Encephalitozoon cuniculi infection in cats: European guidelines from the ABCD on prevention and management.

OVERVIEW: Encephalitozoon cuniculi is a common obligate intracellular microsporidian parasite of rabbits that is increasingly recognised as a pathogen of cats and other mammalian species. These guidelines aim to review the literature on feline E cuniculi infection and provide recommendations on prevention and management. INFECTION IN CATS: E cuniculi infection should be considered as a differential diagnosis in cases of feline uveitis and cataract formation. It is not significantly associated with either chronic kidney disease or meningoencephalitis. E cuniculi infection is more common in stray or feral cats than in pet cats. DIAGNOSIS AND TREATMENT: Serological tests for antibody detection in the blood are easy to perform and can be useful for diagnosis, but their specificity is low as antibodies have been found in apparently healthy cats. PCR appears to be more sensitive than histopathology for diagnosis, and is more sensitive when performed on cataractous lenses compared with aqueous humour, although ease of sampling is an obvious limitation. Treatment is with fenbendazole for 3 weeks and phacoemulsification to remove microsporidia from cataractous lenses. ZOONOTIC RISK: E cuniculi is a potential zoonotic agent, and there is a particular risk to immunocompromised humans posed by infected rabbits. Albeit infrequent, spore shedding has been identified in cats, so care should be taken around infected cats.

Cataract formation associated with ocular toxocariasis.

PURPOSE: To report the clinical features of cataracts in eyes with ocular toxocariasis. SETTING: Department of Ophthalmology, Seoul National University Bundang Hosptal, Seongnam, South Korea. DESIGN: Retrospective observational case series. METHODS: The clinical diagnosis of ocular toxocariasis was based on the following characteristic features: retinal granuloma with or without ocular inflammation and positive results in serum antibody enzyme-linked immunosorbent assay. Patients younger than 60 years who presented with a unilateral cataract and were diagnosed with ocular toxocariasis between January 2009 and January 2012 were included. Demographic and ocular examination data for all patients showing atypical cataract features were collected. All cataracts were documented with anterior segment photography. RESULTS: Seven of 83 patients (8.4%) presented with an atypical cataract in the eye with ocular toxocariasis only. The mean patient age was 49.7 years ± 8.3 (SD) (range 38 to 59 years). All patients had small, round, white lens opacities resembling retinal granulomas. The granuloma-like opacities were located primarily in the lens midperiphery and in the subcapsular level. The lens opacity migrated in 1 patient. CONCLUSIONS: Ocular toxocariasis can cause a cataract with distinctive clinical features. These cataracts show a granuloma-like opacity primarily in the posterior subcapsular level; the opacity can migrate. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Clinical manifestations of ocular toxoplasmosis.

Clinical manifestations of ocular toxoplasmosis are reviewed. Findings of congenital and acute acquired ocular toxoplasmosis include retinal scars, white-appearing lesions in the active phase often associated with vitritis. Complications can include fibrous bands, secondary serous or rhegmatogenous retinal detachments, optic neuritis and neuropathy, cataracts, increased intraocular pressure during active infection, and choroidal neovascular membranes. Recurrences in untreated congenital toxoplasmosis occur in teenage years. Manifestations at birth are less severe, and recurrences are fewer in those who were treated promptly early in the course of their disease in utero and in the first year of life. Severe retinal involvement is common at diagnosis of symptomatic congenital toxoplasmosis in the United States and Brazil. Acute acquired infections also may be complicated by toxoplasmic retinochoroiditis, with recurrences most common close to the time of acquisition. Suppressive treatment can reduce recurrent disease.

Eye fluke-induced cataracts in natural fish populations: is there potential for host manipulation?

