Feline intralenticular Encephalitozoon cuniculi: three cases from California

Abstract

Case series summary: Three domestic shorthair cats from California presented to veterinary ophthalmologists with immature cataracts. Other presenting clinical signs included corneal edema, anisocoria, anterior uveitis, elevated intraocular pressure, blepharospasm and/or lethargy. All patients were immunocompromised due to concurrent diseases and/or immunomodulatory drugs. Diagnostics included serial comprehensive ophthalmic examinations with tonometry, ocular ultrasound, electroretinogram and testing for other causes of feline uveitis. Testing for Encephalitozoon cuniculi included serology, histopathology and/or PCR of aqueous humor, lens material or paraffin-embedded whole eye. Treatments included antiparasitic medication, anti-inflammatory medication and supportive care in all three cases. Surgical treatment included enucleation (one case), bilateral phacoemulsification and unilateral intraocular lens placement (one case) and bilateral phacoemulsification with bilateral endolaser ciliary body ablation and bilateral intraocular lens implantation (one case). Both cats for which serologic testing for E cuniculi was performed were positive (1:64-1:4096). In all cats, diagnosis of intraocular E cuniculi was based on at least one of the following: lens histopathology or PCR of aqueous humor, lens material or paraffin-embedded ocular tissue. The clinical visual outcome was best in the patient undergoing phacoemulsification at the earliest stage of the cataract.

Relevance and novel information: Encephalitozoon cuniculi should be considered as a differential cause of cataracts and uveitis in cats in California, the rest of the USA and likely worldwide.

Keywords: Encephalitozoon cuniculi; cataracts; phacoemulsification; uveitis.

Figure 1

Case 1: (a,b,d) clinical photos and (c) ultrasound image. Pupils were pharmacologically dilated with 1% tropicamide ophthalmic in (a), (b) and (d) (Akorn). (a,b) OD focal anterior subcapsular to anterior cortical cataract and focal pigment on lens capsule. The lens capsule appeared focally wrinkled at the site of the cataract clinically, but no capsular tears were visible on slit-lamp examination. (c) OS: vertical ultrasound image showing echoic dorsal anterior subcapsular cataract with anterior cortical to nuclear extension. The lens capsule was interpreted to be intact via ultrasound. Other than lens abnormalities, anterior and posterior segments were within normal limits. (d) OS: clinical photo showing retro-illumination of focal subcapsular to anterior cortical cataract (dark lenticular opacities). Images courtesy of Dr Mitzi Zarfoss

Figure 2

Case 3. Both pupils were dilated with 1% tropicamide (Akorn). (a) OD (initial examination): no aqueous flare, mild keratic precipitates, incipient peripheral cortical cataracts, fluorescein negative. (b) OS (first recheck after 3 weeks): mild iris thickening, trace aqueous humor cells, keratic precipitates, incipient peripheral cortical cataract, fluorescein negative. Images courtesy of Dr Holly Hamilton

Figure 3

Histopathology. (a) Case 3, hematoxylin and eosin, × 2 magnification showing lymphoplasmacytic iritis. (b) Case 3, hematoxylin and eosin, × 4 magnification showing regionally severe equatorial lens fiber degeneration. (c) Case 3, hematoxylin and eosin, × 40 magnification showing innumerable Encephalitozoon cuniculi organisms within the lens, with swollen lens fibers/Morgagnian globules (top center) and a few neutrophils outside the capsule (upper left). (d) Case 1, histopathology. Ziehl–Neelsen acid fast stain, × 60 magnification, lens material and E cuniculi organisms. Images (a), (b) and (c) courtesy of Dr Christopher Reilly, DACVP. Image (d) courtesy of Dr Barbara Nell