scars was better for visual field (in 70% of the instances) than for visual acuity (33%). Moderate to severe functional impairment was registered in 65.2% for visual field, and in 27.5% for visual acuity. CONCLUSION: In its quiescent stage, ocular toxoplasmosis was associated with permanent visual field defects in >94% of the eyes studied. Hence, standard automated perimetry may better reflect the functional damage encountered by ocular toxoplasmosis than visual acuity.

Toxoplasmic retinochoroiditis presenting in childhood: clinical findings in a UK survey.

AIM: To compare the clinical findings in children with symptomatic toxoplasmic ocular lesions attributable to infection acquired before or after birth. METHODS: Cases were prospectively ascertained for 24 months through national surveillance units and reference laboratories in the British Isles. Age and presenting symptoms, site of lesion and visual impairment in children who were classified as acquiring infection either before or after birth on the basis of clinical and serological findings were compared. RESULTS: 31 children had toxoplasmic retinochoroiditis, 15 had congenital infection and all but three of these presented before the age of 4 years. The remaining 16 children acquired toxoplasmosis postnatally, and 14 of 16 presented after the age of 10 years. A further four children had retinochoroiditis due to other causes. The presence of bilateral, multiple or posterior pole lesions did not distinguish between the two groups, but most children (16/19; 84%) presenting with acute ocular symptoms had postnatally acquired infection. Unilateral visual impairment (Snellen < or =6/18) was equally prevalent in the two groups (4/9 before birth v 7/16 after birth; p>0.5). Only two children had bilateral visual impairment, both of whom had congenital infection. No child was blind. CONCLUSIONS: About 50% of children with ocular lesions due to toxoplasmosis had postnatal infection. Retinochoroidal lesions due to infection before and after birth were indistinguishable. The prognosis for bilateral visual function was good, regardless of when infection was acquired.

Acanthamoeba keratitis challenges a case report.

Acanthamoeba keratitis is a rare, chronic, mainly contact lens-related infection caused by a free-living amoeba found ubiquitously in water and soil. A case of a 9-year-old child, who presented to our clinic with painful, red left eye, associated with photophobia, and decreased visual acuity, wais reported. The clinical examination revealed a discoid opacity inferiorly bounded by a dense, gray infiltrate. The progressive nature of the corneal infiltrate, the epithelial defect, and the lack of response to treatment was highly suggestive for Acanthamoeba keratitis. The distinctiveness of this case was the presence of Acanthamoeba keratitis in a child without a history of trauma or contact lens usage, the lack of an appropriate diagnosis and management of this vision-threatening infection.

Results of penetrating keratoplasty for visual rehabilitation after Acanthamoeba keratitis.

PURPOSE: To assess the results of penetrating keratoplasty in quiet eyes after resolution of Acanthamoeba keratitis. DESIGN: A retrospective interventional case series. METHODS: Penetrating keratoplasty was undertaken in 13 eyes of 13 patients with an average age of 29 +/- 13 years and a history of Acanthamoeba keratitis that was diagnosed by culture and/or confocal microscopy between January 1995 and September 2004. All eyes were observed for at least 3 months (average, 5 months) after the discontinuation of antiamebic therapy that had been administered for at least 4.5 months. In vivo confocal microscopy was used to ensure that no residual amoeba were present before the operation. Two keratoplasties were combined with a valve insertion; five keratoplasties were combined with cataract extraction, and one keratoplasty was preceded by a ciliary laser ablation. RESULTS: Postoperative best-corrected visual acuity ranged from 20/40 to 20/15, with the exception of one eye with advanced glaucoma that did not improve from a preoperative vision of light perception. No eye experienced rejection or amoebic recurrences, and 12 grafts remained clear throughout the follow-up period (8 months to 9 years; median, 23 months). One graft failed at 4 months because of uncontrolled glaucoma. The eye was regrafted, and the graft remained clear during the 28 months of follow-up evaluation. Two eyes with preoperatively diagnosed glaucoma needed subsequent surgery to control their intraocular pressure. CONCLUSION: Penetrating keratoplasty for visual restoration after Acanthamoeba keratitis appears to have an excellent long-term prognosis, provided amoebic infection has resolved and concurrent glaucoma is controlled.

A randomized, double-blind, controlled trial of the effects of ivermectin at normal and high doses, given annually or three-monthly, against Onchocerca volvulus: ophthalmological results.

A three-year randomized, controlled, double-blind trial was conducted in Cameroon to determine whether ivermectin, given at three-monthly intervals and/or at high doses (800 microg/kg), had a greater effect on adult Onchocerca volvulus than standard doses (150 microg/kg annually). As several patients complained of transitory subjective visual problems after treatment, some of them being of an unexpected type, we organized two series of detailed ophthalmological examinations to evaluate whether they were associated with ocular lesions. Analysis showed that these complaints were significantly more frequent in the two groups treated with high doses of ivermectin than in the reference group. In the ophthalmological examinations, the only differences recorded between the groups were a lower prevalence and mean number of microfilariae in the anterior chamber in the groups treated three-monthly, and, at the first examination round, a higher prevalence of early lesions of the iris in the group treated at high doses annually. These findings do not allow us to explain the cause of the transitory ocular complaints, nor why they were more frequent in the groups treated at high doses. However, one may conclude that using doses of ivermectin higher than the standard one should be considered with caution.

First reported case of intraocular Gnathostoma spinigerum in Cambodia.

A live intraocular nematode was identified from a 37 year-old man presented with iritis, pain, redness, lacrimation, swelling, vision loss and intermittent blindness during many hours per day of the left eye. By using slit lamp examination, a worm was removed from iris in an ophthalmology outpatient department setting and sent to the Medical Microbiology Laboratory, Institut Pasteur du Cambodge. Gnathostoma spinigerum was identified, based on its typical morphology via microscopic examination. Based on our diagnosis, the patient was treated by oral albendazole and responded well to this therapy.

Onchocerciasis in Malawi. 2. Subjective complaints and decreased weight in persons infected with Onchocerca volvulus in the Thyolo highlands.

In the course of an onchocerciasis survey in southern Malawi, body weight was recorded for 10,335 persons aged 20 years and older, and the body mass index was calculated for 5572. A history of symptomatic complaints was elicited from 5653 persons 20 years of age and older. Persons with microfilariae in the skin snips weighed significantly less than persons with negative skin snips. Symptomatic complaints of musculoskeletal pains, itching, dizziness and poor vision were reported more commonly in the group with microfilariae. These findings suggest that onchocerciasis should no longer be considered a disease affecting the eye and skin only but an infection which produces systemic effects as well. Systemic effects of onchocerciasis may lessen productivity of an endemic region by a process distinct from the effects of visual impairment.

Onchocerciasis in Malawi. 1. Prevalence, intensity and geographical distribution of Onchocerca volvulus infection in the Thyolo highlands.

Skin snips from 23,373 persons living in the Thyolo (formerly Cholo) highlands focus of southern Malawi showed infection with Onchocerca volvulus to be unevenly distributed within the highland area. In the centre of the focus most adults were infected, though intensity of infection was light, not exceeding a geometric mean of 8 microfilariae per mg of skin. It was estimated that 327,000 persons live in areas where prevalence of infection exceeds 10% and, of these, 94,500 persons over the age of one year are infected with O. volvulus. There is a significant relationship between infection with O. volvulus and bilateral blindness in the Thyolo focus, although the number of persons blind from onchocerciasis is probably less than 300.