Manipulation of host phenotype (e.g. behaviour, appearance) is suggested to be a common strategy to enhance transmission in trophically transmitted parasites. However, in many systems, evidence of manipulation comes exclusively from laboratory studies and its occurrence in natural host populations is poorly understood. Here, we examined the potential for host manipulation by Diplostomum eye flukes indirectly by quantifying the physiological effects of parasites on fish. Earlier laboratory studies have shown that Diplostomum infection predisposes fish to predation by birds (definitive hosts of the parasites) by reducing fish vision through cataract formation. However, occurrence of cataracts and the subsequent potential for host manipulation in natural fish populations has remained poorly explored. We studied the occurrence of eye fluke-induced cataracts from 7 common fish species (Gymnocephalus cernuus, Rutilus rutilus, Leuciscus leuciscus, Alburnus alburnus, Osmerus eperlanus, Coregonus lavaretus and Gasterosteus aculeatus) from the Bothnian Bay in the Baltic Sea. We found that the parasite-induced cataracts were common in fish and they also reached high levels which are likely to predispose fish to predation. However, we observed such cataracts only in species with the highest parasite abundances, which suggests that only certain hosts may be strongly affected by the infection.

Priming of host resistance to protect cultured rainbow trout Oncorhynchus mykiss against eye flukes and parasite-induced cataracts.

In the present study, immunologically naive rainbow trout Oncorhynchus mykiss were experimentally exposed to a low-level Diplostomum spathaceum (Trematoda) infection to stimulate acquired resistance and, along with unexposed controls, were subsequently exposed to natural infection for 8 weeks. The priming of the host resistance, designed to simulate a procedure applicable in aquaculture, decreased the number of establishing parasites compared to untreated controls by the end of the experiment. This effect was slow and did not protect the fish against the parasite-induced cataracts. The results suggest that this type of priming of host resistance is probably inefficient in preventing the deleterious effects of D. spathaceum infection in aquaculture conditions.

Quantitative genetic architecture of parasite-induced cataract in rainbow trout, Oncorhynchus mykiss.

Parasites impose costs on their hosts. The capability to fight against them is of great advantage, but may also be traded off with other traits. Although often observed at the phenotypic level, our knowledge of the extent to which such trade-offs are genetically determined is relatively poor. We tested this possibility with a farmed rainbow trout population suffering from natural Diplostomum spp. infections that cause cataracts in fish. We estimated the heritability of cataract severity and examined phenotypic and genetic correlations between cataract and a set of performance traits measured three times during a 3-year rearing period. A cataract score was used as an indicator of the host's capability to resist and/or tolerate the parasite. Our results showed moderate heritability for the cataract. Nevertheless, we found no evidence for a genetic or phenotypic trade-off between parasite resistance/tolerance and the measured performance traits. Initial body weight was not correlated with the cataract score. Phenotypic and genetic correlations of cataract severity with body mass and condition measured in the second and third year were strongly negative, indicating reduced growth and condition in fish with a high cataract score. The reduced body size and condition in cataract-bearing fish were probably reflected in the phenotypic association between a high cataract score and delayed maturity age in females. Put together, our study did not provide evidence of genetic or phenotypic trade-offs between Diplostomum resistance/tolerance and a number of performance traits. Therefore, selection for lessened Diplostomum-caused cataracts is unlikely to have a negative impact on the studied performance traits.

Acanthamoeba keratitis--importance of the early diagnosis.

This is a case report of Acanthamoeba as a causative agent of keratitis at the Department of Ophthalmology, University Hospital Rijeka. Delay in treatment led to an advanced stage of the disease with multiple complications. Initially, presented symptoms were similar to those of herpetic keratitis. In the mean time progression of the disease led to a cloudy cornea with a stromal ring infiltrate, poor vision, elevated intraocular pressure, a mature cataract and finally corneal melt. Corneal scrapings were obtained from a 28 years old female patient, wearing soft contact lenses and with poor lens hygiene. Acanthamoeba cysts were identified by the cytological examination. Culture of the corneal scraping had confirmed Acanthamoeba as the etiological agent. Making the diagnosis of Acanthamoeba is difficult. We presented this case of delayed diagnosis and unfavorable outcome as a reminder that clinical suspicion remains the most important diagnostic tool. Contact lens wears with a new diagnosis of herpes simplex keratitis are in high risk group, especially those with significant pain or poor response to conventional therapy. We also wanted to point out the possibility of an early, prompt and inexpensive diagnosis with the cytological examination.

