VN April 2023

Vetnews | April 2023 39 Often the ocular discharge is a white colouration, and this certainly can be due to purulent material, but also, the rabbit tears have a high centration of lipids. When working up a case of dacrocystitis, taking a swab for culture and antibiogram is worthwhile. Often cultures show Pasteurellamultocida or Staphyloccus sp. This problem is predominantly associated with dental disease; thus, assessment and treatment of the animal’s teeth and their problems must be concurrent with managing the ocular condition. Treatment must involve generous flushing of the lacrimal duct system together with topical antibiotic eye drops and try and refrain from ointments that could clog the punctum again. In some cases, systemic medication may be required. Cataracts : Like in any animal, a lens opacity is referred to as a cataract and can be caused by various problems, including trauma and old age. Besides these causes, rabbits have a further unique cause: Encephalitozoon cuniculi. The life cycle of this obligate intracellular organism is very interesting. It is proposed that the microsporidian organism generally infects rabbits through ingestion of contaminated urine and may cause renal or neurological symptoms. But the cataract occurs when the parasite is transmitted transplacentally and enters the rabbit while still in utero . If the organism migrates to the developing lens, it is able to burrow through the lens capsule at this time and then may lie dormant for many months before moving through the lens, causing the cataract changes. After birth, the parasite’s mouthparts can no longer penetrate the lens capsule and enter the lens. I.e., cataract formation from E cuniculi is an in-utero phenomenon only. As an adult animal, it is not uncommon to find that the parasite then erupts through the anterior lens capsule allowing the antigenic lens protein material to be released into the anterior chamber. This damage elicits a lens- induced uveitis, which, although it may cause the cardinal signs of intraocular inflammation, namely miosis, iridal redness, swelling, and hypopyon. It may more likely result in a white or pink mass protruding into the eye’s anterior chamber [see photo]. Whilst this is very typical of E cuniculi one must not be confused with uveitis associated with Staphylococcus or Pasteurella . The bacterial causes generally have a slightly yellow-cream-coloured mass, while E cuniculi is more white. Thus, obtaining an E. cuniculi titer is always helpful in rabbits presenting with these abnormalities. These uveitis cases should be treated with topical anti- inflammatory medication – steroid drops such as prednisolone acetate (Pred Forte] or dexamethasone (Maxidex]. Topical NSAIDs like Kelopt or Acular can also be considered. Oral fenbendazole [Panacur] should be considered where E cuniculi is suspected. The cataract potentially could be managed by phacoemulsification as we perform in our dogs and cats, but rabbits show a very common phenomenon of aggressive regrowth of lens tissue. Corneal ulceration : There is no doubt that corneal ulceration is themost serious corneal condition in rabbits. Ocular surface trauma is common due to the bulging globes and low blink rate in rabbits. Most corneal ulcers should heal and be fluorescein negative in 7 days when topical antibiotics and ocular lubricants are used. This result is often not the case, and ulceration in rabbits can be a frustrating problem Regulars I Ophthalmology Column >>>40