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October 2022

Animal: Domestic rabbit (Oryctolagus cuniculus), 9-month-old, female.

Organ: Right eye.

History: The right eye was enucleated and sent for histopathologic examination due to suspected uveitis of two weeks of duration. There were no other remarkable findings on clinical examination.

Gross findings: There was a focal and extensive white opacity visualized through the cornea. Upon cut section, the opacity corresponded to ruptured lens proptosing to the anterior chamber, which was filled with whitish and dense exudate extending to the adjacent uvea.  Anterior and posterior synechiae was evidenced and the retina was partly detached.

Histopathological findings: The anterior lens capsule was ruptured with release of lenticular material associated to large numbers of infiltrating heterophils, foamy macrophages, few lymphocytes and plasma cells and small numbers of free spherical microspores (up to 2 μm, dark blue structures when stained with Gram). Diffusely, the iris and ciliary body were infiltrated by identical inflammatory cells and there was adherence of the ciliary cleft, iridocorneal angle and pupillary margin of the iris to the lens (anterior and posterior synechiae). The retina was segmentally detached with tombstoning appearance.

Morphologic diagnosis: Endophthalmitis, pyogranulomatous, diffuse, severe with lens rupture (phacoclastic), anterior and posterior synechiae and segmental retinal detachment

Name of the condition: Phacoclastic uveitis

Etiology: Encephalitozoon cuniculi.

Comments: Phacoclastic uveitis in rabbits is a unique condition associated with intralenticularinfestation with the microsporidian protozoa Encephalitozoon cuniculi. Intrauterine infection is the proposed route of transmission of ocular encephalitozoonosis in this species. The organism permeates the developing lens causing cataract formation, spontaneous rupture of lens capsule and release of lens substance resulting in phacoclastic uveitis with pyogranulomatous or granulomatous inflammation. Ocular lesions are mostly unilateral. Rabbits with ocular manifestation generally do not show extra-ocular clinical signs.


Grahn B, Peiffer R, Wilcock B (2018). Histologic manifestations of disorders of the uvea. In: Histologic basis of ocular disease in animals. John Wiley & Sons. pp. 224-227.

Felchle LM, Sigler RL (2002). Phacoemulsification for the management of Encephalitozoon cuniculi-induced phacoclastic uveitis in a rabbit. Vet Ophthalmol. 5:211-215.

Investigation and photo by: Kristel Kegler and Satu Leppänen . Department of Veterinary Biosciences, Pathology Unit, Faculty of Veterinary Medicine, University of Helsinki, Finland.