Freshwater sponge spicules: a new agent of ocular pathology

In a recent outbreak of human ocular injuries that occurred in the town of Araguatins, at the right bank of Araguaia river, state of Tocantins, Brazil, along the low water period of 2005, two patients (8 and 12-year-old boys) presented inferior adherent leukoma in the left eye (OS), and peripherical uveites, with snowbanking in the inferior pars plana. The third one (13-year-old girl) showed posterior uveites in OS, also with snowbanking. Histopathological analysis of lensectomy material from the three patients and vitrectomy from the last one revealed several silicious spicules (gemmoscleres) of the freshwater sponges Drulia uruguayensis and D. ctenosclera. This work brings material evidences, for the first time in the literature, that freshwater sponge spicules may be a surprising new etiological agent of ocular pathology.

Freshwater sponge spicules: a new agent of ocular pathology.

In a recent outbreak of human ocular injuries that occurred in the town of Araguatins, at the right bank of Araguaia river, state of Tocantins, Brazil, along the low water period of 2005, two patients (8 and 12-year-old boys) presented inferior adherent leukoma in the left eye (OS), and peripherical uveites, with snowbanking in the inferior pars plana. The third one (13-year-old girl) showed posterior uveites in OS, also with snowbanking. Histopathological analysis of lensectomy material from the three patients and vitrectomy from the last one revealed several silicious spicules (gemmoscleres) of the freshwater sponges Drulia uruguayensis and D. ctenosclera. This work brings material evidences, for the first time in the literature, that freshwater sponge spicules may be a surprising new etiological agent of ocular pathology.

Surgical removal of cataracts due to Diplostomum species in Gulf sturgeon (Acipenser oxyrinchus desotoi).

Twenty 6-yr-old (1995-yr-class) Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi) were diagnosed as having bilateral cataracts. Histopathologic assessment of the lenses of two of the fish revealed the presence of a diplostomid trematode. Pharmacological treatment of the trematodes may be effective for killing the parasites, but the damage to the lenses and resulting cataracts are nonreversible. Because these animals were to be used in a subsequent study as sentinels in the natural environment, it was necessary to return the animals' vision to as close to normal as possible. Electroretinograms were performed on each fish's eyes to ensure that retinal function was present. Cataracts then were surgically removed by phacoemulsification and aspiration. The animals tolerated the surgical procedures well. This report is the first known report of surgical correction of cataracts in sturgeon species. It also is the first known attempt to correct vision problems in fish being returned to the wild.

Eye fluke-induced cataract formation in fish: quantitative analysis using an ophthalmological microscope.

We examined the parasite-induced cataract formation in rainbow trout (Oncorhynchus mykiss) using slit-lamp microscopy to determine the relationship between cataract intensity and number of Diplostomum spathaceum parasites that were established in the lens. Cataract intensity increased significantly with parasite burden, but was also affected by the pattern of exposure to the parasite cercariae. The slit-lamp methodology proved useful in scoring the cataracts since it provides a 3-dimensional view into the lens and gives an actual picture of the location and intensity of the cataracts, which allows detailed investigations of mechanisms underlying cataract formation in various fish species. Potential applications of the method in fish farming and parasitological studies are discussed.

Parasite resistance and avoidance behaviour in preventing eye fluke infections in fish.

This paper examines the efficiency of acquired resistance in protecting the fish host, rainbow trout (Oncorhynchus mykiss), against the trematode parasite Diplostomum spathaceum, and the hypothesis that fish recognize areas where infective stages are aggregated and show avoidance behaviour. We found that when fish with a low level of infection were held in restricted cages in natural conditions they became infected and developed cataracts as a result of this infection. This suggests that acquired resistance is insufficient in protecting fish against the parasite or the deleterious effects of infection in conditions where fish could not avoid the parasite. Behavioural experiments in the laboratory showed that fish reacted to the parasite cercariae by avoiding the infection source, which decreased the rate of parasite establishment. We conclude that by using a combination of behavioural avoidance and physiological resistance, fish could defend against the parasite more effectively.

Encephalitozoonosis (nosematosis) causing bilateral cataract in a rabbit.

Bilateral cataract due to a microsporidan believed to be Encephalitozoon cuniculi (also called Nosema cuniculi) is described as an incidental finding in a laboratory rabbit. The route of infection and the significance of the findings are discussed. This is apparently the first report of cataract due to this cause.